| blob | 3b759e8c8be4d924894b46f39418c6a416519f0a |
1 /* Fold a constant sub-tree into a single node for C-compiler
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000 Free Software Foundation, Inc.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
10 any later version.
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
22 /*@@ This file should be rewritten to use an arbitrary precision
23 @@ representation for "struct tree_int_cst" and "struct tree_real_cst".
24 @@ Perhaps the routines could also be used for bc/dc, and made a lib.
25 @@ The routines that translate from the ap rep should
26 @@ warn if precision et. al. is lost.
27 @@ This would also make life easier when this technology is used
28 @@ for cross-compilers. */
31 /* The entry points in this file are fold, size_int_wide, size_binop
32 and force_fit_type.
34 fold takes a tree as argument and returns a simplified tree.
36 size_binop takes a tree code for an arithmetic operation
37 and two operands that are trees, and produces a tree for the
38 result, assuming the type comes from `sizetype'.
40 size_int takes an integer value, and creates a tree constant
41 with type from `sizetype'.
43 force_fit_type takes a constant and prior overflow indicator, and
44 forces the value to fit the type. It returns an overflow indicator. */
48 #include <setjmp.h>
58 HOST_WIDE_INT));
61 HOST_WIDE_INT *));
84 HOST_WIDE_INT *,
105 #ifndef BRANCH_COST
106 #define BRANCH_COST 1
107 #endif
109 #if defined(HOST_EBCDIC)
110 /* bit 8 is significant in EBCDIC */
111 #define CHARMASK 0xff
112 #else
113 #define CHARMASK 0x7f
114 #endif
117 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
118 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
119 and SUM1. Then this yields nonzero if overflow occurred during the
120 addition.
122 Overflow occurs if A and B have the same sign, but A and SUM differ in
123 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
124 sign. */
125 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
126 \f
127 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
128 We do that by representing the two-word integer in 4 words, with only
129 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
130 number. The value of the word is LOWPART + HIGHPART * BASE. */
132 #define LOWPART(x) \
133 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
134 #define HIGHPART(x) \
135 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
136 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
138 /* Unpack a two-word integer into 4 words.
139 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
140 WORDS points to the array of HOST_WIDE_INTs. */
142 static void
146 HOST_WIDE_INT hi;
147 {
152 }
154 /* Pack an array of 4 words into a two-word integer.
155 WORDS points to the array of words.
156 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
158 static void
163 {
166 }
167 \f
168 /* Make the integer constant T valid for its type by setting to 0 or 1 all
169 the bits in the constant that don't belong in the type.
171 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
172 nonzero, a signed overflow has already occurred in calculating T, so
173 propagate it.
175 Make the real constant T valid for its type by calling CHECK_FLOAT_VALUE,
176 if it exists. */
178 int
180 tree t;
182 {
184 HOST_WIDE_INT high;
188 {
189 #ifdef CHECK_FLOAT_VALUE
191 overflow);
192 #endif
194 }
204 else
207 /* First clear all bits that are beyond the type's precision. */
210 ;
214 else
215 {
219 }
221 /* Unsigned types do not suffer sign extension or overflow. */
225 /* If the value's sign bit is set, extend the sign. */
233 {
234 /* Value is negative:
235 set to 1 all the bits that are outside this type's precision. */
239 else
240 {
244 }
245 }
247 /* Return nonzero if signed overflow occurred. */
248 return
251 }
252 \f
253 /* Add two doubleword integers with doubleword result.
254 Each argument is given as two `HOST_WIDE_INT' pieces.
255 One argument is L1 and H1; the other, L2 and H2.
256 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
258 int
264 {
266 HOST_WIDE_INT h;
274 }
276 /* Negate a doubleword integer with doubleword result.
277 Return nonzero if the operation overflows, assuming it's signed.
278 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
279 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
281 int
284 HOST_WIDE_INT h1;
287 {
289 {
293 }
294 else
295 {
299 }
300 }
301 \f
302 /* Multiply two doubleword integers with doubleword result.
303 Return nonzero if the operation overflows, assuming it's signed.
304 Each argument is given as two `HOST_WIDE_INT' pieces.
305 One argument is L1 and H1; the other, L2 and H2.
306 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
308 int
314 {
329 {
332 {
334 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
336 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
340 }
342 }
346 /* Check for overflow by calculating the top half of the answer in full;
347 it should agree with the low half's sign bit. */
350 {
353 }
355 {
358 }
360 }
361 \f
362 /* Shift the doubleword integer in L1, H1 left by COUNT places
363 keeping only PREC bits of result.
364 Shift right if COUNT is negative.
365 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
366 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
368 void
376 {
378 {
381 }
383 #ifdef SHIFT_COUNT_TRUNCATED
386 #endif
389 {
390 /* Shifting by the host word size is undefined according to the
391 ANSI standard, so we must handle this as a special case. */
394 }
396 {
399 }
400 else
401 {
405 }
406 }
408 /* Shift the doubleword integer in L1, H1 right by COUNT places
409 keeping only PREC bits of result. COUNT must be positive.
410 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
411 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
413 void
421 {
424 signmask = (arith
428 #ifdef SHIFT_COUNT_TRUNCATED
431 #endif
434 {
435 /* Shifting by the host word size is undefined according to the
436 ANSI standard, so we must handle this as a special case. */
439 }
441 {
445 }
446 else
447 {
452 }
453 }
454 \f
455 /* Rotate the doubleword integer in L1, H1 left by COUNT places
456 keeping only PREC bits of result.
457 Rotate right if COUNT is negative.
458 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
460 void
467 {
479 }
481 /* Rotate the doubleword integer in L1, H1 left by COUNT places
482 keeping only PREC bits of result. COUNT must be positive.
483 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
485 void
492 {
504 }
505 \f
506 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
507 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
508 CODE is a tree code for a kind of division, one of
509 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
510 or EXACT_DIV_EXPR
511 It controls how the quotient is rounded to a integer.
512 Return nonzero if the operation overflows.
513 UNS nonzero says do unsigned division. */
515 int
522 HOST_WIDE_INT hnum_orig;
524 HOST_WIDE_INT hden_orig;
527 {
543 /* calculate quotient sign and convert operands to unsigned. */
545 {
547 {
549 /* (minimum integer) / (-1) is the only overflow case. */
553 }
555 {
558 }
559 }
564 /* This unsigned division rounds toward zero. */
567 }
571 /* hden != 0 already checked. */
576 }
586 /* Special code for when the divisor < BASE. */
588 {
589 /* hnum != 0 already checked. */
591 {
595 }
596 }
597 else
598 {
599 /* Full double precision division,
600 with thanks to Don Knuth's "Seminumerical Algorithms". */
604 /* Find the highest non-zero divisor digit. */
609 }
611 /* Insure that the first digit of the divisor is at least BASE/2.
612 This is required by the quotient digit estimation algorithm. */
619 {
623 }
628 {
633 }
634 }
638 /* Main loop */
640 {
641 /* Guess the next quotient digit, quo_est, by dividing the first
642 two remaining dividend digits by the high order quotient digit.
643 quo_est is never low and is at most 2 high. */
650 else
653 /* Refine quo_est so it's usually correct, and at most one high. */
658 quo_est--;
660 /* Try QUO_EST as the quotient digit, by multiplying the
661 divisor by QUO_EST and subtracting from the remaining dividend.
662 Keep in mind that QUO_EST is the I - 1st digit. */
666 {
672 }
674 /* If quo_est was high by one, then num[i] went negative and
675 we need to correct things. */
677 {
678 quo_est--;
681 {
685 }
688 }
690 /* Store the quotient digit. */
692 }
693 }
697 finish_up:
698 /* if result is negative, make it so. */
702 /* compute trial remainder: rem = num - (quo * den) */
708 {
717 {
718 /* quo = quo - 1; */
721 }
722 else
729 {
732 }
733 else
739 {
745 /* Get absolute values */
751 /* If (2 * abs (lrem) >= abs (lden)) */
760 {
762 /* quo = quo - 1; */
765 else
766 /* quo = quo + 1; */
769 }
770 else
772 }
777 }
779 /* compute true remainder: rem = num - (quo * den) */
784 }
785 \f
786 #ifndef REAL_ARITHMETIC
787 /* Effectively truncate a real value to represent the nearest possible value
788 in a narrower mode. The result is actually represented in the same data
789 type as the argument, but its value is usually different.
791 A trap may occur during the FP operations and it is the responsibility
792 of the calling function to have a handler established. */
794 REAL_VALUE_TYPE
797 REAL_VALUE_TYPE arg;
798 {
800 }
802 #if TARGET_FLOAT_FORMAT == IEEE_FLOAT_FORMAT
804 /* Check for infinity in an IEEE double precision number. */
806 int
808 REAL_VALUE_TYPE x;
809 {
810 /* The IEEE 64-bit double format. */
812 REAL_VALUE_TYPE d;
829 {
834 }
835 else
836 {
841 }
842 }
844 /* Check whether an IEEE double precision number is a NaN. */
846 int
848 REAL_VALUE_TYPE x;
849 {
850 /* The IEEE 64-bit double format. */
852 REAL_VALUE_TYPE d;
869 {
874 }
875 else
876 {
881 }
882 }
884 /* Check for a negative IEEE double precision number. */
886 int
888 REAL_VALUE_TYPE x;
889 {
890 /* The IEEE 64-bit double format. */
892 REAL_VALUE_TYPE d;
909 {
912 }
913 else
914 {
917 }
918 }
921 /* Let's assume other float formats don't have infinity.
922 (This can be overridden by redefining REAL_VALUE_ISINF.) */
924 int
926 REAL_VALUE_TYPE x ATTRIBUTE_UNUSED;
927 {
929 }
931 /* Let's assume other float formats don't have NaNs.
