@c Copyright (C) 2002-2018 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.

@node Source Tree
@chapter Source Tree Structure and Build System

This chapter describes the structure of the GCC source tree, and how
GCC is built.  The user documentation for building and installing GCC
is in a separate manual (@uref{http://gcc.gnu.org/install/}), with
which it is presumed that you are familiar.

@menu
* Configure Terms:: Configuration terminology and history.
* Top Level::       The top level source directory.
* gcc Directory::   The @file{gcc} subdirectory.
@end menu

@include configterms.texi

@node Top Level
@section Top Level Source Directory

The top level source directory in a GCC distribution contains several
files and directories that are shared with other software
distributions such as that of GNU Binutils.  It also contains several
subdirectories that contain parts of GCC and its runtime libraries:

@table @file
@item boehm-gc
The Boehm conservative garbage collector, optionally used as part of
the ObjC runtime library when configured with @option{--enable-objc-gc}.

@item config
Autoconf macros and Makefile fragments used throughout the tree.

@item contrib
Contributed scripts that may be found useful in conjunction with GCC@.
One of these, @file{contrib/texi2pod.pl}, is used to generate man
pages from Texinfo manuals as part of the GCC build process.

@item fixincludes
The support for fixing system headers to work with GCC@.  See
@file{fixincludes/README} for more information.  The headers fixed by
this mechanism are installed in @file{@var{libsubdir}/include-fixed}.
Along with those headers, @file{README-fixinc} is also installed, as
@file{@var{libsubdir}/include-fixed/README}.

@item gcc
The main sources of GCC itself (except for runtime libraries),
including optimizers, support for different target architectures,
language front ends, and testsuites.  @xref{gcc Directory, , The
@file{gcc} Subdirectory}, for details.

@item gnattools
Support tools for GNAT.

@item include
Headers for the @code{libiberty} library.

@item intl
GNU @code{libintl}, from GNU @code{gettext}, for systems which do not
include it in @code{libc}.

@item libada
The Ada runtime library.

@item libatomic
The runtime support library for atomic operations (e.g. for @code{__sync}
and @code{__atomic}).

@item libcpp
The C preprocessor library.

@item libdecnumber
The Decimal Float support library.

@item libffi
The @code{libffi} library, used as part of the Go runtime library.

@item libgcc
The GCC runtime library.

@item libgfortran
The Fortran runtime library.

@item libgo
The Go runtime library.  The bulk of this library is mirrored from the
@uref{https://github.com/@/golang/go, master Go repository}.

@item libgomp
The GNU Offloading and Multi Processing Runtime Library.

@item libiberty
The @code{libiberty} library, used for portability and for some
generally useful data structures and algorithms.  @xref{Top, ,
Introduction, libiberty, @sc{gnu} libiberty}, for more information
about this library.

@item libitm
The runtime support library for transactional memory.

@item libobjc
The Objective-C and Objective-C++ runtime library.

@item libquadmath
The runtime support library for quad-precision math operations.

@item libssp
The Stack protector runtime library.

@item libstdc++-v3
The C++ runtime library.

@item lto-plugin
Plugin used by the linker if link-time optimizations are enabled.

@item maintainer-scripts
Scripts used by the @code{gccadmin} account on @code{gcc.gnu.org}.

@item zlib
The @code{zlib} compression library, used for compressing and
uncompressing GCC's intermediate language in LTO object files.
@end table

The build system in the top level directory, including how recursion
into subdirectories works and how building runtime libraries for
multilibs is handled, is documented in a separate manual, included
with GNU Binutils.  @xref{Top, , GNU configure and build system,
configure, The GNU configure and build system}, for details.

@node gcc Directory
@section The @file{gcc} Subdirectory

The @file{gcc} directory contains many files that are part of the C
sources of GCC, other files used as part of the configuration and
build process, and subdirectories including documentation and a
testsuite.  The files that are sources of GCC are documented in a
separate chapter.  @xref{Passes, , Passes and Files of the Compiler}.

@menu
* Subdirectories:: Subdirectories of @file{gcc}.
* Configuration::  The configuration process, and the files it uses.
* Build::          The build system in the @file{gcc} directory.
* Makefile::       Targets in @file{gcc/Makefile}.
* Library Files::  Library source files and headers under @file{gcc/}.
* Headers::        Headers installed by GCC.
* Documentation::  Building documentation in GCC.
* Front End::      Anatomy of a language front end.
* Back End::       Anatomy of a target back end.
@end menu

@node Subdirectories
@subsection Subdirectories of @file{gcc}

The @file{gcc} directory contains the following subdirectories:

@table @file
@item @var{language}
Subdirectories for various languages.  Directories containing a file
@file{config-lang.in} are language subdirectories.  The contents of
the subdirectories @file{c} (for C), @file{cp} (for C++),
@file{objc} (for Objective-C), @file{objcp} (for Objective-C++),
and @file{lto} (for LTO) are documented in this
manual (@pxref{Passes, , Passes and Files of the Compiler});
those for other languages are not.  @xref{Front End, ,
Anatomy of a Language Front End}, for details of the files in these
directories.

@item common
Source files shared between the compiler drivers (such as
@command{gcc}) and the compilers proper (such as @file{cc1}).  If an
architecture defines target hooks shared between those places, it also
has a subdirectory in @file{common/config}.  @xref{Target Structure}.

@item config
Configuration files for supported architectures and operating
systems.  @xref{Back End, , Anatomy of a Target Back End}, for
details of the files in this directory.

@item doc
Texinfo documentation for GCC, together with automatically generated
man pages and support for converting the installation manual to
HTML@.  @xref{Documentation}.

@item ginclude
System headers installed by GCC, mainly those required by the C
standard of freestanding implementations.  @xref{Headers, , Headers
Installed by GCC}, for details of when these and other headers are
installed.

@item po
Message catalogs with translations of messages produced by GCC into
various languages, @file{@var{language}.po}.  This directory also
contains @file{gcc.pot}, the template for these message catalogues,
@file{exgettext}, a wrapper around @command{gettext} to extract the
messages from the GCC sources and create @file{gcc.pot}, which is run
by @samp{make gcc.pot}, and @file{EXCLUDES}, a list of files from
which messages should not be extracted.

@item testsuite
The GCC testsuites (except for those for runtime libraries).
@xref{Testsuites}.
@end table

@node Configuration
@subsection Configuration in the @file{gcc} Directory

The @file{gcc} directory is configured with an Autoconf-generated
script @file{configure}.  The @file{configure} script is generated
from @file{configure.ac} and @file{aclocal.m4}.  From the files
@file{configure.ac} and @file{acconfig.h}, Autoheader generates the
file @file{config.in}.  The file @file{cstamp-h.in} is used as a
timestamp.

@menu
* Config Fragments::     Scripts used by @file{configure}.
* System Config::        The @file{config.build}, @file{config.host}, and
                         @file{config.gcc} files.
* Configuration Files::  Files created by running @file{configure}.
@end menu

@node Config Fragments
@subsubsection Scripts Used by @file{configure}

@file{configure} uses some other scripts to help in its work:

@itemize @bullet
@item The standard GNU @file{config.sub} and @file{config.guess}
files, kept in the top level directory, are used.

@item The file @file{config.gcc} is used to handle configuration
specific to the particular target machine.  The file
@file{config.build} is used to handle configuration specific to the
particular build machine.  The file @file{config.host} is used to handle
configuration specific to the particular host machine.  (In general,
these should only be used for features that cannot reasonably be tested in
Autoconf feature tests.)
@xref{System Config, , The @file{config.build}; @file{config.host};
and @file{config.gcc} Files}, for details of the contents of these files.

@item Each language subdirectory has a file
@file{@var{language}/config-lang.in} that is used for
front-end-specific configuration.  @xref{Front End Config, , The Front
End @file{config-lang.in} File}, for details of this file.

@item A helper script @file{configure.frag} is used as part of
creating the output of @file{configure}.
@end itemize

@node System Config
@subsubsection The @file{config.build}; @file{config.host}; and @file{config.gcc} Files

The @file{config.build} file contains specific rules for particular systems
which GCC is built on.  This should be used as rarely as possible, as the
behavior of the build system can always be detected by autoconf.

The @file{config.host} file contains specific rules for particular systems
which GCC will run on.  This is rarely needed.

The @file{config.gcc} file contains specific rules for particular systems
which GCC will generate code for.  This is usually needed.

Each file has a list of the shell variables it sets, with descriptions, at the
top of the file.

FIXME: document the contents of these files, and what variables should
be set to control build, host and target configuration.

@include configfiles.texi

@node Build
@subsection Build System in the @file{gcc} Directory

FIXME: describe the build system, including what is built in what
stages.  Also list the various source files that are used in the build
process but aren't source files of GCC itself and so aren't documented
below (@pxref{Passes}).

@include makefile.texi

@node Library Files
@subsection Library Source Files and Headers under the @file{gcc} Directory

FIXME: list here, with explanation, all the C source files and headers
under the @file{gcc} directory that aren't built into the GCC
executable but rather are part of runtime libraries and object files,
such as @file{crtstuff.c} and @file{unwind-dw2.c}.  @xref{Headers, ,
Headers Installed by GCC}, for more information about the
@file{ginclude} directory.

@node Headers
@subsection Headers Installed by GCC

In general, GCC expects the system C library to provide most of the
headers to be used with it.  However, GCC will fix those headers if
necessary to make them work with GCC, and will install some headers
required of freestanding implementations.  These headers are installed
in @file{@var{libsubdir}/include}.  Headers for non-C runtime
libraries are also installed by GCC; these are not documented here.
(FIXME: document them somewhere.)

Several of the headers GCC installs are in the @file{ginclude}
directory.  These headers, @file{iso646.h},
@file{stdarg.h}, @file{stdbool.h}, and @file{stddef.h},
are installed in @file{@var{libsubdir}/include},
unless the target Makefile fragment (@pxref{Target Fragment})
overrides this by setting @code{USER_H}.

In addition to these headers and those generated by fixing system
headers to work with GCC, some other headers may also be installed in
@file{@var{libsubdir}/include}.  @file{config.gcc} may set
@code{extra_headers}; this specifies additional headers under
@file{config} to be installed on some systems.

GCC installs its own version of @code{<float.h>}, from @file{ginclude/float.h}.
This is done to cope with command-line options that change the
representation of floating point numbers.

GCC also installs its own version of @code{<limits.h>}; this is generated
from @file{glimits.h}, together with @file{limitx.h} and
@file{limity.h} if the system also has its own version of
@code{<limits.h>}.  (GCC provides its own header because it is
required of ISO C freestanding implementations, but needs to include
the system header from its own header as well because other standards
such as POSIX specify additional values to be defined in
@code{<limits.h>}.)  The system's @code{<limits.h>} header is used via
@file{@var{libsubdir}/include/syslimits.h}, which is copied from
@file{gsyslimits.h} if it does not need fixing to work with GCC; if it
needs fixing, @file{syslimits.h} is the fixed copy.

GCC can also install @code{<tgmath.h>}.  It will do this when
@file{config.gcc} sets @code{use_gcc_tgmath} to @code{yes}.

@node Documentation
@subsection Building Documentation

The main GCC documentation is in the form of manuals in Texinfo
format.  These are installed in Info format; DVI versions may be
generated by @samp{make dvi}, PDF versions by @samp{make pdf}, and
HTML versions by @samp{make html}.  In addition, some man pages are
generated from the Texinfo manuals, there are some other text files
with miscellaneous documentation, and runtime libraries have their own
documentation outside the @file{gcc} directory.  FIXME: document the
documentation for runtime libraries somewhere.

@menu
* Texinfo Manuals::      GCC manuals in Texinfo format.
* Man Page Generation::  Generating man pages from Texinfo manuals.
* Miscellaneous Docs::   Miscellaneous text files with documentation.
@end menu

@node Texinfo Manuals
@subsubsection Texinfo Manuals

The manuals for GCC as a whole, and the C and C++ front ends, are in
files @file{doc/*.texi}.  Other front ends have their own manuals in
files @file{@var{language}/*.texi}.  Common files
@file{doc/include/*.texi} are provided which may be included in
multiple manuals; the following files are in @file{doc/include}:

@table @file
@item fdl.texi
The GNU Free Documentation License.
@item funding.texi
The section ``Funding Free Software''.
@item gcc-common.texi
Common definitions for manuals.
@item gpl_v3.texi
The GNU General Public License.
@item texinfo.tex
A copy of @file{texinfo.tex} known to work with the GCC manuals.
@end table

DVI-formatted manuals are generated by @samp{make dvi}, which uses
@command{texi2dvi} (via the Makefile macro @code{$(TEXI2DVI)}).
PDF-formatted manuals are generated by @samp{make pdf}, which uses
@command{texi2pdf} (via the Makefile macro @code{$(TEXI2PDF)}).  HTML
formatted manuals are generated by @samp{make html}.  Info
manuals are generated by @samp{make info} (which is run as part of
a bootstrap); this generates the manuals in the source directory,
using @command{makeinfo} via the Makefile macro @code{$(MAKEINFO)},
and they are included in release distributions.

