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| author | Roger Sayle <roger@nextmovesoftware.com> | 2022-02-09 14:21:08 +0000 |
|---|---|---|
| committer | Roger Sayle <roger@nextmovesoftware.com> | 2022-02-09 14:23:17 +0000 |
| commit | 2d3c477599b02b06e338acd5f5098ee7a3fe6176 (patch) | |
| tree | 8b4b47886d584fd019a8e03583e4ce58ed66f84b /gcc/c/c-fold.cc | |
| parent | be9cd0ca8a5f13cfee6a39b217d439a25c53553a (diff) | |
| download | gcc-2d3c477599b02b06e338acd5f5098ee7a3fe6176.zip gcc-2d3c477599b02b06e338acd5f5098ee7a3fe6176.tar.gz gcc-2d3c477599b02b06e338acd5f5098ee7a3fe6176.tar.bz2 | |
[PATCH] PR tree-optimization/104420: Fix checks for constant folding X*0.0
This patch resolves PR tree-optimization/104420, which is a P1 regression
where, as observed by Jakub Jelinek, the conditions for constant folding
x*0.0 are incorrect (following my patch for PR tree-optimization/96392).
The multiplication x*0.0 may yield a negative zero result, -0.0, if X is
negative (not just if x may be negative zero). Hence (without -ffast-math)
(int)x*0.0 can't be optimized to 0.0, but (unsigned)x*0.0 can be constant
folded. This adds a bunch of test cases to confirm the desired behaviour,
and removes an incorrect test from gcc.dg/pr96392.c which checked for the
wrong behaviour.
2022-02-09 Roger Sayle <roger@nextmovesoftware.com>
gcc/ChangeLog
PR tree-optimization/104420
* match.pd (mult @0 real_zerop): Tweak conditions for constant
folding X*0.0 (or X*-0.0) to HONOR_SIGNED_ZEROS when appropriate.
gcc/testsuite/ChangeLog
PR tree-optimization/104420
* gcc.dg/pr104420-1.c: New test case.
* gcc.dg/pr104420-2.c: New test case.
* gcc.dg/pr104420-3.c: New test case.
* gcc.dg/pr104420-4.c: New test case.
* gcc.dg/pr96392.c: Remove incorrect test.
Diffstat (limited to 'gcc/c/c-fold.cc')
0 files changed, 0 insertions, 0 deletions