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[Bug target/20614] PowerPC - inefficient use of condition register
- From: "segher at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Thu, 30 Mar 2017 22:56:58 +0000
- Subject: [Bug target/20614] PowerPC - inefficient use of condition register
- Auto-submitted: auto-generated
- References: <bug-20614-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=20614
Segher Boessenkool <segher at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |segher at gcc dot gnu.org
Resolution|--- |FIXED
--- Comment #7 from Segher Boessenkool <segher at gcc dot gnu.org> ---
At least as far back as 4.9 GCC does no longer generate subfic; is uses
a mix of cntlzw/srwi, addic/subfe, and cmpw insns. Using more than three
CR fields is a bad idea (you then need to save and restore CR, which is
expensive on any CPU).
No doubt we could generate better code for this, but the reported
problem is no longer there, so I'm closing this bug.