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BBVectorize: Better use of TTI->getShuffleCost

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When flipping the pair of subvectors that form a vector, if the
vector length is 2, we can use the SK_Reverse shuffle kind to get
more-accurate cost information. Also we can use the SK_ExtractSubvector
shuffle kind to get accurate subvector extraction costs.

The current cost model implementations don't yet seem complex enough
for this to make a difference (thus, there are no test cases with this
commit), but it should help in future.

Depending on how the various targets optimize and combine shuffles in
practice, we might be able to get more-accurate costs by combining the
costs of multiple shuffle kinds. For example, the cost of flipping the
subvector pairs could be modeled as two extractions and two subvector
insertions. These changes, however, should probably be motivated
by specific test cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173621 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel 2013-01-27 20:07:01 +00:00
parent 022688c260
commit 245b657ab6
1 changed files with 23 additions and 4 deletions
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27
lib/Transforms/Vectorize/BBVectorize.cpp
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@ -1824,6 +1824,16 @@ namespace {
R->second == PairConnectionSplat) {
int ESContrib = (int) getInstrCost(Instruction::ShuffleVector,
VTy, VTy);
if (VTy->getVectorNumElements() == 2) {
if (R->second == PairConnectionSplat)
ESContrib = std::min(ESContrib, (int) TTI->getShuffleCost(
TargetTransformInfo::SK_Broadcast, VTy));
else
ESContrib = std::min(ESContrib, (int) TTI->getShuffleCost(
TargetTransformInfo::SK_Reverse, VTy));
}
DEBUG(if (DebugPairSelection) dbgs() << "\tcost {" <<
*Q->second.first << " <-> " << *Q->second.second <<
"} -> {" <<
@ -1860,10 +1870,12 @@ namespace {
if (NeedsExtraction) {
int ESContrib;
if (Ty1->isVectorTy())
if (Ty1->isVectorTy()) {
ESContrib = (int) getInstrCost(Instruction::ShuffleVector,
Ty1, VTy);
else
ESContrib = std::min(ESContrib, (int) TTI->getShuffleCost(
TargetTransformInfo::SK_ExtractSubvector, VTy, 0, Ty1));
} else
ESContrib = (int) TTI->getVectorInstrCost(
Instruction::ExtractElement, VTy, 0);
@ -1890,10 +1902,13 @@ namespace {
if (NeedsExtraction) {
int ESContrib;
if (Ty2->isVectorTy())
if (Ty2->isVectorTy()) {
ESContrib = (int) getInstrCost(Instruction::ShuffleVector,
Ty2, VTy);
else
ESContrib = std::min(ESContrib, (int) TTI->getShuffleCost(
TargetTransformInfo::SK_ExtractSubvector, VTy,
Ty1->isVectorTy() ? Ty1->getVectorNumElements() : 1, Ty2));
} else
ESContrib = (int) TTI->getVectorInstrCost(
Instruction::ExtractElement, VTy, 1);
DEBUG(if (DebugPairSelection) dbgs() << "\tcost {" <<
@ -1969,6 +1984,10 @@ namespace {
} else if (IncomingPairs.count(VPR)) {
ESContrib = (int) getInstrCost(Instruction::ShuffleVector,
VTy, VTy);
if (VTy->getVectorNumElements() == 2)
ESContrib = std::min(ESContrib, (int) TTI->getShuffleCost(
TargetTransformInfo::SK_Reverse, VTy));
} else if (!Ty1->isVectorTy() && !Ty2->isVectorTy()) {
ESContrib = (int) TTI->getVectorInstrCost(
Instruction::InsertElement, VTy, 0);