932 (This can be overridden by redefining REAL_VALUE_ISNAN.) */
934 int
936 REAL_VALUE_TYPE x ATTRIBUTE_UNUSED;
937 {
939 }
941 /* Let's assume other float formats don't have minus zero.
942 (This can be overridden by redefining REAL_VALUE_NEGATIVE.) */
944 int
946 REAL_VALUE_TYPE x;
947 {
949 }
952 /* Try to change R into its exact multiplicative inverse in machine mode
953 MODE. Return nonzero function value if successful. */
955 int
959 {
961 union
962 {
966 #ifdef CHECK_FLOAT_VALUE
968 #endif
970 /* Usually disable if bounds checks are not reliable. */
974 /* Set array index to the less significant bits in the unions, depending
975 on the endian-ness of the host doubles.
976 Disable if insufficient information on the data structure. */
977 #if HOST_FLOAT_FORMAT == UNKNOWN_FLOAT_FORMAT
979 #else
980 #if HOST_FLOAT_FORMAT == VAX_FLOAT_FORMAT
981 #define K 2
982 #else
983 #if HOST_FLOAT_FORMAT == IBM_FLOAT_FORMAT
984 #define K 2
985 #else
986 #define K (2 * HOST_FLOAT_WORDS_BIG_ENDIAN)
987 #endif
988 #endif
989 #endif
992 {
993 /* Don't do the optimization if there was an arithmetic error. */
994 fail:
997 }
1000 /* Domain check the argument. */
1005 #ifdef REAL_INFINITY
1008 #endif
1010 /* Compute the reciprocal and check for numerical exactness.
1011 It is unnecessary to check all the significand bits to determine
1012 whether X is a power of 2. If X is not, then it is impossible for
1013 the bottom half significand of both X and 1/X to be all zero bits.
1014 Hence we ignore the data structure of the top half and examine only
1015 the low order bits of the two significands. */
1020 /* Truncate to the required mode and range-check the result. */
1022 #ifdef CHECK_FLOAT_VALUE
1026 #endif
1028 /* Fail if truncation changed the value. */
1032 #ifdef REAL_INFINITY
1035 #endif
1037 /* Output the reciprocal and return success flag. */
1041 }
1043 /* Convert C9X hexadecimal floating point string constant S. Return
1044 real value type in mode MODE. This function uses the host computer's
1045 floating point arithmetic when there is no REAL_ARITHMETIC. */
1047 REAL_VALUE_TYPE
1051 {
1052 REAL_VALUE_TYPE ip;
1071 /* Sign, if any, comes first. */
1074 {
1077 }
1079 /* The string is supposed to start with 0x or 0X . */
1081 {
1085 else
1087 }
1088 else
1098 {
1101 {
1107 else
1111 {
1117 }
1118 else
1119 {
1120 /* Record nonzero lost bits. */
1124 }
1126 }
1128 {
1131 }
1134 {
1137 /* Sign of exponent. */
1139 {
1142 }
1144 /* Value of exponent.
1145 The exponent field is a decimal integer. */
1147 {
1150 }
1153 /* F suffix is ambiguous in the significand part
1154 so it must appear after the decimal exponent field. */
1156 {
1160 }
1161 }
1164 {
1167 }
1168 else
1170 }
1172 /* Abort if last character read was not legitimate. */
1177 /* There must be either one decimal point or one p. */
1185 /* Normalize. */
1188 {
1192 }
1194 /* Leave a high guard bit for carry-out. */
1196 {
1201 }
1204 {
1208 }
1211 {
1215 }
1218 {
1219 /* Keep 24 bits precision, bits 0x7fffff80.
1220 Rounding bit is 0x40. */
1224 {
1227 }
1229 }
1230 else
1231 {
1232 /* We need real.c to do long double formats, so here default
1233 to double precision. */
1234 #if HOST_FLOAT_FORMAT == IEEE_FLOAT_FORMAT
1235 /* IEEE double.
1236 Keep 53 bits precision, bits 0x7fffffff fffffc00.
1237 Rounding bit is low word 0x200. */
1240 {
1242 {
1246 }
1247 }
1249 #else
1250 /* Assume it's a VAX with 56-bit significand,
1251 bits 0x7fffffff ffffff80. */
1254 {
1256 {
1260 }
1261 }
1263 #endif
1264 }
1268 /* Apply shifts and exponent value as power of 2. */
1274 }
1277 \f
1278 /* Given T, an expression, return the negation of T. Allow for T to be
1279 null, in which case return null. */
1281 static tree
1283 tree t;
1284 {
1285 tree type;
1286 tree tem;
1295 {
1308 /* - (A - B) -> B - A */
1318 }
1321 }
1322 \f
1323 /* Split a tree IN into a constant, literal and variable parts that could be
1324 combined with CODE to make IN. "constant" means an expression with
1325 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1326 commutative arithmetic operation. Store the constant part into *CONP,
1327 the literal in &LITP and return the variable part. If a part isn't
1328 present, set it to null. If the tree does not decompose in this way,
1329 return the entire tree as the variable part and the other parts as null.
1331 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1332 case, we negate an operand that was subtracted. If NEGATE_P is true, we
1333 are negating all of IN.
1335 If IN is itself a literal or constant, return it as appropriate.
1337 Note that we do not guarantee that any of the three values will be the
1338 same type as IN, but they will have the same signedness and mode. */
1340 static tree
1342 tree in;
1346 {
1352 /* Strip any conversions that don't change the machine mode or signedness. */
1362 /* We can associate addition and subtraction together (even
1363 though the C standard doesn't say so) for integers because
1364 the value is not affected. For reals, the value might be
1365 affected, so we can't. */
1368 {
1374 /* First see if either of the operands is a literal, then a constant. */
1385 /* If we haven't dealt with either operand, this is not a case we can
1386 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1391 else
1394 /* Now do any needed negations. */
1398 }
1399 else
1403 {
1407 }
1410 }
1412 /* Re-associate trees split by the above function. T1 and T2 are either
1413 expressions to associate or null. Return the new expression, if any. If
1414 we build an operation, do it in TYPE and with CODE, except if CODE is a
1415 MINUS_EXPR, in which case we use PLUS_EXPR since split_tree will already
1416 have taken care of the negations. */
1418 static tree
1422 tree type;
1423 {
1432 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1433 try to fold this since we will have infinite recursion. But do
1434 deal with any NEGATE_EXPRs. */
1437 {
1444 else
1446 }
1449 }
1450 \f
1451 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1452 to produce a new constant.
1454 If NOTRUNC is nonzero, do not truncate the result to fit the data type.
1455 If FORSIZE is nonzero, compute overflow for unsigned types. */
1457 static tree
1462 {
1466 HOST_WIDE_INT hi;
1468 HOST_WIDE_INT garbageh;
1480 {
1500 /* It's unclear from the C standard whether shifts can overflow.
1501 The following code ignores overflow; perhaps a C standard
1502 interpretation ruling is needed. */
1532 /* This is a shortcut for a common special case. */
1537 {
1543 }
1545 /* ... fall through ... */
1549 {
1552 }
1555 {
1558 }
1566 /* This is a shortcut for a common special case. */
1571 {
1576 }
1578 /* ... fall through ... */
1594 else
1600 else
1606 }
1610 else
1611 {
1614 }
1622 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1623 So check if force_fit_type truncated the value. */
1634 }
1636 /* Define input and output argument for const_binop_1. */
1637 struct cb_args
1638 {
1643 };
1645 /* Do the real arithmetic for const_binop while protected by a
1646 float overflow handler. */
1648 static void
1650 PTR data;
1651 {
1653 REAL_VALUE_TYPE value;
1655 #ifdef REAL_ARITHMETIC
1657 #else
1659 {
1673 #ifndef REAL_INFINITY
1676 #endif
1691 }
1694 args->t
1697 }
1699 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1700 constant. We assume ARG1 and ARG2 have the same data type, or at least
1701 are the same kind of constant and the same machine mode.
1703 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1705 static tree
1710 {
1716 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
1718 {
1719 REAL_VALUE_TYPE d1;
1720 REAL_VALUE_TYPE d2;
1722 tree t;
1728 /* If either operand is a NaN, just return it. Otherwise, set up
1729 for floating-point trap; we return an overflow. */
1735 /* Setup input for const_binop_1() */
1742 /* Receive output from const_binop_1. */
1744 else
1745 {
1746 /* We got an exception from const_binop_1. */
1749 }
1759 }
1762 {
1771 {
1791 notrunc),
1797 notrunc));
1801 {
1802 register tree magsquared
1806 notrunc);
1809 const_binop
1814 notrunc),
1816 notrunc),
1817 notrunc),
1819 const_binop
1824 notrunc),
1826 notrunc),
1827 notrunc),
1829 }
1834 }
1836 }
1838 }
1839 \f
1840 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1841 bits are given by NUMBER and of the sizetype represented by KIND. */
1843 tree
1845 HOST_WIDE_INT number;
1847 {
1849 }
1851 /* Likewise, but the desired type is specified explicitly. */
1853 tree
1855 HOST_WIDE_INT number;
1856 tree type;
1857 {
1858 /* Type-size nodes already made for small sizes. */
1861 tree t;
1864 {
1868 }
1870 /* If this is a positive number that fits in the table we use to hold
1871 cached entries, see if it is already in the table and put it there
1872 if not. */
1874 {
1881 {
1882 /* Make this a permanent node. */
1885 }
1896 }
1902 }
1904 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1905 is a tree code. The type of the result is taken from the operands.
