diff options
| author | jakub <jakub@138bc75d-0d04-0410-961f-82ee72b054a4> | 2014-05-15 10:01:11 +0000 |
|---|---|---|
| committer | jakub <jakub@138bc75d-0d04-0410-961f-82ee72b054a4> | 2014-05-15 10:01:11 +0000 |
| commit | d0a5f61cb3eb3be9966036fbaff89e3700d4ad80 (patch) | |
| tree | 31b84afe27a71436ba3b93702a5cb9d603f125fc /gcc/fold-const.c | |
| parent | 30566810bc8aba091a8763c87865522cc91ebf13 (diff) | |
| download | gcc-d0a5f61cb3eb3be9966036fbaff89e3700d4ad80.tar.gz | |
PR tree-optimization/61158
* fold-const.c (fold_binary_loc): If X is zero-extended and
shiftc >= prec, make sure zerobits is all ones instead of
invoking undefined behavior.
* gcc.dg/pr61158.c: New test.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@210467 138bc75d-0d04-0410-961f-82ee72b054a4
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 5e064dfa98c..8f659db76a2 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -11972,11 +11972,17 @@ fold_binary_loc (location_t loc, /* See if we can shorten the right shift. */ if (shiftc < prec) shift_type = inner_type; + /* Otherwise X >> C1 is all zeros, so we'll optimize + it into (X, 0) later on by making sure zerobits + is all ones. */ } } zerobits = ~(unsigned HOST_WIDE_INT) 0; - zerobits >>= HOST_BITS_PER_WIDE_INT - shiftc; - zerobits <<= prec - shiftc; + if (shiftc < prec) + { + zerobits >>= HOST_BITS_PER_WIDE_INT - shiftc; + zerobits <<= prec - shiftc; + } /* For arithmetic shift if sign bit could be set, zerobits can contain actually sign bits, so no transformation is possible, unless MASK masks them all away. In that @@ -11994,7 +12000,7 @@ fold_binary_loc (location_t loc, /* ((X << 16) & 0xff00) is (X, 0). */ if ((mask & zerobits) == mask) return omit_one_operand_loc (loc, type, - build_int_cst (type, 0), arg0); + build_int_cst (type, 0), arg0); newmask = mask | zerobits; if (newmask != mask && (newmask & (newmask + 1)) == 0) |