[Bug tree-optimization/79534] New: tree-ifcombine aarch64 regression with trunk@245151

["brzycki at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79534

            Bug ID: 79534
           Summary: tree-ifcombine aarch64 regression with trunk@245151
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: brzycki at gmail dot com
  Target Milestone: ---

Created attachment 40752
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40752&action=edit
Reduced test-case. Larger scores are better.

I am seeing about a 6-10% performance regression on a proprietary benchmark on
AArch64, depending on the target micro-architecture.

# SHA d2c3261, trunk@245149, patch immediately preceding regression
/gcc/2017-02-03-12-17-59-d2c3261-master/bin/aarch64-sarc-linux-gnu-g++ -O3
-mcpu=cortex-a57 -std=c++11 -c a.cpp -o a.o
/gcc/2017-02-03-12-17-59-d2c3261-master/bin/aarch64-sarc-linux-gnu-g++  -o a
a.o
(best of 3 runs)
  SCORE_DIRECTION ==> larger is better
  SCORE ==> 1619.832509

# SHA f56c861, trunk@245151, regressing patch
/gcc/2017-02-03-14-03-35-f56c861-master/bin/aarch64-sarc-linux-gnu-g++ -O3
-mcpu=cortex-a57 -std=c++11 -c a.cpp -o a.o
/gcc/2017-02-03-14-03-35-f56c861-master/bin/aarch64-sarc-linux-gnu-g++  -o a
a.o
(best of 3 runs)
  SCORE_DIRECTION ==> larger is better
  SCORE ==> 1468.440527

# SHA e502db7, a recent 2/14/2017 tip build
/gcc/2017-02-14-23-11-19-e502db7-master/bin/aarch64-sarc-linux-gnu-g++ -O3
-mcpu=cortex-a57 -std=c++11 -c a.cpp -o a.o
/gcc/2017-02-14-23-11-19-e502db7-master/bin/aarch64-sarc-linux-gnu-g++  -o a
a.o
  SCORE_DIRECTION ==> larger is better
  SCORE ==> 1483.952217


I do not see the slowdown when testing on x86_64.