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| author | Richard Biener <rguenther@suse.de> | 2018-01-26 10:30:36 +0000 |
|---|---|---|
| committer | Richard Biener <rguenth@gcc.gnu.org> | 2018-01-26 10:30:36 +0000 |
| commit | 5b55e6e333c97aaefc1db6c9d8411de578d05614 (patch) | |
| tree | 21db3fe6e8247b8085351073439c65bef3bda73c /gcc/fold-const.c | |
| parent | af2e3244f56152d94a18c1339a18a4c0b0e33060 (diff) | |
| download | gcc-5b55e6e333c97aaefc1db6c9d8411de578d05614.zip gcc-5b55e6e333c97aaefc1db6c9d8411de578d05614.tar.gz gcc-5b55e6e333c97aaefc1db6c9d8411de578d05614.tar.bz2 | |
re PR tree-optimization/81082 (Failure to vectorise after reassociating index computation)
2018-01-26 Richard Biener <rguenther@suse.de>
PR tree-optimization/81082
* fold-const.c (fold_plusminus_mult_expr): Do not perform the
association if it requires casting to unsigned.
* match.pd ((A * C) +- (B * C) -> (A+-B)): New patterns derived
from fold_plusminus_mult_expr to catch important cases late when
range info is available.
* gcc.dg/vect/pr81082.c: New testcase.
* gcc.dg/tree-ssa/loop-15.c: XFAIL the (int)((unsigned)n + -1U) * n + n
simplification to n * n.
From-SVN: r257077
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 744c355..c86c3f9 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -7097,7 +7097,7 @@ fold_plusminus_mult_expr (location_t loc, enum tree_code code, tree type, /* Same may be zero and thus the operation 'code' may overflow. Likewise same may be minus one and thus the multiplication may overflow. Perform - the operations in an unsigned type. */ + the sum operation in an unsigned type. */ tree utype = unsigned_type_for (type); tree tem = fold_build2_loc (loc, code, utype, fold_convert_loc (loc, utype, alt0), @@ -7110,9 +7110,9 @@ fold_plusminus_mult_expr (location_t loc, enum tree_code code, tree type, return fold_build2_loc (loc, MULT_EXPR, type, fold_convert (type, tem), same); - return fold_convert_loc (loc, type, - fold_build2_loc (loc, MULT_EXPR, utype, tem, - fold_convert_loc (loc, utype, same))); + /* Do not resort to unsigned multiplication because + we lose the no-overflow property of the expression. */ + return NULL_TREE; } /* Subroutine of native_encode_expr. Encode the INTEGER_CST |