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[Bug tree-optimization/61383] [4.8/4.9/4.10 Regression] wrong code at -O2 and -O3 on x86_64-linux-gnu
- From: "ebotcazou at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 02 Jun 2014 20:59:03 +0000
- Subject: [Bug tree-optimization/61383] [4.8/4.9/4.10 Regression] wrong code at -O2 and -O3 on x86_64-linux-gnu
- Auto-submitted: auto-generated
- References: <bug-61383-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61383
Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |ebotcazou at gcc dot gnu.org
--- Comment #6 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> There is similar issue in RTL PRE GCSE [1], PR45223.
Right, there are various similar old issues in the RTL optimizers, but we must
be extra careful because we really don't want to pessimize the common case to
fix some artificial testcases.
Note that we have some backup here: the (green) Dragon Book gives a code motion
algorithm that is subject to this kind of issues and the authors elegantly
write "For this reason, it is wise to use the following algorithm for code
motion only if optimization may be inhibited by the programmer". :-)