1906 Both must be the same type integer type and it must be a size type.
1907 If the operands are constant, so is the result. */
1909 tree
1913 {
1920 /* Handle the special case of two integer constants faster. */
1922 {
1923 /* And some specific cases even faster than that. */
1932 /* Handle general case of two integer constants. */
1934 }
1940 }
1942 /* Given two values, either both of sizetype or both of bitsizetype,
1943 compute the difference between the two values. Return the value
1944 in signed type corresponding to the type of the operands. */
1946 tree
1949 {
1951 tree ctype;
1957 /* If the type is already signed, just do the simple thing. */
1964 /* If either operand is not a constant, do the conversions to the signed
1965 type and subtract. The hardware will do the right thing with any
1966 overflow in the subtraction. */
1971 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1972 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1973 overflow) and negate (which can't either). Special-case a result
1974 of zero while we're here. */
1979 else
1982 }
1983 \f
1984 /* This structure is used to communicate arguments to fold_convert_1. */
1985 struct fc_args
1986 {
1990 };
1992 /* Function to convert floating-point constants, protected by floating
1993 point exception handler. */
1995 static void
1997 PTR data;
1998 {
2004 }
2006 /* Given T, a tree representing type conversion of ARG1, a constant,
2007 return a constant tree representing the result of conversion. */
2009 static tree
2013 {
2018 {
2020 {
2021 /* If we would build a constant wider than GCC supports,
2022 leave the conversion unfolded. */
2026 /* If we are trying to make a sizetype for a small integer, use
2027 size_int to pick up cached types to reduce duplicate nodes. */
2032 /* Given an integer constant, make new constant with new type,
2033 appropriately sign-extended or truncated. */
2037 /* Indicate an overflow if (1) ARG1 already overflowed,
2038 or (2) force_fit_type indicates an overflow.
2039 Tell force_fit_type that an overflow has already occurred
2040 if ARG1 is a too-large unsigned value and T is signed.
2041 But don't indicate an overflow if converting a pointer. */
2051 }
2052 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
2054 {
2055 /* Don't initialize these, use assignments.
2056 Initialized local aggregates don't work on old compilers. */
2057 REAL_VALUE_TYPE x;
2058 REAL_VALUE_TYPE l;
2059 REAL_VALUE_TYPE u;
2070 /* See if X will be in range after truncation towards 0.
2071 To compensate for truncation, move the bounds away from 0,
2072 but reject if X exactly equals the adjusted bounds. */
2073 #ifdef REAL_ARITHMETIC
2077 #else
2078 l--;
2080 u++;
2081 #endif
2082 /* If X is a NaN, use zero instead and show we have an overflow.
2083 Otherwise, range check. */
2087 && !no_upper_bound
2091 #ifndef REAL_ARITHMETIC
2092 {
2094 HOST_WIDE_INT half_word
2103 {
2106 }
2107 else
2112 }
2113 #else
2114 {
2118 }
2119 #endif
2125 }
2128 }
2130 {
2131 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
2136 {
2140 {
2144 }
2146 /* Setup input for fold_convert_1() */
2151 {
2152 /* Receive output from fold_convert_1() */
2154 }
2155 else
2156 {
2157 /* We got an exception from fold_convert_1() */
2160 }
2167 }
2168 }
2171 }
2172 \f
2173 /* Return an expr equal to X but certainly not valid as an lvalue. */
2175 tree
2177 tree x;
2178 {
2179 tree result;
2181 /* These things are certainly not lvalues. */
2192 }
2194 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
2195 Zero means allow extended lvalues. */
2199 /* When pedantic, return an expr equal to X but certainly not valid as a
2200 pedantic lvalue. Otherwise, return X. */
2202 tree
2204 tree x;
2205 {
2208 else
2210 }
2211 \f
2212 /* Given a tree comparison code, return the code that is the logical inverse
2213 of the given code. It is not safe to do this for floating-point
2214 comparisons, except for NE_EXPR and EQ_EXPR. */
2216 static enum tree_code
2219 {
2221 {
2236 }
2237 }
2239 /* Similar, but return the comparison that results if the operands are
2240 swapped. This is safe for floating-point. */
2242 static enum tree_code
2245 {
2247 {
2261 }
2262 }
2264 /* Return nonzero if CODE is a tree code that represents a truth value. */
2266 static int
2269 {
2274 }
2275 \f
2276 /* Return nonzero if two operands are necessarily equal.
2277 If ONLY_CONST is non-zero, only return non-zero for constants.
2278 This function tests whether the operands are indistinguishable;
2279 it does not test whether they are equal using C's == operation.
2280 The distinction is important for IEEE floating point, because
2281 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
2282 (2) two NaNs may be indistinguishable, but NaN!=NaN. */
2284 int
2288 {
2289 /* If both types don't have the same signedness, then we can't consider
2290 them equal. We must check this before the STRIP_NOPS calls
2291 because they may change the signedness of the arguments. */
2299 /* This is needed for conversions and for COMPONENT_REF.
2300 Might as well play it safe and always test this. */
2306 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
2307 We don't care about side effects in that case because the SAVE_EXPR
2308 takes care of that for us. In all other cases, two expressions are
2309 equal if they have no side effects. If we have two identical
2310 expressions with side effects that should be treated the same due
2311 to the only side effects being identical SAVE_EXPR's, that will
2312 be detected in the recursive calls below. */
2318 /* Next handle constant cases, those for which we can return 1 even
2319 if ONLY_CONST is set. */
2322 {
2336 only_const)
2338 only_const));
2351 }
2357 {
2359 /* Two conversions are equal only if signedness and modes match. */
2375 /* For commutative ops, allow the other order. */
2388 /* If either of the pointer (or reference) expressions we are dereferencing
2389 contain a side effect, these cannot be equal. */
2395 {
2416 }
2425 }
2426 }
2427 \f
2428 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2429 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2431 When in doubt, return 0. */
2433 static int
2436 tree other;
2437 {
2449 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2450 and see if the inner values are the same. This removes any
2451 signedness comparison, which doesn't matter here. */
2457 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2458 actual comparison operand, ARG0.
2460 First throw away any conversions to wider types
2461 already present in the operands. */
2470 {
2473 /* Make sure shorter operand is extended the right way
2474 to match the longer operand. */
2477 primarg1);
2481 }
2484 }
2485 \f
2486 /* See if ARG is an expression that is either a comparison or is performing
2487 arithmetic on comparisons. The comparisons must only be comparing
2488 two different values, which will be stored in *CVAL1 and *CVAL2; if
2489 they are non-zero it means that some operands have already been found.
2490 No variables may be used anywhere else in the expression except in the
2491 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2492 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2494 If this is true, return 1. Otherwise, return zero. */
2496 static int
2498 tree arg;
2501 {
2505 /* We can handle some of the 'e' cases here. */
2515 {
2516 /* If we've already found a CVAL1 or CVAL2, this expression is
2517 two complex to handle. */
2523 }
2526 {
2549 /* First see if we can handle the first operand, then the second. For
2550 the second operand, we know *CVAL1 can't be zero. It must be that
2551 one side of the comparison is each of the values; test for the
2552 case where this isn't true by failing if the two operands
2553 are the same. */
2562 ;
2566 ;
2567 else
2571 ;
2575 ;
2576 else
2583 }
2584 }
2585 \f
2586 /* ARG is a tree that is known to contain just arithmetic operations and
2587 comparisons. Evaluate the operations in the tree substituting NEW0 for
2588 any occurrence of OLD0 as an operand of a comparison and likewise for
2589 NEW1 and OLD1. */
2591 static tree
2593 tree arg;
2595 {
2600 /* We can handle some of the 'e' cases here. */
2608 {
2623 {
2640 }
2641 /* fall through - ??? */
2644 {
2648 /* We need to check both for exact equality and tree equality. The
2649 former will be true if the operand has a side-effect. In that
2650 case, we know the operand occurred exactly once. */
2663 }
2667 }
2668 }
2669 \f
2670 /* Return a tree for the case when the result of an expression is RESULT
2671 converted to TYPE and OMITTED was previously an operand of the expression
2672 but is now not needed (e.g., we folded OMITTED * 0).
2674 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2675 the conversion of RESULT to TYPE. */
2677 static tree
2680 {
2687 }
2689 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2691 static tree
2694 {
2701 }
2704 \f
2705 /* Return a simplified tree node for the truth-negation of ARG. This
2706 never alters ARG itself. We assume that ARG is an operation that
2707 returns a truth value (0 or 1). */
2709 tree
2711 tree arg;
2712 {
2719 /* If this is a comparison, we can simply invert it, except for
2720 floating-point non-equality comparisons, in which case we just
2721 enclose a TRUTH_NOT_EXPR around what we have. */
2724 {
2728 else
2731 }
2734 {
2749 /* Here we can invert either operand. We invert the first operand
2750 unless the second operand is a TRUTH_NOT_EXPR in which case our
2751 result is the XOR of the first operand with the inside of the
2752 negation of the second operand. */
2757 else
2812 }
2816 }
2818 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2819 operands are another bit-wise operation with a common input. If so,
2820 distribute the bit operations to save an operation and possibly two if
2821 constants are involved. For example, convert
2822 (A | B) & (A | C) into A | (B & C)
2823 Further simplification will occur if B and C are constants.
2825 If this optimization cannot be done, 0 will be returned. */
2827 static tree
2830 tree type;
2832 {
2833 tree common;
2843 {
2847 }
2849 {
2853 }
2855 {
2859 }
2861 {
2865 }
2866 else
2871 }
2872 \f
2873 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2874 starting at BITPOS. The field is unsigned if UNSIGNEDP is non-zero. */
2876 static tree
2878 tree inner;
2879 tree type;
2882 {
2889 }
2891 /* Optimize a bit-field compare.