Manuals are also provided on the GCC web site, in both HTML and
PostScript forms.  This is done via the script
@file{maintainer-scripts/update_web_docs_svn}.  Each manual to be
provided online must be listed in the definition of @code{MANUALS} in
that file; a file @file{@var{name}.texi} must only appear once in the
source tree, and the output manual must have the same name as the
source file.  (However, other Texinfo files, included in manuals but
not themselves the root files of manuals, may have names that appear
more than once in the source tree.)  The manual file
@file{@var{name}.texi} should only include other files in its own
directory or in @file{doc/include}.  HTML manuals will be generated by
@samp{makeinfo --html}, PostScript manuals by @command{texi2dvi}
and @command{dvips}, and PDF manuals by @command{texi2pdf}.
All Texinfo files that are parts of manuals must
be version-controlled, even if they are generated files, for the
generation of online manuals to work.

The installation manual, @file{doc/install.texi}, is also provided on
the GCC web site.  The HTML version is generated by the script
@file{doc/install.texi2html}.

@node Man Page Generation
@subsubsection Man Page Generation

Because of user demand, in addition to full Texinfo manuals, man pages
are provided which contain extracts from those manuals.  These man
pages are generated from the Texinfo manuals using
@file{contrib/texi2pod.pl} and @command{pod2man}.  (The man page for
@command{g++}, @file{cp/g++.1}, just contains a @samp{.so} reference
to @file{gcc.1}, but all the other man pages are generated from
Texinfo manuals.)

Because many systems may not have the necessary tools installed to
generate the man pages, they are only generated if the
@file{configure} script detects that recent enough tools are
installed, and the Makefiles allow generating man pages to fail
without aborting the build.  Man pages are also included in release
distributions.  They are generated in the source directory.

Magic comments in Texinfo files starting @samp{@@c man} control what
parts of a Texinfo file go into a man page.  Only a subset of Texinfo
is supported by @file{texi2pod.pl}, and it may be necessary to add
support for more Texinfo features to this script when generating new
man pages.  To improve the man page output, some special Texinfo
macros are provided in @file{doc/include/gcc-common.texi} which
@file{texi2pod.pl} understands:

@table @code
@item @@gcctabopt
Use in the form @samp{@@table @@gcctabopt} for tables of options,
where for printed output the effect of @samp{@@code} is better than
that of @samp{@@option} but for man page output a different effect is
wanted.
@item @@gccoptlist
Use for summary lists of options in manuals.
@item @@gol
Use at the end of each line inside @samp{@@gccoptlist}.  This is
necessary to avoid problems with differences in how the
@samp{@@gccoptlist} macro is handled by different Texinfo formatters.
@end table

FIXME: describe the @file{texi2pod.pl} input language and magic
comments in more detail.

@node Miscellaneous Docs
@subsubsection Miscellaneous Documentation

In addition to the formal documentation that is installed by GCC,
there are several other text files in the @file{gcc} subdirectory
with miscellaneous documentation:

@table @file
@item ABOUT-GCC-NLS
Notes on GCC's Native Language Support.  FIXME: this should be part of
this manual rather than a separate file.
@item ABOUT-NLS
Notes on the Free Translation Project.
@item COPYING
@itemx COPYING3
The GNU General Public License, Versions 2 and 3.
@item COPYING.LIB
@itemx COPYING3.LIB
The GNU Lesser General Public License, Versions 2.1 and 3.
@item *ChangeLog*
@itemx */ChangeLog*
Change log files for various parts of GCC@.
@item LANGUAGES
Details of a few changes to the GCC front-end interface.  FIXME: the
information in this file should be part of general documentation of
the front-end interface in this manual.
@item ONEWS
Information about new features in old versions of GCC@.  (For recent
versions, the information is on the GCC web site.)
@item README.Portability
Information about portability issues when writing code in GCC@.  FIXME:
why isn't this part of this manual or of the GCC Coding Conventions?
@end table

FIXME: document such files in subdirectories, at least @file{config},
@file{c}, @file{cp}, @file{objc}, @file{testsuite}.

@node Front End
@subsection Anatomy of a Language Front End

A front end for a language in GCC has the following parts:

@itemize @bullet
@item
A directory @file{@var{language}} under @file{gcc} containing source
files for that front end.  @xref{Front End Directory, , The Front End
@file{@var{language}} Directory}, for details.
@item
A mention of the language in the list of supported languages in
@file{gcc/doc/install.texi}.
@item
A mention of the name under which the language's runtime library is
recognized by @option{--enable-shared=@var{package}} in the
documentation of that option in @file{gcc/doc/install.texi}.
@item
A mention of any special prerequisites for building the front end in
the documentation of prerequisites in @file{gcc/doc/install.texi}.
@item
Details of contributors to that front end in
@file{gcc/doc/contrib.texi}.  If the details are in that front end's
own manual then there should be a link to that manual's list in
@file{contrib.texi}.
@item
Information about support for that language in
@file{gcc/doc/frontends.texi}.
@item
Information about standards for that language, and the front end's
support for them, in @file{gcc/doc/standards.texi}.  This may be a
link to such information in the front end's own manual.
@item
Details of source file suffixes for that language and @option{-x
@var{lang}} options supported, in @file{gcc/doc/invoke.texi}.
@item
Entries in @code{default_compilers} in @file{gcc.c} for source file
suffixes for that language.
@item
Preferably testsuites, which may be under @file{gcc/testsuite} or
runtime library directories.  FIXME: document somewhere how to write
testsuite harnesses.
@item
Probably a runtime library for the language, outside the @file{gcc}
directory.  FIXME: document this further.
@item
Details of the directories of any runtime libraries in
@file{gcc/doc/sourcebuild.texi}.
@item
Check targets in @file{Makefile.def} for the top-level @file{Makefile}
to check just the compiler or the compiler and runtime library for the
language.
@end itemize

If the front end is added to the official GCC source repository, the
following are also necessary:

@itemize @bullet
@item
At least one Bugzilla component for bugs in that front end and runtime
libraries.  This category needs to be added to the Bugzilla database.
@item
Normally, one or more maintainers of that front end listed in
@file{MAINTAINERS}.
@item
Mentions on the GCC web site in @file{index.html} and
@file{frontends.html}, with any relevant links on
@file{readings.html}.  (Front ends that are not an official part of
GCC may also be listed on @file{frontends.html}, with relevant links.)
@item
A news item on @file{index.html}, and possibly an announcement on the
@email{gcc-announce@@gcc.gnu.org} mailing list.
@item
The front end's manuals should be mentioned in
@file{maintainer-scripts/update_web_docs_svn} (@pxref{Texinfo Manuals})
and the online manuals should be linked to from
@file{onlinedocs/index.html}.
@item
Any old releases or CVS repositories of the front end, before its
inclusion in GCC, should be made available on the GCC FTP site
@uref{ftp://gcc.gnu.org/pub/gcc/old-releases/}.
@item
The release and snapshot script @file{maintainer-scripts/gcc_release}
should be updated to generate appropriate tarballs for this front end.
@item
If this front end includes its own version files that include the
current date, @file{maintainer-scripts/update_version} should be
updated accordingly.
@end itemize

@menu
* Front End Directory::  The front end @file{@var{language}} directory.
* Front End Config::     The front end @file{config-lang.in} file.
* Front End Makefile::   The front end @file{Make-lang.in} file.
@end menu

@node Front End Directory
@subsubsection The Front End @file{@var{language}} Directory

A front end @file{@var{language}} directory contains the source files
of that front end (but not of any runtime libraries, which should be
outside the @file{gcc} directory).  This includes documentation, and
possibly some subsidiary programs built alongside the front end.
Certain files are special and other parts of the compiler depend on
their names:

@table @file
@item config-lang.in
This file is required in all language subdirectories.  @xref{Front End
Config, , The Front End @file{config-lang.in} File}, for details of
its contents
@item Make-lang.in
This file is required in all language subdirectories.  @xref{Front End
Makefile, , The Front End @file{Make-lang.in} File}, for details of its
contents.
@item lang.opt
This file registers the set of switches that the front end accepts on
the command line, and their @option{--help} text.  @xref{Options}.
@item lang-specs.h
This file provides entries for @code{default_compilers} in
@file{gcc.c} which override the default of giving an error that a
compiler for that language is not installed.
@item @var{language}-tree.def
This file, which need not exist, defines any language-specific tree
codes.
@end table

@node Front End Config
@subsubsection The Front End @file{config-lang.in} File

Each language subdirectory contains a @file{config-lang.in} file.
This file is a shell script that may define some variables describing
the language:

@table @code
@item language
This definition must be present, and gives the name of the language
for some purposes such as arguments to @option{--enable-languages}.
@item lang_requires
If defined, this variable lists (space-separated) language front ends
other than C that this front end requires to be enabled (with the
names given being their @code{language} settings).  For example, the
Obj-C++ front end depends on the C++ and ObjC front ends, so sets
@samp{lang_requires="objc c++"}.
@item subdir_requires
If defined, this variable lists (space-separated) front end directories
other than C that this front end requires to be present.  For example,
the Objective-C++ front end uses source files from the C++ and
Objective-C front ends, so sets @samp{subdir_requires="cp objc"}.
@item target_libs
If defined, this variable lists (space-separated) targets in the top
level @file{Makefile} to build the runtime libraries for this
language, such as @code{target-libobjc}.
@item lang_dirs
If defined, this variable lists (space-separated) top level
directories (parallel to @file{gcc}), apart from the runtime libraries,
that should not be configured if this front end is not built.
@item build_by_default
If defined to @samp{no}, this language front end is not built unless
enabled in a @option{--enable-languages} argument.  Otherwise, front
ends are built by default, subject to any special logic in
@file{configure.ac} (as is present to disable the Ada front end if the
Ada compiler is not already installed).
@item boot_language
If defined to @samp{yes}, this front end is built in stage1 of the
bootstrap.  This is only relevant to front ends written in their own
languages.
@item compilers
If defined, a space-separated list of compiler executables that will
be run by the driver.  The names here will each end
with @samp{\$(exeext)}.
@item outputs
If defined, a space-separated list of files that should be generated
by @file{configure} substituting values in them.  This mechanism can
be used to create a file @file{@var{language}/Makefile} from
@file{@var{language}/Makefile.in}, but this is deprecated, building
everything from the single @file{gcc/Makefile} is preferred.
@item gtfiles
If defined, a space-separated list of files that should be scanned by
@file{gengtype.c} to generate the garbage collection tables and routines for
this language.  This excludes the files that are common to all front
ends.  @xref{Type Information}.

@end table

@node Front End Makefile
@subsubsection The Front End @file{Make-lang.in} File

Each language subdirectory contains a @file{Make-lang.in} file.  It contains
targets @code{@var{lang}.@var{hook}} (where @code{@var{lang}} is the
setting of @code{language} in @file{config-lang.in}) for the following
values of @code{@var{hook}}, and any other Makefile rules required to
build those targets (which may if necessary use other Makefiles
specified in @code{outputs} in @file{config-lang.in}, although this is
deprecated).  It also adds any testsuite targets that can use the
standard rule in @file{gcc/Makefile.in} to the variable
@code{lang_checks}.

@table @code
@item all.cross
@itemx start.encap
@itemx rest.encap
FIXME: exactly what goes in each of these targets?
@item tags
Build an @command{etags} @file{TAGS} file in the language subdirectory
in the source tree.
@item info
Build info documentation for the front end, in the build directory.
This target is only called by @samp{make bootstrap} if a suitable
version of @command{makeinfo} is available, so does not need to check
for this, and should fail if an error occurs.
@item dvi
Build DVI documentation for the front end, in the build directory.
This should be done using @code{$(TEXI2DVI)}, with appropriate
@option{-I} arguments pointing to directories of included files.
@item pdf
Build PDF documentation for the front end, in the build directory.
This should be done using @code{$(TEXI2PDF)}, with appropriate
@option{-I} arguments pointing to directories of included files.
@item html
Build HTML documentation for the front end, in the build directory.
@item man
Build generated man pages for the front end from Texinfo manuals
(@pxref{Man Page Generation}), in the build directory.  This target
is only called if the necessary tools are available, but should ignore
errors so as not to stop the build if errors occur; man pages are
optional and the tools involved may be installed in a broken way.
@item install-common
Install everything that is part of the front end, apart from the
compiler executables listed in @code{compilers} in
@file{config-lang.in}.
@item install-info
Install info documentation for the front end, if it is present in the
source directory.  This target should have dependencies on info files
that should be installed.
@item install-man
Install man pages for the front end.  This target should ignore
errors.
@item install-plugin
Install headers needed for plugins.
@item srcextra
Copies its dependencies into the source directory.  This generally should
be used for generated files such as Bison output files which are not
version-controlled, but should be included in any release tarballs.  This
target will be executed during a bootstrap if
@samp{--enable-generated-files-in-srcdir} was specified as a
@file{configure} option.
@item srcinfo
@itemx srcman
Copies its dependencies into the source directory.  These targets will be
executed during a bootstrap if @samp{--enable-generated-files-in-srcdir}
was specified as a @file{configure} option.
@item uninstall
Uninstall files installed by installing the compiler.  This is
currently documented not to be supported, so the hook need not do
anything.
@item mostlyclean
@itemx clean
@itemx distclean
@itemx maintainer-clean
The language parts of the standard GNU
@samp{*clean} targets.  @xref{Standard Targets, , Standard Targets for
Users, standards, GNU Coding Standards}, for details of the standard
targets.  For GCC, @code{maintainer-clean} should delete
all generated files in the source directory that are not version-controlled,
but should not delete anything that is.
@end table

@file{Make-lang.in} must also define a variable @code{@var{lang}_OBJS}
to a list of host object files that are used by that language.

