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Teach the cost model about the optimization in r169904: Truncation of induction variables costs the same as scalar trunc.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170051 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem
2012-12-13 00:21:03 +00:00
parent 0fabd08066
commit 807dad62a0
3 changed files with 21 additions and 3 deletions
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19
lib/Transforms/Vectorize/LoopVectorize.cpp
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@@ -106,8 +106,7 @@ struct LoopVectorize : public LoopPass {
}
DEBUG(dbgs() << "LV: Found a vectorizable loop ("<< VF << ") in "<<
L->getHeader()->getParent()->getParent()->getModuleIdentifier()<<
"\n");
F->getParent()->getModuleIdentifier()<<"\n");
// If we decided that it is *legal* to vectorizer the loop then do it.
InnerLoopVectorizer LB(L, SE, LI, DT, DL, VF);
@@ -1849,6 +1848,15 @@ LoopVectorizationLegality::isInductionVariable(PHINode *Phi) {
return NoInduction;
}
bool LoopVectorizationLegality::isInductionVariable(const Value *V) {
Value *In0 = const_cast<Value*>(V);
PHINode *PN = dyn_cast_or_null<PHINode>(In0);
if (!PN)
return false;
return Inductions.count(PN);
}
bool LoopVectorizationLegality::blockNeedsPredication(BasicBlock *BB) {
assert(TheLoop->contains(BB) && "Unknown block used");
@@ -2110,6 +2118,13 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
case Instruction::Trunc:
case Instruction::FPTrunc:
case Instruction::BitCast: {
// We optimize the truncation of induction variable.
// The cost of these is the same as the scalar operation.
if (I->getOpcode() == Instruction::Trunc &&
Legal->isInductionVariable(I->getOperand(0)))
return VTTI->getCastInstrCost(I->getOpcode(), I->getType(),
I->getOperand(0)->getType());
Type *SrcVecTy = ToVectorTy(I->getOperand(0)->getType(), VF);
return VTTI->getCastInstrCost(I->getOpcode(), VectorTy, SrcVecTy);
}