2893 There are two cases: First is a compare against a constant and the
2894 second is a comparison of two items where the fields are at the same
2895 bit position relative to the start of a chunk (byte, halfword, word)
2896 large enough to contain it. In these cases we can avoid the shift
2897 implicit in bitfield extractions.
2899 For constants, we emit a compare of the shifted constant with the
2900 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2901 compared. For two fields at the same position, we do the ANDs with the
2902 similar mask and compare the result of the ANDs.
2904 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2905 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2906 are the left and right operands of the comparison, respectively.
2908 If the optimization described above can be done, we return the resulting
2909 tree. Otherwise we return zero. */
2911 static tree
2914 tree compare_type;
2916 {
2926 tree mask;
2927 tree offset;
2929 /* Get all the information about the extractions being done. If the bit size
2930 if the same as the size of the underlying object, we aren't doing an
2931 extraction at all and so can do nothing. We also don't want to
2932 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2933 then will no longer be able to replace it. */
2941 {
2942 /* If this is not a constant, we can only do something if bit positions,
2943 sizes, and signedness are the same. */
2951 }
2953 /* See if we can find a mode to refer to this field. We should be able to,
2954 but fail if we can't. */
2963 /* Set signed and unsigned types of the precision of this mode for the
2964 shifts below. */
2968 /* Compute the bit position and size for the new reference and our offset
2969 within it. If the new reference is the same size as the original, we
2970 won't optimize anything, so return zero. */
2980 /* Make the mask to be used against the extracted field. */
2990 /* If not comparing with constant, just rework the comparison
2991 and return. */
2996 mask),
3000 mask));
3002 /* Otherwise, we are handling the constant case. See if the constant is too
3003 big for the field. Warn and return a tree of for 0 (false) if so. We do
3004 this not only for its own sake, but to avoid having to test for this
3005 error case below. If we didn't, we might generate wrong code.
3007 For unsigned fields, the constant shifted right by the field length should
3008 be all zero. For signed fields, the high-order bits should agree with
3009 the sign bit. */
3012 {
3016 {
3022 }
3023 }
3024 else
3025 {
3029 {
3035 }
3036 }
3038 /* Single-bit compares should always be against zero. */
3040 {
3043 }
3045 /* Make a new bitfield reference, shift the constant over the
3046 appropriate number of bits and mask it with the computed mask
3047 (in case this was a signed field). If we changed it, make a new one. */
3050 {
3053 }
3063 rhs);
3064 }
3065 \f
3066 /* Subroutine for fold_truthop: decode a field reference.
3068 If EXP is a comparison reference, we return the innermost reference.
3070 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
3071 set to the starting bit number.
3073 If the innermost field can be completely contained in a mode-sized
3074 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
3076 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
3077 otherwise it is not changed.
3079 *PUNSIGNEDP is set to the signedness of the field.
3081 *PMASK is set to the mask used. This is either contained in a
3082 BIT_AND_EXPR or derived from the width of the field.
3084 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
3086 Return 0 if this is not a component reference or is one that we can't
3087 do anything with. */
3089 static tree
3092 tree exp;
3098 {
3101 tree unsigned_type;
3105 /* All the optimizations using this function assume integer fields.
3106 There are problems with FP fields since the type_for_size call
3107 below can fail for, e.g., XFmode. */
3114 {
3120 }
3130 /* Compute the mask to access the bitfield. */
3140 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3148 }
3150 /* Return non-zero if MASK represents a mask of SIZE ones in the low-order
3151 bit positions. */
3153 static int
3155 tree mask;
3157 {
3160 tree tmask;
3165 return
3172 }
3174 /* Subroutine for fold_truthop: determine if an operand is simple enough
3175 to be evaluated unconditionally. */
3177 static int
3179 tree exp;
3180 {
3181 /* Strip any conversions that don't change the machine mode. */
3193 /* Don't regard global variables as simple. They may be
3194 allocated in ways unknown to the compiler (shared memory,
3195 #pragma weak, etc). */
3198 /* Loading a static variable is unduly expensive, but global
3199 registers aren't expensive. */
3201 }
3202 \f
3203 /* The following functions are subroutines to fold_range_test and allow it to
3204 try to change a logical combination of comparisons into a range test.
3206 For example, both
3207 X == 2 && X == 3 && X == 4 && X == 5
3208 and
3209 X >= 2 && X <= 5
3210 are converted to
3211 (unsigned) (X - 2) <= 3
3213 We describe each set of comparisons as being either inside or outside
3214 a range, using a variable named like IN_P, and then describe the
3215 range with a lower and upper bound. If one of the bounds is omitted,
3216 it represents either the highest or lowest value of the type.
3218 In the comments below, we represent a range by two numbers in brackets
3219 preceded by a "+" to designate being inside that range, or a "-" to
3220 designate being outside that range, so the condition can be inverted by
3221 flipping the prefix. An omitted bound is represented by a "-". For
3222 example, "- [-, 10]" means being outside the range starting at the lowest
3223 possible value and ending at 10, in other words, being greater than 10.
3224 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3225 always false.
3227 We set up things so that the missing bounds are handled in a consistent
3228 manner so neither a missing bound nor "true" and "false" need to be
3229 handled using a special case. */
3231 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3232 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3233 and UPPER1_P are nonzero if the respective argument is an upper bound
3234 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3235 must be specified for a comparison. ARG1 will be converted to ARG0's
3236 type if both are specified. */
3238 static tree
3241 tree type;
3244 {
3245 tree tem;
3249 /* If neither arg represents infinity, do the normal operation.
3250 Else, if not a comparison, return infinity. Else handle the special
3251 comparison rules. Note that most of the cases below won't occur, but
3252 are handled for consistency. */
3255 {
3260 }
3265 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3266 for neither. In real maths, we cannot assume open ended ranges are
3267 the same. But, this is computer arithmetic, where numbers are finite.
3268 We can therefore make the transformation of any unbounded range with
3269 the value Z, Z being greater than any representable number. This permits
3270 us to treat unbounded ranges as equal. */
3274 {
3295 }
3298 }
3299 \f
3300 /* Given EXP, a logical expression, set the range it is testing into
3301 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3302 actually being tested. *PLOW and *PHIGH will have be made the same type
3303 as the returned expression. If EXP is not a comparison, we will most
3304 likely not be returning a useful value and range. */
3306 static tree
3308 tree exp;
3311 {
3318 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3319 and see if we can refine the range. Some of the cases below may not
3320 happen, but it doesn't seem worth worrying about this. We "continue"
3321 the outer loop when we've changed something; otherwise we "break"
3322 the switch, which will "break" the while. */
3327 {
3331 {
3342 }
3344 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
3345 lose a cast by accident. */
3350 {
3357 /* We can only do something if the range is testing for zero
3358 and if the second operand is an integer constant. Note that
3359 saying something is "in" the range we make is done by
3360 complementing IN_P since it will set in the initial case of
3361 being not equal to zero; "out" is leaving it alone. */
3368 {
3389 }
3393 /* If this is an unsigned comparison, we also know that EXP is
3394 greater than or equal to zero. We base the range tests we make
3395 on that fact, so we record it here so we can parse existing
3396 range tests. */
3398 {
3401 NULL_TREE))
3406 /* If the high bound is missing, but we
3407 have a low bound, reverse the range so
3408 it goes from zero to the low bound minus 1. */
3410 {
3415 }
3416 }
3420 /* (-x) IN [a,b] -> x in [-b, -a] */
3430 /* ~ X -> -X - 1 */
3439 /* If EXP is signed, any overflow in the computation is undefined,
3440 so we don't worry about it so long as our computations on
3441 the bounds don't overflow. For unsigned, overflow is defined
3442 and this is exactly the right thing. */
3451 /* Check for an unsigned range which has wrapped around the maximum
3452 value thus making n_high < n_low, and normalize it. */
3454 {
3460 /* If the range is of the form +/- [ x+1, x ], we won't
3461 be able to normalize it. But then, it represents the
3462 whole range or the empty set, so make it
3463 +/- [ -, - ]. */
3467 else
3469 }
3470 else
3493 /* If we're converting from an unsigned to a signed type,
3494 we will be doing the comparison as unsigned. The tests above
3495 have already verified that LOW and HIGH are both positive.
3497 So we have to make sure that the original unsigned value will
3498 be interpreted as positive. */
3500 {
3502 tree high_positive;
3504 /* A range without an upper bound is, naturally, unbounded.
3505 Since convert would have cropped a very large value, use
3506 the max value for the destination type. */
3507 high_positive
3515 /* If the low bound is specified, "and" the range with the
3516 range for which the original unsigned value will be
3517 positive. */
3519 {
3523 high_positive))
3527 }
3528 else
3529 {
3530 /* Otherwise, "or" the range with the range of the input
3531 that will be interpreted as negative. */
3535 high_positive))
3539 }
3540 }
3548 }
3551 }
3553 /* If EXP is a constant, we can evaluate whether this is true or false. */
3555 {
3562 }
3566 }
3567 \f
3568 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3569 type, TYPE, return an expression to test if EXP is in (or out of, depending
3570 on IN_P) the range. */
3572 static tree
3574 tree type;
3575 tree exp;
3578 {
3602 {
3606 }
3613 else
3615 }
3616 \f
3617 /* Given two ranges, see if we can merge them into one. Return 1 if we
3618 can, 0 if we can't. Set the output range into the specified parameters. */
3620 static int
3626 {
3630 tree tem;
3640 /* Make range 0 be the range that starts first, or ends last if they
3641 start at the same value. Swap them if it isn't. */
3644 || (lowequal
3647 {
3651 }
3653 /* Now flag two cases, whether the ranges are disjoint or whether the
3654 second range is totally subsumed in the first. Note that the tests
3655 below are simplified by the ones above. */
3661 /* We now have four cases, depending on whether we are including or
3662 excluding the two ranges. */
3664 {
3665 /* If they don't overlap, the result is false. If the second range
3666 is a subset it is the result. Otherwise, the range is from the start
3667 of the second to the end of the first. */
3672 else
3674 }
3677 {
3678 /* If they don't overlap, the result is the first range. If they are
3679 equal, the result is false. If the second range is a subset of the
3680 first, and the ranges begin at the same place, we go from just after
3681 the end of the first range to the end of the second. If the second
3682 range is not a subset of the first, or if it is a subset and both
3683 ranges end at the same place, the range starts at the start of the
3684 first range and ends just before the second range.