@node Back End
@subsection Anatomy of a Target Back End

A back end for a target architecture in GCC has the following parts:

@itemize @bullet
@item
A directory @file{@var{machine}} under @file{gcc/config}, containing a
machine description @file{@var{machine}.md} file (@pxref{Machine Desc,
, Machine Descriptions}), header files @file{@var{machine}.h} and
@file{@var{machine}-protos.h} and a source file @file{@var{machine}.c}
(@pxref{Target Macros, , Target Description Macros and Functions}),
possibly a target Makefile fragment @file{t-@var{machine}}
(@pxref{Target Fragment, , The Target Makefile Fragment}), and maybe
some other files.  The names of these files may be changed from the
defaults given by explicit specifications in @file{config.gcc}.
@item
If necessary, a file @file{@var{machine}-modes.def} in the
@file{@var{machine}} directory, containing additional machine modes to
represent condition codes.  @xref{Condition Code}, for further details.
@item
An optional @file{@var{machine}.opt} file in the @file{@var{machine}}
directory, containing a list of target-specific options.  You can also
add other option files using the @code{extra_options} variable in
@file{config.gcc}.  @xref{Options}.
@item
Entries in @file{config.gcc} (@pxref{System Config, , The
@file{config.gcc} File}) for the systems with this target
architecture.
@item
Documentation in @file{gcc/doc/invoke.texi} for any command-line
options supported by this target (@pxref{Run-time Target, , Run-time
Target Specification}).  This means both entries in the summary table
of options and details of the individual options.
@item
Documentation in @file{gcc/doc/extend.texi} for any target-specific
attributes supported (@pxref{Target Attributes, , Defining
target-specific uses of @code{__attribute__}}), including where the
same attribute is already supported on some targets, which are
enumerated in the manual.
@item
Documentation in @file{gcc/doc/extend.texi} for any target-specific
pragmas supported.
@item
Documentation in @file{gcc/doc/extend.texi} of any target-specific
built-in functions supported.
@item
Documentation in @file{gcc/doc/extend.texi} of any target-specific
format checking styles supported.
@item
Documentation in @file{gcc/doc/md.texi} of any target-specific
constraint letters (@pxref{Machine Constraints, , Constraints for
Particular Machines}).
@item
A note in @file{gcc/doc/contrib.texi} under the person or people who
contributed the target support.
@item
Entries in @file{gcc/doc/install.texi} for all target triplets
supported with this target architecture, giving details of any special
notes about installation for this target, or saying that there are no
special notes if there are none.
@item
Possibly other support outside the @file{gcc} directory for runtime
libraries.  FIXME: reference docs for this.  The @code{libstdc++} porting
manual needs to be installed as info for this to work, or to be a
chapter of this manual.
@end itemize

The @file{@var{machine}.h} header is included very early in GCC's
standard sequence of header files, while @file{@var{machine}-protos.h}
is included late in the sequence.  Thus @file{@var{machine}-protos.h}
can include declarations referencing types that are not defined when
@file{@var{machine}.h} is included, specifically including those from
@file{rtl.h} and @file{tree.h}.  Since both RTL and tree types may not
be available in every context where @file{@var{machine}-protos.h} is
included, in this file you should guard declarations using these types
inside appropriate @code{#ifdef RTX_CODE} or @code{#ifdef TREE_CODE}
conditional code segments.

If the backend uses shared data structures that require @code{GTY} markers 
for garbage collection (@pxref{Type Information}), you must declare those
in @file{@var{machine}.h} rather than @file{@var{machine}-protos.h}.  
Any definitions required for building libgcc must also go in
@file{@var{machine}.h}.

GCC uses the macro @code{IN_TARGET_CODE} to distinguish between
machine-specific @file{.c} and @file{.cc} files and
machine-independent @file{.c} and @file{.cc} files.  Machine-specific
files should use the directive:

@example
#define IN_TARGET_CODE 1
@end example

before including @code{config.h}.

If the back end is added to the official GCC source repository, the
following are also necessary:

@itemize @bullet
@item
An entry for the target architecture in @file{readings.html} on the
GCC web site, with any relevant links.
@item
Details of the properties of the back end and target architecture in
@file{backends.html} on the GCC web site.
@item
A news item about the contribution of support for that target
architecture, in @file{index.html} on the GCC web site.
@item
Normally, one or more maintainers of that target listed in
@file{MAINTAINERS}.  Some existing architectures may be unmaintained,
but it would be unusual to add support for a target that does not have
a maintainer when support is added.
@item
Target triplets covering all @file{config.gcc} stanzas for the target,
in the list in @file{contrib/config-list.mk}.
@end itemize

@node Testsuites
@chapter Testsuites

GCC contains several testsuites to help maintain compiler quality.
Most of the runtime libraries and language front ends in GCC have
testsuites.  Currently only the C language testsuites are documented
here; FIXME: document the others.

@menu
* Test Idioms::     Idioms used in testsuite code.
* Test Directives:: Directives used within DejaGnu tests.
* Ada Tests::       The Ada language testsuites.
* C Tests::         The C language testsuites.
* LTO Testing::     Support for testing link-time optimizations.
* gcov Testing::    Support for testing gcov.
* profopt Testing:: Support for testing profile-directed optimizations.
* compat Testing::  Support for testing binary compatibility.
* Torture Tests::   Support for torture testing using multiple options.
* GIMPLE Tests::    Support for testing GIMPLE passes.
* RTL Tests::       Support for testing RTL passes.
@end menu

@node Test Idioms
@section Idioms Used in Testsuite Code

In general, C testcases have a trailing @file{-@var{n}.c}, starting
with @file{-1.c}, in case other testcases with similar names are added
later.  If the test is a test of some well-defined feature, it should
have a name referring to that feature such as
@file{@var{feature}-1.c}.  If it does not test a well-defined feature
but just happens to exercise a bug somewhere in the compiler, and a
bug report has been filed for this bug in the GCC bug database,
@file{pr@var{bug-number}-1.c} is the appropriate form of name.
Otherwise (for miscellaneous bugs not filed in the GCC bug database),
and previously more generally, test cases are named after the date on
which they were added.  This allows people to tell at a glance whether
a test failure is because of a recently found bug that has not yet
been fixed, or whether it may be a regression, but does not give any
other information about the bug or where discussion of it may be
found.  Some other language testsuites follow similar conventions.

In the @file{gcc.dg} testsuite, it is often necessary to test that an
error is indeed a hard error and not just a warning---for example,
where it is a constraint violation in the C standard, which must
become an error with @option{-pedantic-errors}.  The following idiom,
where the first line shown is line @var{line} of the file and the line
that generates the error, is used for this:

@smallexample
/* @{ dg-bogus "warning" "warning in place of error" @} */
/* @{ dg-error "@var{regexp}" "@var{message}" @{ target *-*-* @} @var{line} @} */
@end smallexample

It may be necessary to check that an expression is an integer constant
expression and has a certain value.  To check that @code{@var{E}} has
value @code{@var{V}}, an idiom similar to the following is used:

@smallexample
char x[((E) == (V) ? 1 : -1)];
@end smallexample

In @file{gcc.dg} tests, @code{__typeof__} is sometimes used to make
assertions about the types of expressions.  See, for example,
@file{gcc.dg/c99-condexpr-1.c}.  The more subtle uses depend on the
exact rules for the types of conditional expressions in the C
standard; see, for example, @file{gcc.dg/c99-intconst-1.c}.

It is useful to be able to test that optimizations are being made
properly.  This cannot be done in all cases, but it can be done where
the optimization will lead to code being optimized away (for example,
where flow analysis or alias analysis should show that certain code
cannot be called) or to functions not being called because they have
been expanded as built-in functions.  Such tests go in
@file{gcc.c-torture/execute}.  Where code should be optimized away, a
call to a nonexistent function such as @code{link_failure ()} may be
inserted; a definition

@smallexample
#ifndef __OPTIMIZE__
void
link_failure (void)
@{
  abort ();
@}
#endif
@end smallexample

@noindent
will also be needed so that linking still succeeds when the test is
run without optimization.  When all calls to a built-in function
should have been optimized and no calls to the non-built-in version of
the function should remain, that function may be defined as
@code{static} to call @code{abort ()} (although redeclaring a function
as static may not work on all targets).

All testcases must be portable.  Target-specific testcases must have
appropriate code to avoid causing failures on unsupported systems;
unfortunately, the mechanisms for this differ by directory.

FIXME: discuss non-C testsuites here.

@node Test Directives
@section Directives used within DejaGnu tests

@menu
* Directives::  Syntax and descriptions of test directives.
* Selectors:: Selecting targets to which a test applies.
* Effective-Target Keywords:: Keywords describing target attributes.
* Add Options:: Features for @code{dg-add-options}
* Require Support:: Variants of @code{dg-require-@var{support}}
* Final Actions:: Commands for use in @code{dg-final}
@end menu

@node Directives
@subsection Syntax and Descriptions of test directives

Test directives appear within comments in a test source file and begin
with @code{dg-}.  Some of these are defined within DejaGnu and others
are local to the GCC testsuite.

The order in which test directives appear in a test can be important:
directives local to GCC sometimes override information used by the
DejaGnu directives, which know nothing about the GCC directives, so the
DejaGnu directives must precede GCC directives.

Several test directives include selectors (@pxref{Selectors, , })
which are usually preceded by the keyword @code{target} or @code{xfail}.

@subsubsection Specify how to build the test

@table @code
@item @{ dg-do @var{do-what-keyword} [@{ target/xfail @var{selector} @}] @}
@var{do-what-keyword} specifies how the test is compiled and whether
it is executed.  It is one of:

@table @code
@item preprocess
Compile with @option{-E} to run only the preprocessor.
@item compile
Compile with @option{-S} to produce an assembly code file.
@item assemble
Compile with @option{-c} to produce a relocatable object file.
@item link
Compile, assemble, and link to produce an executable file.
@item run
Produce and run an executable file, which is expected to return
an exit code of 0.
@end table

The default is @code{compile}.  That can be overridden for a set of
tests by redefining @code{dg-do-what-default} within the @code{.exp}
file for those tests.

If the directive includes the optional @samp{@{ target @var{selector} @}}
then the test is skipped unless the target system matches the
@var{selector}.

If @var{do-what-keyword} is @code{run} and the directive includes
the optional @samp{@{ xfail @var{selector} @}} and the selector is met
then the test is expected to fail.  The @code{xfail} clause is ignored
for other values of @var{do-what-keyword}; those tests can use
directive @code{dg-xfail-if}.
@end table

@subsubsection Specify additional compiler options

@table @code
@item @{ dg-options @var{options} [@{ target @var{selector} @}] @}
This DejaGnu directive provides a list of compiler options, to be used
if the target system matches @var{selector}, that replace the default
options used for this set of tests.

@item @{ dg-add-options @var{feature} @dots{} @}
Add any compiler options that are needed to access certain features.
This directive does nothing on targets that enable the features by
default, or that don't provide them at all.  It must come after
all @code{dg-options} directives.
For supported values of @var{feature} see @ref{Add Options, ,}.

@item @{ dg-additional-options @var{options} [@{ target @var{selector} @}] @}
This directive provides a list of compiler options, to be used
if the target system matches @var{selector}, that are added to the default
options used for this set of tests.
@end table

@subsubsection Modify the test timeout value

The normal timeout limit, in seconds, is found by searching the
following in order:

@itemize @bullet
@item the value defined by an earlier @code{dg-timeout} directive in
the test

@item variable @var{tool_timeout} defined by the set of tests

@item @var{gcc},@var{timeout} set in the target board

@item 300
@end itemize

@table @code
@item @{ dg-timeout @var{n} [@{target @var{selector} @}] @}
Set the time limit for the compilation and for the execution of the test
to the specified number of seconds.

@item @{ dg-timeout-factor @var{x} [@{ target @var{selector} @}] @}
Multiply the normal time limit for compilation and execution of the test
by the specified floating-point factor.
@end table

@subsubsection Skip a test for some targets

@table @code
@item @{ dg-skip-if @var{comment} @{ @var{selector} @} [@{ @var{include-opts} @} [@{ @var{exclude-opts} @}]] @}
Arguments @var{include-opts} and @var{exclude-opts} are lists in which
each element is a string of zero or more GCC options.
Skip the test if all of the following conditions are met:
@itemize @bullet
@item the test system is included in @var{selector}

@item for at least one of the option strings in @var{include-opts},
every option from that string is in the set of options with which
the test would be compiled; use @samp{"*"} for an @var{include-opts} list
that matches any options; that is the default if @var{include-opts} is
not specified

@item for each of the option strings in @var{exclude-opts}, at least one
option from that string is not in the set of options with which the test
would be compiled; use @samp{""} for an empty @var{exclude-opts} list;
that is the default if @var{exclude-opts} is not specified
@end itemize

For example, to skip a test if option @code{-Os} is present:

@smallexample
/* @{ dg-skip-if "" @{ *-*-* @}  @{ "-Os" @} @{ "" @} @} */
@end smallexample

To skip a test if both options @code{-O2} and @code{-g} are present:

@smallexample
/* @{ dg-skip-if "" @{ *-*-* @}  @{ "-O2 -g" @} @{ "" @} @} */
@end smallexample

To skip a test if either @code{-O2} or @code{-O3} is present:

@smallexample
/* @{ dg-skip-if "" @{ *-*-* @}  @{ "-O2" "-O3" @} @{ "" @} @} */
@end smallexample

To skip a test unless option @code{-Os} is present:

@smallexample
/* @{ dg-skip-if "" @{ *-*-* @}  @{ "*" @} @{ "-Os" @} @} */
@end smallexample

To skip a test if either @code{-O2} or @code{-O3} is used with @code{-g}
but not if @code{-fpic} is also present:

@smallexample
/* @{ dg-skip-if "" @{ *-*-* @}  @{ "-O2 -g" "-O3 -g" @} @{ "-fpic" @} @} */
@end smallexample

@item @{ dg-require-effective-target @var{keyword} [@{ @var{selector} @}] @}
Skip the test if the test target, including current multilib flags,
is not covered by the effective-target keyword.
If the directive includes the optional @samp{@{ @var{selector} @}}
then the effective-target test is only performed if the target system
matches the @var{selector}.
This directive must appear after any @code{dg-do} directive in the test
and before any @code{dg-additional-sources} directive.
@xref{Effective-Target Keywords, , }.

