gcc/config/cris/cris-modes.def

   1 /* Definitions of target machine for GNU compiler, for CRIS.
   2    Copyright (C) 2002-2024 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 3, or (at your option)
   9 any later version.
  10
  11 GCC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 /* Node: Condition Code */
  21
  22 /* The mode used for condition-codes depends on both the way the
  23    condition-codes are generated (the CC-setter, typically the compare
  24    instruction), and used (the CC-user, typically a branch).  For CRIS, we
  25    have ordinary compares and incidental condition-code settings from
  26    preceding instructions, setting a subset of N, Z, V and C to usable
  27    values, from the perspective of comparing the result against zero
  28    (referred to below as "fpcraz").  The two subsets meaningful to gcc are
  29    all of N, Z, V, C versus just N, Z; some CC-users care only about N
  30    and/or Z and some that care about at least one of those flags together
  31    with V and/or C.
  32
  33    The plain "CC_MODE (CC)" (which is always present in gcc), is used to
  34    reflect the "unoptimized" state, where the CC-setter is a compare
  35    against zero and the CC-user is any branch or s<condition> instruction,
  36    before reload.  After reload, a need for C or V is reflected as
  37    CC_NZVCmode in both setters and users, and others remain CCmode, until
  38    or if optimization of CC-setter and CC-users, when CCmode setters can
  39    be changed or replaced by either CC_NZmode or CC_NZVCmode.  To wit, all
  40    users that require CC_NZVCmode must match only that mode at any time.
  41    All other users must match all of CCmode, CC_NZmode, and CC_NZVCmode.
  42    All setters that set only CC_NZmode must match setting only that mode.
  43    All other setters must match setting all of CCmode, CC_NZmode, and
  44    CC_NZVCmode.
  45
  46    There's also other modes (i.e. CC_ZnNmode) with a separate set of
  47    setters and users not matched by the others. */
  48
  49 /* Z and N flags only.  For a condition-code setter: only the Z and N
  50    flags are set to usable values, fpcraz.  For a condition-code user: the
  51    operation using the condition codes only care about the Z and N flags.  */
  52 CC_MODE (CC_NZ);
  53
  54 /* Z and N *and* V and C flags.  For a condition-code setter: all flags
  55    are set to usable values, fpcraz.  For a condition-code user: at least
  56    one of V and C are used and possibly N and Z too.  */
  57 CC_MODE (CC_NZVC);
  58
  59 /* The result of a btst / btstq instruction for extracting a single bit
  60    goes negated into the N flag, or in olde cc0-parlance, CC_Z_IN_NOT_N.  */
  61 CC_MODE (CC_ZnN);