| blob | 7cefaeaef0e756d50dad8337df76905df9b889f1 |
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, 2001 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
10 version.
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
20 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. */
30 /* The entry points in this file are fold, size_int_wide, size_binop
31 and force_fit_type.
33 fold takes a tree as argument and returns a simplified tree.
35 size_binop takes a tree code for an arithmetic operation
36 and two operands that are trees, and produces a tree for the
37 result, assuming the type comes from `sizetype'.
39 size_int takes an integer value, and creates a tree constant
40 with type from `sizetype'.
42 force_fit_type takes a constant and prior overflow indicator, and
43 forces the value to fit the type. It returns an overflow indicator. */
57 HOST_WIDE_INT));
60 HOST_WIDE_INT *));
61 #ifndef REAL_ARITHMETIC
63 #endif
86 HOST_WIDE_INT *,
106 static tree fold_binary_op_with_conditional_arg
109 #ifndef BRANCH_COST
110 #define BRANCH_COST 1
111 #endif
113 #if defined(HOST_EBCDIC)
114 /* bit 8 is significant in EBCDIC */
115 #define CHARMASK 0xff
116 #else
117 #define CHARMASK 0x7f
118 #endif
120 /* We know that A1 + B1 = SUM1, using 2's complement arithmetic and ignoring
121 overflow. Suppose A, B and SUM have the same respective signs as A1, B1,
122 and SUM1. Then this yields nonzero if overflow occurred during the
123 addition.
125 Overflow occurs if A and B have the same sign, but A and SUM differ in
126 sign. Use `^' to test whether signs differ, and `< 0' to isolate the
127 sign. */
128 #define OVERFLOW_SUM_SIGN(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)
129 \f
130 /* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
131 We do that by representing the two-word integer in 4 words, with only
132 HOST_BITS_PER_WIDE_INT / 2 bits stored in each word, as a positive
133 number. The value of the word is LOWPART + HIGHPART * BASE. */
135 #define LOWPART(x) \
136 ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2)) - 1))
137 #define HIGHPART(x) \
138 ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT / 2)
139 #define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT / 2)
141 /* Unpack a two-word integer into 4 words.
142 LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
143 WORDS points to the array of HOST_WIDE_INTs. */
145 static void
149 HOST_WIDE_INT hi;
150 {
155 }
157 /* Pack an array of 4 words into a two-word integer.
158 WORDS points to the array of words.
159 The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces. */
161 static void
166 {
169 }
170 \f
171 /* Make the integer constant T valid for its type by setting to 0 or 1 all
172 the bits in the constant that don't belong in the type.
174 Return 1 if a signed overflow occurs, 0 otherwise. If OVERFLOW is
175 nonzero, a signed overflow has already occurred in calculating T, so
176 propagate it.
178 Make the real constant T valid for its type by calling CHECK_FLOAT_VALUE,
179 if it exists. */
181 int
183 tree t;
185 {
187 HOST_WIDE_INT high;
191 {
192 #ifdef CHECK_FLOAT_VALUE
194 overflow);
195 #endif
197 }
207 else
210 /* First clear all bits that are beyond the type's precision. */
213 ;
217 else
218 {
222 }
224 /* Unsigned types do not suffer sign extension or overflow unless they
225 are a sizetype. */
231 /* If the value's sign bit is set, extend the sign. */
239 {
240 /* Value is negative:
241 set to 1 all the bits that are outside this type's precision. */
245 else
246 {
250 }
251 }
253 /* Return nonzero if signed overflow occurred. */
254 return
257 }
258 \f
259 /* Add two doubleword integers with doubleword result.
260 Each argument is given as two `HOST_WIDE_INT' pieces.
261 One argument is L1 and H1; the other, L2 and H2.
262 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
264 int
270 {
272 HOST_WIDE_INT h;
280 }
282 /* Negate a doubleword integer with doubleword result.
283 Return nonzero if the operation overflows, assuming it's signed.
284 The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
285 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
287 int
290 HOST_WIDE_INT h1;
293 {
295 {
299 }
300 else
301 {
305 }
306 }
307 \f
308 /* Multiply two doubleword integers with doubleword result.
309 Return nonzero if the operation overflows, assuming it's signed.
310 Each argument is given as two `HOST_WIDE_INT' pieces.
311 One argument is L1 and H1; the other, L2 and H2.
312 The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV. */
314 int
320 {
335 {
338 {
340 /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000. */
342 /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF. */
346 }
348 }
352 /* Check for overflow by calculating the top half of the answer in full;
353 it should agree with the low half's sign bit. */
356 {
359 }
361 {
364 }
366 }
367 \f
368 /* Shift the doubleword integer in L1, H1 left by COUNT places
369 keeping only PREC bits of result.
370 Shift right if COUNT is negative.
371 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
372 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
374 void
382 {
384 {
387 }
389 #ifdef SHIFT_COUNT_TRUNCATED
392 #endif
395 {
396 /* Shifting by the host word size is undefined according to the
397 ANSI standard, so we must handle this as a special case. */
400 }
402 {
405 }
406 else
407 {
411 }
412 }
414 /* Shift the doubleword integer in L1, H1 right by COUNT places
415 keeping only PREC bits of result. COUNT must be positive.
416 ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
417 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
419 void
427 {
430 signmask = (arith
434 #ifdef SHIFT_COUNT_TRUNCATED
437 #endif
440 {
441 /* Shifting by the host word size is undefined according to the
442 ANSI standard, so we must handle this as a special case. */
445 }
447 {
451 }
452 else
453 {
458 }
459 }
460 \f
461 /* Rotate the doubleword integer in L1, H1 left by COUNT places
462 keeping only PREC bits of result.
463 Rotate right if COUNT is negative.
464 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
466 void
473 {
485 }
487 /* Rotate the doubleword integer in L1, H1 left by COUNT places
488 keeping only PREC bits of result. COUNT must be positive.
489 Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV. */
491 void
498 {
510 }
511 \f
512 /* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
513 for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
514 CODE is a tree code for a kind of division, one of
515 TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
516 or EXACT_DIV_EXPR
517 It controls how the quotient is rounded to a integer.
518 Return nonzero if the operation overflows.
519 UNS nonzero says do unsigned division. */
521 int
528 HOST_WIDE_INT hnum_orig;
530 HOST_WIDE_INT hden_orig;
533 {
549 /* calculate quotient sign and convert operands to unsigned. */
551 {
553 {
555 /* (minimum integer) / (-1) is the only overflow case. */
559 }
561 {
564 }
565 }
570 /* This unsigned division rounds toward zero. */
573 }
577 /* hden != 0 already checked. */
582 }
592 /* Special code for when the divisor < BASE. */
594 {
595 /* hnum != 0 already checked. */
597 {
601 }
602 }
603 else
604 {
605 /* Full double precision division,
606 with thanks to Don Knuth's "Seminumerical Algorithms". */
610 /* Find the highest non-zero divisor digit. */
613 {
616 }
618 /* Insure that the first digit of the divisor is at least BASE/2.
619 This is required by the quotient digit estimation algorithm. */
626 {
630 }
635 {
640 }
641 }
645 /* Main loop */
647 {
648 /* Guess the next quotient digit, quo_est, by dividing the first
649 two remaining dividend digits by the high order quotient digit.
650 quo_est is never low and is at most 2 high. */
657 else
660 /* Refine quo_est so it's usually correct, and at most one high. */
665 quo_est--;
667 /* Try QUO_EST as the quotient digit, by multiplying the
668 divisor by QUO_EST and subtracting from the remaining dividend.
669 Keep in mind that QUO_EST is the I - 1st digit. */
673 {
679 }
681 /* If quo_est was high by one, then num[i] went negative and
682 we need to correct things. */
684 {
685 quo_est--;
688 {
692 }
695 }
697 /* Store the quotient digit. */
699 }
700 }
704 finish_up:
705 /* if result is negative, make it so. */
709 /* compute trial remainder: rem = num - (quo * den) */
715 {
724 {
725 /* quo = quo - 1; */
728 }
729 else
736 {
739 }
740 else
746 {
752 /* Get absolute values */
758 /* If (2 * abs (lrem) >= abs (lden)) */
767 {
769 /* quo = quo - 1; */
772 else
773 /* quo = quo + 1; */
776 }
777 else
779 }
784 }
786 /* compute true remainder: rem = num - (quo * den) */
791 }
792 \f
793 #ifndef REAL_ARITHMETIC
794 /* Effectively truncate a real value to represent the nearest possible value
795 in a narrower mode. The result is actually represented in the same data
796 type as the argument, but its value is usually different.
798 A trap may occur during the FP operations and it is the responsibility
799 of the calling function to have a handler established. */
801 REAL_VALUE_TYPE
804 REAL_VALUE_TYPE arg;
805 {
807 }
809 #if TARGET_FLOAT_FORMAT == IEEE_FLOAT_FORMAT
811 /* Check for infinity in an IEEE double precision number. */
813 int
815 REAL_VALUE_TYPE x;
816 {
817 /* The IEEE 64-bit double format. */
819 REAL_VALUE_TYPE d;
836 {
841 }
842 else
843 {
848 }
849 }
851 /* Check whether an IEEE double precision number is a NaN. */
853 int
855 REAL_VALUE_TYPE x;
856 {
857 /* The IEEE 64-bit double format. */
859 REAL_VALUE_TYPE d;
876 {
881 }
882 else
883 {
888 }
889 }
891 /* Check for a negative IEEE double precision number. */
893 int
895 REAL_VALUE_TYPE x;
896 {
897 /* The IEEE 64-bit double format. */
899 REAL_VALUE_TYPE d;
916 {
919 }
920 else
921 {
924 }
925 }
928 /* Let's assume other float formats don't have infinity.
929 (This can be overridden by redefining REAL_VALUE_ISINF.) */
931 int
933 REAL_VALUE_TYPE x ATTRIBUTE_UNUSED;
934 {
936 }
938 /* Let's assume other float formats don't have NaNs.
939 (This can be overridden by redefining REAL_VALUE_ISNAN.) */
941 int
943 REAL_VALUE_TYPE x ATTRIBUTE_UNUSED;
944 {
946 }
948 /* Let's assume other float formats don't have minus zero.
949 (This can be overridden by redefining REAL_VALUE_NEGATIVE.) */
951 int
953 REAL_VALUE_TYPE x;
954 {
956 }
959 /* Try to change R into its exact multiplicative inverse in machine mode
960 MODE. Return nonzero function value if successful. */
961 struct exact_real_inverse_args
962 {
966 };
968 static void
970 PTR p;
971 {
978 union
979 {
982 }
984 #ifdef CHECK_FLOAT_VALUE
986 #endif
988 /* Set array index to the less significant bits in the unions, depending
989 on the endian-ness of the host doubles. */
990 #if HOST_FLOAT_FORMAT == VAX_FLOAT_FORMAT \
991 || HOST_FLOAT_FORMAT == IBM_FLOAT_FORMAT
992 # define K 2
993 #else
994 # define K (2 * HOST_FLOAT_WORDS_BIG_ENDIAN)
995 #endif
997 /* Domain check the argument. */
1002 #ifdef REAL_INFINITY
1005 #endif
1007 /* Compute the reciprocal and check for numerical exactness.
