gas/doc/c-d10v.texi

@c Copyright (C) 1996-2021 Free Software Foundation, Inc.
@c This is part of the GAS manual.
@c For copying conditions, see the file as.texinfo.
@ifset GENERIC
@page
@node D10V-Dependent
@chapter D10V Dependent Features
@end ifset
@ifclear GENERIC
@node Machine Dependencies
@chapter D10V Dependent Features
@end ifclear

@cindex D10V support
@menu
* D10V-Opts::                   D10V Options
* D10V-Syntax::                 Syntax
* D10V-Float::                  Floating Point
* D10V-Opcodes::                Opcodes
@end menu

@node D10V-Opts
@section D10V Options
@cindex options, D10V
@cindex D10V options
The Mitsubishi D10V version of @code{@value{AS}} has a few machine
dependent options.

@table @samp
@item -O
The D10V can often execute two sub-instructions in parallel. When this option
is used, @code{@value{AS}} will attempt to optimize its output by detecting when
instructions can be executed in parallel.
@item --nowarnswap
To optimize execution performance, @code{@value{AS}} will sometimes swap the
order of instructions. Normally this generates a warning. When this option
is used, no warning will be generated when instructions are swapped.
@item --gstabs-packing
@itemx --no-gstabs-packing
@code{@value{AS}} packs adjacent short instructions into a single packed
instruction. @samp{--no-gstabs-packing} turns instruction packing off if
@samp{--gstabs} is specified as well; @samp{--gstabs-packing} (the
default) turns instruction packing on even when @samp{--gstabs} is
specified.
@end table

@node D10V-Syntax
@section Syntax
@cindex D10V syntax
@cindex syntax, D10V

The D10V syntax is based on the syntax in Mitsubishi's D10V architecture manual.
The differences are detailed below.

@menu
* D10V-Size::                 Size Modifiers
* D10V-Subs::                 Sub-Instructions
* D10V-Chars::                Special Characters
* D10V-Regs::                 Register Names
* D10V-Addressing::           Addressing Modes
* D10V-Word::                 @@WORD Modifier
@end menu


@node D10V-Size
@subsection Size Modifiers
@cindex D10V size modifiers
@cindex size modifiers, D10V
The D10V version of @code{@value{AS}} uses the instruction names in the D10V
Architecture Manual.  However, the names in the manual are sometimes ambiguous.
There are instruction names that can assemble to a short or long form opcode.
How does the assembler pick the correct form?  @code{@value{AS}} will always pick the
smallest form if it can.  When dealing with a symbol that is not defined yet when a
line is being assembled, it will always use the long form.  If you need to force the
assembler to use either the short or long form of the instruction, you can append
either @samp{.s} (short) or @samp{.l} (long) to it.  For example, if you are writing
an assembly program and you want to do a branch to a symbol that is defined later
in your program, you can write @samp{bra.s   foo}.
Objdump and GDB will always append @samp{.s} or @samp{.l} to instructions which
have both short and long forms.

@node D10V-Subs
@subsection Sub-Instructions
@cindex D10V sub-instructions
@cindex sub-instructions, D10V
The D10V assembler takes as input a series of instructions, either one-per-line,
or in the special two-per-line format described in the next section.  Some of these
instructions will be short-form or sub-instructions.  These sub-instructions can be packed
into a single instruction.  The assembler will do this automatically.  It will also detect
when it should not pack instructions.  For example, when a label is defined, the next
instruction will never be packaged with the previous one.  Whenever a branch and link
instruction is called, it will not be packaged with the next instruction so the return
address will be valid.  Nops are automatically inserted when necessary.

If you do not want the assembler automatically making these decisions, you can control
the packaging and execution type (parallel or sequential) with the special execution
symbols described in the next section.

@node D10V-Chars
@subsection Special Characters
@cindex line comment character, D10V
@cindex D10V line comment character
A semicolon (@samp{;}) can be used anywhere on a line to start a
comment that extends to the end of the line.

If a @samp{#} appears as the first character of a line, the whole line
is treated as a comment, but in this case the line could also be a
logical line number directive (@pxref{Comments}) or a preprocessor
control command (@pxref{Preprocessing}).