3685 Otherwise, we can't describe this as a single range. */
3691 {
3695 }
3697 {
3701 }
3702 else
3704 }
3707 {
3708 /* If they don't overlap, the result is the second range. If the second
3709 is a subset of the first, the result is false. Otherwise,
3710 the range starts just after the first range and ends at the
3711 end of the second. */
3716 else
3717 {
3721 }
3722 }
3724 else
3725 {
3726 /* The case where we are excluding both ranges. Here the complex case
3727 is if they don't overlap. In that case, the only time we have a
3728 range is if they are adjacent. If the second is a subset of the
3729 first, the result is the first. Otherwise, the range to exclude
3730 starts at the beginning of the first range and ends at the end of the
3731 second. */
3733 {
3740 else
3742 }
3745 else
3747 }
3751 }
3752 \f
3753 /* EXP is some logical combination of boolean tests. See if we can
3754 merge it into some range test. Return the new tree if so. */
3756 static tree
3758 tree exp;
3759 {
3766 tree tem;
3768 /* If this is an OR operation, invert both sides; we will invert
3769 again at the end. */
3773 /* If both expressions are the same, if we can merge the ranges, and we
3774 can build the range test, return it or it inverted. If one of the
3775 ranges is always true or always false, consider it to be the same
3776 expression as the other. */
3786 /* On machines where the branch cost is expensive, if this is a
3787 short-circuited branch and the underlying object on both sides
3788 is the same, make a non-short-circuit operation. */
3793 {
3794 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3795 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3796 which cases we can't do this. */
3805 {
3817 }
3818 }
3821 }
3822 \f
3823 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3824 bit value. Arrange things so the extra bits will be set to zero if and
3825 only if C is signed-extended to its full width. If MASK is nonzero,
3826 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3828 static tree
3830 tree c;
3833 tree mask;
3834 {
3837 tree temp;
3842 /* We work by getting just the sign bit into the low-order bit, then
3843 into the high-order bit, then sign-extend. We then XOR that value
3844 with C. */
3848 /* We must use a signed type in order to get an arithmetic right shift.
3849 However, we must also avoid introducing accidental overflows, so that
3850 a subsequent call to integer_zerop will work. Hence we must
3851 do the type conversion here. At this point, the constant is either
3852 zero or one, and the conversion to a signed type can never overflow.
3853 We could get an overflow if this conversion is done anywhere else. */
3861 /* If necessary, convert the type back to match the type of C. */
3866 }
3867 \f
3868 /* Find ways of folding logical expressions of LHS and RHS:
3869 Try to merge two comparisons to the same innermost item.
3870 Look for range tests like "ch >= '0' && ch <= '9'".
3871 Look for combinations of simple terms on machines with expensive branches
3872 and evaluate the RHS unconditionally.
3874 For example, if we have p->a == 2 && p->b == 4 and we can make an
3875 object large enough to span both A and B, we can do this with a comparison
3876 against the object ANDed with the a mask.
3878 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3879 operations to do this with one comparison.
3881 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3882 function and the one above.
3884 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3885 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3887 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3888 two operands.
3890 We return the simplified tree or 0 if no optimization is possible. */
3892 static tree
3896 {
3897 /* If this is the "or" of two comparisons, we can do something if we
3898 the comparisons are NE_EXPR. If this is the "and", we can do something
3899 if the comparisons are EQ_EXPR. I.e.,
3900 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3902 WANTED_CODE is this operation code. For single bit fields, we can
3903 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3904 comparison for one-bit fields. */
3924 /* Start by getting the comparison codes. Fail if anything is volatile.
3925 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3926 it were surrounded with a NE_EXPR. */
3951 /* If the RHS can be evaluated unconditionally and its operands are
3952 simple, it wins to evaluate the RHS unconditionally on machines
3953 with expensive branches. In this case, this isn't a comparison
3954 that can be merged. Avoid doing this if the RHS is a floating-point
3955 comparison since those can trap. */
3963 /* See if the comparisons can be merged. Then get all the parameters for
3964 each side. */
3988 /* It must be true that the inner operation on the lhs of each
3989 comparison must be the same if we are to be able to do anything.
3990 Then see if we have constants. If not, the same must be true for
3991 the rhs's. */
4002 else
4005 /* If either comparison code is not correct for our logical operation,
4006 fail. However, we can convert a one-bit comparison against zero into
4007 the opposite comparison against that bit being set in the field. */
4011 {
4013 {
4014 /* Make the left operand unsigned, since we are only interested
4015 in the value of one bit. Otherwise we are doing the wrong
4016 thing below. */
4019 }
4020 else
4022 }
4024 /* This is analogous to the code for l_const above. */
4026 {
4028 {
4031 }
4032 else
4034 }
4036 /* See if we can find a mode that contains both fields being compared on
4037 the left. If we can't, fail. Otherwise, update all constants and masks
4038 to be relative to a field of that size. */
4043 volatilep);
4053 {
4056 }
4064 {
4072 {
4076 wanted_code == NE_EXPR
4078 }
4079 }
4081 {
4089 {
4093 wanted_code == NE_EXPR
4095 }
4096 }
4098 /* If the right sides are not constant, do the same for it. Also,
4099 disallow this optimization if a size or signedness mismatch occurs
4100 between the left and right sides. */
4102 {
4105 /* Make sure the two fields on the right
4106 correspond to the left without being swapped. */
4114 volatilep);
4124 {
4127 }
4134 /* Make a mask that corresponds to both fields being compared.
4135 Do this for both items being compared. If the operands are the
4136 same size and the bits being compared are in the same position
4137 then we can do this by masking both and comparing the masked
4138 results. */
4142 {
4154 }
4156 /* There is still another way we can do something: If both pairs of
4157 fields being compared are adjacent, we may be able to make a wider
4158 field containing them both.
4160 Note that we still must mask the lhs/rhs expressions. Furthermore,
4161 the mask must be shifted to account for the shift done by
4162 make_bit_field_ref. */
4167 {
4168 tree type;
4180 /* Convert to the smaller type before masking out unwanted bits. */
4183 {
4185 {
4189 }
4191 {
4195 }
4196 }
4205 }
4208 }
4210 /* Handle the case of comparisons with constants. If there is something in
4211 common between the masks, those bits of the constants must be the same.
4212 If not, the condition is always false. Test for this to avoid generating
4213 incorrect code below. */
4218 {
4220 {
4223 }
4224 else
4225 {
4228 }
4229 }
4231 /* Construct the expression we will return. First get the component
4232 reference we will make. Unless the mask is all ones the width of
4233 that field, perform the mask operation. Then compare with the
4234 merged constant. */
4244 }
4245 \f
4246 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4247 constant. */
4249 static tree
4251 tree t;
4252 {
4257 tree minmax_const;
4259 tree inner;
4269 /* If something does not permit us to optimize, return the original tree. */
4277 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4278 and GT_EXPR, doing the rest with recursive calls using logical
4279 simplifications. */
4281 {
4283 return
4287 return
4289 optimize_minmax_comparison
4291 optimize_minmax_comparison
4296 /* MAX (X, 0) == 0 -> X <= 0 */
4300 /* MAX (X, 0) == 5 -> X == 5 */
4304 /* MAX (X, 0) == -1 -> false */
4308 /* MIN (X, 0) == 0 -> X >= 0 */
4312 /* MIN (X, 0) == 5 -> false */
4315 else
4316 /* MIN (X, 0) == -1 -> X == -1 */
4321 /* MAX (X, 0) > 0 -> X > 0
4322 MAX (X, 0) > 5 -> X > 5 */
4326 /* MAX (X, 0) > -1 -> true */
4330 /* MIN (X, 0) > 0 -> false
4331 MIN (X, 0) > 5 -> false */
4334 else
4335 /* MIN (X, 0) > -1 -> X > -1 */
4340 }
4341 }
4342 \f
4343 /* T is an integer expression that is being multiplied, divided, or taken a
4344 modulus (CODE says which and what kind of divide or modulus) by a
4345 constant C. See if we can eliminate that operation by folding it with
4346 other operations already in T. WIDE_TYPE, if non-null, is a type that
4347 should be used for the computation if wider than our type.
4349 For example, if we are dividing (X * 8) + (Y + 16) by 4, we can return
4350 (X * 2) + (Y + 4). We must, however, be assured that either the original
4351 expression would not overflow or that overflow is undefined for the type
4352 in the language in question.
4354 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4355 the machine has a multiply-accumulate insn or that this is part of an
4356 addressing calculation.
4358 If we return a non-null expression, it is an equivalent form of the
4359 original computation, but need not be in the original type. */
4361 static tree
4363 tree t;
4364 tree c;
4366 tree wide_type;
4367 {
4377 /* Don't deal with constants of zero here; they confuse the code below. */
4387 /* Note that we need not handle conditional operations here since fold
4388 already handles those cases. So just do arithmetic here. */
4390 {
4392 /* For a constant, we can always simplify if we are a multiply
4393 or (for divide and modulus) if it is a multiple of our constant. */
4400 /* Pass the constant down and see if we can make a simplification. If
4401 we can, replace this expression with the inner simplification for
4402 possible later conversion to our or some other type. */
4414 /* If widening the type changes the signedness, then we can't perform
4415 this optimization as that changes the result. */
4419 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4422 {
4428 }
4438 /* If this has not been evaluated and the operand has no side effects,
4439 we can see if we can do something inside it and make a new one.