1008 It is unnecessary to check all the significand bits to determine
1009 whether X is a power of 2. If X is not, then it is impossible for
1010 the bottom half significand of both X and 1/X to be all zero bits.
1011 Hence we ignore the data structure of the top half and examine only
1012 the low order bits of the two significands. */
1017 /* Truncate to the required mode and range-check the result. */
1019 #ifdef CHECK_FLOAT_VALUE
1023 #endif
1025 /* Fail if truncation changed the value. */
1029 #ifdef REAL_INFINITY
1032 #endif
1034 /* Output the reciprocal and return success flag. */
1039 fail:
1043 #undef K
1044 }
1047 int
1051 {
1054 /* Disable if insufficient information on the data structure. */
1055 #if HOST_FLOAT_FORMAT == UNKNOWN_FLOAT_FORMAT
1057 #endif
1059 /* Usually disable if bounds checks are not reliable. */
1069 }
1071 /* Convert C99 hexadecimal floating point string constant S. Return
1072 real value type in mode MODE. This function uses the host computer's
1073 floating point arithmetic when there is no REAL_ARITHMETIC. */
1075 REAL_VALUE_TYPE
1079 {
1080 REAL_VALUE_TYPE ip;
1099 /* Sign, if any, comes first. */
1102 {
1105 }
1107 /* The string is supposed to start with 0x or 0X . */
1109 {
1113 else
1115 }
1116 else
1126 {
1129 {
1135 else
1139 {
1145 }
1146 else
1147 {
1148 /* Record nonzero lost bits. */
1152 }
1154 }
1156 {
1159 }
1162 {
1165 /* Sign of exponent. */
1167 {
1170 }
1172 /* Value of exponent.
1173 The exponent field is a decimal integer. */
1175 {
1178 }
1181 /* F suffix is ambiguous in the significand part
1182 so it must appear after the decimal exponent field. */
1184 {
1188 }
1189 }
1192 {
1195 }
1196 else
1198 }
1200 /* Abort if last character read was not legitimate. */
1205 /* There must be either one decimal point or one p. */
1213 /* Normalize. */
1216 {
1220 }
1222 /* Leave a high guard bit for carry-out. */
1224 {
1229 }
1232 {
1236 }
1239 {
1243 }
1246 {
1247 /* Keep 24 bits precision, bits 0x7fffff80.
1248 Rounding bit is 0x40. */
1252 {
1255 }
1257 }
1258 else
1259 {
1260 /* We need real.c to do long double formats, so here default
1261 to double precision. */
1262 #if HOST_FLOAT_FORMAT == IEEE_FLOAT_FORMAT
1263 /* IEEE double.
1264 Keep 53 bits precision, bits 0x7fffffff fffffc00.
1265 Rounding bit is low word 0x200. */
1268 {
1270 {
1274 }
1275 }
1277 #else
1278 /* Assume it's a VAX with 56-bit significand,
1279 bits 0x7fffffff ffffff80. */
1282 {
1284 {
1288 }
1289 }
1291 #endif
1292 }
1296 /* Apply shifts and exponent value as power of 2. */
1302 }
1305 \f
1306 /* Given T, an expression, return the negation of T. Allow for T to be
1307 null, in which case return null. */
1309 static tree
1311 tree t;
1312 {
1313 tree type;
1314 tree tem;
1323 {
1336 /* - (A - B) -> B - A */
1346 }
1349 }
1350 \f
1351 /* Split a tree IN into a constant, literal and variable parts that could be
1352 combined with CODE to make IN. "constant" means an expression with
1353 TREE_CONSTANT but that isn't an actual constant. CODE must be a
1354 commutative arithmetic operation. Store the constant part into *CONP,
1355 the literal in &LITP and return the variable part. If a part isn't
1356 present, set it to null. If the tree does not decompose in this way,
1357 return the entire tree as the variable part and the other parts as null.
1359 If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR. In that
1360 case, we negate an operand that was subtracted. If NEGATE_P is true, we
1361 are negating all of IN.
1363 If IN is itself a literal or constant, return it as appropriate.
1365 Note that we do not guarantee that any of the three values will be the
1366 same type as IN, but they will have the same signedness and mode. */
1368 static tree
1370 tree in;
1374 {
1380 /* Strip any conversions that don't change the machine mode or signedness. */
1387 /* We can associate addition and subtraction together (even
1388 though the C standard doesn't say so) for integers because
1389 the value is not affected. For reals, the value might be
1390 affected, so we can't. */
1393 {
1399 /* First see if either of the operands is a literal, then a constant. */
1410 /* If we haven't dealt with either operand, this is not a case we can
1411 decompose. Otherwise, VAR is either of the ones remaining, if any. */
1416 else
1419 /* Now do any needed negations. */
1423 }
1426 else
1430 {
1434 }
1437 }
1439 /* Re-associate trees split by the above function. T1 and T2 are either
1440 expressions to associate or null. Return the new expression, if any. If
1441 we build an operation, do it in TYPE and with CODE, except if CODE is a
1442 MINUS_EXPR, in which case we use PLUS_EXPR since split_tree will already
1443 have taken care of the negations. */
1445 static tree
1449 tree type;
1450 {
1459 /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
1460 try to fold this since we will have infinite recursion. But do
1461 deal with any NEGATE_EXPRs. */
1464 {
1471 else
1473 }
1476 }
1477 \f
1478 /* Combine two integer constants ARG1 and ARG2 under operation CODE
1479 to produce a new constant.
1481 If NOTRUNC is nonzero, do not truncate the result to fit the data type.
1482 If FORSIZE is nonzero, compute overflow for unsigned types. */
1484 static tree
1489 {
1493 HOST_WIDE_INT hi;
1495 HOST_WIDE_INT garbageh;
1507 {
1527 /* It's unclear from the C standard whether shifts can overflow.
1528 The following code ignores overflow; perhaps a C standard
1529 interpretation ruling is needed. */
1559 /* This is a shortcut for a common special case. */
1564 {
1570 }
1572 /* ... fall through ... */
1576 {
1579 }
1582 {
1585 }
1593 /* This is a shortcut for a common special case. */
1598 {
1603 }
1605 /* ... fall through ... */
1621 else
1627 else
1633 }
1638 else
1639 {
1642 }
1650 /* If we're doing a size calculation, unsigned arithmetic does overflow.
1651 So check if force_fit_type truncated the value. */
1662 }
1664 /* Define input and output argument for const_binop_1. */
1665 struct cb_args
1666 {
1671 };
1673 /* Do the real arithmetic for const_binop while protected by a
1674 float overflow handler. */
1676 static void
1678 PTR data;
1679 {
1681 REAL_VALUE_TYPE value;
1683 #ifdef REAL_ARITHMETIC
1685 #else
1687 {
1701 #ifndef REAL_INFINITY
1704 #endif
1719 }
1722 args->t
1725 }
1727 /* Combine two constants ARG1 and ARG2 under operation CODE to produce a new
1728 constant. We assume ARG1 and ARG2 have the same data type, or at least
1729 are the same kind of constant and the same machine mode.
1731 If NOTRUNC is nonzero, do not truncate the result to fit the data type. */
1733 static tree
1738 {
1745 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
1747 {
1748 REAL_VALUE_TYPE d1;
1749 REAL_VALUE_TYPE d2;
1751 tree t;
1757 /* If either operand is a NaN, just return it. Otherwise, set up
1758 for floating-point trap; we return an overflow. */
1764 /* Setup input for const_binop_1() */
1771 /* Receive output from const_binop_1. */
1773 else
1774 {
1775 /* We got an exception from const_binop_1. */
1778 }
1788 }
1791 {
1800 {
1820 notrunc),
1826 notrunc));
1830 {
1831 register tree magsquared
1835 notrunc);
1838 const_binop
1843 notrunc),
1845 notrunc),
1846 notrunc),
1848 const_binop
1853 notrunc),
1855 notrunc),
1856 notrunc),
1858 }
1863 }
1865 }
1867 }
1868 \f
1869 /* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
1870 bits are given by NUMBER and of the sizetype represented by KIND. */
1872 tree
1874 HOST_WIDE_INT number;
1876 {
1878 }
1880 /* Likewise, but the desired type is specified explicitly. */
1882 tree
1884 HOST_WIDE_INT number;
1885 tree type;
1886 {
1887 /* Type-size nodes already made for small sizes. */
1890 tree t;
1893 {
1897 }
1899 /* If this is a positive number that fits in the table we use to hold
1900 cached entries, see if it is already in the table and put it there
1901 if not. */
1903 {
1915 }
1921 }
1923 /* Combine operands OP1 and OP2 with arithmetic operation CODE. CODE
1924 is a tree code. The type of the result is taken from the operands.
1925 Both must be the same type integer type and it must be a size type.
1926 If the operands are constant, so is the result. */
1928 tree
1932 {
1939 /* Handle the special case of two integer constants faster. */
1941 {
1942 /* And some specific cases even faster than that. */
1951 /* Handle general case of two integer constants. */
1953 }
1959 }
1961 /* Given two values, either both of sizetype or both of bitsizetype,
1962 compute the difference between the two values. Return the value
1963 in signed type corresponding to the type of the operands. */
1965 tree
1968 {
1970 tree ctype;
1976 /* If the type is already signed, just do the simple thing. */
1983 /* If either operand is not a constant, do the conversions to the signed
1984 type and subtract. The hardware will do the right thing with any
1985 overflow in the subtraction. */
1990 /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
1991 Otherwise, subtract the other way, convert to CTYPE (we know that can't
1992 overflow) and negate (which can't either). Special-case a result
1993 of zero while we're here. */
1998 else
2001 }
2002 \f
2003 /* This structure is used to communicate arguments to fold_convert_1. */
2004 struct fc_args
2005 {
2009 };
2011 /* Function to convert floating-point constants, protected by floating
2012 point exception handler. */
2014 static void
2016 PTR data;
2017 {
2023 }
2025 /* Given T, a tree representing type conversion of ARG1, a constant,
2026 return a constant tree representing the result of conversion. */
2028 static tree
2032 {
2037 {
2039 {
2040 /* If we would build a constant wider than GCC supports,
2041 leave the conversion unfolded. */
2045 /* If we are trying to make a sizetype for a small integer, use
2046 size_int to pick up cached types to reduce duplicate nodes. */
2052 /* Given an integer constant, make new constant with new type,
2053 appropriately sign-extended or truncated. */
2057 /* Indicate an overflow if (1) ARG1 already overflowed,
2058 or (2) force_fit_type indicates an overflow.
