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| author | Ian Lance Taylor <iant@google.com> | 2008-04-14 19:18:31 +0000 |
|---|---|---|
| committer | Ian Lance Taylor <ian@gcc.gnu.org> | 2008-04-14 19:18:31 +0000 |
| commit | 4c9db6e07aba115c21ab02068ccc332ce691775e (patch) | |
| tree | 5476839d99a5b4e7b501ffa138ec06b5cc5cb144 /gcc/fold-const.c | |
| parent | 3a5a8be12000125f4c12efea8bd6a466049a688d (diff) | |
| download | gcc-4c9db6e07aba115c21ab02068ccc332ce691775e.zip gcc-4c9db6e07aba115c21ab02068ccc332ce691775e.tar.gz gcc-4c9db6e07aba115c21ab02068ccc332ce691775e.tar.bz2 | |
flags.h (POINTER_TYPE_OVERFLOW_UNDEFINED): Define.
gcc/:
* flags.h (POINTER_TYPE_OVERFLOW_UNDEFINED): Define.
* fold-const.c (fold_comparison): If appropriate, test
POINTER_TYPE_OVERFLOW_UNDEFINED, and issue an overflow warning.
(fold_binary): Test POINTER_TYPE_OVERFLOW_UNDEFINED when
reassociating a pointer type.
* doc/invoke.texi (Optimize Options): Document that
-fstrict-overflow applies to pointer wraparound.
gcc/testsuite/:
* gcc.dg/strict-overflow-6.c: New.
* gcc.dg/no-strict-overflow-7.c: New.
* gcc.dg/Wstrict-overflow-22.c: New.
From-SVN: r134287
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 66e72a7..ce5673e 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -8568,7 +8568,9 @@ fold_comparison (enum tree_code code, tree type, tree op0, tree op1) because pointer arithmetic is restricted to retain within an object and overflow on pointer differences is undefined as of 6.5.6/8 and /9 with respect to the signed ptrdiff_t. */ - else if (bitpos0 == bitpos1) + else if (bitpos0 == bitpos1 + && ((code == EQ_EXPR || code == NE_EXPR) + || POINTER_TYPE_OVERFLOW_UNDEFINED)) { tree signed_size_type_node; signed_size_type_node = signed_type_for (size_type_node); @@ -8587,6 +8589,12 @@ fold_comparison (enum tree_code code, tree type, tree op0, tree op1) else offset1 = fold_convert (signed_size_type_node, offset1); + if (code != EQ_EXPR && code != NE_EXPR) + fold_overflow_warning (("assuming pointer wraparound does not " + "occur when comparing P +- C1 with " + "P +- C2"), + WARN_STRICT_OVERFLOW_COMPARISON); + return fold_build2 (code, type, offset0, offset1); } } @@ -9711,7 +9719,7 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1) /* With undefined overflow we can only associate constants with one variable. */ - if ((POINTER_TYPE_P (type) + if (((POINTER_TYPE_P (type) && POINTER_TYPE_OVERFLOW_UNDEFINED) || (INTEGRAL_TYPE_P (type) && !TYPE_OVERFLOW_WRAPS (type))) && var0 && var1) { |