http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56935
Bug #: 56935
Summary: Basic block is not SLP-vectorizeed after r197635.
Classification: Unclassified
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: ysrum...@gmail.com
It looks that after cost model changing some performance opportunities were
lost.
It can be seen for the attached test-case:
before this change
t.c:29: note: Cost model analysis:
Vector inside of basic block cost: 5
Vector prologue cost: 0
Vector epilogue cost: 0
Scalar cost of basic block: 6
t.c:29: note: Basic block will be vectorized using SLP
after this change
t.c:29: note: Cost model analysis:
Vector inside of basic block cost: 5
Vector prologue cost: 1
Vector epilogue cost: 0
Scalar cost of basic block: 6
t.c:29: note: not vectorized: vectorization is not profitable.
Note that this test was extracted from 253.perlbench (spec2000) for which we
got -4.5% performance degradation on corei7 (with avx).