2059 Tell force_fit_type that an overflow has already occurred
2060 if ARG1 is a too-large unsigned value and T is signed.
2061 But don't indicate an overflow if converting a pointer. */
2071 }
2072 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
2074 {
2075 /* Don't initialize these, use assignments.
2076 Initialized local aggregates don't work on old compilers. */
2077 REAL_VALUE_TYPE x;
2078 REAL_VALUE_TYPE l;
2079 REAL_VALUE_TYPE u;
2090 /* See if X will be in range after truncation towards 0.
2091 To compensate for truncation, move the bounds away from 0,
2092 but reject if X exactly equals the adjusted bounds. */
2093 #ifdef REAL_ARITHMETIC
2097 #else
2098 l--;
2100 u++;
2101 #endif
2102 /* If X is a NaN, use zero instead and show we have an overflow.
2103 Otherwise, range check. */
2107 && !no_upper_bound
2111 #ifndef REAL_ARITHMETIC
2112 {
2114 HOST_WIDE_INT half_word
2123 {
2126 }
2127 else
2132 }
2133 #else
2134 {
2138 }
2139 #endif
2145 }
2148 }
2150 {
2151 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
2156 {
2160 {
2164 }
2166 /* Setup input for fold_convert_1() */
2171 {
2172 /* Receive output from fold_convert_1() */
2174 }
2175 else
2176 {
2177 /* We got an exception from fold_convert_1() */
2180 }
2187 }
2188 }
2191 }
2192 \f
2193 /* Return an expr equal to X but certainly not valid as an lvalue. */
2195 tree
2197 tree x;
2198 {
2199 tree result;
2201 /* These things are certainly not lvalues. */
2212 }
2214 /* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
2215 Zero means allow extended lvalues. */
2219 /* When pedantic, return an expr equal to X but certainly not valid as a
2220 pedantic lvalue. Otherwise, return X. */
2222 tree
2224 tree x;
2225 {
2228 else
2230 }
2231 \f
2232 /* Given a tree comparison code, return the code that is the logical inverse
2233 of the given code. It is not safe to do this for floating-point
2234 comparisons, except for NE_EXPR and EQ_EXPR. */
2236 static enum tree_code
2239 {
2241 {
2256 }
2257 }
2259 /* Similar, but return the comparison that results if the operands are
2260 swapped. This is safe for floating-point. */
2262 static enum tree_code
2265 {
2267 {
2281 }
2282 }
2284 /* Return nonzero if CODE is a tree code that represents a truth value. */
2286 static int
2289 {
2294 }
2295 \f
2296 /* Return nonzero if two operands are necessarily equal.
2297 If ONLY_CONST is non-zero, only return non-zero for constants.
2298 This function tests whether the operands are indistinguishable;
2299 it does not test whether they are equal using C's == operation.
2300 The distinction is important for IEEE floating point, because
2301 (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
2302 (2) two NaNs may be indistinguishable, but NaN!=NaN. */
2304 int
2308 {
2309 /* If both types don't have the same signedness, then we can't consider
2310 them equal. We must check this before the STRIP_NOPS calls
2311 because they may change the signedness of the arguments. */
2319 /* This is needed for conversions and for COMPONENT_REF.
2320 Might as well play it safe and always test this. */
2326 /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
2327 We don't care about side effects in that case because the SAVE_EXPR
2328 takes care of that for us. In all other cases, two expressions are
2329 equal if they have no side effects. If we have two identical
2330 expressions with side effects that should be treated the same due
2331 to the only side effects being identical SAVE_EXPR's, that will
2332 be detected in the recursive calls below. */
2338 /* Next handle constant cases, those for which we can return 1 even
2339 if ONLY_CONST is set. */
2342 {
2356 only_const)
2358 only_const));
2371 }
2377 {
2379 /* Two conversions are equal only if signedness and modes match. */
2395 /* For commutative ops, allow the other order. */
2408 /* If either of the pointer (or reference) expressions we are dereferencing
2409 contain a side effect, these cannot be equal. */
2415 {
2437 }
2446 }
2447 }
2448 \f
2449 /* Similar to operand_equal_p, but see if ARG0 might have been made by
2450 shorten_compare from ARG1 when ARG1 was being compared with OTHER.
2452 When in doubt, return 0. */
2454 static int
2457 tree other;
2458 {
2470 /* Discard any conversions that don't change the modes of ARG0 and ARG1
2471 and see if the inner values are the same. This removes any
2472 signedness comparison, which doesn't matter here. */
2479 /* Duplicate what shorten_compare does to ARG1 and see if that gives the
2480 actual comparison operand, ARG0.
2482 First throw away any conversions to wider types
2483 already present in the operands. */
2492 {
2495 /* Make sure shorter operand is extended the right way
2496 to match the longer operand. */
2499 primarg1);
2503 }
2506 }
2507 \f
2508 /* See if ARG is an expression that is either a comparison or is performing
2509 arithmetic on comparisons. The comparisons must only be comparing
2510 two different values, which will be stored in *CVAL1 and *CVAL2; if
2511 they are non-zero it means that some operands have already been found.
2512 No variables may be used anywhere else in the expression except in the
2513 comparisons. If SAVE_P is true it means we removed a SAVE_EXPR around
2514 the expression and save_expr needs to be called with CVAL1 and CVAL2.
2516 If this is true, return 1. Otherwise, return zero. */
2518 static int
2520 tree arg;
2523 {
2527 /* We can handle some of the 'e' cases here. */
2537 {
2538 /* If we've already found a CVAL1 or CVAL2, this expression is
2539 two complex to handle. */
2545 }
2548 {
2571 /* First see if we can handle the first operand, then the second. For
2572 the second operand, we know *CVAL1 can't be zero. It must be that
2573 one side of the comparison is each of the values; test for the
2574 case where this isn't true by failing if the two operands
2575 are the same. */
2584 ;
2588 ;
2589 else
2593 ;
2597 ;
2598 else
2605 }
2606 }
2607 \f
2608 /* ARG is a tree that is known to contain just arithmetic operations and
2609 comparisons. Evaluate the operations in the tree substituting NEW0 for
2610 any occurrence of OLD0 as an operand of a comparison and likewise for
2611 NEW1 and OLD1. */
2613 static tree
2615 tree arg;
2617 {
2622 /* We can handle some of the 'e' cases here. */
2630 {
2645 {
2662 }
2663 /* fall through - ??? */
2666 {
2670 /* We need to check both for exact equality and tree equality. The
2671 former will be true if the operand has a side-effect. In that
2672 case, we know the operand occurred exactly once. */
2685 }
2689 }
2690 }
2691 \f
2692 /* Return a tree for the case when the result of an expression is RESULT
2693 converted to TYPE and OMITTED was previously an operand of the expression
2694 but is now not needed (e.g., we folded OMITTED * 0).
2696 If OMITTED has side effects, we must evaluate it. Otherwise, just do
2697 the conversion of RESULT to TYPE. */
2699 static tree
2702 {
2709 }
2711 /* Similar, but call pedantic_non_lvalue instead of non_lvalue. */
2713 static tree
2716 {
2723 }
2724 \f
2725 /* Return a simplified tree node for the truth-negation of ARG. This
2726 never alters ARG itself. We assume that ARG is an operation that
2727 returns a truth value (0 or 1). */
2729 tree
2731 tree arg;
2732 {
2739 /* If this is a comparison, we can simply invert it, except for
2740 floating-point non-equality comparisons, in which case we just
2741 enclose a TRUTH_NOT_EXPR around what we have. */
2744 {
2746 && !flag_unsafe_math_optimizations
2750 else
2753 }
2756 {
2771 /* Here we can invert either operand. We invert the first operand
2772 unless the second operand is a TRUTH_NOT_EXPR in which case our
2773 result is the XOR of the first operand with the inside of the
2774 negation of the second operand. */
2779 else
2834 }
2838 }
2840 /* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
2841 operands are another bit-wise operation with a common input. If so,
2842 distribute the bit operations to save an operation and possibly two if
2843 constants are involved. For example, convert
2844 (A | B) & (A | C) into A | (B & C)
2845 Further simplification will occur if B and C are constants.
2847 If this optimization cannot be done, 0 will be returned. */
2849 static tree
2852 tree type;
2854 {
2855 tree common;
2865 {
2869 }
2871 {
2875 }
2877 {
2881 }
2883 {
2887 }
2888 else
2893 }
2894 \f
2895 /* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
2896 starting at BITPOS. The field is unsigned if UNSIGNEDP is non-zero. */
2898 static tree
2900 tree inner;
2901 tree type;
2904 {
2911 }
2913 /* Optimize a bit-field compare.
2915 There are two cases: First is a compare against a constant and the
2916 second is a comparison of two items where the fields are at the same
2917 bit position relative to the start of a chunk (byte, halfword, word)
2918 large enough to contain it. In these cases we can avoid the shift
2919 implicit in bitfield extractions.
2921 For constants, we emit a compare of the shifted constant with the
2922 BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
2923 compared. For two fields at the same position, we do the ANDs with the
2924 similar mask and compare the result of the ANDs.
2926 CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
2927 COMPARE_TYPE is the type of the comparison, and LHS and RHS
2928 are the left and right operands of the comparison, respectively.
2930 If the optimization described above can be done, we return the resulting
2931 tree. Otherwise we return zero. */
2933 static tree
2936 tree compare_type;
2938 {
2948 tree mask;
2949 tree offset;
2951 /* Get all the information about the extractions being done. If the bit size
2952 if the same as the size of the underlying object, we aren't doing an
2953 extraction at all and so can do nothing. We also don't want to
2954 do anything if the inner expression is a PLACEHOLDER_EXPR since we
2955 then will no longer be able to replace it. */
2963 {
2964 /* If this is not a constant, we can only do something if bit positions,
2965 sizes, and signedness are the same. */
2973 }
2975 /* See if we can find a mode to refer to this field. We should be able to,
2976 but fail if we can't. */
2985 /* Set signed and unsigned types of the precision of this mode for the
2986 shifts below. */
2990 /* Compute the bit position and size for the new reference and our offset
2991 within it. If the new reference is the same size as the original, we
2992 won't optimize anything, so return zero. */
3002 /* Make the mask to be used against the extracted field. */
3012 /* If not comparing with constant, just rework the comparison
3013 and return. */
3018 mask),
3022 mask));
3024 /* Otherwise, we are handling the constant case. See if the constant is too
3025 big for the field. Warn and return a tree of for 0 (false) if so. We do
3026 this not only for its own sake, but to avoid having to test for this
3027 error case below. If we didn't, we might generate wrong code.
