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[Bug tree-optimization/81555] Wrong code at -O1
- From: "glisse at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Wed, 26 Jul 2017 06:44:41 +0000
- Subject: [Bug tree-optimization/81555] Wrong code at -O1
- Auto-submitted: auto-generated
- References: <bug-81555-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81555
--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Dmitry Babokin from comment #2)
> Hmmm, but this one is triggered at -O1, another only at -O2.
-fno-tree-reassoc should help both.
It is often a combination of optimizations that causes the bug. Reassoc is
doing a good transformation, but it leaves wrong information around, which only
matters if some other pass (rightfully) takes advantage of that information.
Still, it was good to report both, and I expect we may add (a modified version
of) both to the testsuite once this is fixed, thanks.