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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
View File

@ -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);

24
test/Transforms/LoopIndexSplit/2009-03-30-undef.ll Normal file
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@ -0,0 +1,24 @@
; RUN: llvm-as < %s | opt -loop-index-split | llvm-dis | not grep undef
define i32 @main() {
entry:
br label %header
header:
%r = phi i32 [ 0, %entry ], [ %r3, %skip ]
%i = phi i32 [ 0, %entry ], [ %i1, %skip ]
%i99 = add i32 %i, 99
%cond = icmp eq i32 %i99, 3
br i1 %cond, label %body, label %skip
body:
br label %skip
skip:
%r3 = phi i32 [ %r, %header ], [ 3, %body ]
%i1 = add i32 %i, 1
%exitcond = icmp eq i32 %i1, 10
br i1 %exitcond, label %exit, label %header
exit:
ret i32 %r3
}