3029 For unsigned fields, the constant shifted right by the field length should
3030 be all zero. For signed fields, the high-order bits should agree with
3031 the sign bit. */
3034 {
3038 {
3044 }
3045 }
3046 else
3047 {
3051 {
3057 }
3058 }
3060 /* Single-bit compares should always be against zero. */
3062 {
3065 }
3067 /* Make a new bitfield reference, shift the constant over the
3068 appropriate number of bits and mask it with the computed mask
3069 (in case this was a signed field). If we changed it, make a new one. */
3072 {
3075 }
3085 rhs);
3086 }
3087 \f
3088 /* Subroutine for fold_truthop: decode a field reference.
3090 If EXP is a comparison reference, we return the innermost reference.
3092 *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
3093 set to the starting bit number.
3095 If the innermost field can be completely contained in a mode-sized
3096 unit, *PMODE is set to that mode. Otherwise, it is set to VOIDmode.
3098 *PVOLATILEP is set to 1 if the any expression encountered is volatile;
3099 otherwise it is not changed.
3101 *PUNSIGNEDP is set to the signedness of the field.
3103 *PMASK is set to the mask used. This is either contained in a
3104 BIT_AND_EXPR or derived from the width of the field.
3106 *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.
3108 Return 0 if this is not a component reference or is one that we can't
3109 do anything with. */
3111 static tree
3114 tree exp;
3120 {
3123 tree unsigned_type;
3127 /* All the optimizations using this function assume integer fields.
3128 There are problems with FP fields since the type_for_size call
3129 below can fail for, e.g., XFmode. */
3136 {
3142 }
3151 /* Compute the mask to access the bitfield. */
3161 /* Merge it with the mask we found in the BIT_AND_EXPR, if any. */
3169 }
3171 /* Return non-zero if MASK represents a mask of SIZE ones in the low-order
3172 bit positions. */
3174 static int
3176 tree mask;
3178 {
3181 tree tmask;
3186 return
3193 }
3195 /* Subroutine for fold_truthop: determine if an operand is simple enough
3196 to be evaluated unconditionally. */
3198 static int
3200 tree exp;
3201 {
3202 /* Strip any conversions that don't change the machine mode. */
3214 /* Don't regard global variables as simple. They may be
3215 allocated in ways unknown to the compiler (shared memory,
3216 #pragma weak, etc). */
3219 /* Loading a static variable is unduly expensive, but global
3220 registers aren't expensive. */
3222 }
3223 \f
3224 /* The following functions are subroutines to fold_range_test and allow it to
3225 try to change a logical combination of comparisons into a range test.
3227 For example, both
3228 X == 2 || X == 3 || X == 4 || X == 5
3229 and
3230 X >= 2 && X <= 5
3231 are converted to
3232 (unsigned) (X - 2) <= 3
3234 We describe each set of comparisons as being either inside or outside
3235 a range, using a variable named like IN_P, and then describe the
3236 range with a lower and upper bound. If one of the bounds is omitted,
3237 it represents either the highest or lowest value of the type.
3239 In the comments below, we represent a range by two numbers in brackets
3240 preceded by a "+" to designate being inside that range, or a "-" to
3241 designate being outside that range, so the condition can be inverted by
3242 flipping the prefix. An omitted bound is represented by a "-". For
3243 example, "- [-, 10]" means being outside the range starting at the lowest
3244 possible value and ending at 10, in other words, being greater than 10.
3245 The range "+ [-, -]" is always true and hence the range "- [-, -]" is
3246 always false.
3248 We set up things so that the missing bounds are handled in a consistent
3249 manner so neither a missing bound nor "true" and "false" need to be
3250 handled using a special case. */
3252 /* Return the result of applying CODE to ARG0 and ARG1, but handle the case
3253 of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
3254 and UPPER1_P are nonzero if the respective argument is an upper bound
3255 and zero for a lower. TYPE, if nonzero, is the type of the result; it
3256 must be specified for a comparison. ARG1 will be converted to ARG0's
3257 type if both are specified. */
3259 static tree
3262 tree type;
3265 {
3266 tree tem;
3270 /* If neither arg represents infinity, do the normal operation.
3271 Else, if not a comparison, return infinity. Else handle the special
3272 comparison rules. Note that most of the cases below won't occur, but
3273 are handled for consistency. */
3276 {
3281 }
3286 /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
3287 for neither. In real maths, we cannot assume open ended ranges are
3288 the same. But, this is computer arithmetic, where numbers are finite.
3289 We can therefore make the transformation of any unbounded range with
3290 the value Z, Z being greater than any representable number. This permits
3291 us to treat unbounded ranges as equal. */
3295 {
3316 }
3319 }
3320 \f
3321 /* Given EXP, a logical expression, set the range it is testing into
3322 variables denoted by PIN_P, PLOW, and PHIGH. Return the expression
3323 actually being tested. *PLOW and *PHIGH will be made of the same type
3324 as the returned expression. If EXP is not a comparison, we will most
3325 likely not be returning a useful value and range. */
3327 static tree
3329 tree exp;
3332 {
3339 /* Start with simply saying "EXP != 0" and then look at the code of EXP
3340 and see if we can refine the range. Some of the cases below may not
3341 happen, but it doesn't seem worth worrying about this. We "continue"
3342 the outer loop when we've changed something; otherwise we "break"
3343 the switch, which will "break" the while. */
3348 {
3352 {
3363 }
3365 /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
3366 lose a cast by accident. */
3371 {
3378 /* We can only do something if the range is testing for zero
3379 and if the second operand is an integer constant. Note that
3380 saying something is "in" the range we make is done by
3381 complementing IN_P since it will set in the initial case of
3382 being not equal to zero; "out" is leaving it alone. */
3389 {
3410 }
3414 /* If this is an unsigned comparison, we also know that EXP is
3415 greater than or equal to zero. We base the range tests we make
3416 on that fact, so we record it here so we can parse existing
3417 range tests. */
3419 {
3422 NULL_TREE))
3427 /* If the high bound is missing, but we
3428 have a low bound, reverse the range so
3429 it goes from zero to the low bound minus 1. */
3431 {
3436 }
3437 }
3441 /* (-x) IN [a,b] -> x in [-b, -a] */
3451 /* ~ X -> -X - 1 */
3460 /* If EXP is signed, any overflow in the computation is undefined,
3461 so we don't worry about it so long as our computations on
3462 the bounds don't overflow. For unsigned, overflow is defined
3463 and this is exactly the right thing. */
3472 /* Check for an unsigned range which has wrapped around the maximum
3473 value thus making n_high < n_low, and normalize it. */
3475 {
3481 /* If the range is of the form +/- [ x+1, x ], we won't
3482 be able to normalize it. But then, it represents the
3483 whole range or the empty set, so make it
3484 +/- [ -, - ]. */
3488 else
3490 }
3491 else
3514 /* If we're converting from an unsigned to a signed type,
3515 we will be doing the comparison as unsigned. The tests above
3516 have already verified that LOW and HIGH are both positive.
3518 So we have to make sure that the original unsigned value will
3519 be interpreted as positive. */
3521 {
3523 tree high_positive;
3525 /* A range without an upper bound is, naturally, unbounded.
3526 Since convert would have cropped a very large value, use
3527 the max value for the destination type. */
3528 high_positive
3536 /* If the low bound is specified, "and" the range with the
3537 range for which the original unsigned value will be
3538 positive. */
3540 {
3544 high_positive))
3548 }
3549 else
3550 {
3551 /* Otherwise, "or" the range with the range of the input
3552 that will be interpreted as negative. */
3556 high_positive))
3560 }
3561 }
3569 }
3572 }
3574 /* If EXP is a constant, we can evaluate whether this is true or false. */
3576 {
3583 }
3587 }
3588 \f
3589 /* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
3590 type, TYPE, return an expression to test if EXP is in (or out of, depending
3591 on IN_P) the range. */
3593 static tree
3595 tree type;
3596 tree exp;
3599 {
3623 {
3627 }
3634 else
3636 }
3637 \f
3638 /* Given two ranges, see if we can merge them into one. Return 1 if we
3639 can, 0 if we can't. Set the output range into the specified parameters. */
3641 static int
3647 {
3651 tree tem;
3661 /* Make range 0 be the range that starts first, or ends last if they
3662 start at the same value. Swap them if it isn't. */
3665 || (lowequal
3668 {
3672 }
3674 /* Now flag two cases, whether the ranges are disjoint or whether the
3675 second range is totally subsumed in the first. Note that the tests
3676 below are simplified by the ones above. */
3682 /* We now have four cases, depending on whether we are including or
3683 excluding the two ranges. */
3685 {
3686 /* If they don't overlap, the result is false. If the second range
3687 is a subset it is the result. Otherwise, the range is from the start
3688 of the second to the end of the first. */
3693 else
3695 }
3698 {
3699 /* If they don't overlap, the result is the first range. If they are
3700 equal, the result is false. If the second range is a subset of the
3701 first, and the ranges begin at the same place, we go from just after
3702 the end of the first range to the end of the second. If the second
3703 range is not a subset of the first, or if it is a subset and both
3704 ranges end at the same place, the range starts at the start of the
3705 first range and ends just before the second range.
3706 Otherwise, we can't describe this as a single range. */
3712 {
3716 }
3718 {
3722 }
3723 else
3725 }
3728 {
3729 /* If they don't overlap, the result is the second range. If the second
3730 is a subset of the first, the result is false. Otherwise,
3731 the range starts just after the first range and ends at the
3732 end of the second. */
3737 else
3738 {
3742 }
3743 }
3745 else
3746 {
3747 /* The case where we are excluding both ranges. Here the complex case
3748 is if they don't overlap. In that case, the only time we have a
3749 range is if they are adjacent. If the second is a subset of the
3750 first, the result is the first. Otherwise, the range to exclude
3751 starts at the beginning of the first range and ends at the end of the
3752 second. */
3754 {
3761 else
3763 }
3766 else
3768 }
3772 }
3773 \f
3774 /* EXP is some logical combination of boolean tests. See if we can
3775 merge it into some range test. Return the new tree if so. */
3777 static tree
3779 tree exp;
3780 {
3787 tree tem;
3789 /* If this is an OR operation, invert both sides; we will invert
3790 again at the end. */
3794 /* If both expressions are the same, if we can merge the ranges, and we
3795 can build the range test, return it or it inverted. If one of the
3796 ranges is always true or always false, consider it to be the same
3797 expression as the other. */
3807 /* On machines where the branch cost is expensive, if this is a
3808 short-circuited branch and the underlying object on both sides
3809 is the same, make a non-short-circuit operation. */
3815 {
3816 /* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
3817 unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
3818 which cases we can't do this. */
3827 {
3839 }
3840 }
3843 }
3844 \f
3845 /* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
3846 bit value. Arrange things so the extra bits will be set to zero if and
3847 only if C is signed-extended to its full width. If MASK is nonzero,
3848 it is an INTEGER_CST that should be AND'ed with the extra bits. */
3850 static tree
3852 tree c;
3855 tree mask;
3856 {
3859 tree temp;
3864 /* We work by getting just the sign bit into the low-order bit, then
3865 into the high-order bit, then sign-extend. We then XOR that value
3866 with C. */
3870 /* We must use a signed type in order to get an arithmetic right shift.