4440 Note that this test is overly conservative since we can do this
4441 if the only reason it had side effects is that it was another
4442 similar SAVE_EXPR, but that isn't worth bothering with. */
4445 wide_type)))
4450 /* If the second operand is constant, this is a multiplication
4451 or floor division, by a power of two, so we can treat it that
4452 way unless the multiplier or divisor overflows. */
4454 /* const_binop may not detect overflow correctly,
4455 so check for it explicitly here. */
4469 /* See if we can eliminate the operation on both sides. If we can, we
4470 can return a new PLUS or MINUS. If we can't, the only remaining
4471 cases where we can do anything are if the second operand is a
4472 constant. */
4479 /* If this was a subtraction, negate OP1 and set it to be an addition.
4480 This simplifies the logic below. */
4487 /* If either OP1 or C are negative, this optimization is not safe for
4488 some of the division and remainder types while for others we need
4489 to change the code. */
4491 {
4502 }
4504 /* Now do the operation and verify it doesn't overflow. */
4509 /* If we have an unsigned type is not a sizetype, we cannot widen
4510 the operation since it will change the result if the original
4511 computation overflowed. */
4517 /* If we were able to eliminate our operation from the first side,
4518 apply our operation to the second side and reform the PLUS. */
4522 /* The last case is if we are a multiply. In that case, we can
4523 apply the distributive law to commute the multiply and addition
4524 if the multiplication of the constants doesn't overflow. */
4529 op1));
4534 /* We have a special case here if we are doing something like
4535 (C * 8) % 4 since we know that's zero. */
4542 /* ... fall through ... */
4546 /* If we can extract our operation from the LHS, do so and return a
4547 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4548 do something only if the second operand is a constant. */
4560 /* If these are the same operation types, we can associate them
4561 assuming no overflow. */
4568 /* If these operations "cancel" each other, we have the main
4569 optimizations of this pass, which occur when either constant is a
4570 multiple of the other, in which case we replace this with either an
4571 operation or CODE or TCODE.
4573 If we have an unsigned type that is not a sizetype, we canot do
4574 this since it will change the result if the original computation
4575 overflowed. */
4583 {
4594 }
4599 }
4602 }
4603 \f
4604 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4605 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4606 that we may sometimes modify the tree. */
4608 static tree
4610 tree t;
4611 tree s;
4612 {
4615 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4620 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4621 don't bother handling any other types. */
4623 {
4627 }
4632 {
4635 }
4638 }
4639 \f
4640 /* Return a node which has the indicated constant VALUE (either 0 or
4641 1), and is of the indicated TYPE. */
4643 static tree
4646 tree type;
4647 {
4652 integer_zero_node);
4653 else
4654 {
4659 }
4660 }
4662 /* Utility function for the following routine, to see how complex a nesting of
4663 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4664 we don't care (to avoid spending too much time on complex expressions.). */
4666 static int
4668 tree expr;
4670 {
4681 }
4682 \f
4683 /* Perform constant folding and related simplification of EXPR.
4684 The related simplifications include x*1 => x, x*0 => 0, etc.,
4685 and application of the associative law.
4686 NOP_EXPR conversions may be removed freely (as long as we
4687 are careful not to change the C type of the overall expression)
4688 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
4689 but we can constant-fold them if they have constant operands. */
4691 tree
4693 tree expr;
4694 {
4697 tree tem;
4703 /* WINS will be nonzero when the switch is done
4704 if all operands are constant. */
4707 /* Don't try to process an RTL_EXPR since its operands aren't trees.
4708 Likewise for a SAVE_EXPR that's already been evaluated. */
4712 /* Return right away if already constant. */
4714 {
4718 }
4720 #ifdef MAX_INTEGER_COMPUTATION_MODE
4722 #endif
4726 {
4727 tree subop;
4729 /* Special case for conversion ops that can have fixed point args. */
4732 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
4738 else
4742 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
4745 )
4746 /* Note that TREE_CONSTANT isn't enough:
4747 static var addresses are constant but we can't
4748 do arithmetic on them. */
4750 }
4752 {
4756 {
4758 tree subop;
4764 {
4765 /* Signedness matters here. Perhaps we can refine this
4766 later. */
4768 }
4769 else
4770 /* Strip any conversions that don't change the mode. */
4775 else
4779 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
4782 )
4783 /* Note that TREE_CONSTANT isn't enough:
4784 static var addresses are constant but we can't
4785 do arithmetic on them. */
4792 }
4793 }
4795 /* If this is a commutative operation, and ARG0 is a constant, move it
4796 to ARG1 to reduce the number of tests below. */
4801 {
4806 }
4808 /* Now WINS is set as described above,
4809 ARG0 is the first operand of EXPR,
4810 and ARG1 is the second operand (if it has more than one operand).
4812 First check for cases where an arithmetic operation is applied to a
4813 compound, conditional, or comparison operation. Push the arithmetic
4814 operation inside the compound or conditional to see if any folding
4815 can then be done. Convert comparison to conditional for this purpose.
4816 The also optimizes non-constant cases that used to be done in
4817 expand_expr.
4819 Before we do that, see if this is a BIT_AND_EXPR or a BIT_OR_EXPR,
4820 one of the operands is a comparison and the other is a comparison, a
4821 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
4822 code below would make the expression more complex. Change it to a
4823 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
4824 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
4836 {
4846 }
4849 {
4854 {
4859 /* If this was a conversion, and all we did was to move into
4860 inside the COND_EXPR, bring it back out. But leave it if
4861 it is a conversion from integer to integer and the
4862 result precision is no wider than a word since such a
4863 conversion is cheap and may be optimized away by combine,
4864 while it couldn't if it were outside the COND_EXPR. Then return
4865 so we don't get into an infinite recursion loop taking the
4866 conversion out and then back in. */
4876 && (INTEGRAL_TYPE_P
4887 }
4892 }
4895 {
4908 {
4913 {
4917 }
4918 else
4919 {
4924 }
4926 /* If ARG0 is complex we want to make sure we only evaluate
4927 it once. Though this is only required if it is volatile, it
4928 might be more efficient even if it is not. However, if we
4929 succeed in folding one part to a constant, we do not need
4930 to make this SAVE_EXPR. Since we do this optimization
4931 primarily to see if we do end up with constant and this
4932 SAVE_EXPR interferes with later optimizations, suppressing
4933 it when we can is important.
4935 If we are not in a function, we can't make a SAVE_EXPR, so don't
4936 try to do so. Don't try to see if the result is a constant
4937 if an arm is a COND_EXPR since we get exponential behavior
4938 in that case. */
4945 {
4955 }
4968 else
4970 }
4983 {
4988 {
4992 }
4993 else
4994 {
4999 }
5006 {
5016 }
5029 else
5031 }
5032 }
5043 {
5058 /* Other kinds of FIX are not handled properly by fold_convert. */
5063 /* Handle cases of two conversions in a row. */
5066 {
5086 /* In addition to the cases of two conversions in a row
5087 handled below, if we are converting something to its own
5088 type via an object of identical or wider precision, neither
5089 conversion is needed. */
5095 /* Likewise, if the intermediate and final types are either both
5096 float or both integer, we don't need the middle conversion if
5097 it is wider than the final type and doesn't change the signedness
5098 (for integers). Avoid this if the final type is a pointer
5099 since then we sometimes need the inner conversion. Likewise if
5100 the outer has a precision not equal to the size of its mode. */
5110 /* If we have a sign-extension of a zero-extended value, we can
5111 replace that by a single zero-extension. */
5117 /* Two conversions in a row are not needed unless:
5118 - some conversion is floating-point (overstrict for now), or
5119 - the intermediate type is narrower than both initial and
5120 final, or
5121 - the intermediate type and innermost type differ in signedness,
5122 and the outermost type is wider than the intermediate, or
5123 - the initial type is a pointer type and the precisions of the
5124 intermediate and final types differ, or
5125 - the final type is a pointer type and the precisions of the
5126 initial and intermediate types differ. */
5140 }
5144 /* Detect assigning a bitfield. */
5147 {
5148 /* Don't leave an assignment inside a conversion
5149 unless assigning a bitfield. */
5152 /* First do the assignment, then return converted constant. */
5156 }
5158 {
5161 }
5166 {
5169 /* Fold an expression like: "foo"[2] */
5173 {
5177 }
5178 }
5184 {
5188 }
5197 {
5199 {
5201 HOST_WIDE_INT high;
5212 }
5215 }
5219 /* Convert - (a - b) to (b - a) for non-floating-point. */
5229 {
5231 {
5234 {
5236 HOST_WIDE_INT high;
5247 }
5248 }
5250 {
5254 }
5255 }
5282 {
5289 }
5295 /* A + (-B) -> A - B */
5298 /* (-A) + B -> B - A */
5302 {
5306 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5307 with a constant, and the two constants have no bits in common,
5308 we should treat this as a BIT_IOR_EXPR since this may produce more
5309 simplifications. */
5317 {
5320 }
5322 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5323 (plus (plus (mult) (mult)) (foo)) so that we can
5324 take advantage of the factoring cases below. */
5329 {
5334 else
5345 parg1));
5350 parg0));
5351 }
5354 {
5358 /* (A * C) + (B * C) -> (A+B) * C.