@item @{ dg-require-@var{support} args @}
Skip the test if the target does not provide the required support.
These directives must appear after any @code{dg-do} directive in the test
and before any @code{dg-additional-sources} directive.
They require at least one argument, which can be an empty string if the
specific procedure does not examine the argument.
@xref{Require Support, , }, for a complete list of these directives.
@end table

@subsubsection Expect a test to fail for some targets

@table @code
@item  @{ dg-xfail-if @var{comment} @{ @var{selector} @} [@{ @var{include-opts} @} [@{ @var{exclude-opts} @}]] @}
Expect the test to fail if the conditions (which are the same as for
@code{dg-skip-if}) are met.  This does not affect the execute step.

@item  @{ dg-xfail-run-if @var{comment} @{ @var{selector} @} [@{ @var{include-opts} @} [@{ @var{exclude-opts} @}]] @}
Expect the execute step of a test to fail if the conditions (which are
the same as for @code{dg-skip-if}) are met.
@end table

@subsubsection Expect the test executable to fail

@table @code
@item  @{ dg-shouldfail @var{comment} [@{ @var{selector} @} [@{ @var{include-opts} @} [@{ @var{exclude-opts} @}]]] @}
Expect the test executable to return a nonzero exit status if the
conditions (which are the same as for @code{dg-skip-if}) are met.
@end table

@subsubsection Verify compiler messages

@table @code
@item @{ dg-error @var{regexp} [@var{comment} [@{ target/xfail @var{selector} @} [@var{line}] ]] @}
This DejaGnu directive appears on a source line that is expected to get
an error message, or else specifies the source line associated with the
message.  If there is no message for that line or if the text of that
message is not matched by @var{regexp} then the check fails and
@var{comment} is included in the @code{FAIL} message.  The check does
not look for the string @samp{error} unless it is part of @var{regexp}.

@item @{ dg-warning @var{regexp} [@var{comment} [@{ target/xfail @var{selector} @} [@var{line}] ]] @}
This DejaGnu directive appears on a source line that is expected to get
a warning message, or else specifies the source line associated with the
message.  If there is no message for that line or if the text of that
message is not matched by @var{regexp} then the check fails and
@var{comment} is included in the @code{FAIL} message.  The check does
not look for the string @samp{warning} unless it is part of @var{regexp}.

@item @{ dg-message @var{regexp} [@var{comment} [@{ target/xfail @var{selector} @} [@var{line}] ]] @}
The line is expected to get a message other than an error or warning.
If there is no message for that line or if the text of that message is
not matched by @var{regexp} then the check fails and @var{comment} is
included in the @code{FAIL} message.

@item @{ dg-bogus @var{regexp} [@var{comment} [@{ target/xfail @var{selector} @} [@var{line}] ]] @}
This DejaGnu directive appears on a source line that should not get a
message matching @var{regexp}, or else specifies the source line
associated with the bogus message.  It is usually used with @samp{xfail}
to indicate that the message is a known problem for a particular set of
targets.

@item @{ dg-line @var{linenumvar} @}
This DejaGnu directive sets the variable @var{linenumvar} to the line number of
the source line.  The variable @var{linenumvar} can then be used in subsequent
@code{dg-error}, @code{dg-warning}, @code{dg-message} and @code{dg-bogus}
directives.  For example:

@smallexample
int a;   /* @{ dg-line first_def_a @} */
float a; /* @{ dg-error "conflicting types of" @} */
/* @{ dg-message "previous declaration of" "" @{ target *-*-* @} first_def_a @} */
@end smallexample

@item @{ dg-excess-errors @var{comment} [@{ target/xfail @var{selector} @}] @}
This DejaGnu directive indicates that the test is expected to fail due
to compiler messages that are not handled by @samp{dg-error},
@samp{dg-warning} or @samp{dg-bogus}.  For this directive @samp{xfail}
has the same effect as @samp{target}.

@item @{ dg-prune-output @var{regexp} @}
Prune messages matching @var{regexp} from the test output.
@end table

@subsubsection Verify output of the test executable

@table @code
@item @{ dg-output @var{regexp} [@{ target/xfail @var{selector} @}] @}
This DejaGnu directive compares @var{regexp} to the combined output
that the test executable writes to @file{stdout} and @file{stderr}.
@end table

@subsubsection Specify additional files for a test

@table @code
@item @{ dg-additional-files "@var{filelist}" @}
Specify additional files, other than source files, that must be copied
to the system where the compiler runs.

@item @{ dg-additional-sources "@var{filelist}" @}
Specify additional source files to appear in the compile line
following the main test file.
@end table

@subsubsection Add checks at the end of a test

@table @code
@item @{ dg-final @{ @var{local-directive} @} @}
This DejaGnu directive is placed within a comment anywhere in the
source file and is processed after the test has been compiled and run.
Multiple @samp{dg-final} commands are processed in the order in which
they appear in the source file.  @xref{Final Actions, , }, for a list
of directives that can be used within @code{dg-final}.
@end table

@node Selectors
@subsection Selecting targets to which a test applies

Several test directives include @var{selector}s to limit the targets
for which a test is run or to declare that a test is expected to fail
on particular targets.

A selector is:
@itemize @bullet
@item one or more target triplets, possibly including wildcard characters;
use @samp{*-*-*} to match any target
@item a single effective-target keyword (@pxref{Effective-Target Keywords})
@item a logical expression
@end itemize

Depending on the context, the selector specifies whether a test is
skipped and reported as unsupported or is expected to fail.  A context
that allows either @samp{target} or @samp{xfail} also allows
@samp{@{ target @var{selector1} xfail @var{selector2} @}}
to skip the test for targets that don't match @var{selector1} and the
test to fail for targets that match @var{selector2}.

A selector expression appears within curly braces and uses a single
logical operator: one of @samp{!}, @samp{&&}, or @samp{||}.  An
operand is another selector expression, an effective-target keyword,
a single target triplet, or a list of target triplets within quotes or
curly braces.  For example:

@smallexample
@{ target @{ ! "hppa*-*-* ia64*-*-*" @} @}
@{ target @{ powerpc*-*-* && lp64 @} @}
@{ xfail @{ lp64 || vect_no_align @} @}
@end smallexample

@node Effective-Target Keywords
@subsection Keywords describing target attributes

Effective-target keywords identify sets of targets that support
particular functionality.  They are used to limit tests to be run only
for particular targets, or to specify that particular sets of targets
are expected to fail some tests.

Effective-target keywords are defined in @file{lib/target-supports.exp} in
the GCC testsuite, with the exception of those that are documented as
being local to a particular test directory.

The @samp{effective target} takes into account all of the compiler options
with which the test will be compiled, including the multilib options.
By convention, keywords ending in @code{_nocache} can also include options
specified for the particular test in an earlier @code{dg-options} or
@code{dg-add-options} directive.

@subsubsection Endianness

@table @code
@item be
Target uses big-endian memory order for multi-byte and multi-word data.

@item le
Target uses little-endian memory order for multi-byte and multi-word data.
@end table

@subsubsection Data type sizes

@table @code
@item ilp32
Target has 32-bit @code{int}, @code{long}, and pointers.

@item lp64
Target has 32-bit @code{int}, 64-bit @code{long} and pointers.

@item llp64
Target has 32-bit @code{int} and @code{long}, 64-bit @code{long long}
and pointers.

@item double64
Target has 64-bit @code{double}.

@item double64plus
Target has @code{double} that is 64 bits or longer.

@item longdouble128
Target has 128-bit @code{long double}.

@item int32plus
Target has @code{int} that is at 32 bits or longer.

@item int16
Target has @code{int} that is 16 bits or shorter.

@item long_neq_int
Target has @code{int} and @code{long} with different sizes.

@item large_double
Target supports @code{double} that is longer than @code{float}.

@item large_long_double
Target supports @code{long double} that is longer than @code{double}.

@item ptr32plus
Target has pointers that are 32 bits or longer.

@item size32plus
Target supports array and structure sizes that are 32 bits or longer.

@item 4byte_wchar_t
Target has @code{wchar_t} that is at least 4 bytes.

@item float@var{n}
Target has the @code{_Float@var{n}} type.

@item float@var{n}x
Target has the @code{_Float@var{n}x} type.

@item float@var{n}_runtime
Target has the @code{_Float@var{n}} type, including runtime support
for any options added with @code{dg-add-options}.

@item float@var{n}x_runtime
Target has the @code{_Float@var{n}x} type, including runtime support
for any options added with @code{dg-add-options}.

@item floatn_nx_runtime
Target has runtime support for any options added with
@code{dg-add-options} for any @code{_Float@var{n}} or
@code{_Float@var{n}x} type.
@end table

@subsubsection Fortran-specific attributes

@table @code
@item fortran_integer_16
Target supports Fortran @code{integer} that is 16 bytes or longer.

@item fortran_real_10
Target supports Fortran @code{real} that is 10 bytes or longer.

@item fortran_real_16
Target supports Fortran @code{real} that is 16 bytes or longer.

@item fortran_large_int
Target supports Fortran @code{integer} kinds larger than @code{integer(8)}.

@item fortran_large_real
Target supports Fortran @code{real} kinds larger than @code{real(8)}.
@end table

@subsubsection Vector-specific attributes

@table @code
@item vect_align_stack_vars
The target's ABI allows stack variables to be aligned to the preferred
vector alignment.

@item vect_condition
Target supports vector conditional operations.

@item vect_cond_mixed
Target supports vector conditional operations where comparison operands
have different type from the value operands.

@item vect_double
Target supports hardware vectors of @code{double}.

@item vect_element_align_preferred
The target's preferred vector alignment is the same as the element
alignment.

@item vect_float
Target supports hardware vectors of @code{float} when
@option{-funsafe-math-optimizations} is in effect.

@item vect_float_strict
Target supports hardware vectors of @code{float} when
@option{-funsafe-math-optimizations} is not in effect.
This implies @code{vect_float}.

@item vect_int
Target supports hardware vectors of @code{int}.

@item vect_long
Target supports hardware vectors of @code{long}.

@item vect_long_long
Target supports hardware vectors of @code{long long}.

@item vect_fully_masked
Target supports fully-masked (also known as fully-predicated) loops,
so that vector loops can handle partial as well as full vectors.

@item vect_masked_store
Target supports vector masked stores.

@item vect_scatter_store
Target supports vector scatter stores.

@item vect_aligned_arrays
Target aligns arrays to vector alignment boundary.

@item vect_hw_misalign
Target supports a vector misalign access.

@item vect_no_align
Target does not support a vector alignment mechanism.

@item vect_peeling_profitable
Target might require to peel loops for alignment purposes.

@item vect_no_int_min_max
Target does not support a vector min and max instruction on @code{int}.

@item vect_no_int_add
Target does not support a vector add instruction on @code{int}.

@item vect_no_bitwise
Target does not support vector bitwise instructions.

@item vect_char_mult
Target supports @code{vector char} multiplication.

@item vect_short_mult
Target supports @code{vector short} multiplication.

@item vect_int_mult
Target supports @code{vector int} multiplication.

@item vect_long_mult
Target supports 64 bit @code{vector long} multiplication.

@item vect_extract_even_odd
Target supports vector even/odd element extraction.

@item vect_extract_even_odd_wide
Target supports vector even/odd element extraction of vectors with elements
@code{SImode} or larger.

@item vect_interleave
Target supports vector interleaving.

@item vect_strided
Target supports vector interleaving and extract even/odd.

@item vect_strided_wide
Target supports vector interleaving and extract even/odd for wide
element types.

@item vect_perm
Target supports vector permutation.

@item vect_perm_byte
Target supports permutation of vectors with 8-bit elements.

@item vect_perm_short
Target supports permutation of vectors with 16-bit elements.

@item vect_perm3_byte
Target supports permutation of vectors with 8-bit elements, and for the
default vector length it is possible to permute:
@example
@{ a0, a1, a2, b0, b1, b2, @dots{} @}
@end example
to:
@example
@{ a0, a0, a0, b0, b0, b0, @dots{} @}
@{ a1, a1, a1, b1, b1, b1, @dots{} @}
@{ a2, a2, a2, b2, b2, b2, @dots{} @}
@end example
using only two-vector permutes, regardless of how long the sequence is.

@item vect_perm3_int
Like @code{vect_perm3_byte}, but for 32-bit elements.

@item vect_perm3_short
Like @code{vect_perm3_byte}, but for 16-bit elements.

@item vect_shift
Target supports a hardware vector shift operation.

@item vect_unaligned_possible
Target prefers vectors to have an alignment greater than element
alignment, but also allows unaligned vector accesses in some
circumstances.

@item vect_variable_length
Target has variable-length vectors.