3871 However, we must also avoid introducing accidental overflows, so that
3872 a subsequent call to integer_zerop will work. Hence we must
3873 do the type conversion here. At this point, the constant is either
3874 zero or one, and the conversion to a signed type can never overflow.
3875 We could get an overflow if this conversion is done anywhere else. */
3883 /* If necessary, convert the type back to match the type of C. */
3888 }
3889 \f
3890 /* Find ways of folding logical expressions of LHS and RHS:
3891 Try to merge two comparisons to the same innermost item.
3892 Look for range tests like "ch >= '0' && ch <= '9'".
3893 Look for combinations of simple terms on machines with expensive branches
3894 and evaluate the RHS unconditionally.
3896 For example, if we have p->a == 2 && p->b == 4 and we can make an
3897 object large enough to span both A and B, we can do this with a comparison
3898 against the object ANDed with the a mask.
3900 If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
3901 operations to do this with one comparison.
3903 We check for both normal comparisons and the BIT_AND_EXPRs made this by
3904 function and the one above.
3906 CODE is the logical operation being done. It can be TRUTH_ANDIF_EXPR,
3907 TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.
3909 TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
3910 two operands.
3912 We return the simplified tree or 0 if no optimization is possible. */
3914 static tree
3918 {
3919 /* If this is the "or" of two comparisons, we can do something if
3920 the comparisons are NE_EXPR. If this is the "and", we can do something
3921 if the comparisons are EQ_EXPR. I.e.,
3922 (a->b == 2 && a->c == 4) can become (a->new == NEW).
3924 WANTED_CODE is this operation code. For single bit fields, we can
3925 convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
3926 comparison for one-bit fields. */
3946 /* Start by getting the comparison codes. Fail if anything is volatile.
3947 If one operand is a BIT_AND_EXPR with the constant one, treat it as if
3948 it were surrounded with a NE_EXPR. */
3973 /* If the RHS can be evaluated unconditionally and its operands are
3974 simple, it wins to evaluate the RHS unconditionally on machines
3975 with expensive branches. In this case, this isn't a comparison
3976 that can be merged. Avoid doing this if the RHS is a floating-point
3977 comparison since those can trap. */
3985 /* See if the comparisons can be merged. Then get all the parameters for
3986 each side. */
4010 /* It must be true that the inner operation on the lhs of each
4011 comparison must be the same if we are to be able to do anything.
4012 Then see if we have constants. If not, the same must be true for
4013 the rhs's. */
4024 else
4027 /* If either comparison code is not correct for our logical operation,
4028 fail. However, we can convert a one-bit comparison against zero into
4029 the opposite comparison against that bit being set in the field. */
4033 {
4035 {
4036 /* Make the left operand unsigned, since we are only interested
4037 in the value of one bit. Otherwise we are doing the wrong
4038 thing below. */
4041 }
4042 else
4044 }
4046 /* This is analogous to the code for l_const above. */
4048 {
4050 {
4053 }
4054 else
4056 }
4058 /* See if we can find a mode that contains both fields being compared on
4059 the left. If we can't, fail. Otherwise, update all constants and masks
4060 to be relative to a field of that size. */
4065 volatilep);
4075 {
4078 }
4086 {
4094 {
4098 wanted_code == NE_EXPR
4100 }
4101 }
4103 {
4111 {
4115 wanted_code == NE_EXPR
4117 }
4118 }
4120 /* If the right sides are not constant, do the same for it. Also,
4121 disallow this optimization if a size or signedness mismatch occurs
4122 between the left and right sides. */
4124 {
4127 /* Make sure the two fields on the right
4128 correspond to the left without being swapped. */
4136 volatilep);
4146 {
4149 }
4156 /* Make a mask that corresponds to both fields being compared.
4157 Do this for both items being compared. If the operands are the
4158 same size and the bits being compared are in the same position
4159 then we can do this by masking both and comparing the masked
4160 results. */
4164 {
4176 }
4178 /* There is still another way we can do something: If both pairs of
4179 fields being compared are adjacent, we may be able to make a wider
4180 field containing them both.
4182 Note that we still must mask the lhs/rhs expressions. Furthermore,
4183 the mask must be shifted to account for the shift done by
4184 make_bit_field_ref. */
4189 {
4190 tree type;
4202 /* Convert to the smaller type before masking out unwanted bits. */
4205 {
4207 {
4211 }
4213 {
4217 }
4218 }
4227 }
4230 }
4232 /* Handle the case of comparisons with constants. If there is something in
4233 common between the masks, those bits of the constants must be the same.
4234 If not, the condition is always false. Test for this to avoid generating
4235 incorrect code below. */
4240 {
4242 {
4245 }
4246 else
4247 {
4250 }
4251 }
4253 /* Construct the expression we will return. First get the component
4254 reference we will make. Unless the mask is all ones the width of
4255 that field, perform the mask operation. Then compare with the
4256 merged constant. */
4266 }
4267 \f
4268 /* Optimize T, which is a comparison of a MIN_EXPR or MAX_EXPR with a
4269 constant. */
4271 static tree
4273 tree t;
4274 {
4279 tree minmax_const;
4281 tree inner;
4291 /* If something does not permit us to optimize, return the original tree. */
4299 /* Now handle all the various comparison codes. We only handle EQ_EXPR
4300 and GT_EXPR, doing the rest with recursive calls using logical
4301 simplifications. */
4303 {
4305 return
4309 return
4311 optimize_minmax_comparison
4313 optimize_minmax_comparison
4318 /* MAX (X, 0) == 0 -> X <= 0 */
4322 /* MAX (X, 0) == 5 -> X == 5 */
4326 /* MAX (X, 0) == -1 -> false */
4330 /* MIN (X, 0) == 0 -> X >= 0 */
4334 /* MIN (X, 0) == 5 -> false */
4337 else
4338 /* MIN (X, 0) == -1 -> X == -1 */
4343 /* MAX (X, 0) > 0 -> X > 0
4344 MAX (X, 0) > 5 -> X > 5 */
4348 /* MAX (X, 0) > -1 -> true */
4352 /* MIN (X, 0) > 0 -> false
4353 MIN (X, 0) > 5 -> false */
4356 else
4357 /* MIN (X, 0) > -1 -> X > -1 */
4362 }
4363 }
4364 \f
4365 /* T is an integer expression that is being multiplied, divided, or taken a
4366 modulus (CODE says which and what kind of divide or modulus) by a
4367 constant C. See if we can eliminate that operation by folding it with
4368 other operations already in T. WIDE_TYPE, if non-null, is a type that
4369 should be used for the computation if wider than our type.
4371 For example, if we are dividing (X * 8) + (Y + 16) by 4, we can return
4372 (X * 2) + (Y + 4). We must, however, be assured that either the original
4373 expression would not overflow or that overflow is undefined for the type
4374 in the language in question.
4376 We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either
4377 the machine has a multiply-accumulate insn or that this is part of an
4378 addressing calculation.
4380 If we return a non-null expression, it is an equivalent form of the
4381 original computation, but need not be in the original type. */
4383 static tree
4385 tree t;
4386 tree c;
4388 tree wide_type;
4389 {
4399 /* Don't deal with constants of zero here; they confuse the code below. */
4409 /* Note that we need not handle conditional operations here since fold
4410 already handles those cases. So just do arithmetic here. */
4412 {
4414 /* For a constant, we can always simplify if we are a multiply
4415 or (for divide and modulus) if it is a multiple of our constant. */
4422 /* If op0 is an expression, and is unsigned, and the type is
4423 smaller than ctype, then we cannot widen the expression. */
4435 /* Pass the constant down and see if we can make a simplification. If
4436 we can, replace this expression with the inner simplification for
4437 possible later conversion to our or some other type. */
4449 /* If widening the type changes the signedness, then we can't perform
4450 this optimization as that changes the result. */
4454 /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */
4457 {
4463 }
4473 /* If this has not been evaluated and the operand has no side effects,
4474 we can see if we can do something inside it and make a new one.
4475 Note that this test is overly conservative since we can do this
4476 if the only reason it had side effects is that it was another
4477 similar SAVE_EXPR, but that isn't worth bothering with. */
4480 wide_type)))
4481 {
4488 }
4492 /* If the second operand is constant, this is a multiplication
4493 or floor division, by a power of two, so we can treat it that
4494 way unless the multiplier or divisor overflows. */
4496 /* const_binop may not detect overflow correctly,
4497 so check for it explicitly here. */
4511 /* See if we can eliminate the operation on both sides. If we can, we
4512 can return a new PLUS or MINUS. If we can't, the only remaining
4513 cases where we can do anything are if the second operand is a
4514 constant. */
4519 /* If not multiplication, we can only do this if either operand
4520 is divisible by c. */
4526 /* If this was a subtraction, negate OP1 and set it to be an addition.
4527 This simplifies the logic below. */
4534 /* If either OP1 or C are negative, this optimization is not safe for
4535 some of the division and remainder types while for others we need
4536 to change the code. */
4538 {
4549 }
4551 /* If it's a multiply or a division/modulus operation of a multiple
4552 of our constant, do the operation and verify it doesn't overflow. */
4555 {
4559 }
4560 else
4563 /* If we have an unsigned type is not a sizetype, we cannot widen
4564 the operation since it will change the result if the original
4565 computation overflowed. */
4571 /* If we were able to eliminate our operation from the first side,
4572 apply our operation to the second side and reform the PLUS. */
4576 /* The last case is if we are a multiply. In that case, we can
4577 apply the distributive law to commute the multiply and addition
4578 if the multiplication of the constants doesn't overflow. */
4583 op1));
4588 /* We have a special case here if we are doing something like
4589 (C * 8) % 4 since we know that's zero. */
4596 /* ... fall through ... */
4600 /* If we can extract our operation from the LHS, do so and return a
4601 new operation. Likewise for the RHS from a MULT_EXPR. Otherwise,
4602 do something only if the second operand is a constant. */
4614 /* If these are the same operation types, we can associate them
4615 assuming no overflow. */
4622 /* If these operations "cancel" each other, we have the main
4623 optimizations of this pass, which occur when either constant is a
4624 multiple of the other, in which case we replace this with either an
4625 operation or CODE or TCODE.
