gcc/conditions.h

   1 /* Definitions for condition code handling in final.c and output routines.
   2    Copyright (C) 1987-2018 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 it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 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 #ifndef GCC_CONDITIONS_H
  21 #define GCC_CONDITIONS_H
  22
  23 /* The variable cc_status says how to interpret the condition code.
  24    It is set by output routines for an instruction that sets the cc's
  25    and examined by output routines for jump instructions.
  26
  27    cc_status contains two components named `value1' and `value2'
  28    that record two equivalent expressions for the values that the
  29    condition codes were set from.  (Either or both may be null if
  30    there is no useful expression to record.)  These fields are
  31    used for eliminating redundant test and compare instructions
  32    in the cases where the condition codes were already set by the
  33    previous instruction.
  34
  35    cc_status.flags contains flags which say that the condition codes
  36    were set in a nonstandard manner.  The output of jump instructions
  37    uses these flags to compensate and produce the standard result
  38    with the nonstandard condition codes.  Standard flags are defined here.
  39    The tm.h file can also define other machine-dependent flags.
  40
  41    cc_status also contains a machine-dependent component `mdep'
  42    whose type, `CC_STATUS_MDEP', may be defined as a macro in the
  43    tm.h file.  */
  44
  45 #ifndef CC_STATUS_MDEP
  46 #define CC_STATUS_MDEP int
  47 #endif
  48
  49 #ifndef CC_STATUS_MDEP_INIT
  50 #define CC_STATUS_MDEP_INIT 0
  51 #endif
  52
  53 struct CC_STATUS {int flags; rtx value1, value2; CC_STATUS_MDEP mdep;};
  54
  55 /* While outputting an insn as assembler code,
  56    this is the status BEFORE that insn.  */
  57 extern CC_STATUS cc_prev_status;
  58
  59 /* While outputting an insn as assembler code,
  60    this is being altered to the status AFTER that insn.  */
  61 extern CC_STATUS cc_status;
  62
  63 /* These are the machine-independent flags:  */
  64
  65 /* Set if the sign of the cc value is inverted:
  66    output a following jump-if-less as a jump-if-greater, etc.  */
  67 #define CC_REVERSED 1
  68
  69 /* This bit means that the current setting of the N bit is bogus
  70    and conditional jumps should use the Z bit in its place.
  71    This state obtains when an extraction of a signed single-bit field
  72    or an arithmetic shift right of a byte by 7 bits
  73    is turned into a btst, because btst does not set the N bit.  */
  74 #define CC_NOT_POSITIVE 2
  75
  76 /* This bit means that the current setting of the N bit is bogus
  77    and conditional jumps should pretend that the N bit is clear.
  78    Used after extraction of an unsigned bit
  79    or logical shift right of a byte by 7 bits is turned into a btst.
  80    The btst does not alter the N bit, but the result of that shift
  81    or extract is never negative.  */
  82 #define CC_NOT_NEGATIVE 4
  83
  84 /* This bit means that the current setting of the overflow flag
  85    is bogus and conditional jumps should pretend there is no overflow.  */
  86 /* ??? Note that for most targets this macro is misnamed as it applies
  87    to the carry flag, not the overflow flag.  */
  88 #define CC_NO_OVERFLOW 010
  89
  90 /* This bit means that what ought to be in the Z bit
  91    should be tested as the complement of the N bit.  */
  92 #define CC_Z_IN_NOT_N 020
  93
  94 /* This bit means that what ought to be in the Z bit
  95    should be tested as the N bit.  */
  96 #define CC_Z_IN_N 040
  97
  98 /* Nonzero if we must invert the sense of the following branch, i.e.
  99    change EQ to NE.  This is not safe for IEEE floating point operations!
 100    It is intended for use only when a combination of arithmetic
 101    or logical insns can leave the condition codes set in a fortuitous
 102    (though inverted) state.  */
 103 #define CC_INVERTED 0100
 104
 105 /* Nonzero if we must convert signed condition operators to unsigned.
 106    This is only used by machine description files.  */
 107 #define CC_NOT_SIGNED 0200
 108
 109 /* This is how to initialize the variable cc_status.
 110    final does this at appropriate moments.  */
 111
 112 /* FIXME: We want to get rid of these ifndefs.  */
 113 #ifndef CC_STATUS_INIT
 114 #define CC_STATUS_INIT  \
 115  (cc_status.flags = 0, cc_status.value1 = 0, cc_status.value2 = 0,  \
 116   CC_STATUS_MDEP_INIT)
 117 #endif
 118 #endif /* GCC_CONDITIONS_H */