@item vect_widen_sum_hi_to_si
Target supports a vector widening summation of @code{short} operands
into @code{int} results, or can promote (unpack) from @code{short}
to @code{int}.

@item vect_widen_sum_qi_to_hi
Target supports a vector widening summation of @code{char} operands
into @code{short} results, or can promote (unpack) from @code{char}
to @code{short}.

@item vect_widen_sum_qi_to_si
Target supports a vector widening summation of @code{char} operands
into @code{int} results.

@item vect_widen_mult_qi_to_hi
Target supports a vector widening multiplication of @code{char} operands
into @code{short} results, or can promote (unpack) from @code{char} to
@code{short} and perform non-widening multiplication of @code{short}.

@item vect_widen_mult_hi_to_si
Target supports a vector widening multiplication of @code{short} operands
into @code{int} results, or can promote (unpack) from @code{short} to
@code{int} and perform non-widening multiplication of @code{int}.

@item vect_widen_mult_si_to_di_pattern
Target supports a vector widening multiplication of @code{int} operands
into @code{long} results.

@item vect_sdot_qi
Target supports a vector dot-product of @code{signed char}.

@item vect_udot_qi
Target supports a vector dot-product of @code{unsigned char}.

@item vect_sdot_hi
Target supports a vector dot-product of @code{signed short}.

@item vect_udot_hi
Target supports a vector dot-product of @code{unsigned short}.

@item vect_pack_trunc
Target supports a vector demotion (packing) of @code{short} to @code{char}
and from @code{int} to @code{short} using modulo arithmetic.

@item vect_unpack
Target supports a vector promotion (unpacking) of @code{char} to @code{short}
and from @code{char} to @code{int}.

@item vect_intfloat_cvt
Target supports conversion from @code{signed int} to @code{float}.

@item vect_uintfloat_cvt
Target supports conversion from @code{unsigned int} to @code{float}.

@item vect_floatint_cvt
Target supports conversion from @code{float} to @code{signed int}.

@item vect_floatuint_cvt
Target supports conversion from @code{float} to @code{unsigned int}.

@item vect_intdouble_cvt
Target supports conversion from @code{signed int} to @code{double}.

@item vect_doubleint_cvt
Target supports conversion from @code{double} to @code{signed int}.

@item vect_max_reduc
Target supports max reduction for vectors.

@item vect_sizes_16B_8B
Target supports 16- and 8-bytes vectors.

@item vect_sizes_32B_16B
Target supports 32- and 16-bytes vectors.

@item vect_logical_reduc
Target supports AND, IOR and XOR reduction on vectors.

@item vect_fold_extract_last
Target supports the @code{fold_extract_last} optab.
@end table

@subsubsection Thread Local Storage attributes

@table @code
@item tls
Target supports thread-local storage.

@item tls_native
Target supports native (rather than emulated) thread-local storage.

@item tls_runtime
Test system supports executing TLS executables.
@end table

@subsubsection Decimal floating point attributes

@table @code
@item dfp
Targets supports compiling decimal floating point extension to C.

@item dfp_nocache
Including the options used to compile this particular test, the
target supports compiling decimal floating point extension to C.

@item dfprt
Test system can execute decimal floating point tests.

@item dfprt_nocache
Including the options used to compile this particular test, the
test system can execute decimal floating point tests.

@item hard_dfp
Target generates decimal floating point instructions with current options.
@end table

@subsubsection ARM-specific attributes

@table @code
@item arm32
ARM target generates 32-bit code.

@item arm_eabi
ARM target adheres to the ABI for the ARM Architecture.

@item arm_fp_ok
@anchor{arm_fp_ok}
ARM target defines @code{__ARM_FP} using @code{-mfloat-abi=softfp} or
equivalent options.  Some multilibs may be incompatible with these
options.

@item arm_hf_eabi
ARM target adheres to the VFP and Advanced SIMD Register Arguments
variant of the ABI for the ARM Architecture (as selected with
@code{-mfloat-abi=hard}).

@item arm_softfloat
ARM target uses the soft-float ABI with no floating-point instructions
used whatsoever (as selected with @code{-mfloat-abi=soft}).

@item arm_hard_vfp_ok
ARM target supports @code{-mfpu=vfp -mfloat-abi=hard}.
Some multilibs may be incompatible with these options.

@item arm_iwmmxt_ok
ARM target supports @code{-mcpu=iwmmxt}.
Some multilibs may be incompatible with this option.

@item arm_neon
ARM target supports generating NEON instructions.

@item arm_tune_string_ops_prefer_neon
Test CPU tune supports inlining string operations with NEON instructions.

@item arm_neon_hw
Test system supports executing NEON instructions.

@item arm_neonv2_hw
Test system supports executing NEON v2 instructions.

@item arm_neon_ok
@anchor{arm_neon_ok}
ARM Target supports @code{-mfpu=neon -mfloat-abi=softfp} or compatible
options.  Some multilibs may be incompatible with these options.

@item arm_neon_ok_no_float_abi
@anchor{arm_neon_ok_no_float_abi}
ARM Target supports NEON with @code{-mfpu=neon}, but without any
-mfloat-abi= option.  Some multilibs may be incompatible with this
option.

@item arm_neonv2_ok
@anchor{arm_neonv2_ok}
ARM Target supports @code{-mfpu=neon-vfpv4 -mfloat-abi=softfp} or compatible
options.  Some multilibs may be incompatible with these options.

@item arm_fp16_ok
@anchor{arm_fp16_ok}
Target supports options to generate VFP half-precision floating-point
instructions.  Some multilibs may be incompatible with these
options.  This test is valid for ARM only.

@item arm_fp16_hw
Target supports executing VFP half-precision floating-point
instructions.  This test is valid for ARM only.

@item arm_neon_fp16_ok
@anchor{arm_neon_fp16_ok}
ARM Target supports @code{-mfpu=neon-fp16 -mfloat-abi=softfp} or compatible
options, including @code{-mfp16-format=ieee} if necessary to obtain the
@code{__fp16} type.  Some multilibs may be incompatible with these options.

@item arm_neon_fp16_hw
Test system supports executing Neon half-precision float instructions.
(Implies previous.)

@item arm_fp16_alternative_ok
ARM target supports the ARM FP16 alternative format.  Some multilibs
may be incompatible with the options needed.

@item arm_fp16_none_ok
ARM target supports specifying none as the ARM FP16 format.

@item arm_thumb1_ok
ARM target generates Thumb-1 code for @code{-mthumb}.

@item arm_thumb2_ok
ARM target generates Thumb-2 code for @code{-mthumb}.

@item arm_vfp_ok
ARM target supports @code{-mfpu=vfp -mfloat-abi=softfp}.
Some multilibs may be incompatible with these options.

@item arm_vfp3_ok
@anchor{arm_vfp3_ok}
ARM target supports @code{-mfpu=vfp3 -mfloat-abi=softfp}.
Some multilibs may be incompatible with these options.

@item arm_v8_vfp_ok
ARM target supports @code{-mfpu=fp-armv8 -mfloat-abi=softfp}.
Some multilibs may be incompatible with these options.

@item arm_v8_neon_ok
ARM target supports @code{-mfpu=neon-fp-armv8 -mfloat-abi=softfp}.
Some multilibs may be incompatible with these options.

@item arm_v8_1a_neon_ok
@anchor{arm_v8_1a_neon_ok}
ARM target supports options to generate ARMv8.1-A Adv.SIMD instructions.
Some multilibs may be incompatible with these options.

@item arm_v8_1a_neon_hw
ARM target supports executing ARMv8.1-A Adv.SIMD instructions.  Some
multilibs may be incompatible with the options needed.  Implies
arm_v8_1a_neon_ok.

@item arm_acq_rel
ARM target supports acquire-release instructions.

@item arm_v8_2a_fp16_scalar_ok
@anchor{arm_v8_2a_fp16_scalar_ok}
ARM target supports options to generate instructions for ARMv8.2-A and
scalar instructions from the FP16 extension.  Some multilibs may be
incompatible with these options.

@item arm_v8_2a_fp16_scalar_hw
ARM target supports executing instructions for ARMv8.2-A and scalar
instructions from the FP16 extension.  Some multilibs may be
incompatible with these options.  Implies arm_v8_2a_fp16_neon_ok.

@item arm_v8_2a_fp16_neon_ok
@anchor{arm_v8_2a_fp16_neon_ok}
ARM target supports options to generate instructions from ARMv8.2-A with
the FP16 extension.  Some multilibs may be incompatible with these
options.  Implies arm_v8_2a_fp16_scalar_ok.

@item arm_v8_2a_fp16_neon_hw
ARM target supports executing instructions from ARMv8.2-A with the FP16
extension.  Some multilibs may be incompatible with these options.
Implies arm_v8_2a_fp16_neon_ok and arm_v8_2a_fp16_scalar_hw.

@item arm_v8_2a_dotprod_neon_ok
@anchor{arm_v8_2a_dotprod_neon_ok}
ARM target supports options to generate instructions from ARMv8.2-A with
the Dot Product extension. Some multilibs may be incompatible with these
options.

@item arm_v8_2a_dotprod_neon_hw
ARM target supports executing instructions from ARMv8.2-A with the Dot
Product extension. Some multilibs may be incompatible with these options.
Implies arm_v8_2a_dotprod_neon_ok.

@item arm_fp16fml_neon_ok
@anchor{arm_fp16fml_neon_ok}
ARM target supports extensions to generate the @code{VFMAL} and @code{VFMLS}
half-precision floating-point instructions available from ARMv8.2-A and
onwards.  Some multilibs may be incompatible with these options.

@item arm_prefer_ldrd_strd
ARM target prefers @code{LDRD} and @code{STRD} instructions over
@code{LDM} and @code{STM} instructions.

@item arm_thumb1_movt_ok
ARM target generates Thumb-1 code for @code{-mthumb} with @code{MOVW}
and @code{MOVT} instructions available.

@item arm_thumb1_cbz_ok
ARM target generates Thumb-1 code for @code{-mthumb} with
@code{CBZ} and @code{CBNZ} instructions available.

@item arm_divmod_simode
ARM target for which divmod transform is disabled, if it supports hardware
div instruction.

@item arm_cmse_ok
ARM target supports ARMv8-M Security Extensions, enabled by the @code{-mcmse}
option.

@item arm_coproc1_ok
@anchor{arm_coproc1_ok}
ARM target supports the following coprocessor instructions: @code{CDP},
@code{LDC}, @code{STC}, @code{MCR} and @code{MRC}.

@item arm_coproc2_ok
@anchor{arm_coproc2_ok}
ARM target supports all the coprocessor instructions also listed as supported
in @ref{arm_coproc1_ok} in addition to the following: @code{CDP2}, @code{LDC2},
@code{LDC2l}, @code{STC2}, @code{STC2l}, @code{MCR2} and @code{MRC2}.

@item arm_coproc3_ok
@anchor{arm_coproc3_ok}
ARM target supports all the coprocessor instructions also listed as supported
in @ref{arm_coproc2_ok} in addition the following: @code{MCRR} and @code{MRRC}.

@item arm_coproc4_ok
ARM target supports all the coprocessor instructions also listed as supported
in @ref{arm_coproc3_ok} in addition the following: @code{MCRR2} and @code{MRRC2}.
@end table

@subsubsection AArch64-specific attributes

@table @code
@item aarch64_asm_<ext>_ok
AArch64 assembler supports the architecture extension @code{ext} via the
@code{.arch_extension} pseudo-op.
@item aarch64_tiny
AArch64 target which generates instruction sequences for tiny memory model.
@item aarch64_small
AArch64 target which generates instruction sequences for small memory model.
@item aarch64_large
AArch64 target which generates instruction sequences for large memory model.
@item aarch64_little_endian
AArch64 target which generates instruction sequences for little endian.
@item aarch64_big_endian
AArch64 target which generates instruction sequences for big endian.
@item aarch64_small_fpic
Binutils installed on test system supports relocation types required by -fpic
for AArch64 small memory model.

@end table

@subsubsection MIPS-specific attributes

@table @code
@item mips64
MIPS target supports 64-bit instructions.

@item nomips16
MIPS target does not produce MIPS16 code.

@item mips16_attribute
MIPS target can generate MIPS16 code.

@item mips_loongson
MIPS target is a Loongson-2E or -2F target using an ABI that supports
the Loongson vector modes.

@item mips_msa
MIPS target supports @code{-mmsa}, MIPS SIMD Architecture (MSA).

@item mips_newabi_large_long_double
MIPS target supports @code{long double} larger than @code{double}
when using the new ABI.

@item mpaired_single
MIPS target supports @code{-mpaired-single}.
@end table

@subsubsection PowerPC-specific attributes

@table @code

@item dfp_hw
PowerPC target supports executing hardware DFP instructions.

@item p8vector_hw
PowerPC target supports executing VSX instructions (ISA 2.07).

@item powerpc64
Test system supports executing 64-bit instructions.

@item powerpc_altivec
PowerPC target supports AltiVec.

@item powerpc_altivec_ok
PowerPC target supports @code{-maltivec}.

@item powerpc_eabi_ok
PowerPC target supports @code{-meabi}.

@item powerpc_elfv2
PowerPC target supports @code{-mabi=elfv2}.

@item powerpc_fprs
PowerPC target supports floating-point registers.

@item powerpc_hard_double
PowerPC target supports hardware double-precision floating-point.

