[X86] Disable loop unrolling in loop vectorization pass when VF is 1.

The patch disabled unrolling in loop vectorization pass when VF==1 on x86 architecture,
by setting MaxInterleaveFactor to 1. Unrolling in loop vectorization pass may introduce
the cost of overflow check, memory boundary check and extra prologue/epilogue code when
regular unroller will unroll the loop another time. Disable it when VF==1 remove the
unnecessary cost on x86. The same can be done for other platforms after verifying
interleaving/memory bound checking to be not perf critical on those platforms.

Differential Revision: http://reviews.llvm.org/D9515

llvm-svn: 236613

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/TargetTransformInfo.cpp b/llvm/lib/Analysis/TargetTransformInfo.cpp
index a1519de25ee..e1744d1f296 100644
--- a/llvm/lib/Analysis/TargetTransformInfo.cpp
+++ b/llvm/lib/Analysis/TargetTransformInfo.cpp
@@ -186,8 +186,8 @@ unsigned TargetTransformInfo::getRegisterBitWidth(bool Vector) const {
   return TTIImpl->getRegisterBitWidth(Vector);
 }
 
-unsigned TargetTransformInfo::getMaxInterleaveFactor() const {
-  return TTIImpl->getMaxInterleaveFactor();
+unsigned TargetTransformInfo::getMaxInterleaveFactor(unsigned VF) const {
+  return TTIImpl->getMaxInterleaveFactor(VF);
 }
 
 unsigned TargetTransformInfo::getArithmeticInstrCost(