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

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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


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236613 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Wei Mi
2015-05-06 17:12:25 +00:00
parent 530a574a9d
commit cac51be31f
16 changed files with 64 additions and 19 deletions
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8
lib/Target/X86/X86TargetTransformInfo.cpp
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@@ -66,7 +66,13 @@ unsigned X86TTIImpl::getRegisterBitWidth(bool Vector) {
}
unsigned X86TTIImpl::getMaxInterleaveFactor() {
unsigned X86TTIImpl::getMaxInterleaveFactor(unsigned VF) {
// If the loop will not be vectorized, don't interleave the loop.
// Let regular unroll to unroll the loop, which saves the overflow
// check and memory check cost.
if (VF == 1)
return 1;
if (ST->isAtom())
return 1;