@cindex sub-instruction ordering, D10V
@cindex D10V sub-instruction ordering
Sub-instructions may be executed in order, in reverse-order, or in parallel.
Instructions listed in the standard one-per-line format will be executed sequentially.
To specify the executing order, use the following symbols:
@table @samp
@item ->
Sequential with instruction on the left first.
@item <-
Sequential with instruction on the right first.
@item ||
Parallel
@end table
The D10V syntax allows either one instruction per line, one instruction per line with
the execution symbol, or two instructions per line.  For example
@table @code
@item abs       a1      ->      abs     r0
Execute these sequentially.  The instruction on the right is in the right
container and is executed second.
@item abs       r0      <-      abs     a1
Execute these reverse-sequentially.  The instruction on the right is in the right
container, and is executed first.
@item ld2w    r2,@@r8+         ||      mac     a0,r0,r7
Execute these in parallel.
@item ld2w    r2,@@r8+         ||
@itemx mac     a0,r0,r7
Two-line format. Execute these in parallel.
@item ld2w    r2,@@r8+
@itemx mac     a0,r0,r7
Two-line format. Execute these sequentially.  Assembler will
put them in the proper containers.
@item ld2w    r2,@@r8+         ->
@itemx mac     a0,r0,r7
Two-line format. Execute these sequentially.  Same as above but
second instruction will always go into right container.
@end table
@cindex symbol names, @samp{$} in
@cindex @code{$} in symbol names
Since @samp{$} has no special meaning, you may use it in symbol names.

@node D10V-Regs
@subsection Register Names
@cindex D10V registers
@cindex registers, D10V
You can use the predefined symbols @samp{r0} through @samp{r15} to refer to the D10V
registers.  You can also use @samp{sp} as an alias for @samp{r15}.  The accumulators
are @samp{a0} and @samp{a1}.  There are special register-pair names that may
optionally be used in opcodes that require even-numbered registers. Register names are
not case sensitive.

Register Pairs
@table @code
@item r0-r1
@item r2-r3
@item r4-r5
@item r6-r7
@item r8-r9
@item r10-r11
@item r12-r13
@item r14-r15
@end table

The D10V also has predefined symbols for these control registers and status bits:
@table @code
@item psw
Processor Status Word
@item bpsw
Backup Processor Status Word
@item pc
Program Counter
@item bpc
Backup Program Counter
@item rpt_c
Repeat Count
@item rpt_s
Repeat Start address
@item rpt_e
Repeat End address
@item mod_s
Modulo Start address
@item mod_e
Modulo End address
@item iba
Instruction Break Address
@item f0
Flag 0
@item f1
Flag 1
@item c
Carry flag
@end table

@node D10V-Addressing
@subsection Addressing Modes
@cindex addressing modes, D10V
@cindex D10V addressing modes
@code{@value{AS}} understands the following addressing modes for the D10V.
@code{R@var{n}} in the following refers to any of the numbered
registers, but @emph{not} the control registers.
@table @code
@item R@var{n}
Register direct
@item @@R@var{n}
Register indirect
@item @@R@var{n}+
Register indirect with post-increment
@item @@R@var{n}-
Register indirect with post-decrement
@item @@-SP
Register indirect with pre-decrement
@item @@(@var{disp}, R@var{n})
Register indirect with displacement
@item @var{addr}
PC relative address (for branch or rep).
@item #@var{imm}
Immediate data (the @samp{#} is optional and ignored)
@end table

@node D10V-Word
@subsection @@WORD Modifier
@cindex D10V @@word modifier
@cindex @@word modifier, D10V
Any symbol followed by @code{@@word} will be replaced by the symbol's value
shifted right by 2.  This is used in situations such as loading a register
with the address of a function (or any other code fragment).  For example, if
you want to load a register with the location of the function @code{main} then
jump to that function, you could do it as follows:
@smallexample
@group
ldi     r2, main@@word
jmp     r2
@end group
@end smallexample

@node D10V-Float
@section Floating Point
@cindex floating point, D10V
@cindex D10V floating point
The D10V has no hardware floating point, but the @code{.float} and @code{.double}
directives generates @sc{ieee} floating-point numbers for compatibility
with other development tools.

@node D10V-Opcodes
@section Opcodes
@cindex D10V opcode summary
@cindex opcode summary, D10V
@cindex mnemonics, D10V
@cindex instruction summary, D10V
For detailed information on the D10V machine instruction set, see
@cite{D10V Architecture: A VLIW Microprocessor for Multimedia Applications}
(Mitsubishi Electric Corp.).
@code{@value{AS}} implements all the standard D10V opcodes.  The only changes are those
described in the section on size modifiers