4627 If we have an unsigned type that is not a sizetype, we canot do
4628 this since it will change the result if the original computation
4629 overflowed. */
4636 {
4647 }
4652 }
4655 }
4656 \f
4657 /* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
4658 S, a SAVE_EXPR, return the expression actually being evaluated. Note
4659 that we may sometimes modify the tree. */
4661 static tree
4663 tree t;
4664 tree s;
4665 {
4668 /* See if this is the COMPOUND_EXPR we want to eliminate. */
4673 /* See if this is a COND_EXPR or a simple arithmetic operator. We
4674 don't bother handling any other types. */
4676 {
4680 }
4685 {
4688 }
4691 }
4692 \f
4693 /* Return a node which has the indicated constant VALUE (either 0 or
4694 1), and is of the indicated TYPE. */
4696 static tree
4699 tree type;
4700 {
4705 integer_zero_node);
4706 else
4707 {
4712 }
4713 }
4715 /* Utility function for the following routine, to see how complex a nesting of
4716 COND_EXPRs can be. EXPR is the expression and LIMIT is a count beyond which
4717 we don't care (to avoid spending too much time on complex expressions.). */
4719 static int
4721 tree expr;
4723 {
4734 }
4736 /* Transform `a + (b ? x : y)' into `x ? (a + b) : (a + y)'.
4737 Transform, `a + (x < y)' into `(x < y) ? (a + 1) : (a + 0)'. Here
4738 CODE corresponds to the `+', COND to the `(b ? x : y)' or `(x < y)'
4739 expression, and ARG to `a'. If COND_FIRST_P is non-zero, then the
4740 COND is the first argument to CODE; otherwise (as in the example
4741 given here), it is the second argument. TYPE is the type of the
4742 original expression. */
4744 static tree
4747 tree type;
4748 tree cond;
4749 tree arg;
4751 {
4755 /* In the end, we'll produce a COND_EXPR. Both arms of the
4756 conditional expression will be binary operations. The left-hand
4757 side of the expression to be executed if the condition is true
4758 will be pointed to by TRUE_LHS. Similarly, the right-hand side
4759 of the expression to be executed if the condition is true will be
4760 pointed to by TRUE_RHS. FALSE_LHS and FALSE_RHS are analagous --
4761 but apply to the expression to be executed if the conditional is
4762 false. */
4767 /* These are the codes to use for the left-hand side and right-hand
4768 side of the COND_EXPR. Normally, they are the same as CODE. */
4771 /* And these are the types of the expressions. */
4776 {
4780 }
4781 else
4782 {
4786 }
4789 {
4793 /* If this operand throws an expression, then it does not make
4794 sense to try to perform a logical or arithmetic operation
4795 involving it. Instead of building `a + throw 3' for example,
4796 we simply build `a, throw 3'. */
4798 {
4802 }
4804 {
4808 }
4809 }
4810 else
4811 {
4816 }
4818 /* If ARG is complex we want to make sure we only evaluate
4819 it once. Though this is only required if it is volatile, it
4820 might be more efficient even if it is not. However, if we
4821 succeed in folding one part to a constant, we do not need
4822 to make this SAVE_EXPR. Since we do this optimization
4823 primarily to see if we do end up with constant and this
4824 SAVE_EXPR interferes with later optimizations, suppressing
4825 it when we can is important.
4827 If we are not in a function, we can't make a SAVE_EXPR, so don't
4828 try to do so. Don't try to see if the result is a constant
4829 if an arm is a COND_EXPR since we get exponential behavior
4830 in that case. */
4837 {
4847 }
4860 else
4862 }
4864 \f
4865 /* Perform constant folding and related simplification of EXPR.
4866 The related simplifications include x*1 => x, x*0 => 0, etc.,
4867 and application of the associative law.
4868 NOP_EXPR conversions may be removed freely (as long as we
4869 are careful not to change the C type of the overall expression)
4870 We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
4871 but we can constant-fold them if they have constant operands. */
4873 tree
4875 tree expr;
4876 {
4879 tree tem;
4885 /* WINS will be nonzero when the switch is done
4886 if all operands are constant. */
4889 /* Don't try to process an RTL_EXPR since its operands aren't trees.
4890 Likewise for a SAVE_EXPR that's already been evaluated. */
4894 /* Return right away if a constant. */
4898 #ifdef MAX_INTEGER_COMPUTATION_MODE
4900 #endif
4903 {
4904 tree subop;
4906 /* Special case for conversion ops that can have fixed point args. */
4909 /* Don't use STRIP_NOPS, because signedness of argument type matters. */
4915 else
4919 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
4922 )
4923 /* Note that TREE_CONSTANT isn't enough:
4924 static var addresses are constant but we can't
4925 do arithmetic on them. */
4927 }
4929 {
4933 {
4935 tree subop;
4941 {
4942 /* Signedness matters here. Perhaps we can refine this
4943 later. */
4945 }
4946 else
4947 /* Strip any conversions that don't change the mode. */
4952 else
4956 #if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
4959 )
4960 /* Note that TREE_CONSTANT isn't enough:
4961 static var addresses are constant but we can't
4962 do arithmetic on them. */
4969 }
4970 }
4972 /* If this is a commutative operation, and ARG0 is a constant, move it
4973 to ARG1 to reduce the number of tests below. */
4978 {
4983 }
4985 /* Now WINS is set as described above,
4986 ARG0 is the first operand of EXPR,
4987 and ARG1 is the second operand (if it has more than one operand).
4989 First check for cases where an arithmetic operation is applied to a
4990 compound, conditional, or comparison operation. Push the arithmetic
4991 operation inside the compound or conditional to see if any folding
4992 can then be done. Convert comparison to conditional for this purpose.
4993 The also optimizes non-constant cases that used to be done in
4994 expand_expr.
4996 Before we do that, see if this is a BIT_AND_EXPR or a BIT_IOR_EXPR,
4997 one of the operands is a comparison and the other is a comparison, a
4998 BIT_AND_EXPR with the constant 1, or a truth value. In that case, the
4999 code below would make the expression more complex. Change it to a
5000 TRUTH_{AND,OR}_EXPR. Likewise, convert a similar NE_EXPR to
5001 TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR. */
5013 {
5023 }
5026 {
5031 {
5036 /* If this was a conversion, and all we did was to move into
5037 inside the COND_EXPR, bring it back out. But leave it if
5038 it is a conversion from integer to integer and the
5039 result precision is no wider than a word since such a
5040 conversion is cheap and may be optimized away by combine,
5041 while it couldn't if it were outside the COND_EXPR. Then return
5042 so we don't get into an infinite recursion loop taking the
5043 conversion out and then back in. */
5053 && (INTEGRAL_TYPE_P
5064 }
5069 }
5072 {
5085 return
5099 return
5102 }
5113 {
5128 /* Other kinds of FIX are not handled properly by fold_convert. */
5133 /* Handle cases of two conversions in a row. */
5136 {
5156 /* In addition to the cases of two conversions in a row
5157 handled below, if we are converting something to its own
5158 type via an object of identical or wider precision, neither
5159 conversion is needed. */
5165 /* Likewise, if the intermediate and final types are either both
5166 float or both integer, we don't need the middle conversion if
5167 it is wider than the final type and doesn't change the signedness
5168 (for integers). Avoid this if the final type is a pointer
5169 since then we sometimes need the inner conversion. Likewise if
5170 the outer has a precision not equal to the size of its mode. */
5180 /* If we have a sign-extension of a zero-extended value, we can
5181 replace that by a single zero-extension. */
5187 /* Two conversions in a row are not needed unless:
5188 - some conversion is floating-point (overstrict for now), or
5189 - the intermediate type is narrower than both initial and
5190 final, or
5191 - the intermediate type and innermost type differ in signedness,
5192 and the outermost type is wider than the intermediate, or
5193 - the initial type is a pointer type and the precisions of the
5194 intermediate and final types differ, or
5195 - the final type is a pointer type and the precisions of the
5196 initial and intermediate types differ. */
5210 }
5214 /* Detect assigning a bitfield. */
5217 {
5218 /* Don't leave an assignment inside a conversion
5219 unless assigning a bitfield. */
5222 /* First do the assignment, then return converted constant. */
5226 }
5228 {
5231 }
5236 {
5239 /* Fold an expression like: "foo"[2] */
5243 {
5247 }
5248 }
5254 {
5258 }
5267 {
5269 {
5271 HOST_WIDE_INT high;
5282 }
5285 }
5289 /* Convert - (a - b) to (b - a) for non-floating-point. */
5299 {
5301 {
5302 /* If the value is unsigned, then the absolute value is
5303 the same as the ordinary value. */
5306 /* Similarly, if the value is non-negative. */
5309 /* If the value is negative, then the absolute value is
5310 its negation. */
5311 else
5312 {
5314 HOST_WIDE_INT high;
5325 }
5326 }
5328 {
5332 }
5333 }
5360 {
5367 }
5373 /* A + (-B) -> A - B */
5376 /* (-A) + B -> B - A */
5380 {
5384 /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
5385 with a constant, and the two constants have no bits in common,
5386 we should treat this as a BIT_IOR_EXPR since this may produce more
5387 simplifications. */
5395 {
5398 }
5400 /* Reassociate (plus (plus (mult) (foo)) (mult)) as
5401 (plus (plus (mult) (mult)) (foo)) so that we can
5402 take advantage of the factoring cases below. */
5407 {
5412 else
5423 parg1));
5428 parg0));
5429 }
5432 {
5436 /* (A * C) + (B * C) -> (A+B) * C.