@item powerpc_htm_ok
PowerPC target supports @code{-mhtm}

@item powerpc_p8vector_ok
PowerPC target supports @code{-mpower8-vector}

@item powerpc_popcntb_ok
PowerPC target supports the @code{popcntb} instruction, indicating
that this target supports @code{-mcpu=power5}.

@item powerpc_ppu_ok
PowerPC target supports @code{-mcpu=cell}.

@item powerpc_spe
PowerPC target supports PowerPC SPE.

@item powerpc_spe_nocache
Including the options used to compile this particular test, the
PowerPC target supports PowerPC SPE.

@item powerpc_spu
PowerPC target supports PowerPC SPU.

@item powerpc_vsx_ok
PowerPC target supports @code{-mvsx}.

@item powerpc_405_nocache
Including the options used to compile this particular test, the
PowerPC target supports PowerPC 405.

@item ppc_recip_hw
PowerPC target supports executing reciprocal estimate instructions.

@item spu_auto_overlay
SPU target has toolchain that supports automatic overlay generation.

@item vmx_hw
PowerPC target supports executing AltiVec instructions.

@item vsx_hw
PowerPC target supports executing VSX instructions (ISA 2.06).
@end table

@subsubsection Other hardware attributes

@c Please keep this table sorted alphabetically.
@table @code
@item autoincdec
Target supports autoincrement/decrement addressing.

@item avx
Target supports compiling @code{avx} instructions.

@item avx_runtime
Target supports the execution of @code{avx} instructions.

@item avx2
Target supports compiling @code{avx2} instructions.

@item avx2_runtime
Target supports the execution of @code{avx2} instructions.

@item avx512f
Target supports compiling @code{avx512f} instructions.

@item avx512f_runtime
Target supports the execution of @code{avx512f} instructions.

@item cell_hw
Test system can execute AltiVec and Cell PPU instructions.

@item coldfire_fpu
Target uses a ColdFire FPU.

@item divmod
Target supporting hardware divmod insn or divmod libcall.

@item divmod_simode
Target supporting hardware divmod insn or divmod libcall for SImode.

@item hard_float
Target supports FPU instructions.

@item non_strict_align
Target does not require strict alignment.

@item pie_copyreloc
The x86-64 target linker supports PIE with copy reloc.

@item rdrand
Target supports x86 @code{rdrand} instruction.

@item sqrt_insn
Target has a square root instruction that the compiler can generate.

@item sse
Target supports compiling @code{sse} instructions.

@item sse_runtime
Target supports the execution of @code{sse} instructions.

@item sse2
Target supports compiling @code{sse2} instructions.

@item sse2_runtime
Target supports the execution of @code{sse2} instructions.

@item sync_char_short
Target supports atomic operations on @code{char} and @code{short}.

@item sync_int_long
Target supports atomic operations on @code{int} and @code{long}.

@item ultrasparc_hw
Test environment appears to run executables on a simulator that
accepts only @code{EM_SPARC} executables and chokes on @code{EM_SPARC32PLUS}
or @code{EM_SPARCV9} executables.

@item vect_cmdline_needed
Target requires a command line argument to enable a SIMD instruction set.

@item xorsign
Target supports the xorsign optab expansion.

@end table

@subsubsection Environment attributes

@table @code
@item c
The language for the compiler under test is C.

@item c++
The language for the compiler under test is C++.

@item c99_runtime
Target provides a full C99 runtime.

@item correct_iso_cpp_string_wchar_protos
Target @code{string.h} and @code{wchar.h} headers provide C++ required
overloads for @code{strchr} etc. functions.

@item dummy_wcsftime
Target uses a dummy @code{wcsftime} function that always returns zero.

@item fd_truncate
Target can truncate a file from a file descriptor, as used by
@file{libgfortran/io/unix.c:fd_truncate}; i.e. @code{ftruncate} or
@code{chsize}.

@item freestanding
Target is @samp{freestanding} as defined in section 4 of the C99 standard.
Effectively, it is a target which supports no extra headers or libraries
other than what is considered essential.

@item gettimeofday
Target supports @code{gettimeofday}.

@item init_priority
Target supports constructors with initialization priority arguments.

@item inttypes_types
Target has the basic signed and unsigned types in @code{inttypes.h}.
This is for tests that GCC's notions of these types agree with those
in the header, as some systems have only @code{inttypes.h}.

@item lax_strtofp
Target might have errors of a few ULP in string to floating-point
conversion functions and overflow is not always detected correctly by
those functions.

@item mempcpy
Target provides @code{mempcpy} function.

@item mmap
Target supports @code{mmap}.

@item newlib
Target supports Newlib.

@item pow10
Target provides @code{pow10} function.

@item pthread
Target can compile using @code{pthread.h} with no errors or warnings.

@item pthread_h
Target has @code{pthread.h}.

@item run_expensive_tests
Expensive testcases (usually those that consume excessive amounts of CPU
time) should be run on this target.  This can be enabled by setting the
@env{GCC_TEST_RUN_EXPENSIVE} environment variable to a non-empty string.

@item simulator
Test system runs executables on a simulator (i.e. slowly) rather than
hardware (i.e. fast).

@item signal
Target has @code{signal.h}.

@item stabs
Target supports the stabs debugging format.

@item stdint_types
Target has the basic signed and unsigned C types in @code{stdint.h}.
This will be obsolete when GCC ensures a working @code{stdint.h} for
all targets.

@item stpcpy
Target provides @code{stpcpy} function.

@item trampolines
Target supports trampolines.

@item uclibc
Target supports uClibc.

@item unwrapped
Target does not use a status wrapper.

@item vxworks_kernel
Target is a VxWorks kernel.

@item vxworks_rtp
Target is a VxWorks RTP.

@item wchar
Target supports wide characters.
@end table

@subsubsection Other attributes

@table @code
@item automatic_stack_alignment
Target supports automatic stack alignment.

@item branch_cost
Target supports @option{-branch-cost=N}.

@item cxa_atexit
Target uses @code{__cxa_atexit}.

@item default_packed
Target has packed layout of structure members by default.

@item fgraphite
Target supports Graphite optimizations.

@item fixed_point
Target supports fixed-point extension to C.

@item fopenacc
Target supports OpenACC via @option{-fopenacc}.

@item fopenmp
Target supports OpenMP via @option{-fopenmp}.

@item fpic
Target supports @option{-fpic} and @option{-fPIC}.

@item freorder
Target supports @option{-freorder-blocks-and-partition}.

@item fstack_protector
Target supports @option{-fstack-protector}.

@item gas
Target uses GNU @command{as}.

@item gc_sections
Target supports @option{--gc-sections}.

@item gld
Target uses GNU @command{ld}.

@item keeps_null_pointer_checks
Target keeps null pointer checks, either due to the use of
@option{-fno-delete-null-pointer-checks} or hardwired into the target.

@item lto
Compiler has been configured to support link-time optimization (LTO).

@item naked_functions
Target supports the @code{naked} function attribute.

@item named_sections
Target supports named sections.

@item natural_alignment_32
Target uses natural alignment (aligned to type size) for types of
32 bits or less.

@item target_natural_alignment_64
Target uses natural alignment (aligned to type size) for types of
64 bits or less.

@item nonpic
Target does not generate PIC by default.

@item pie_enabled
Target generates PIE by default.

@item pcc_bitfield_type_matters
Target defines @code{PCC_BITFIELD_TYPE_MATTERS}.

@item pe_aligned_commons
Target supports @option{-mpe-aligned-commons}.

@item pie
Target supports @option{-pie}, @option{-fpie} and @option{-fPIE}.

@item rdynamic
Target supports @option{-rdynamic}.

@item section_anchors
Target supports section anchors.

@item short_enums
Target defaults to short enums.

@item stack_size
@anchor{stack_size_et}
Target has limited stack size.  The stack size limit can be obtained using the
STACK_SIZE macro defined by @ref{stack_size_ao,,@code{dg-add-options} feature
@code{stack_size}}.

@item static
Target supports @option{-static}.

@item static_libgfortran
Target supports statically linking @samp{libgfortran}.

@item string_merging
Target supports merging string constants at link time.

@item ucn
Target supports compiling and assembling UCN.

@item ucn_nocache
Including the options used to compile this particular test, the
target supports compiling and assembling UCN.

@item unaligned_stack
Target does not guarantee that its @code{STACK_BOUNDARY} is greater than
or equal to the required vector alignment.

@item vector_alignment_reachable
Vector alignment is reachable for types of 32 bits or less.

@item vector_alignment_reachable_for_64bit
Vector alignment is reachable for types of 64 bits or less.

@item wchar_t_char16_t_compatible
Target supports @code{wchar_t} that is compatible with @code{char16_t}.

@item wchar_t_char32_t_compatible
Target supports @code{wchar_t} that is compatible with @code{char32_t}.

@item comdat_group
Target uses comdat groups.
@end table

@subsubsection Local to tests in @code{gcc.target/i386}

@table @code
@item 3dnow
Target supports compiling @code{3dnow} instructions.

@item aes
Target supports compiling @code{aes} instructions.

@item fma4
Target supports compiling @code{fma4} instructions.

@item ms_hook_prologue
Target supports attribute @code{ms_hook_prologue}.

@item pclmul
Target supports compiling @code{pclmul} instructions.

@item sse3
Target supports compiling @code{sse3} instructions.

@item sse4
Target supports compiling @code{sse4} instructions.

@item sse4a
Target supports compiling @code{sse4a} instructions.

@item ssse3
Target supports compiling @code{ssse3} instructions.

@item vaes
Target supports compiling @code{vaes} instructions.

@item vpclmul
Target supports compiling @code{vpclmul} instructions.

@item xop
Target supports compiling @code{xop} instructions.
@end table

@subsubsection Local to tests in @code{gcc.target/spu/ea}

@table @code
@item ealib
Target @code{__ea} library functions are available.
@end table

@subsubsection Local to tests in @code{gcc.test-framework}

@table @code
@item no
Always returns 0.

@item yes
Always returns 1.
@end table

@node Add Options
@subsection Features for @code{dg-add-options}

The supported values of @var{feature} for directive @code{dg-add-options}
are:

@table @code
@item arm_fp
@code{__ARM_FP} definition.  Only ARM targets support this feature, and only then
in certain modes; see the @ref{arm_fp_ok,,arm_fp_ok effective target
keyword}.

@item arm_neon
NEON support.  Only ARM targets support this feature, and only then
in certain modes; see the @ref{arm_neon_ok,,arm_neon_ok effective target
keyword}.

@item arm_fp16
VFP half-precision floating point support.  This does not select the
FP16 format; for that, use @ref{arm_fp16_ieee,,arm_fp16_ieee} or
@ref{arm_fp16_alternative,,arm_fp16_alternative} instead.  This
feature is only supported by ARM targets and then only in certain
modes; see the @ref{arm_fp16_ok,,arm_fp16_ok effective target
keyword}.

@item arm_fp16_ieee
@anchor{arm_fp16_ieee}
ARM IEEE 754-2008 format VFP half-precision floating point support.
This feature is only supported by ARM targets and then only in certain
modes; see the @ref{arm_fp16_ok,,arm_fp16_ok effective target
keyword}.

@item arm_fp16_alternative
@anchor{arm_fp16_alternative}
ARM Alternative format VFP half-precision floating point support.
This feature is only supported by ARM targets and then only in certain
modes; see the @ref{arm_fp16_ok,,arm_fp16_ok effective target
keyword}.

@item arm_neon_fp16
NEON and half-precision floating point support.  Only ARM targets
support this feature, and only then in certain modes; see
the @ref{arm_neon_fp16_ok,,arm_neon_fp16_ok effective target keyword}.

@item arm_vfp3
arm vfp3 floating point support; see
the @ref{arm_vfp3_ok,,arm_vfp3_ok effective target keyword}.

@item arm_v8_1a_neon
Add options for ARMv8.1-A with Adv.SIMD support, if this is supported
by the target; see the @ref{arm_v8_1a_neon_ok,,arm_v8_1a_neon_ok}
effective target keyword.

@item arm_v8_2a_fp16_scalar
Add options for ARMv8.2-A with scalar FP16 support, if this is
supported by the target; see the
@ref{arm_v8_2a_fp16_scalar_ok,,arm_v8_2a_fp16_scalar_ok} effective
target keyword.

@item arm_v8_2a_fp16_neon
Add options for ARMv8.2-A with Adv.SIMD FP16 support, if this is
supported by the target; see the
@ref{arm_v8_2a_fp16_neon_ok,,arm_v8_2a_fp16_neon_ok} effective target
keyword.

@item arm_v8_2a_dotprod_neon
Add options for ARMv8.2-A with Adv.SIMD Dot Product support, if this is
supported by the target; see the
@ref{arm_v8_2a_dotprod_neon_ok} effective target keyword.

@item arm_fp16fml_neon
Add options to enable generation of the @code{VFMAL} and @code{VFMSL}
instructions, if this is supported by the target; see the
@ref{arm_fp16fml_neon_ok} effective target keyword.

@item bind_pic_locally
Add the target-specific flags needed to enable functions to bind
locally when using pic/PIC passes in the testsuite.

@item c99_runtime
Add the target-specific flags needed to access the C99 runtime.

@item float@var{n}
Add the target-specific flags needed to use the @code{_Float@var{n}} type.

@item float@var{n}x
Add the target-specific flags needed to use the @code{_Float@var{n}x} type.

@item ieee
Add the target-specific flags needed to enable full IEEE
compliance mode.

@item mips16_attribute
@code{mips16} function attributes.
Only MIPS targets support this feature, and only then in certain modes.

