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[Bug tree-optimization/86270] Simple loop needs an extra register and an extra instruction
- 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: Thu, 21 Jun 2018 22:16:42 +0000
- Subject: [Bug tree-optimization/86270] Simple loop needs an extra register and an extra instruction
- Auto-submitted: auto-generated
- References: <bug-86270-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86270
--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> ---
:-(
So many transforms seem to have this kind of drawback...
We could always add a pair of single_use checks, but we are going to miss some
optimizations if we do that. Maybe it is slightly relevant that one +1 is in
the loop and the other +1 is outside of the loop?
It looks like it would work better if +1 and mov were done in the opposite
order (kind of like rotating the loop, but maybe that's more like moving one
instruction past the other and adapting the addressing in the mov).