5437 We are most concerned about the case where C is a constant,
5438 but other combinations show up during loop reduction. Since
5439 it is not difficult, try all four possibilities. */
5456 /* No identical multiplicands; see if we can find a common
5457 power-of-two factor in non-power-of-two multiplies. This
5458 can help in multi-dimensional array access. */
5463 {
5468 /* Move min of absolute values to int11. */
5471 {
5475 }
5478 {
5483 }
5484 }
5489 same));
5490 }
5491 }
5492 /* In IEEE floating point, x+0 may not equal x. */
5497 /* x+(-0) equals x, even for IEEE. */
5502 bit_rotate:
5503 /* (A << C1) + (A >> C2) if A is unsigned and C1+C2 is the size of A
5504 is a rotate of A by C1 bits. */
5505 /* (A << B) + (A >> (Z - B)) if A is unsigned and Z is the size of A
5506 is a rotate of A by B bits. */
5507 {
5516 {
5535 {
5543 TYPE_PRECISION
5548 ? LROTATE_EXPR
5551 }
5553 {
5561 TYPE_PRECISION
5566 ? LROTATE_EXPR
5569 }
5570 }
5571 }
5573 associate:
5574 /* In most languages, can't associate operations on floats through
5575 parentheses. Rather than remember where the parentheses were, we
5576 don't associate floats at all. It shouldn't matter much. However,
5577 associating multiplications is only very slightly inaccurate, so do
5578 that if -funsafe-math-optimizations is specified. */
5583 {
5586 /* Split both trees into variables, constants, and literals. Then
5587 associate each group together, the constants with literals,
5588 then the result with variables. This increases the chances of
5589 literals being recombined later and of generating relocatable
5590 expressions for the sum of a constant and literal. */
5594 /* Only do something if we found more than two objects. Otherwise,
5595 nothing has changed and we risk infinite recursion. */
5598 {
5604 }
5605 }
5607 binary:
5608 #if defined (REAL_IS_NOT_DOUBLE) && ! defined (REAL_ARITHMETIC)
5615 {
5616 /* The return value should always have
5617 the same type as the original expression. */
5622 }
5626 /* A - (-B) -> A + B */
5629 /* (-A) - CST -> (-CST) - A for floating point (what about ints ?) */
5631 return
5638 {
5644 /* (A * C) - (B * C) -> (A-B) * C. Since we are most concerned
5645 about the case where C is a constant, just try one of the
5646 four possibilities. */
5656 }
5660 {
5661 /* Except with IEEE floating point, 0-x equals -x. */
5664 /* Except with IEEE floating point, x-0 equals x. */
5667 }
5669 /* Fold &x - &x. This can happen from &x.foo - &x.
5670 This is unsafe for certain floats even in non-IEEE formats.
5671 In IEEE, it is unsafe because it does wrong for NaNs.
5672 Also note that operand_equal_p is always false if an operand
5673 is volatile. */
5682 /* (-A) * (-B) -> A * B */
5688 {
5694 /* (a * (1 << b)) is (a << b) */
5709 }
5710 else
5711 {
5712 /* x*0 is 0, except for IEEE floating point. */
5717 /* In IEEE floating point, x*1 is not equivalent to x for snans.
5718 However, ANSI says we can drop signals,
5719 so we can do this anyway. */
5722 /* x*2 is x+x */
5725 {
5728 }
5729 }
5733 bit_ior:
5742 /* Convert (or (not arg0) (not arg1)) to (not (and (arg0) (arg1))).
5744 This results in more efficient code for machines without a NAND
5745 instruction. Combine will canonicalize to the first form
5746 which will allow use of NAND instructions provided by the
5747 backend if they exist. */
5750 {
5755 }
5757 /* See if this can be simplified into a rotate first. If that
5758 is unsuccessful continue in the association code. */
5767 /* If we are XORing two BIT_AND_EXPR's, both of which are and'ing
5768 with a constant, and the two constants have no bits in common,
5769 we should treat this as a BIT_IOR_EXPR since this may produce more
5770 simplifications. */
5778 {
5781 }
5783 /* See if this can be simplified into a rotate first. If that
5784 is unsuccessful continue in the association code. */
5788 bit_and:
5796 /* Simplify ((int)c & 0x377) into (int)c, if c is unsigned char. */
5799 {
5800 unsigned int prec
5807 }
5810 {
5811 unsigned int prec
5818 }
5820 /* Convert (and (not arg0) (not arg1)) to (not (or (arg0) (arg1))).
5822 This results in more efficient code for machines without a NOR
5823 instruction. Combine will canonicalize to the first form
5824 which will allow use of NOR instructions provided by the
5825 backend if they exist. */
5828 {
5833 }
5843 {
5847 }
5851 /* In most cases, do nothing with a divide by zero. */
5852 #if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
5853 #ifndef REAL_INFINITY
5856 #endif
5859 /* (-A) / (-B) -> A / B */
5864 /* In IEEE floating point, x/1 is not equivalent to x for snans.
5865 However, ANSI says we can drop signals, so we can do this anyway. */
5869 /* If ARG1 is a constant, we can convert this to a multiply by the
5870 reciprocal. This does not have the same rounding properties,
5871 so only do this if -funsafe-math-optimizations. We can actually
5872 always safely do it if ARG1 is a power of two, but it's hard to
5873 tell if it is or not in a portable manner. */
5875 {
5880 /* Find the reciprocal if optimizing and the result is exact. */
5882 {
5883 REAL_VALUE_TYPE r;
5886 {
5889 }
5890 }
5891 }
5892 /* Convert A/B/C to A/(B*C). */
5895 {
5898 arg1)));
5899 }
5900 /* Convert A/(B/C) to (A/B)*C. */
5903 {
5908 }
5921 /* If arg0 is a multiple of arg1, then rewrite to the fastest div
5922 operation, EXACT_DIV_EXPR.
5924 Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
5925 At one time others generated faster code, it's not clear if they do
5926 after the last round to changes to the DIV code in expmed.c. */
5960 /* Since negative shift count is not well-defined,
5961 don't try to compute it in the compiler. */
5964 /* Rewrite an LROTATE_EXPR by a constant into an
5965 RROTATE_EXPR by a new constant. */
5967 {
5971 = const_binop
5978 }
5980 /* If we have a rotate of a bit operation with the rotate count and
5981 the second operand of the bit operation both constant,
5982 permute the two operations. */
5995 /* Two consecutive rotates adding up to the width of the mode can
5996 be ignored. */
6027 /* Note that the operand of this must be an int
6028 and its values must be 0 or 1.
6029 ("true" is a fixed value perhaps depending on the language,
6030 but we don't handle values other than 1 correctly yet.) */
6032 /* Avoid infinite recursion. */
6038 /* Note that the operands of this must be ints
6039 and their values must be 0 or 1.
6040 ("true" is a fixed value perhaps depending on the language.) */
6041 /* If first arg is constant zero, return it. */
6045 /* If either arg is constant true, drop it. */
6049 /* Preserve sequence points. */
6052 /* If second arg is constant zero, result is zero, but first arg
6053 must be evaluated. */
6056 /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
6057 case will be handled here. */
6061 truth_andor:
6062 /* We only do these simplifications if we are optimizing. */
6066 /* Check for things like (A || B) && (A || C). We can convert this
6067 to A || (B && C). Note that either operator can be any of the four
6068 truth and/or operations and the transformation will still be
6069 valid. Also note that we only care about order for the
6070 ANDIF and ORIF operators. If B contains side effects, this
6071 might change the truth-value of A. */
6078 {
6098 /* This case if tricky because we must either have commutative
6099 operators or else A10 must not have side-effects. */
6105 a01));
6106 }
6108 /* See if we can build a range comparison. */
6112 /* Check for the possibility of merging component references. If our
6113 lhs is another similar operation, try to merge its rhs with our
6114 rhs. Then try to merge our lhs and rhs. */
6126 /* Note that the operands of this must be ints
6127 and their values must be 0 or true.
6128 ("true" is a fixed value perhaps depending on the language.) */
6129 /* If first arg is constant true, return it. */
6133 /* If either arg is constant zero, drop it. */
6137 /* Preserve sequence points. */
6140 /* If second arg is constant true, result is true, but we must
6141 evaluate first arg. */
6144 /* Likewise for first arg, but note this only occurs here for
6145 TRUTH_OR_EXPR. */
6151 /* If either arg is constant zero, drop it. */
6156 /* If either arg is constant true, this is a logical inversion. */
6170 {
6171 /* (-a) CMP (-b) -> b CMP a */
6176 /* (-a) CMP CST -> a swap(CMP) (-CST) */
6178 return
6184 /* IEEE doesn't distinguish +0 and -0 in comparisons. */
6185 /* a CMP (-0) -> a CMP 0 */
6190 }
6192 /* If one arg is a constant integer, put it last. */
6195 {
6202 }
6204 /* Convert foo++ == CONST into ++foo == CONST + INCR.
6205 First, see if one arg is constant; find the constant arg
6206 and the other one. */
6207 {
6217 {
6218 /* This optimization is invalid for ordered comparisons
6219 if CONST+INCR overflows or if foo+incr might overflow.
6220 This optimization is invalid for floating point due to rounding.
6221 For pointer types we assume overflow doesn't happen. */
6225 {
6226 tree newconst
6230 /* Do not overwrite the current varop to be a preincrement,
6231 create a new node so that we won't confuse our caller who
6232 might create trees and throw them away, reusing the
6233 arguments that they passed to build. This shows up in
6234 the THEN or ELSE parts of ?: being postincrements. */
6239 /* If VAROP is a reference to a bitfield, we must mask
6240 the constant by the width of the field. */
6244 {
6245 int size
6247 (TREE_OPERAND
6251 tree folded_compare;
6253 /* First check whether the comparison would come out
6254 always the same. If we don't do that we would
6255 change the meaning with the masking. */
6259 else
6262 constop));
6277 mask)));
6278 }
6284 }
6285 }
6287 {
6291 {
6292 tree newconst
6296 /* Do not overwrite the current varop to be a predecrement,
6297 create a new node so that we won't confuse our caller who
6298 might create trees and throw them away, reusing the
6299 arguments that they passed to build. This shows up in
6300 the THEN or ELSE parts of ?: being postdecrements. */
6308 {
6309 int size
6311 (TREE_OPERAND
6315 tree folded_compare;
6320 else
6323 constop));
6338 mask)));
6339 }
6345 }
6346 }
6347 }
6349 /* Change X >= CST to X > (CST - 1) if CST is positive. */
6353 {
6355 {
6370 }
6371 }
6373 /* If this is an EQ or NE comparison of a constant with a PLUS_EXPR or
6374 a MINUS_EXPR of a constant, we can convert it into a comparison with
6375 a revised constant as long as no overflow occurs. */
6387 /* Similarly for a NEGATE_EXPR. */
6396 /* If we have X - Y == 0, we can convert that to X == Y and similarly
6397 for !=. Don't do this for ordered comparisons due to overflow. */
6403 /* If we are widening one operand of an integer comparison,
6404 see if the other operand is similarly being widened. Perhaps we
6405 can do the comparison in the narrower type. */
6415 /* If this is comparing a constant with a MIN_EXPR or a MAX_EXPR of a
6416 constant, we can simplify it. */
6423 /* If we are comparing an ABS_EXPR with a constant, we can
6424 convert all the cases into explicit comparisons, but they may
6425 well not be faster than doing the ABS and one comparison.