5359 We are most concerned about the case where C is a constant,
5360 but other combinations show up during loop reduction. Since
5361 it is not difficult, try all four possibilities. */
5378 /* No identical multiplicands; see if we can find a common
5379 power-of-two factor in non-power-of-two multiplies. This
5380 can help in multi-dimensional array access. */
5385 {
5390 /* Move min of absolute values to int11. */
5393 {
5397 }
5400 {
5405 }
5406 }
5411 same));
5412 }
5413 }
5414 /* In IEEE floating point, x+0 may not equal x. */
5419 /* x+(-0) equals x, even for IEEE. */
5424 bit_rotate:
5425 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
5426 is a rotate of A by C1 bits. */
5427 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
5428 is a rotate of A by B bits. */
5429 {
5438 {
5457 {
5465 TYPE_PRECISION
5470 ? LROTATE_EXPR
5473 }
5475 {
5483 TYPE_PRECISION
5488 ? LROTATE_EXPR
5491 }
5492 }
5493 }
5496 associate:
5497 /* In most languages, can't associate operations on floats through
5498 parentheses. Rather than remember where the parentheses were, we
5499 don't associate floats at all. It shouldn't matter much. However,
5500 associating multiplications is only very slightly inaccurate, so do
5501 that if -ffast-math is specified. */
5506 {
5509 /* Split both trees into variables, constants, and literals. Then
5510 associate each group together, the constants with literals,
5511 then the result with variables. This increases the chances of
5512 literals being recombined later and of generating relocatable
5513 expressions for the sum of a constant and literal. */
5517 /* Only do something if we found more than two objects. Otherwise,
5518 nothing has changed and we risk infinite recursion. */
5521 {
5527 }
5528 }
5530 binary:
5531 #if defined (REAL_IS_NOT_DOUBLE) && ! defined (REAL_ARITHMETIC)
5538 {
5539 /* The return value should always have
5540 the same type as the original expression. */
5545 }
5549 /* A - (-B) -> A + B */
5552 /* (-A) - CST -> (-CST) - A for floating point (what about ints ?) */
5554 return
5561 {
5567 /* (A * C) - (B * C) -> (A-B) * C. Since we are most concerned
5568 about the case where C is a constant, just try one of the
5569 four possibilities. */
5579 }
5583 {
5584 /* Except with IEEE floating point, 0-x equals -x. */
5587 /* Except with IEEE floating point, x-0 equals x. */
5590 }
5592 /* Fold &x - &x. This can happen from &x.foo - &x.
5593 This is unsafe for certain floats even in non-IEEE formats.
5594 In IEEE, it is unsafe because it does wrong for NaNs.
5595 Also note that operand_equal_p is always false if an operand
5596 is volatile. */
5605 /* (-A) * (-B) -> A * B */
5611 {
5617 /* (a * (1 << b)) is (a << b) */
5632 }
5633 else
5634 {
5635 /* x*0 is 0, except for IEEE floating point. */
5640 /* In IEEE floating point, x*1 is not equivalent to x for snans.
5641 However, ANSI says we can drop signals,
5642 so we can do this anyway. */
5645 /* x*2 is x+x */
5648 {
5651 }
5652 }
5656 bit_ior:
5665 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
5667 This results in more efficient code for machines without a NAND
5668 instruction. Combine will canonicalize to the first form
5669 which will allow use of NAND instructions provided by the
5670 backend if they exist. */
5673 {
5678 }
5680 /* See if this can be simplified into a rotate first. If that
5681 is unsuccessful continue in the association code. */
5690 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
5691 with a constant, and the two constants have no bits in common,
5692 we should treat this as a BIT_IOR_EXPR since this may produce more
5693 simplifications. */
5701 {
5704 }
5706 /* See if this can be simplified into a rotate first. If that
5707 is unsuccessful continue in the association code. */
5711 bit_and:
5719 /* Simplify ((int)c & 0x377) into (int)c, if c is unsigned char. */
5722 {
5723 unsigned int prec
5730 }
5733 {
5734 unsigned int prec
5741 }
5743 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
5745 This results in more efficient code for machines without a NOR
5746 instruction. Combine will canonicalize to the first form
5747 which will allow use of NOR instructions provided by the
5748 backend if they exist. */
5751 {
5756 }
5766 {
5770 }
5774 /* In most cases, do nothing with a divide by zero. */
5775 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
5776 #ifndef REAL_INFINITY
5779 #endif
5782 /* (-A) / (-B) -> A / B */
5787 /* In IEEE floating point, x/1 is not equivalent to x for snans.
5788 However, ANSI says we can drop signals, so we can do this anyway. */
5792 /* If ARG1 is a constant, we can convert this to a multiply by the
5793 reciprocal. This does not have the same rounding properties,
5794 so only do this if -ffast-math. We can actually always safely
5795 do it if ARG1 is a power of two, but it's hard to tell if it is
5796 or not in a portable manner. */
5798 {
5803 /* Find the reciprocal if optimizing and the result is exact. */
5805 {
5806 REAL_VALUE_TYPE r;
5809 {
5812 }
5813 }
5814 }
5827 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
5828 operation, EXACT_DIV_EXPR.
5830 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
5831 At one time others generated faster code, it's not clear if they do
5832 after the last round to changes to the DIV code in expmed.c. */
5866 /* Since negative shift count is not well-defined,
5867 don't try to compute it in the compiler. */
5870 /* Rewrite an LROTATE_EXPR by a constant into an
5871 RROTATE_EXPR by a new constant. */
5873 {
5877 = const_binop
5884 }
5886 /* If we have a rotate of a bit operation with the rotate count and
5887 the second operand of the bit operation both constant,
5888 permute the two operations. */
5901 /* Two consecutive rotates adding up to the width of the mode can
5902 be ignored. */
5933 /* Note that the operand of this must be an int
5934 and its values must be 0 or 1.
5935 ("true" is a fixed value perhaps depending on the language,
5936 but we don't handle values other than 1 correctly yet.) */
5938 /* Avoid infinite recursion. */
5944 /* Note that the operands of this must be ints
5945 and their values must be 0 or 1.
5946 ("true" is a fixed value perhaps depending on the language.) */
5947 /* If first arg is constant zero, return it. */
5951 /* If either arg is constant true, drop it. */
5956 /* If second arg is constant zero, result is zero, but first arg
5957 must be evaluated. */
5960 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
5961 case will be handled here. */
5965 truth_andor:
5966 /* We only do these simplifications if we are optimizing. */
5970 /* Check for things like (A || B) && (A || C). We can convert this
5971 to A || (B && C). Note that either operator can be any of the four
5972 truth and/or operations and the transformation will still be
5973 valid. Also note that we only care about order for the
5974 ANDIF and ORIF operators. If B contains side effects, this
5975 might change the truth-value of A. */
5982 {
6002 /* This case if tricky because we must either have commutative
6003 operators or else A10 must not have side-effects. */
6009 a01));
6010 }
6012 /* See if we can build a range comparison. */
6016 /* Check for the possibility of merging component references. If our
6017 lhs is another similar operation, try to merge its rhs with our
6018 rhs. Then try to merge our lhs and rhs. */
6030 /* Note that the operands of this must be ints
6031 and their values must be 0 or true.
6032 ("true" is a fixed value perhaps depending on the language.) */
6033 /* If first arg is constant true, return it. */
6037 /* If either arg is constant zero, drop it. */
6042 /* If second arg is constant true, result is true, but we must
6043 evaluate first arg. */
6046 /* Likewise for first arg, but note this only occurs here for
6047 TRUTH_OR_EXPR. */
6053 /* If either arg is constant zero, drop it. */
6058 /* If either arg is constant true, this is a logical inversion. */
6072 {
6073 /* (-a) CMP (-b) -> b CMP a */
6078 /* (-a) CMP CST -> a swap(CMP) (-CST) */
6080 return
6086 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
6087 /* a CMP (-0) -> a CMP 0 */
6092 }
6095 /* If one arg is a constant integer, put it last. */
6098 {
6105 }
6107 /* Convert foo++ == CONST into ++foo == CONST + INCR.
6108 First, see if one arg is constant; find the constant arg
6109 and the other one. */
6110 {
6120 {
6121 /* This optimization is invalid for ordered comparisons
6122 if CONST+INCR overflows or if foo+incr might overflow.
6123 This optimization is invalid for floating point due to rounding.
6124 For pointer types we assume overflow doesn't happen. */
6128 {
6129 tree newconst
6134 /* If VAROP is a reference to a bitfield, we must mask
6135 the constant by the width of the field. */
6139 {
6140 int size
6142 (TREE_OPERAND
6146 tree folded_compare;
6148 /* First check whether the comparison would come out
6149 always the same. If we don't do that we would
6150 change the meaning with the masking. */
6154 else
6157 constop));
6172 mask)));
6173 }
6180 }
6181 }
6183 {
6187 {
6188 tree newconst
6196 {
6197 int size
6199 (TREE_OPERAND
6203 tree folded_compare;
6208 else
6211 constop));
6226 mask)));
6227 }
6234 }
6235 }
6236 }
6238 /* Change X >= CST to X > (CST - 1) if CST is positive. */
6242 {
6244 {
6259 }
6260 }
6262 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
6263 a MINUS_EXPR of a constant, we can convert it into a comparison with
6264 a revised constant as long as no overflow occurs. */
6276 /* Similarly for a NEGATE_EXPR. */
6285 /* If we have X - Y == 0, we can convert that to X == Y and similarly
6286 for !=. Don't do this for ordered comparisons due to overflow. */
6292 /* If we are widening one operand of an integer comparison,
6293 see if the other operand is similarly being widened. Perhaps we
6294 can do the comparison in the narrower type. */
6304 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
6305 constant, we can simplify it. */
6312 /* If we are comparing an ABS_EXPR with a constant, we can
6313 convert all the cases into explicit comparisons, but they may
6314 well not be faster than doing the ABS and one comparison.
