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| author | Jeff Law <law@redhat.com> | 2020-11-05 20:42:17 -0700 |
|---|---|---|
| committer | Jeff Law <law@redhat.com> | 2020-11-05 20:46:00 -0700 |
| commit | 32ee472864ada44ef05b2a3b087b8ce413bee282 (patch) | |
| tree | 058c571d79ef476500b22795e764f3cce62c755d /gcc | |
| parent | 6483f05989ef31ebf2583deeb4753211ca2b7e17 (diff) | |
| download | gcc-32ee472864ada44ef05b2a3b087b8ce413bee282.zip gcc-32ee472864ada44ef05b2a3b087b8ce413bee282.tar.gz gcc-32ee472864ada44ef05b2a3b087b8ce413bee282.tar.bz2 | |
Improve overflow check
Convert
x < (short) ((unsigned short)x + const)
to
x <= SHORT_MAX – const
(and similarly for other integral types) if const is not 0.
gcc/
PR tree-optimization/97223
* match.pd (overflow detection and optimization): Handle conversions.
gcc/testsuite/
* gcc.dg/no-strict-overflow-4.c: Adjust expected output.
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/match.pd | 16 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.dg/no-strict-overflow-4.c | 5 |
2 files changed, 13 insertions, 8 deletions
diff --git a/gcc/match.pd b/gcc/match.pd index d82a620..349eab6 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -4945,18 +4945,22 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) /* When one argument is a constant, overflow detection can be simplified. Currently restricted to single use so as not to interfere too much with ADD_OVERFLOW detection in tree-ssa-math-opts.c. - A + CST CMP A -> A CMP' CST' */ + CONVERT?(CONVERT?(A) + CST) CMP A -> A CMP' CST' */ (for cmp (lt le ge gt) out (gt gt le le) (simplify - (cmp:c (plus@2 @0 INTEGER_CST@1) @0) - (if (TYPE_UNSIGNED (TREE_TYPE (@0)) - && TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0)) + (cmp:c (convert?@3 (plus@2 (convert?@4 @0) INTEGER_CST@1)) @0) + (if (TYPE_OVERFLOW_WRAPS (TREE_TYPE (@2)) + && types_match (TREE_TYPE (@0), TREE_TYPE (@3)) + && tree_nop_conversion_p (TREE_TYPE (@4), TREE_TYPE (@0)) && wi::to_wide (@1) != 0 && single_use (@2)) - (with { unsigned int prec = TYPE_PRECISION (TREE_TYPE (@0)); } + (with { + unsigned int prec = TYPE_PRECISION (TREE_TYPE (@0)); + signop sign = TYPE_SIGN (TREE_TYPE (@0)); + } (out @0 { wide_int_to_tree (TREE_TYPE (@0), - wi::max_value (prec, UNSIGNED) + wi::max_value (prec, sign) - wi::to_wide (@1)); }))))) /* To detect overflow in unsigned A - B, A < B is simpler than A - B > A. diff --git a/gcc/testsuite/gcc.dg/no-strict-overflow-4.c b/gcc/testsuite/gcc.dg/no-strict-overflow-4.c index b6d3da3..90145ff9 100644 --- a/gcc/testsuite/gcc.dg/no-strict-overflow-4.c +++ b/gcc/testsuite/gcc.dg/no-strict-overflow-4.c @@ -4,7 +4,8 @@ /* Source: Ian Lance Taylor. Dual of strict-overflow-4.c. */ /* We can only simplify the conditional when using strict overflow - semantics. */ + semantics or when using wrap overflow semantics. -fno-strict-overflow is + equivalent to -fwrapv. */ int foo (int i) @@ -12,4 +13,4 @@ foo (int i) return i + 1 > i; } -/* { dg-final { scan-tree-dump "\[^ \]*_.(\\\(D\\\))? (>|<) \[^ \]*_." "optimized" } } */ +/* { dg-final { scan-tree-dump "\[^ \]*_.(\\\(D\\\))? != \[0-9]+" "optimized" } } */ |