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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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