6315 But ABS (X) <= C is a range comparison, which becomes a subtraction
6316 and a comparison, and is probably faster. */
6328 /* If this is an EQ or NE comparison with zero and ARG0 is
6329 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
6330 two operations, but the latter can be done in one less insn
6331 on machines that have only two-operand insns or on which a
6332 constant cannot be the first operand. */
6335 {
6338 return
6346 integer_one_node)),
6347 arg1));
6350 return
6358 integer_one_node)),
6359 arg1));
6360 }
6362 /* If this is an NE or EQ comparison of zero against the result of a
6363 signed MOD operation whose second operand is a power of 2, make
6364 the MOD operation unsigned since it is simpler and equivalent. */
6373 {
6380 }
6382 /* If this is an NE comparison of zero with an AND of one, remove the
6383 comparison since the AND will give the correct value. */
6389 /* If we have (A & C) == C where C is a power of 2, convert this into
6390 (A & C) != 0. Similarly for NE_EXPR. */
6398 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
6399 and similarly for >= into !=. */
6415 return
6422 /* Simplify comparison of something with itself. (For IEEE
6423 floating-point, we can only do some of these simplifications.) */
6425 {
6427 {
6438 /* For NE, we can only do this simplification if integer. */
6441 /* ... fall through ... */
6447 }
6448 }
6450 /* An unsigned comparison against 0 can be simplified. */
6455 {
6457 {
6469 arg0);
6473 arg0);
6476 }
6477 }
6479 /* Comparisons with the highest or lowest possible integer of
6480 the specified size will have known values and an unsigned
6481 <= 0x7fffffff can be simplified. */
6482 {
6490 {
6496 {
6500 arg0);
6508 arg0);
6515 }
6522 {
6526 arg0);
6534 arg0);
6541 }
6549 {
6553 arg0),
6555 integer_zero_node)));
6559 arg0),
6561 integer_zero_node)));
6565 }
6566 }
6567 }
6569 /* If we are comparing an expression that just has comparisons
6570 of two integer values, arithmetic expressions of those comparisons,
6571 and constants, we can simplify it. There are only three cases
6572 to check: the two values can either be equal, the first can be
6573 greater, or the second can be greater. Fold the expression for
6574 those three values. Since each value must be 0 or 1, we have
6575 eight possibilities, each of which corresponds to the constant 0
6576 or 1 or one of the six possible comparisons.
6578 This handles common cases like (a > b) == 0 but also handles
6579 expressions like ((x > y) - (y > x)) > 0, which supposedly
6580 occur in macroized code. */
6583 {
6588 /* Don't handle degenerate cases here; they should already
6589 have been handled anyway. */
6598 {
6602 /* We can't just pass T to eval_subst in case cval1 or cval2
6603 was the same as ARG1. */
6605 tree high_result
6608 arg1));
6609 tree equal_result
6612 arg1));
6613 tree low_result
6616 arg1));
6618 /* All three of these results should be 0 or 1. Confirm they
6619 are. Then use those values to select the proper code
6620 to use. */
6628 {
6629 /* Make a 3-bit mask with the high-order bit being the
6630 value for `>', the next for '=', and the low for '<'. */
6634 {
6636 /* Always false. */
6657 /* Always true. */
6659 }
6664 else
6666 }
6667 }
6668 }
6670 /* If this is a comparison of a field, we may be able to simplify it. */
6674 /* Handle the constant case even without -O
6675 to make sure the warnings are given. */
6677 {
6680 }
6682 /* If this is a comparison of complex values and either or both sides
6683 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
6684 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
6685 This may prevent needless evaluations. */
6692 {
6705 type,
6708 }
6710 /* From here on, the only cases we handle are when the result is
6711 known to be a constant.
6713 To compute GT, swap the arguments and do LT.
6714 To compute GE, do LT and invert the result.
6715 To compute LE, swap the arguments, do LT and invert the result.
6716 To compute NE, do EQ and invert the result.
6718 Therefore, the code below must handle only EQ and LT. */
6721 {
6724 }
6726 /* Note that it is safe to invert for real values here because we
6727 will check below in the one case that it matters. */
6732 {
6735 }
6737 /* Compute a result for LT or EQ if args permit;
6738 otherwise return T. */
6740 {
6743 else
6748 }
6751 /* Assume a nonexplicit constant cannot equal an explicit one,
6752 since such code would be undefined anyway.
6753 Exception: on sysvr4, using #pragma weak,
6754 a label can come out as 0. */
6761 #endif
6762 /* Two real constants can be compared explicitly. */
6764 {
6765 /* If either operand is a NaN, the result is false with two
6766 exceptions: First, an NE_EXPR is true on NaNs, but that case
6767 is already handled correctly since we will be inverting the
6768 result for NE_EXPR. Second, if we had inverted a LE_EXPR
6769 or a GE_EXPR into a LT_EXPR, we must return true so that it
6770 will be inverted into false. */
6780 else
6784 }
6798 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
6799 so all simple results must be passed through pedantic_non_lvalue. */
6801 return pedantic_non_lvalue
6806 /* If the second operand is zero, invert the comparison and swap
6807 the second and third operands. Likewise if the second operand
6808 is constant and the third is not or if the third operand is
6809 equivalent to the first operand of the comparison. */
6817 {
6818 /* See if this can be inverted. If it can't, possibly because
6819 it was a floating-point inequality comparison, don't do
6820 anything. */
6824 {
6828 /* arg1 should be the first argument of the new T. */
6831 }
6832 }
6834 /* If we have A op B ? A : C, we may be able to convert this to a
6835 simpler expression, depending on the operation and the values
6836 of B and C. IEEE floating point prevents this though,
6837 because A or B might be -0.0 or a NaN. */
6845 {
6851 /* If we have A op 0 ? A : -A, this is A, -A, abs (A), or abs (-A),
6852 depending on the comparison operation. */
6859 {
6861 return
6869 return pedantic_non_lvalue
6876 return pedantic_non_lvalue
6880 arg1)))));
6883 }
6885 /* If this is A != 0 ? A : 0, this is simply A. For ==, it is
6886 always zero. */
6889 {
6894 }
6896 /* If this is A op B ? A : B, this is either A, B, min (A, B),
6897 or max (A, B), depending on the operation. */
6901 {
6906 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
6911 {
6918 /* In C++ a ?: expression can be an lvalue, so put the
6919 operand which will be used if they are equal first
6920 so that we can convert this back to the
6921 corresponding COND_EXPR. */
6922 return pedantic_non_lvalue
6931 return pedantic_non_lvalue
6940 }
6941 }
6943 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
6944 we might still be able to simplify this. For example,
6945 if C1 is one less or one more than C2, this might have started
6946 out as a MIN or MAX and been transformed by this function.
6947 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
6953 {
6955 /* We can replace A with C1 in this case. */
6962 /* If C1 is C2 + 1, this is min(A, C2). */
6967 return pedantic_non_lvalue
6972 /* If C1 is C2 - 1, this is min(A, C2). */
6977 return pedantic_non_lvalue
6982 /* If C1 is C2 - 1, this is max(A, C2). */
6987 return pedantic_non_lvalue
6992 /* If C1 is C2 + 1, this is max(A, C2). */
6997 return pedantic_non_lvalue
7004 }
7005 }
7007 /* If the second operand is simpler than the third, swap them
7008 since that produces better jump optimization results. */
7014 {
7015 /* See if this can be inverted. If it can't, possibly because
7016 it was a floating-point inequality comparison, don't do
7017 anything. */
7021 {
7025 /* arg1 should be the first argument of the new T. */
7028 }
7029 }
7031 /* Convert A ? 1 : 0 to simply A. */
7034 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
7035 call to fold will try to move the conversion inside
7036 a COND, which will recurse. In that case, the COND_EXPR
7037 is probably the best choice, so leave it alone. */
7041 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
7042 operation is simply A & 2. */
7056 /* When pedantic, a compound expression can be neither an lvalue
7057 nor an integer constant expression. */
7060 /* Don't let (0, 0) be null pointer constant. */
7102 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
7103 appropriate. */
7108 {
7112 tree arg01;
7123 {
7137 arg01));
7138 }
7141 }
7146 }
7148 /* Determine if first argument is a multiple of second argument. Return 0 if
7149 it is not, or we cannot easily determined it to be.
7151 An example of the sort of thing we care about (at this point; this routine
7152 could surely be made more general, and expanded to do what the *_DIV_EXPR's
7153 fold cases do now) is discovering that
7155 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7157 is a multiple of
7159 SAVE_EXPR (J * 8)
7161 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
7163 This code also handles discovering that
7165 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7167 is a multiple of 8 so we don't have to worry about dealing with a
7168 possible remainder.
7170 Note that we *look* inside a SAVE_EXPR only to determine how it was
7171 calculated; it is not safe for fold to do much of anything else with the
7172 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
7173 at run time. For example, the latter example above *cannot* be implemented
7174 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
7175 evaluation time of the original SAVE_EXPR is not necessarily the same at
7176 the time the new expression is evaluated. The only optimization of this
7177 sort that would be valid is changing
7179 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
7181 divided by 8 to
7183 SAVE_EXPR (I) * SAVE_EXPR (J)
7185 (where the same SAVE_EXPR (J) is used in the original and the
7186 transformed version). */
7188 static int
7190 tree type;
7191 tree top;
7192 tree bottom;
7193 {
7201 {
7212 /* Can't handle conversions from non-integral or wider integral type. */
7218 /* .. fall through ... */
7233 }
7234 }