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Loop Index Split can eliminate a loop if it can determin if loop body is executed only once. There was a bug in determining IV based value of the iteration for which the loop body is executed. Fix it.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@68071 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel
2009-03-30 22:24:10 +00:00
parent 2048cdb08e
commit b23c232fc8
2 changed files with 48 additions and 8 deletions
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32
lib/Transforms/Scalar/LoopIndexSplit.cpp
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@@ -48,6 +48,7 @@
#include "llvm/Analysis/Dominators.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/Compiler.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
@@ -345,10 +346,25 @@ bool LoopIndexSplit::processOneIterationLoop() {
if (!L->isLoopInvariant(SplitValue))
return false;
Instruction *OPI = dyn_cast<Instruction>(OPV);
if (!OPI) return false;
if (!OPI)
return false;
if (OPI->getParent() != Header || isUsedOutsideLoop(OPI, L))
return false;
Value *StartValue = IVStartValue;
Value *ExitValue = IVExitValue;;
if (OPV != IndVar) {
// If BR operand is IV based then use this operand to calculate
// effective conditions for loop body.
BinaryOperator *BOPV = dyn_cast<BinaryOperator>(OPV);
if (!BOPV)
return false;
if (BOPV->getOpcode() != Instruction::Add)
return false;
StartValue = BinaryOperator::CreateAdd(OPV, StartValue, "" , BR);
ExitValue = BinaryOperator::CreateAdd(OPV, ExitValue, "" , BR);
}
if (!cleanBlock(Header))
return false;
@@ -399,13 +415,13 @@ bool LoopIndexSplit::processOneIterationLoop() {
// and i32 c1, c2
Instruction *C1 = new ICmpInst(ExitCondition->isSignedPredicate() ?
ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE,
SplitValue, IVStartValue, "lisplit", BR);
SplitValue, StartValue, "lisplit", BR);
CmpInst::Predicate C2P = ExitCondition->getPredicate();
BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
if (LatchBR->getOperand(0) != Header)
C2P = CmpInst::getInversePredicate(C2P);
Instruction *C2 = new ICmpInst(C2P, SplitValue, IVExitValue, "lisplit", BR);
Instruction *C2 = new ICmpInst(C2P, SplitValue, ExitValue, "lisplit", BR);
Instruction *NSplitCond = BinaryOperator::CreateAnd(C1, C2, "lisplit", BR);
SplitCondition->replaceAllUsesWith(NSplitCond);
@@ -419,11 +435,11 @@ bool LoopIndexSplit::processOneIterationLoop() {
if (Header != *SI)
LatchSucc = *SI;
}
LatchBR->setUnconditionalDest(LatchSucc);
// Remove IVIncrement
IVIncrement->replaceAllUsesWith(UndefValue::get(IVIncrement->getType()));
IVIncrement->eraseFromParent();
// Clean up latch block.
Value *LatchBRCond = LatchBR->getCondition();
LatchBR->setUnconditionalDest(LatchSucc);
RecursivelyDeleteTriviallyDeadInstructions(LatchBRCond);
LPM->deleteLoopFromQueue(L);