@item stack_size
@anchor{stack_size_ao}
Add the flags needed to define macro STACK_SIZE and set it to the stack size
limit associated with the @ref{stack_size_et,,@code{stack_size} effective
target}.

@item tls
Add the target-specific flags needed to use thread-local storage.
@end table

@node Require Support
@subsection Variants of @code{dg-require-@var{support}}

A few of the @code{dg-require} directives take arguments.

@table @code
@item dg-require-iconv @var{codeset}
Skip the test if the target does not support iconv.  @var{codeset} is
the codeset to convert to.

@item dg-require-profiling @var{profopt}
Skip the test if the target does not support profiling with option
@var{profopt}.

@item dg-require-stack-check @var{check}
Skip the test if the target does not support the @code{-fstack-check}
option.  If @var{check} is @code{""}, support for @code{-fstack-check}
is checked, for @code{-fstack-check=("@var{check}")} otherwise.

@item dg-require-stack-size @var{size}
Skip the test if the target does not support a stack size of @var{size}.

@item dg-require-visibility @var{vis}
Skip the test if the target does not support the @code{visibility} attribute.
If @var{vis} is @code{""}, support for @code{visibility("hidden")} is
checked, for @code{visibility("@var{vis}")} otherwise.
@end table

The original @code{dg-require} directives were defined before there
was support for effective-target keywords.  The directives that do not
take arguments could be replaced with effective-target keywords.

@table @code
@item dg-require-alias ""
Skip the test if the target does not support the @samp{alias} attribute.

@item dg-require-ascii-locale ""
Skip the test if the host does not support an ASCII locale.

@item dg-require-compat-dfp ""
Skip this test unless both compilers in a @file{compat} testsuite
support decimal floating point.

@item dg-require-cxa-atexit ""
Skip the test if the target does not support @code{__cxa_atexit}.
This is equivalent to @code{dg-require-effective-target cxa_atexit}.

@item dg-require-dll ""
Skip the test if the target does not support DLL attributes.

@item dg-require-fork ""
Skip the test if the target does not support @code{fork}.

@item dg-require-gc-sections ""
Skip the test if the target's linker does not support the
@code{--gc-sections} flags.
This is equivalent to @code{dg-require-effective-target gc-sections}.

@item dg-require-host-local ""
Skip the test if the host is remote, rather than the same as the build
system.  Some tests are incompatible with DejaGnu's handling of remote
hosts, which involves copying the source file to the host and compiling
it with a relative path and "@code{-o a.out}".

@item dg-require-mkfifo ""
Skip the test if the target does not support @code{mkfifo}.

@item dg-require-named-sections ""
Skip the test is the target does not support named sections.
This is equivalent to @code{dg-require-effective-target named_sections}.

@item dg-require-weak ""
Skip the test if the target does not support weak symbols.

@item dg-require-weak-override ""
Skip the test if the target does not support overriding weak symbols.
@end table

@node Final Actions
@subsection Commands for use in @code{dg-final}

The GCC testsuite defines the following directives to be used within
@code{dg-final}.

@subsubsection Scan a particular file

@table @code
@item scan-file @var{filename} @var{regexp} [@{ target/xfail @var{selector} @}]
Passes if @var{regexp} matches text in @var{filename}.
@item scan-file-not @var{filename} @var{regexp} [@{ target/xfail @var{selector} @}]
Passes if @var{regexp} does not match text in @var{filename}.
@item scan-module @var{module} @var{regexp} [@{ target/xfail @var{selector} @}]
Passes if @var{regexp} matches in Fortran module @var{module}.
@end table

@subsubsection Scan the assembly output

@table @code
@item scan-assembler @var{regex} [@{ target/xfail @var{selector} @}]
Passes if @var{regex} matches text in the test's assembler output.

@item scan-assembler-not @var{regex} [@{ target/xfail @var{selector} @}]
Passes if @var{regex} does not match text in the test's assembler output.

@item scan-assembler-times @var{regex} @var{num} [@{ target/xfail @var{selector} @}]
Passes if @var{regex} is matched exactly @var{num} times in the test's
assembler output.

@item scan-assembler-dem @var{regex} [@{ target/xfail @var{selector} @}]
Passes if @var{regex} matches text in the test's demangled assembler output.

@item scan-assembler-dem-not @var{regex} [@{ target/xfail @var{selector} @}]
Passes if @var{regex} does not match text in the test's demangled assembler
output.

@item scan-hidden @var{symbol} [@{ target/xfail @var{selector} @}]
Passes if @var{symbol} is defined as a hidden symbol in the test's
assembly output.

@item scan-not-hidden @var{symbol} [@{ target/xfail @var{selector} @}]
Passes if @var{symbol} is not defined as a hidden symbol in the test's
assembly output.
@end table

@subsubsection Scan optimization dump files

These commands are available for @var{kind} of @code{tree}, @code{rtl},
and @code{ipa}.

@table @code
@item scan-@var{kind}-dump @var{regex} @var{suffix} [@{ target/xfail @var{selector} @}]
Passes if @var{regex} matches text in the dump file with suffix @var{suffix}.

@item scan-@var{kind}-dump-not @var{regex} @var{suffix} [@{ target/xfail @var{selector} @}]
Passes if @var{regex} does not match text in the dump file with suffix
@var{suffix}.

@item scan-@var{kind}-dump-times @var{regex} @var{num} @var{suffix} [@{ target/xfail @var{selector} @}]
Passes if @var{regex} is found exactly @var{num} times in the dump file
with suffix @var{suffix}.

@item scan-@var{kind}-dump-dem @var{regex} @var{suffix} [@{ target/xfail @var{selector} @}]
Passes if @var{regex} matches demangled text in the dump file with
suffix @var{suffix}.

@item scan-@var{kind}-dump-dem-not @var{regex} @var{suffix} [@{ target/xfail @var{selector} @}]
Passes if @var{regex} does not match demangled text in the dump file with
suffix @var{suffix}.
@end table

@subsubsection Verify that an output files exists or not

@table @code
@item output-exists [@{ target/xfail @var{selector} @}]
Passes if compiler output file exists.

@item output-exists-not [@{ target/xfail @var{selector} @}]
Passes if compiler output file does not exist.
@end table

@subsubsection Check for LTO tests

@table @code
@item scan-symbol @var{regexp} [@{ target/xfail @var{selector} @}]
Passes if the pattern is present in the final executable.
@end table

@subsubsection Checks for @command{gcov} tests

@table @code
@item run-gcov @var{sourcefile}
Check line counts in @command{gcov} tests.

@item run-gcov [branches] [calls] @{ @var{opts} @var{sourcefile} @}
Check branch and/or call counts, in addition to line counts, in
@command{gcov} tests.
@end table

@subsubsection Clean up generated test files

Usually the test-framework removes files that were generated during
testing. If a testcase, for example, uses any dumping mechanism to
inspect a passes dump file, the testsuite recognized the dump option
passed to the tool and schedules a final cleanup to remove these files.

There are, however, following additional cleanup directives that can be
used to annotate a testcase "manually".
@table @code
@item cleanup-coverage-files
Removes coverage data files generated for this test.

@item cleanup-modules "@var{list-of-extra-modules}"
Removes Fortran module files generated for this test, excluding the
module names listed in keep-modules.
Cleaning up module files is usually done automatically by the testsuite
by looking at the source files and removing the modules after the test
has been executed.
@smallexample
module MoD1
end module MoD1
module Mod2
end module Mod2
module moD3
end module moD3
module mod4
end module mod4
! @{ dg-final @{ cleanup-modules "mod1 mod2" @} @} ! redundant
! @{ dg-final @{ keep-modules "mod3 mod4" @} @}
@end smallexample

@item keep-modules "@var{list-of-modules-not-to-delete}"
Whitespace separated list of module names that should not be deleted by
cleanup-modules.
If the list of modules is empty, all modules defined in this file are kept.
@smallexample
module maybe_unneeded
end module maybe_unneeded
module keep1
end module keep1
module keep2
end module keep2
! @{ dg-final @{ keep-modules "keep1 keep2" @} @} ! just keep these two
! @{ dg-final @{ keep-modules "" @} @} ! keep all
@end smallexample

@item dg-keep-saved-temps "@var{list-of-suffixes-not-to-delete}"
Whitespace separated list of suffixes that should not be deleted
automatically in a testcase that uses @option{-save-temps}.
@smallexample
// @{ dg-options "-save-temps -fpch-preprocess -I." @}
int main() @{ return 0; @}
// @{ dg-keep-saved-temps ".s" @} ! just keep assembler file
// @{ dg-keep-saved-temps ".s" ".i" @} ! ... and .i
// @{ dg-keep-saved-temps ".ii" ".o" @} ! or just .ii and .o
@end smallexample

@item cleanup-profile-file
Removes profiling files generated for this test.

@item cleanup-repo-files
Removes files generated for this test for @option{-frepo}.

@end table

@node Ada Tests
@section Ada Language Testsuites

The Ada testsuite includes executable tests from the ACATS
testsuite, publicly available at
@uref{http://www.ada-auth.org/acats.html}.

These tests are integrated in the GCC testsuite in the
@file{ada/acats} directory, and
enabled automatically when running @code{make check}, assuming
the Ada language has been enabled when configuring GCC@.

You can also run the Ada testsuite independently, using
@code{make check-ada}, or run a subset of the tests by specifying which
chapter to run, e.g.:

@smallexample
$ make check-ada CHAPTERS="c3 c9"
@end smallexample

The tests are organized by directory, each directory corresponding to
a chapter of the Ada Reference Manual.  So for example, @file{c9} corresponds
to chapter 9, which deals with tasking features of the language.

The tests are run using two @command{sh} scripts: @file{run_acats} and
@file{run_all.sh}.  To run the tests using a simulator or a cross
target, see the small
customization section at the top of @file{run_all.sh}.

These tests are run using the build tree: they can be run without doing
a @code{make install}.

@node C Tests
@section C Language Testsuites

GCC contains the following C language testsuites, in the
@file{gcc/testsuite} directory:

@table @file
@item gcc.dg
This contains tests of particular features of the C compiler, using the
more modern @samp{dg} harness.  Correctness tests for various compiler
features should go here if possible.

Magic comments determine whether the file
is preprocessed, compiled, linked or run.  In these tests, error and warning
message texts are compared against expected texts or regular expressions
given in comments.  These tests are run with the options @samp{-ansi -pedantic}
unless other options are given in the test.  Except as noted below they
are not run with multiple optimization options.
@item gcc.dg/compat
This subdirectory contains tests for binary compatibility using
@file{lib/compat.exp}, which in turn uses the language-independent support
(@pxref{compat Testing, , Support for testing binary compatibility}).
@item gcc.dg/cpp
This subdirectory contains tests of the preprocessor.
@item gcc.dg/debug
This subdirectory contains tests for debug formats.  Tests in this
subdirectory are run for each debug format that the compiler supports.
@item gcc.dg/format
This subdirectory contains tests of the @option{-Wformat} format
checking.  Tests in this directory are run with and without
@option{-DWIDE}.
@item gcc.dg/noncompile
This subdirectory contains tests of code that should not compile and
does not need any special compilation options.  They are run with
multiple optimization options, since sometimes invalid code crashes
the compiler with optimization.
@item gcc.dg/special
FIXME: describe this.

@item gcc.c-torture
This contains particular code fragments which have historically broken easily.
These tests are run with multiple optimization options, so tests for features
which only break at some optimization levels belong here.  This also contains
tests to check that certain optimizations occur.  It might be worthwhile to
separate the correctness tests cleanly from the code quality tests, but
it hasn't been done yet.

@item gcc.c-torture/compat
FIXME: describe this.

This directory should probably not be used for new tests.
@item gcc.c-torture/compile
This testsuite contains test cases that should compile, but do not
need to link or run.  These test cases are compiled with several
different combinations of optimization options.  All warnings are
disabled for these test cases, so this directory is not suitable if
you wish to test for the presence or absence of compiler warnings.
While special options can be set, and tests disabled on specific
platforms, by the use of @file{.x} files, mostly these test cases
should not contain platform dependencies.  FIXME: discuss how defines
such as @code{STACK_SIZE} are used.
@item gcc.c-torture/execute
This testsuite contains test cases that should compile, link and run;
otherwise the same comments as for @file{gcc.c-torture/compile} apply.
@item gcc.c-torture/execute/ieee
This contains tests which are specific to IEEE floating point.
@item gcc.c-torture/unsorted
FIXME: describe this.

This directory should probably not be used for new tests.
@item gcc.misc-tests
This directory contains C tests that require special handling.  Some
of these tests have individual expect files, and others share
special-purpose expect files:

@table @file
@item @code{bprob*.c}
Test @option{-fbranch-probabilities} using
@file{gcc.misc-tests/bprob.exp}, which
in turn uses the generic, language-independent framework
(@pxref{profopt Testing, , Support for testing profile-directed
optimizations}).

@item @code{gcov*.c}
Test @command{gcov} output using @file{gcov.exp}, which in turn uses the
language-independent support (@pxref{gcov Testing, , Support for testing gcov}).

@item @code{i386-pf-*.c}
Test i386-specific support for data prefetch using @file{i386-prefetch.exp}.
@end table

@item gcc.test-framework
@table @file
@item @code{dg-*.c}
Test the testsuite itself using @file{gcc.test-framework/test-framework.exp}.
@end table

@end table

FIXME: merge in @file{testsuite/README.gcc} and discuss the format of
test cases and magic comments more.

