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Add support for loops that don't start with Zero.

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This is important for loops in the LAPACK test-suite.
These loops start at 1 because they are auto-converted from fortran.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167084 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem
2012-10-31 00:45:26 +00:00
parent e6d781fd3c
commit 462d1ca428
3 changed files with 103 additions and 12 deletions
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lib/Transforms/Vectorize/LoopVectorize.cpp
+19 -12
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@@ -633,6 +633,10 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
BasicBlock *ExitBlock = OrigLoop->getExitBlock();
assert(ExitBlock && "Must have an exit block");
// The loop index does not have to start at Zero. It starts with this value.
OldInduction = Legal->getInduction();
Value *StartIdx = OldInduction->getIncomingValueForBlock(BypassBlock);
assert(OrigLoop->getNumBlocks() == 1 && "Invalid loop");
assert(BypassBlock && "Invalid loop structure");
@@ -648,7 +652,6 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
"scalar.preheader");
// Find the induction variable.
BasicBlock *OldBasicBlock = OrigLoop->getHeader();
OldInduction = Legal->getInduction();
assert(OldInduction && "We must have a single phi node.");
Type *IdxTy = OldInduction->getType();
@@ -658,7 +661,6 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
// Generate the induction variable.
Induction = Builder.CreatePHI(IdxTy, 2, "index");
Constant *Zero = ConstantInt::get(IdxTy, 0);
Constant *Step = ConstantInt::get(IdxTy, VF);
// Find the loop boundaries.
@@ -682,15 +684,22 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
// Count holds the overall loop count (N).
Value *Count = Exp.expandCodeFor(ExitCount, Induction->getType(), Loc);
// Add the start index to the loop count to get the new end index.
Value *IdxEnd = BinaryOperator::CreateAdd(Count, StartIdx, "end.idx", Loc);
// Now we need to generate the expression for N - (N % VF), which is
// the part that the vectorized body will execute.
Constant *CIVF = ConstantInt::get(IdxTy, VF);
Value *R = BinaryOperator::CreateURem(Count, CIVF, "n.mod.vf", Loc);
Value *CountRoundDown = BinaryOperator::CreateSub(Count, R, "n.vec", Loc);
Value *IdxEndRoundDown = BinaryOperator::CreateAdd(CountRoundDown, StartIdx,
"end.idx.rnd.down", Loc);
// Now, compare the new count to zero. If it is zero, jump to the scalar part.
Value *Cmp = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ,
CountRoundDown, ConstantInt::getNullValue(IdxTy),
IdxEndRoundDown,
StartIdx,
"cmp.zero", Loc);
BranchInst::Create(MiddleBlock, VectorPH, Cmp, Loc);
// Remove the old terminator.
@@ -699,8 +708,8 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
// Add a check in the middle block to see if we have completed
// all of the iterations in the first vector loop.
// If (N - N%VF) == N, then we *don't* need to run the remainder.
Value *CmpN = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, Count,
CountRoundDown, "cmp.n",
Value *CmpN = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, IdxEnd,
IdxEndRoundDown, "cmp.n",
MiddleBlock->getTerminator());
BranchInst::Create(ExitBlock, ScalarPH, CmpN, MiddleBlock->getTerminator());
@@ -709,10 +718,10 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
// Create i+1 and fill the PHINode.
Value *NextIdx = Builder.CreateAdd(Induction, Step, "index.next");
Induction->addIncoming(Zero, VectorPH);
Induction->addIncoming(StartIdx, VectorPH);
Induction->addIncoming(NextIdx, VecBody);
// Create the compare.
Value *ICmp = Builder.CreateICmpEQ(NextIdx, CountRoundDown);
Value *ICmp = Builder.CreateICmpEQ(NextIdx, IdxEndRoundDown);
Builder.CreateCondBr(ICmp, MiddleBlock, VecBody);
// Now we have two terminators. Remove the old one from the block.
@@ -720,7 +729,7 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
// Fix the scalar body iteration count.
unsigned BlockIdx = OldInduction->getBasicBlockIndex(ScalarPH);
OldInduction->setIncomingValue(BlockIdx, CountRoundDown);
OldInduction->setIncomingValue(BlockIdx, IdxEndRoundDown);
// Get ready to start creating new instructions into the vectorized body.
Builder.SetInsertPoint(VecBody->getFirstInsertionPt());
@@ -748,7 +757,6 @@ SingleBlockLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
LoopBypassBlock = BypassBlock;
}
/// This function returns the identity element (or neutral element) for
/// the operation K.
static unsigned
@@ -1518,10 +1526,9 @@ bool LoopVectorizationLegality::isInductionVariable(PHINode *Phi) {
return false;
}
const SCEV *Step = AR->getStepRecurrence(*SE);
const SCEV *Start = AR->getStart();
if (!Step->isOne() || !Start->isZero()) {
DEBUG(dbgs() << "LV: PHI does not start at zero or steps by one.\n");
if (!Step->isOne()) {
DEBUG(dbgs() << "LV: PHI stride does not equal one.\n");
return false;
}
return true;