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Make LoopDeletion work on loops with multiple edges, as long as the incoming

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values from all of the loop's exiting blocks are equal. Patch by Andrew Clinton.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126253 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Cameron Zwarich
2011-02-22 22:25:39 +00:00
parent 00743c2218
commit c4f3d51e12
2 changed files with 41 additions and 8 deletions
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23
lib/Transforms/Scalar/LoopDeletion.cpp
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@ -78,7 +78,6 @@ bool LoopDeletion::IsLoopDead(Loop* L,
SmallVector<BasicBlock*, 4>& exitingBlocks,
SmallVector<BasicBlock*, 4>& exitBlocks,
bool &Changed, BasicBlock *Preheader) {
BasicBlock* exitingBlock = exitingBlocks[0];
BasicBlock* exitBlock = exitBlocks[0];
// Make sure that all PHI entries coming from the loop are loop invariant.
@ -88,11 +87,21 @@ bool LoopDeletion::IsLoopDead(Loop* L,
// of the loop.
BasicBlock::iterator BI = exitBlock->begin();
while (PHINode* P = dyn_cast<PHINode>(BI)) {
Value* incoming = P->getIncomingValueForBlock(exitingBlock);
Value* incoming = P->getIncomingValueForBlock(exitingBlocks[0]);
// Make sure all exiting blocks produce the same incoming value for the exit
// block. If there are different incoming values for different exiting
// blocks, then it is impossible to statically determine which value should
// be used.
for (unsigned i = 1; i < exitingBlocks.size(); ++i) {
if (incoming != P->getIncomingValueForBlock(exitingBlocks[i]))
return false;
}
if (Instruction* I = dyn_cast<Instruction>(incoming))
if (!L->makeLoopInvariant(I, Changed, Preheader->getTerminator()))
return false;
++BI;
}
@ -147,10 +156,6 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
if (exitBlocks.size() != 1)
return false;
// Loops with multiple exits are too complicated to handle correctly.
if (exitingBlocks.size() != 1)
return false;
// Finally, we have to check that the loop really is dead.
bool Changed = false;
if (!IsLoopDead(L, exitingBlocks, exitBlocks, Changed, preheader))
@ -166,7 +171,6 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
// Now that we know the removal is safe, remove the loop by changing the
// branch from the preheader to go to the single exit block.
BasicBlock* exitBlock = exitBlocks[0];
BasicBlock* exitingBlock = exitingBlocks[0];
// Because we're deleting a large chunk of code at once, the sequence in which
// we remove things is very important to avoid invalidation issues. Don't
@ -183,9 +187,12 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
// Rewrite phis in the exit block to get their inputs from
// the preheader instead of the exiting block.
BasicBlock* exitingBlock = exitingBlocks[0];
BasicBlock::iterator BI = exitBlock->begin();
while (PHINode* P = dyn_cast<PHINode>(BI)) {
P->replaceUsesOfWith(exitingBlock, preheader);
for (unsigned i = 1; i < exitingBlocks.size(); ++i)
P->removeIncomingValue(exitingBlocks[i]);
++BI;
}