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Annotation of researchv10dc/cmd/gcc/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 distributed in the hope that it will be useful,
        !             7: but WITHOUT ANY WARRANTY.  No author or distributor
        !             8: accepts responsibility to anyone for the consequences of using it
        !             9: or for whether it serves any particular purpose or works at all,
        !            10: unless he says so in writing.  Refer to the GNU CC General Public
        !            11: License for full details.
        !            12: 
        !            13: Everyone is granted permission to copy, modify and redistribute
        !            14: GNU CC, but only under the conditions described in the
        !            15: GNU CC General Public License.   A copy of this license is
        !            16: supposed to have been given to you along with GNU CC so you
        !            17: can know your rights and responsibilities.  It should be in a
        !            18: file named COPYING.  Among other things, the copyright notice
        !            19: and this notice must be preserved on all copies.  */
        !            20: 
        !            21: 
        !            22: /* The variable cc_status says how to interpret the condition code.
        !            23:    It is set by output routines for an instruction that sets the cc's
        !            24:    and examined by output routines for jump instructions.
        !            25: 
        !            26:    cc_status contains two components named `value1' and `value2'
        !            27:    that record two equivalent expressions for the values that the
        !            28:    condition codes were set from.  (Either or both may be null if
        !            29:    there is no useful expression to record.)  These fields are
        !            30:    used for eliminating redundant test and compare instructions
        !            31:    in the cases where the condition codes were already set by the
        !            32:    previous instruction.
        !            33: 
        !            34:    cc_status.flags contains flags which say that the condition codes
        !            35:    were set in a nonstandard manner.  The output of jump instructions
        !            36:    uses these flags to compensate and produce the standard result
        !            37:    with the nonstandard condition codes.  Standard flags are defined here.
        !            38:    The tm- file can also define other machine-dependent flags.
        !            39: 
        !            40:    cc_status also contains a machine-dependent component `mdep'
        !            41:    whose type, `CC_STATUS_MDEP', may be defined as a macro in the
        !            42:    tm- file.  */
        !            43: 
        !            44: #ifndef CC_STATUS_MDEP
        !            45: #define CC_STATUS_MDEP int
        !            46: #endif
        !            47: 
        !            48: #ifndef CC_STATUS_MDEP_INIT
        !            49: #define CC_STATUS_MDEP_INIT 0
        !            50: #endif
        !            51: 
        !            52: typedef struct {int flags; rtx value1, value2; CC_STATUS_MDEP mdep;} CC_STATUS;
        !            53: 
        !            54: /* While outputting an insn as assembler code,
        !            55:    this is the status BEFORE that insn.  */
        !            56: extern CC_STATUS cc_prev_status;
        !            57: 
        !            58: /* While outputting an insn as assembler code,
        !            59:    this is being altered to the status AFTER that insn.  */
        !            60: extern CC_STATUS cc_status;
        !            61: 
        !            62: /* These are the machine-independent flags:  */
        !            63: 
        !            64: /* Set if the sign of the cc value is inverted:
        !            65:    output a following jump-if-less as a jump-if-greater, etc.  */
        !            66: #define CC_REVERSED 1
        !            67: 
        !            68: /* This bit means that the current setting of the N bit is bogus
        !            69:    and conditional jumps should use the Z bit in its place.
        !            70:    This state obtains when an extraction of a signed single-bit field
        !            71:    or an arithmetic shift right of a byte by 7 bits
        !            72:    is turned into a btst, because btst does not set the N bit.  */
        !            73: #define CC_NOT_POSITIVE 2
        !            74: 
        !            75: /* This bit means that the current setting of the N bit is bogus
        !            76:    and conditional jumps should pretend that the N bit is clear.
        !            77:    Used after extraction of an unsigned bit
        !            78:    or logical shift right of a byte by 7 bits is turned into a btst.
        !            79:    The btst does not alter the N bit, but the result of that shift
        !            80:    or extract is never negative.  */
        !            81: #define CC_NOT_NEGATIVE 4
        !            82: 
        !            83: /* This bit means that the current setting of the overflow flag
        !            84:    is bogus and conditional jumps should pretend there is no overflow.  */
        !            85: #define CC_NO_OVERFLOW 010
        !            86: 
        !            87: /* This bit means that what ought to be in the Z bit
        !            88:    should be tested as the complement of the N bit.  */
        !            89: #define CC_Z_IN_NOT_N 020
        !            90: 
        !            91: /* This is how to initialize the variable cc_status.
        !            92:    final does this at appropriate moments.  */
        !            93: 
        !            94: #define CC_STATUS_INIT  \
        !            95:  (cc_status.flags = 0, cc_status.value1 = 0, cc_status.value2 = 0,  \
        !            96:   CC_STATUS_MDEP_INIT)

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