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From: "ysrumyan at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/62012] New: Loop is not vectorized after function inlining (SCEV)
Date: Mon, 04 Aug 2014 14:48:00 -0000
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X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 4.10.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62012

            Bug ID: 62012
           Summary: Loop is not vectorized after function inlining (SCEV)
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ysrumyan at gmail dot com

We noticed that for one important benchmark using '-lto' options leads to
performance degradation which is caused by not-vectorizing the hottest loop
after function inlining. I can able to reproduce this deficiency using simple
test-case:
if we passed class by reference to function (it need to be compiled with
-DPARAM macros) loop is vectorized:
g++ -Ofast -m64 -march=core-avx2 -c test.cpp  -fdump-tree-vect-details -fopenmp
-DPARAM; grep 'note: vectorized' test.cpp.114t.vect                             
test.cpp:45:1: note: vectorized 1 loops in function.

But if we compile it without macros we get:
g++ -Ofast -m64 -march=core-avx2 -c test.cpp  -fdump-tree-vect-details
-fopenmp; grep 'note: vectorized' test.cpp.114t.vect
test.cpp:45:1: note: vectorized 0 loops in function.

It looks like SCEV issue.