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SLP vectorizer: Don't hoist vector extracts of phis.

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Extracts coming from phis were being hoisted, while all others were
sunk to their uses. This was inconsistent and didn't seem to serve a
purpose. Changing all extracts to be sunk to uses is a prerequisite
for adding block frequency to the SLP vectorizer's cost model.

I benchmarked the change in isolation (without block frequency). I
only saw noise on x86 and some potentially significant improvements on
ARM. No major regressions is good enough for me.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204699 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick 2014-03-25 02:18:47 +00:00
parent b13d54f588
commit f5bf687cf7
1 changed files with 1 additions and 6 deletions
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7
lib/Transforms/Vectorize/SLPVectorizer.cpp
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@ -1690,12 +1690,7 @@ Value *BoUpSLP::vectorizeTree() {
Value *Lane = Builder.getInt32(it->Lane);
// Generate extracts for out-of-tree users.
// Find the insertion point for the extractelement lane.
if (PHINode *PN = dyn_cast<PHINode>(Vec)) {
Builder.SetInsertPoint(PN->getParent()->getFirstInsertionPt());
Value *Ex = Builder.CreateExtractElement(Vec, Lane);
CSEBlocks.insert(PN->getParent());
User->replaceUsesOfWith(Scalar, Ex);
} else if (isa<Instruction>(Vec)){
if (isa<Instruction>(Vec)){
if (PHINode *PH = dyn_cast<PHINode>(User)) {
for (int i = 0, e = PH->getNumIncomingValues(); i != e; ++i) {
if (PH->getIncomingValue(i) == Scalar) {