@node LTO Testing
@section Support for testing link-time optimizations

Tests for link-time optimizations usually require multiple source files
that are compiled separately, perhaps with different sets of options.
There are several special-purpose test directives used for these tests.

@table @code
@item @{ dg-lto-do @var{do-what-keyword} @}
@var{do-what-keyword} specifies how the test is compiled and whether
it is executed.  It is one of:

@table @code
@item assemble
Compile with @option{-c} to produce a relocatable object file.
@item link
Compile, assemble, and link to produce an executable file.
@item run
Produce and run an executable file, which is expected to return
an exit code of 0.
@end table

The default is @code{assemble}.  That can be overridden for a set of
tests by redefining @code{dg-do-what-default} within the @code{.exp}
file for those tests.

Unlike @code{dg-do}, @code{dg-lto-do} does not support an optional
@samp{target} or @samp{xfail} list.  Use @code{dg-skip-if},
@code{dg-xfail-if}, or @code{dg-xfail-run-if}.

@item @{ dg-lto-options @{ @{ @var{options} @} [@{ @var{options} @}] @} [@{ target @var{selector} @}]@}
This directive provides a list of one or more sets of compiler options
to override @var{LTO_OPTIONS}.  Each test will be compiled and run with
each of these sets of options.

@item @{ dg-extra-ld-options @var{options} [@{ target @var{selector} @}]@}
This directive adds @var{options} to the linker options used.

@item @{ dg-suppress-ld-options @var{options} [@{ target @var{selector} @}]@}
This directive removes @var{options} from the set of linker options used.
@end table

@node gcov Testing
@section Support for testing @command{gcov}

Language-independent support for testing @command{gcov}, and for checking
that branch profiling produces expected values, is provided by the
expect file @file{lib/gcov.exp}.  @command{gcov} tests also rely on procedures
in @file{lib/gcc-dg.exp} to compile and run the test program.  A typical
@command{gcov} test contains the following DejaGnu commands within comments:

@smallexample
@{ dg-options "-fprofile-arcs -ftest-coverage" @}
@{ dg-do run @{ target native @} @}
@{ dg-final @{ run-gcov sourcefile @} @}
@end smallexample

Checks of @command{gcov} output can include line counts, branch percentages,
and call return percentages.  All of these checks are requested via
commands that appear in comments in the test's source file.
Commands to check line counts are processed by default.
Commands to check branch percentages and call return percentages are
processed if the @command{run-gcov} command has arguments @code{branches}
or @code{calls}, respectively.  For example, the following specifies
checking both, as well as passing @option{-b} to @command{gcov}:

@smallexample
@{ dg-final @{ run-gcov branches calls @{ -b sourcefile @} @} @}
@end smallexample

A line count command appears within a comment on the source line
that is expected to get the specified count and has the form
@code{count(@var{cnt})}.  A test should only check line counts for
lines that will get the same count for any architecture.

Commands to check branch percentages (@code{branch}) and call
return percentages (@code{returns}) are very similar to each other.
A beginning command appears on or before the first of a range of
lines that will report the percentage, and the ending command
follows that range of lines.  The beginning command can include a
list of percentages, all of which are expected to be found within
the range.  A range is terminated by the next command of the same
kind.  A command @code{branch(end)} or @code{returns(end)} marks
the end of a range without starting a new one.  For example:

@smallexample
if (i > 10 && j > i && j < 20)  /* @r{branch(27 50 75)} */
                                /* @r{branch(end)} */
  foo (i, j);
@end smallexample

For a call return percentage, the value specified is the
percentage of calls reported to return.  For a branch percentage,
the value is either the expected percentage or 100 minus that
value, since the direction of a branch can differ depending on the
target or the optimization level.

Not all branches and calls need to be checked.  A test should not
check for branches that might be optimized away or replaced with
predicated instructions.  Don't check for calls inserted by the
compiler or ones that might be inlined or optimized away.

A single test can check for combinations of line counts, branch
percentages, and call return percentages.  The command to check a
line count must appear on the line that will report that count, but
commands to check branch percentages and call return percentages can
bracket the lines that report them.

@node profopt Testing
@section Support for testing profile-directed optimizations

The file @file{profopt.exp} provides language-independent support for
checking correct execution of a test built with profile-directed
optimization.  This testing requires that a test program be built and
executed twice.  The first time it is compiled to generate profile
data, and the second time it is compiled to use the data that was
generated during the first execution.  The second execution is to
verify that the test produces the expected results.

To check that the optimization actually generated better code, a
test can be built and run a third time with normal optimizations to
verify that the performance is better with the profile-directed
optimizations.  @file{profopt.exp} has the beginnings of this kind
of support.

@file{profopt.exp} provides generic support for profile-directed
optimizations.  Each set of tests that uses it provides information
about a specific optimization:

@table @code
@item tool
tool being tested, e.g., @command{gcc}

@item profile_option
options used to generate profile data

@item feedback_option
options used to optimize using that profile data

@item prof_ext
suffix of profile data files

@item PROFOPT_OPTIONS
list of options with which to run each test, similar to the lists for
torture tests

@item @{ dg-final-generate @{ @var{local-directive} @} @}
This directive is similar to @code{dg-final}, but the
@var{local-directive} is run after the generation of profile data.

@item @{ dg-final-use @{ @var{local-directive} @} @}
The @var{local-directive} is run after the profile data have been
used.
@end table

@node compat Testing
@section Support for testing binary compatibility

The file @file{compat.exp} provides language-independent support for
binary compatibility testing.  It supports testing interoperability of
two compilers that follow the same ABI, or of multiple sets of
compiler options that should not affect binary compatibility.  It is
intended to be used for testsuites that complement ABI testsuites.

A test supported by this framework has three parts, each in a
separate source file: a main program and two pieces that interact
with each other to split up the functionality being tested.

@table @file
@item @var{testname}_main.@var{suffix}
Contains the main program, which calls a function in file
@file{@var{testname}_x.@var{suffix}}.

@item @var{testname}_x.@var{suffix}
Contains at least one call to a function in
@file{@var{testname}_y.@var{suffix}}.

@item @var{testname}_y.@var{suffix}
Shares data with, or gets arguments from,
@file{@var{testname}_x.@var{suffix}}.
@end table

Within each test, the main program and one functional piece are
compiled by the GCC under test.  The other piece can be compiled by
an alternate compiler.  If no alternate compiler is specified,
then all three source files are all compiled by the GCC under test.
You can specify pairs of sets of compiler options.  The first element
of such a pair specifies options used with the GCC under test, and the
second element of the pair specifies options used with the alternate
compiler.  Each test is compiled with each pair of options.

@file{compat.exp} defines default pairs of compiler options.
These can be overridden by defining the environment variable
@env{COMPAT_OPTIONS} as:

@smallexample
COMPAT_OPTIONS="[list [list @{@var{tst1}@} @{@var{alt1}@}]
  @dots{}[list @{@var{tstn}@} @{@var{altn}@}]]"
@end smallexample

where @var{tsti} and @var{alti} are lists of options, with @var{tsti}
used by the compiler under test and @var{alti} used by the alternate
compiler.  For example, with
@code{[list [list @{-g -O0@} @{-O3@}] [list @{-fpic@} @{-fPIC -O2@}]]},
the test is first built with @option{-g -O0} by the compiler under
test and with @option{-O3} by the alternate compiler.  The test is
built a second time using @option{-fpic} by the compiler under test
and @option{-fPIC -O2} by the alternate compiler.

An alternate compiler is specified by defining an environment
variable to be the full pathname of an installed compiler; for C
define @env{ALT_CC_UNDER_TEST}, and for C++ define
@env{ALT_CXX_UNDER_TEST}.  These will be written to the
@file{site.exp} file used by DejaGnu.  The default is to build each
test with the compiler under test using the first of each pair of
compiler options from @env{COMPAT_OPTIONS}.  When
@env{ALT_CC_UNDER_TEST} or
@env{ALT_CXX_UNDER_TEST} is @code{same}, each test is built using
the compiler under test but with combinations of the options from
@env{COMPAT_OPTIONS}.

To run only the C++ compatibility suite using the compiler under test
and another version of GCC using specific compiler options, do the
following from @file{@var{objdir}/gcc}:

@smallexample
rm site.exp
make -k \
  ALT_CXX_UNDER_TEST=$@{alt_prefix@}/bin/g++ \
  COMPAT_OPTIONS="@var{lists as shown above}" \
  check-c++ \
  RUNTESTFLAGS="compat.exp"
@end smallexample

A test that fails when the source files are compiled with different
compilers, but passes when the files are compiled with the same
compiler, demonstrates incompatibility of the generated code or
runtime support.  A test that fails for the alternate compiler but
passes for the compiler under test probably tests for a bug that was
fixed in the compiler under test but is present in the alternate
compiler.

The binary compatibility tests support a small number of test framework
commands that appear within comments in a test file.

@table @code
@item dg-require-*
These commands can be used in @file{@var{testname}_main.@var{suffix}}
to skip the test if specific support is not available on the target.

@item dg-options
The specified options are used for compiling this particular source
file, appended to the options from @env{COMPAT_OPTIONS}.  When this
command appears in @file{@var{testname}_main.@var{suffix}} the options
are also used to link the test program.

@item dg-xfail-if
This command can be used in a secondary source file to specify that
compilation is expected to fail for particular options on particular
targets.
@end table

@node Torture Tests
@section Support for torture testing using multiple options

Throughout the compiler testsuite there are several directories whose
tests are run multiple times, each with a different set of options.
These are known as torture tests.
@file{lib/torture-options.exp} defines procedures to
set up these lists:

@table @code
@item torture-init
Initialize use of torture lists.
@item set-torture-options
Set lists of torture options to use for tests with and without loops.
Optionally combine a set of torture options with a set of other
options, as is done with Objective-C runtime options.
@item torture-finish
Finalize use of torture lists.
@end table

The @file{.exp} file for a set of tests that use torture options must
include calls to these three procedures if:

@itemize @bullet
@item It calls @code{gcc-dg-runtest} and overrides @var{DG_TORTURE_OPTIONS}.

@item It calls @var{$@{tool@}}@code{-torture} or
@var{$@{tool@}}@code{-torture-execute}, where @var{tool} is @code{c},
@code{fortran}, or @code{objc}.

@item It calls @code{dg-pch}.
@end itemize

It is not necessary for a @file{.exp} file that calls @code{gcc-dg-runtest}
to call the torture procedures if the tests should use the list in
@var{DG_TORTURE_OPTIONS} defined in @file{gcc-dg.exp}.

Most uses of torture options can override the default lists by defining
@var{TORTURE_OPTIONS} or add to the default list by defining
@var{ADDITIONAL_TORTURE_OPTIONS}.  Define these in a @file{.dejagnurc}
file or add them to the @file{site.exp} file; for example

@smallexample
set ADDITIONAL_TORTURE_OPTIONS  [list \
  @{ -O2 -ftree-loop-linear @} \
  @{ -O2 -fpeel-loops @} ]
@end smallexample

@node GIMPLE Tests
@section Support for testing GIMPLE passes

As of gcc 7, C functions can be tagged with @code{__GIMPLE} to indicate
that the function body will be GIMPLE, rather than C.  The compiler requires
the option @option{-fgimple} to enable this functionality.  For example:

@smallexample
/* @{ dg-do compile @} */
/* @{ dg-options "-O -fgimple" @} */

void __GIMPLE (startwith ("dse2")) foo ()
@{
  int a;

bb_2:
  if (a > 4)
    goto bb_3;
  else
    goto bb_4;

bb_3:
  a_2 = 10;
  goto bb_5;

bb_4:
  a_3 = 20;

bb_5:
  a_1 = __PHI (bb_3: a_2, bb_4: a_3);
  a_4 = a_1 + 4;

  return;
@}
@end smallexample

The @code{startwith} argument indicates at which pass to begin.

Use the dump modifier @code{-gimple} (e.g. @option{-fdump-tree-all-gimple})
to make tree dumps more closely follow the format accepted by the GIMPLE
parser.

Example DejaGnu tests of GIMPLE can be seen in the source tree at
@file{gcc/testsuite/gcc.dg/gimplefe-*.c}.

The @code{__GIMPLE} parser is integrated with the C tokenizer and
preprocessor, so it should be possible to use macros to build out
test coverage.

@node RTL Tests
@section Support for testing RTL passes

As of gcc 7, C functions can be tagged with @code{__RTL} to indicate that the
function body will be RTL, rather than C.  For example:

@smallexample
double __RTL (startwith ("ira")) test (struct foo *f, const struct bar *b)
@{
  (function "test"
     [...snip; various directives go in here...]
  ) ;; function "test"
@}
@end smallexample

The @code{startwith} argument indicates at which pass to begin.

The parser expects the RTL body to be in the format emitted by this
dumping function:

@smallexample
DEBUG_FUNCTION void
print_rtx_function (FILE *outfile, function *fn, bool compact);
@end smallexample

when "compact" is true.  So you can capture RTL in the correct format
from the debugger using:

@smallexample
(gdb) print_rtx_function (stderr, cfun, true);
@end smallexample

and copy and paste the output into the body of the C function.

Example DejaGnu tests of RTL can be seen in the source tree under
@file{gcc/testsuite/gcc.dg/rtl}.

The @code{__RTL} parser is not integrated with the C tokenizer or
preprocessor, and works simply by reading the relevant lines within
the braces.  In particular, the RTL body must be on separate lines from
the enclosing braces, and the preprocessor is not usable within it.