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Annotation of GNUtools/cc/conditions.h, revision 1.1

1.1     ! root        1: /* Definitions for condition code handling in final.c and output routines.
        !             2:    Copyright (C) 1987 Free Software Foundation, Inc.
        !             3: 
        !             4: This file is part of GNU CC.
        !             5: 
        !             6: GNU CC 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 2, or (at your option)
        !             9: any later version.
        !            10: 
        !            11: GNU CC 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 GNU CC; see the file COPYING.  If not, write to
        !            18: the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
        !            19: 
        !            20: /* None of the things in the files exist if we don't use CC0.  */
        !            21: 
        !            22: #ifdef HAVE_cc0
        !            23: 
        !            24: /* The variable cc_status says how to interpret the condition code.
        !            25:    It is set by output routines for an instruction that sets the cc's
        !            26:    and examined by output routines for jump instructions.
        !            27: 
        !            28:    cc_status contains two components named `value1' and `value2'
        !            29:    that record two equivalent expressions for the values that the
        !            30:    condition codes were set from.  (Either or both may be null if
        !            31:    there is no useful expression to record.)  These fields are
        !            32:    used for eliminating redundant test and compare instructions
        !            33:    in the cases where the condition codes were already set by the
        !            34:    previous instruction.
        !            35: 
        !            36:    cc_status.flags contains flags which say that the condition codes
        !            37:    were set in a nonstandard manner.  The output of jump instructions
        !            38:    uses these flags to compensate and produce the standard result
        !            39:    with the nonstandard condition codes.  Standard flags are defined here.
        !            40:    The tm.h file can also define other machine-dependent flags.
        !            41: 
        !            42:    cc_status also contains a machine-dependent component `mdep'
        !            43:    whose type, `CC_STATUS_MDEP', may be defined as a macro in the
        !            44:    tm.h file.  */
        !            45: 
        !            46: #ifndef CC_STATUS_MDEP
        !            47: #define CC_STATUS_MDEP int
        !            48: #endif
        !            49: 
        !            50: #ifndef CC_STATUS_MDEP_INIT
        !            51: #define CC_STATUS_MDEP_INIT 0
        !            52: #endif
        !            53: 
        !            54: typedef struct {int flags; rtx value1, value2; CC_STATUS_MDEP mdep;} CC_STATUS;
        !            55: 
        !            56: /* While outputting an insn as assembler code,
        !            57:    this is the status BEFORE that insn.  */
        !            58: extern CC_STATUS cc_prev_status;
        !            59: 
        !            60: /* While outputting an insn as assembler code,
        !            61:    this is being altered to the status AFTER that insn.  */
        !            62: extern CC_STATUS cc_status;
        !            63: 
        !            64: /* These are the machine-independent flags:  */
        !            65: 
        !            66: /* Set if the sign of the cc value is inverted:
        !            67:    output a following jump-if-less as a jump-if-greater, etc.  */
        !            68: #define CC_REVERSED 1
        !            69: 
        !            70: /* This bit means that the current setting of the N bit is bogus
        !            71:    and conditional jumps should use the Z bit in its place.
        !            72:    This state obtains when an extraction of a signed single-bit field
        !            73:    or an arithmetic shift right of a byte by 7 bits
        !            74:    is turned into a btst, because btst does not set the N bit.  */
        !            75: #define CC_NOT_POSITIVE 2
        !            76: 
        !            77: /* This bit means that the current setting of the N bit is bogus
        !            78:    and conditional jumps should pretend that the N bit is clear.
        !            79:    Used after extraction of an unsigned bit
        !            80:    or logical shift right of a byte by 7 bits is turned into a btst.
        !            81:    The btst does not alter the N bit, but the result of that shift
        !            82:    or extract is never negative.  */
        !            83: #define CC_NOT_NEGATIVE 4
        !            84: 
        !            85: /* This bit means that the current setting of the overflow flag
        !            86:    is bogus and conditional jumps should pretend there is no overflow.  */
        !            87: #define CC_NO_OVERFLOW 010
        !            88: 
        !            89: /* This bit means that what ought to be in the Z bit
        !            90:    should be tested as the complement of the N bit.  */
        !            91: #define CC_Z_IN_NOT_N 020
        !            92: 
        !            93: /* This bit means that what ought to be in the Z bit
        !            94:    should be tested as the N bit.  */
        !            95: #define CC_Z_IN_N 040
        !            96: 
        !            97: /* Nonzero if we must invert the sense of the following branch, i.e.
        !            98:    change EQ to NE.  This is not safe for IEEE floating point operations!
        !            99:    It is intended for use only when a combination of arithmetic
        !           100:    or logical insns can leave the condition codes set in a fortuitous
        !           101:    (though inverted) state.  */
        !           102: #define CC_INVERTED 0100
        !           103: 
        !           104: /* Nonzero if we must convert signed condition operators to unsigned.
        !           105:    This is only used by machine description files. */
        !           106: #define CC_NOT_SIGNED 0200
        !           107: 
        !           108: /* This is how to initialize the variable cc_status.
        !           109:    final does this at appropriate moments.  */
        !           110: 
        !           111: #define CC_STATUS_INIT  \
        !           112:  (cc_status.flags = 0, cc_status.value1 = 0, cc_status.value2 = 0,  \
        !           113:   CC_STATUS_MDEP_INIT)
        !           114: 
        !           115: #endif

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