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Do not eliminate loop when it is invalid to do so. For example,

Browse Source 
for(int i = 0; i < N; i++) {
	if ( i == XYZ) {
		A;
	else
		B;
	}
	C;
	D;
}



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42058 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel 2007-09-17 21:01:05 +00:00
parent 5279d064bc
commit 8893ca6dab
1 changed files with 35 additions and 14 deletions
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47
lib/Transforms/Scalar/LoopIndexSplit.cpp
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@ -528,6 +528,20 @@ bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD) {
if (!safeExitingBlock(SD, ExitCondition->getParent())) if (!safeExitingBlock(SD, ExitCondition->getParent()))
return false; return false;
// If split condition is not safe then do not process this loop.
// For example,
// for(int i = 0; i < N; i++) {
// if ( i == XYZ) {
// A;
// else
// B;
// }
// C;
// D;
// }
if (!safeSplitCondition(SD))
return false;
// Update CFG. // Update CFG.
// Replace index variable with split value in loop body. Loop body is executed // Replace index variable with split value in loop body. Loop body is executed
@ -956,24 +970,11 @@ void LoopIndexSplit::removeBlocks(BasicBlock *DeadBB, Loop *LP,
bool LoopIndexSplit::safeSplitCondition(SplitInfo &SD) { bool LoopIndexSplit::safeSplitCondition(SplitInfo &SD) {
BasicBlock *SplitCondBlock = SD.SplitCondition->getParent(); BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
// Unable to handle triange loops at the moment.
// In triangle loop, split condition is in header and one of the
// the split destination is loop latch. If split condition is EQ
// then such loops are already handle in processOneIterationLoop().
BasicBlock *Latch = L->getLoopLatch(); BasicBlock *Latch = L->getLoopLatch();
BranchInst *SplitTerminator = BranchInst *SplitTerminator =
cast<BranchInst>(SplitCondBlock->getTerminator()); cast<BranchInst>(SplitCondBlock->getTerminator());
BasicBlock *Succ0 = SplitTerminator->getSuccessor(0); BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
BasicBlock *Succ1 = SplitTerminator->getSuccessor(1); BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
if (L->getHeader() == SplitCondBlock
&& (Latch == Succ0 || Latch == Succ1))
return false;
// If split condition branches heads do not have single predecessor,
// SplitCondBlock, then is not possible to remove inactive branch.
if (!Succ0->getSinglePredecessor() || !Succ1->getSinglePredecessor())
return false;
// Finally this split condition is safe only if merge point for // Finally this split condition is safe only if merge point for
// split condition branch is loop latch. This check along with previous // split condition branch is loop latch. This check along with previous
@ -1196,6 +1197,26 @@ bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
if (!safeSplitCondition(SD)) if (!safeSplitCondition(SD))
return false; return false;
BasicBlock *SplitCondBlock = SD.SplitCondition->getParent();
// Unable to handle triange loops at the moment.
// In triangle loop, split condition is in header and one of the
// the split destination is loop latch. If split condition is EQ
// then such loops are already handle in processOneIterationLoop().
BasicBlock *Latch = L->getLoopLatch();
BranchInst *SplitTerminator =
cast<BranchInst>(SplitCondBlock->getTerminator());
BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
if (L->getHeader() == SplitCondBlock
&& (Latch == Succ0 || Latch == Succ1))
return false;
// If split condition branches heads do not have single predecessor,
// SplitCondBlock, then is not possible to remove inactive branch.
if (!Succ0->getSinglePredecessor() || !Succ1->getSinglePredecessor())
return false;
// After loop is cloned there are two loops. // After loop is cloned there are two loops.
// //
// First loop, referred as ALoop, executes first part of loop's iteration // First loop, referred as ALoop, executes first part of loop's iteration