GCC Middle and Back End API Reference
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1 /* Definitions for condition code handling in final.c and output routines.
2  Copyright (C) 1987-2013 Free Software Foundation, Inc.
4 This file is part of GCC.
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.
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.
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/>. */
20 /* None of the things in the files exist if we don't use CC0. */
22 #ifdef HAVE_cc0
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.
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.
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.
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. */
46 #ifndef CC_STATUS_MDEP
47 #define CC_STATUS_MDEP int
48 #endif
51 #define CC_STATUS_MDEP_INIT 0
52 #endif
54 typedef struct {int flags; rtx value1, value2; CC_STATUS_MDEP mdep;} CC_STATUS;
56 /* While outputting an insn as assembler code,
57  this is the status BEFORE that insn. */
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;
64 /* These are the machine-independent flags: */
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
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
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
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 /* ??? Note that for most targets this macro is misnamed as it applies
88  to the carry flag, not the overflow flag. */
89 #define CC_NO_OVERFLOW 010
91 /* This bit means that what ought to be in the Z bit
92  should be tested as the complement of the N bit. */
93 #define CC_Z_IN_NOT_N 020
95 /* This bit means that what ought to be in the Z bit
96  should be tested as the N bit. */
97 #define CC_Z_IN_N 040
99 /* Nonzero if we must invert the sense of the following branch, i.e.
100  change EQ to NE. This is not safe for IEEE floating point operations!
101  It is intended for use only when a combination of arithmetic
102  or logical insns can leave the condition codes set in a fortuitous
103  (though inverted) state. */
104 #define CC_INVERTED 0100
106 /* Nonzero if we must convert signed condition operators to unsigned.
107  This is only used by machine description files. */
108 #define CC_NOT_SIGNED 0200
110 /* This is how to initialize the variable cc_status.
111  final does this at appropriate moments. */
113 #define CC_STATUS_INIT \
114  (cc_status.flags = 0, cc_status.value1 = 0, cc_status.value2 = 0, \
117 #endif