[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, 1 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index 0533355b01d..ed27cf84bbb 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -419,7 +419,7 @@ unsigned AArch64TTIImpl::getCostOfKeepingLiveOverCall(ArrayRef<Type *> Tys) {
   return Cost;
 }
 
-unsigned AArch64TTIImpl::getMaxInterleaveFactor() {
+unsigned AArch64TTIImpl::getMaxInterleaveFactor(unsigned VF) {
   if (ST->isCortexA57())
     return 4;
   return 2;