6426 But ABS (X) <= C is a range comparison, which becomes a subtraction
6427 and a comparison, and is probably faster. */
6439 /* If this is an EQ or NE comparison with zero and ARG0 is
6440 (1 << foo) & bar, convert it to (bar >> foo) & 1. Both require
6441 two operations, but the latter can be done in one less insn
6442 on machines that have only two-operand insns or on which a
6443 constant cannot be the first operand. */
6446 {
6449 return
6457 integer_one_node)),
6458 arg1));
6461 return
6469 integer_one_node)),
6470 arg1));
6471 }
6473 /* If this is an NE or EQ comparison of zero against the result of a
6474 signed MOD operation whose second operand is a power of 2, make
6475 the MOD operation unsigned since it is simpler and equivalent. */
6484 {
6491 }
6493 /* If this is an NE comparison of zero with an AND of one, remove the
6494 comparison since the AND will give the correct value. */
6500 /* If we have (A & C) == C where C is a power of 2, convert this into
6501 (A & C) != 0. Similarly for NE_EXPR. */
6509 /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
6510 and similarly for >= into !=. */
6526 return
6533 /* Simplify comparison of something with itself. (For IEEE
6534 floating-point, we can only do some of these simplifications.) */
6536 {
6538 {
6549 /* For NE, we can only do this simplification if integer. */
6552 /* ... fall through ... */
6558 }
6559 }
6561 /* An unsigned comparison against 0 can be simplified. */
6566 {
6568 {
6580 arg0);
6584 arg0);
6587 }
6588 }
6590 /* Comparisons with the highest or lowest possible integer of
6591 the specified size will have known values and an unsigned
6592 <= 0x7fffffff can be simplified. */
6593 {
6601 {
6607 {
6611 arg0);
6619 arg0);
6626 }
6633 {
6637 arg0);
6645 arg0);
6652 }
6658 /* signed_type does not work on pointer types. */
6662 {
6666 arg0),
6668 integer_zero_node)));
6672 arg0),
6674 integer_zero_node)));
6678 }
6679 }
6680 }
6682 /* If we are comparing an expression that just has comparisons
6683 of two integer values, arithmetic expressions of those comparisons,
6684 and constants, we can simplify it. There are only three cases
6685 to check: the two values can either be equal, the first can be
6686 greater, or the second can be greater. Fold the expression for
6687 those three values. Since each value must be 0 or 1, we have
6688 eight possibilities, each of which corresponds to the constant 0
6689 or 1 or one of the six possible comparisons.
6691 This handles common cases like (a > b) == 0 but also handles
6692 expressions like ((x > y) - (y > x)) > 0, which supposedly
6693 occur in macroized code. */
6696 {
6701 /* Don't handle degenerate cases here; they should already
6702 have been handled anyway. */
6711 {
6715 /* We can't just pass T to eval_subst in case cval1 or cval2
6716 was the same as ARG1. */
6718 tree high_result
6721 arg1));
6722 tree equal_result
6725 arg1));
6726 tree low_result
6729 arg1));
6731 /* All three of these results should be 0 or 1. Confirm they
6732 are. Then use those values to select the proper code
6733 to use. */
6741 {
6742 /* Make a 3-bit mask with the high-order bit being the
6743 value for `>', the next for '=', and the low for '<'. */
6747 {
6749 /* Always false. */
6770 /* Always true. */
6772 }
6777 else
6779 }
6780 }
6781 }
6783 /* If this is a comparison of a field, we may be able to simplify it. */
6787 /* Handle the constant case even without -O
6788 to make sure the warnings are given. */
6790 {
6793 }
6795 /* If this is a comparison of complex values and either or both sides
6796 are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
6797 comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
6798 This may prevent needless evaluations. */
6805 {
6818 type,
6821 }
6823 /* From here on, the only cases we handle are when the result is
6824 known to be a constant.
6826 To compute GT, swap the arguments and do LT.
6827 To compute GE, do LT and invert the result.
6828 To compute LE, swap the arguments, do LT and invert the result.
6829 To compute NE, do EQ and invert the result.
6831 Therefore, the code below must handle only EQ and LT. */
6834 {
6837 }
6839 /* Note that it is safe to invert for real values here because we
6840 will check below in the one case that it matters. */
6845 {
6848 }
6850 /* Compute a result for LT or EQ if args permit;
6851 otherwise return T. */
6853 {
6856 else
6861 }
6864 /* Assume a nonexplicit constant cannot equal an explicit one,
6865 since such code would be undefined anyway.
6866 Exception: on sysvr4, using #pragma weak,
6867 a label can come out as 0. */
6874 #endif
6875 /* Two real constants can be compared explicitly. */
6877 {
6878 /* If either operand is a NaN, the result is false with two
6879 exceptions: First, an NE_EXPR is true on NaNs, but that case
6880 is already handled correctly since we will be inverting the
6881 result for NE_EXPR. Second, if we had inverted a LE_EXPR
6882 or a GE_EXPR into a LT_EXPR, we must return true so that it
6883 will be inverted into false. */
6893 else
6897 }
6911 /* Pedantic ANSI C says that a conditional expression is never an lvalue,
6912 so all simple results must be passed through pedantic_non_lvalue. */
6914 return pedantic_non_lvalue
6919 /* If the second operand is zero, invert the comparison and swap
6920 the second and third operands. Likewise if the second operand
6921 is constant and the third is not or if the third operand is
6922 equivalent to the first operand of the comparison. */
6930 {
6931 /* See if this can be inverted. If it can't, possibly because
6932 it was a floating-point inequality comparison, don't do
6933 anything. */
6937 {
6941 /* arg1 should be the first argument of the new T. */
6944 }
6945 }
6947 /* If we have A op B ? A : C, we may be able to convert this to a
6948 simpler expression, depending on the operation and the values
6949 of B and C. IEEE floating point prevents this though,
6950 because A or B might be -0.0 or a NaN. */
6958 {
6964 /* If we have A op 0 ? A : -A, this is A, -A, abs (A), or abs (-A),
6965 depending on the comparison operation. */
6972 {
6974 return
6975 pedantic_non_lvalue
6977 negate_expr
6979 arg1))));
6987 return pedantic_non_lvalue
6994 return pedantic_non_lvalue
6998 arg1)))));
7001 }
7003 /* If this is A != 0 ? A : 0, this is simply A. For ==, it is
7004 always zero. */
7007 {
7012 }
7014 /* If this is A op B ? A : B, this is either A, B, min (A, B),
7015 or max (A, B), depending on the operation. */
7019 {
7024 /* Avoid adding NOP_EXPRs in case this is an lvalue. */
7029 {
7036 /* In C++ a ?: expression can be an lvalue, so put the
7037 operand which will be used if they are equal first
7038 so that we can convert this back to the
7039 corresponding COND_EXPR. */
7040 return pedantic_non_lvalue
7049 return pedantic_non_lvalue
7058 }
7059 }
7061 /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
7062 we might still be able to simplify this. For example,
7063 if C1 is one less or one more than C2, this might have started
7064 out as a MIN or MAX and been transformed by this function.
7065 Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE. */
7071 {
7073 /* We can replace A with C1 in this case. */
7080 /* If C1 is C2 + 1, this is min(A, C2). */
7085 return pedantic_non_lvalue
7090 /* If C1 is C2 - 1, this is min(A, C2). */
7095 return pedantic_non_lvalue
7100 /* If C1 is C2 - 1, this is max(A, C2). */
7105 return pedantic_non_lvalue
7110 /* If C1 is C2 + 1, this is max(A, C2). */
7115 return pedantic_non_lvalue
7122 }
7123 }
7125 /* If the second operand is simpler than the third, swap them
7126 since that produces better jump optimization results. */
7132 {
7133 /* See if this can be inverted. If it can't, possibly because
7134 it was a floating-point inequality comparison, don't do
7135 anything. */
7139 {
7143 /* arg1 should be the first argument of the new T. */
7146 }
7147 }
7149 /* Convert A ? 1 : 0 to simply A. */
7152 /* If we try to convert TREE_OPERAND (t, 0) to our type, the
7153 call to fold will try to move the conversion inside
7154 a COND, which will recurse. In that case, the COND_EXPR
7155 is probably the best choice, so leave it alone. */
7159 /* Look for expressions of the form A & 2 ? 2 : 0. The result of this
7160 operation is simply A & 2. */
7174 /* When pedantic, a compound expression can be neither an lvalue
7175 nor an integer constant expression. */
7178 /* Don't let (0, 0) be null pointer constant. */
7220 /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
7221 appropriate. */
7226 {
7230 tree arg01;
7241 {
7255 arg01));
7256 }
7259 }
7262 /* Check for a built-in function. */
7267 {
7271 }
7277 }
7279 /* Determine if first argument is a multiple of second argument. Return 0 if
7280 it is not, or we cannot easily determined it to be.
7282 An example of the sort of thing we care about (at this point; this routine
7283 could surely be made more general, and expanded to do what the *_DIV_EXPR's
7284 fold cases do now) is discovering that
7286 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7288 is a multiple of
7290 SAVE_EXPR (J * 8)
7292 when we know that the two SAVE_EXPR (J * 8) nodes are the same node.
7294 This code also handles discovering that
7296 SAVE_EXPR (I) * SAVE_EXPR (J * 8)
7298 is a multiple of 8 so we don't have to worry about dealing with a
7299 possible remainder.
7301 Note that we *look* inside a SAVE_EXPR only to determine how it was
7302 calculated; it is not safe for fold to do much of anything else with the
7303 internals of a SAVE_EXPR, since it cannot know when it will be evaluated
7304 at run time. For example, the latter example above *cannot* be implemented
7305 as SAVE_EXPR (I) * J or any variant thereof, since the value of J at
7306 evaluation time of the original SAVE_EXPR is not necessarily the same at
7307 the time the new expression is evaluated. The only optimization of this
7308 sort that would be valid is changing
7310 SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
7312 divided by 8 to
7314 SAVE_EXPR (I) * SAVE_EXPR (J)
7316 (where the same SAVE_EXPR (J) is used in the original and the
7317 transformed version). */
7319 static int
7321 tree type;
7322 tree top;
7323 tree bottom;
7324 {
7332 {
7344 {
7348 /* const_binop may not detect overflow correctly,
7349 so check for it explicitly here. */
7358 }
7362 /* Can't handle conversions from non-integral or wider integral type. */
7368 /* .. fall through ... */
7384 }
7385 }
7387 /* Return true if `t' is known to be non-negative. */
7389 int
7391 tree t;
7392 {
7394 {
7435 /* Truth values evaluate to 0 or 1, which is nonnegative. */
7437 else
7438 /* We don't know sign of `t', so be conservative and return false. */
7440 }
7441 }
7443 /* Return true if `r' is known to be non-negative.
7444 Only handles constants at the moment. */
7446 int
7448 rtx r;
7449 {
7451 {
7462 /* These are always nonnegative. */
7467 }
7468 }