gcc/config/cris/cris-modes.def

/* Definitions of target machine for GNU compiler, for CRIS.
   Copyright (C) 2002-2021 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

/* Node: Condition Code */

/* The mode used for condition-codes depends on both the way the
   condition-codes are generated (the CC-setter, typically the compare
   instruction), and used (the CC-user, typically a branch).  For CRIS, we
   have ordinary compares and incidental condition-code settings from
   preceding instructions, setting a subset of N, Z, V and C to usable
   values, from the perspective of comparing the result against zero
   (referred to below as "fpcraz").  The two subsets meaningful to gcc are
   all of N, Z, V, C versus just N, Z; some CC-users care only about N
   and/or Z and some that care about at least one of those flags together
   with V and/or C.

   The plain "CC_MODE (CC)" (which is always present in gcc), is used to
   reflect the "unoptimized" state, where the CC-setter is a compare
   against zero and the CC-user is any branch or s<condition> instruction,
   before reload.  After reload, a need for C or V is reflected as
   CC_NZVCmode in both setters and users, and others remain CCmode, until
   or if optimization of CC-setter and CC-users, when CCmode setters can
   be changed or replaced by either CC_NZmode or CC_NZVCmode.  To wit, all
   users that require CC_NZVCmode must match only that mode at any time.
   All other users must match all of CCmode, CC_NZmode, and CC_NZVCmode.
   All setters that set only CC_NZmode must match setting only that mode.
   All other setters must match setting all of CCmode, CC_NZmode, and
   CC_NZVCmode.

   There's also other modes (i.e. CC_ZnNmode) with a separate set of
   setters and users not matched by the others. */

/* Z and N flags only.  For a condition-code setter: only the Z and N
   flags are set to usable values, fpcraz.  For a condition-code user: the
   operation using the condition codes only care about the Z and N flags.  */
CC_MODE (CC_NZ);

/* Z and N *and* V and C flags.  For a condition-code setter: all flags
   are set to usable values, fpcraz.  For a condition-code user: at least
   one of V and C are used and possibly N and Z too.  */
CC_MODE (CC_NZVC);

/* The result of a btst / btstq instruction for extracting a single bit
   goes negated into the N flag, or in olde cc0-parlance, CC_Z_IN_NOT_N.  */
CC_MODE (CC_ZnN);