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| author | Jakub Jelinek <jakub@redhat.com> | 2013-01-21 18:55:34 +0100 |
|---|---|---|
| committer | Jakub Jelinek <jakub@gcc.gnu.org> | 2013-01-21 18:55:34 +0100 |
| commit | 8f498c1bdcb9d3b99905f654faa0a343c3e9ef99 (patch) | |
| tree | a3bdef1e25a778da35e6160d0a5f3bf467d3ae9b /gcc/fold-const.c | |
| parent | 35d59da7f7e282a68589d8c857ee7f0503d588d2 (diff) | |
| download | gcc-8f498c1bdcb9d3b99905f654faa0a343c3e9ef99.zip gcc-8f498c1bdcb9d3b99905f654faa0a343c3e9ef99.tar.gz gcc-8f498c1bdcb9d3b99905f654faa0a343c3e9ef99.tar.bz2 | |
re PR tree-optimization/56051 (Wrong expression evaluation)
PR tree-optimization/56051
* fold-const.c (fold_binary_loc): Don't fold
X < (cast) (1 << Y) into (X >> Y) != 0 if cast is either
a narrowing conversion, or widening conversion from signed
to unsigned.
* gcc.c-torture/execute/pr56051.c: New test.
From-SVN: r195343
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 4e1e63b..efad9a9 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -13556,10 +13556,22 @@ fold_binary_loc (location_t loc, TREE_OPERAND (arg1, 1)), build_zero_cst (TREE_TYPE (arg0))); + /* Similarly for X < (cast) (1 << Y). But cast can't be narrowing, + otherwise Y might be >= # of bits in X's type and thus e.g. + (unsigned char) (1 << Y) for Y 15 might be 0. + If the cast is widening, then 1 << Y should have unsigned type, + otherwise if Y is number of bits in the signed shift type minus 1, + we can't optimize this. E.g. (unsigned long long) (1 << Y) for Y + 31 might be 0xffffffff80000000. */ if ((code == LT_EXPR || code == GE_EXPR) && TYPE_UNSIGNED (TREE_TYPE (arg0)) && CONVERT_EXPR_P (arg1) && TREE_CODE (TREE_OPERAND (arg1, 0)) == LSHIFT_EXPR + && (TYPE_PRECISION (TREE_TYPE (arg1)) + >= TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (arg1, 0)))) + && (TYPE_UNSIGNED (TREE_TYPE (TREE_OPERAND (arg1, 0))) + || (TYPE_PRECISION (TREE_TYPE (arg1)) + == TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (arg1, 0))))) && integer_onep (TREE_OPERAND (TREE_OPERAND (arg1, 0), 0))) { tem = build2 (RSHIFT_EXPR, TREE_TYPE (arg0), arg0, |