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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50384 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2008-04-29 00:45:15 +00:00
parent d3d5b888d9
commit e54cfdb32a
1 changed files with 21 additions and 0 deletions
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21
lib/Transforms/Scalar/DeadLoopElimination.cpp
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@ -162,6 +162,12 @@ bool DeadLoopElimination::runOnLoop(Loop* L, LPPassManager& LPM) {
L->getUniqueExitBlocks(exitBlocks);
BasicBlock* exitBlock = exitBlocks[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
// mess with this unless you have good reason and know what you're doing.
// Move simple loop-invariant expressions out of the loop, since they
// might be needed by the exit phis.
for (Loop::block_iterator LI = L->block_begin(), LE = L->block_end();
LI != LE; ++LI)
for (BasicBlock::iterator BI = (*LI)->begin(), BE = (*LI)->end();
@ -171,6 +177,7 @@ bool DeadLoopElimination::runOnLoop(Loop* L, LPPassManager& LPM) {
I->moveBefore(preheader->getTerminator());
}
// Connect the preheader directly to the exit block.
TerminatorInst* TI = preheader->getTerminator();
if (BranchInst* BI = dyn_cast<BranchInst>(TI)) {
if (BI->isUnconditional())
@ -180,9 +187,12 @@ bool DeadLoopElimination::runOnLoop(Loop* L, LPPassManager& LPM) {
else
BI->setSuccessor(1, exitBlock);
} else {
// FIXME: Support switches
return false;
}
// Rewrite phis in the exit block to get their inputs from
// the preheader instead of the exiting block.
BasicBlock::iterator BI = exitBlock->begin();
while (PHINode* P = dyn_cast<PHINode>(BI)) {
unsigned i = P->getBasicBlockIndex(exitingBlock);
@ -190,9 +200,12 @@ bool DeadLoopElimination::runOnLoop(Loop* L, LPPassManager& LPM) {
BI++;
}
// Update lots of internal structures...
DominatorTree& DT = getAnalysis<DominatorTree>();
for (Loop::block_iterator LI = L->block_begin(), LE = L->block_end();
LI != LE; ++LI) {
// Move all of the block's children to be children of the preheader, which
// allows us to remove the domtree entry for the block.
SmallPtrSet<DomTreeNode*, 8> childNodes;
childNodes.insert(DT[*LI]->begin(), DT[*LI]->end());
for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = childNodes.begin(),
@ -201,6 +214,8 @@ bool DeadLoopElimination::runOnLoop(Loop* L, LPPassManager& LPM) {
DT.eraseNode(*LI);
// Drop all references between the instructions and the block so
// that we don't have reference counting problems later.
for (BasicBlock::iterator BI = (*LI)->begin(), BE = (*LI)->end();
BI != BE; ++BI) {
BI->dropAllReferences();
@ -209,6 +224,8 @@ bool DeadLoopElimination::runOnLoop(Loop* L, LPPassManager& LPM) {
(*LI)->dropAllReferences();
}
// Erase the instructions and the blocks without having to worry
// about ordering because we already dropped the references.
for (Loop::block_iterator LI = L->block_begin(), LE = L->block_end();
LI != LE; ++LI) {
for (BasicBlock::iterator BI = (*LI)->begin(), BE = (*LI)->end();
@ -220,6 +237,8 @@ bool DeadLoopElimination::runOnLoop(Loop* L, LPPassManager& LPM) {
(*LI)->eraseFromParent();
}
// Finally, the blocks from loopinfo. This has to happen late because
// otherwise our loop iterators won't work.
LoopInfo& loopInfo = getAnalysis<LoopInfo>();
SmallPtrSet<BasicBlock*, 8> blocks;
blocks.insert(L->block_begin(), L->block_end());
@ -227,6 +246,8 @@ bool DeadLoopElimination::runOnLoop(Loop* L, LPPassManager& LPM) {
E = blocks.end(); I != E; ++I)
loopInfo.removeBlock(*I);
// The last step is to inform the loop pass manager that we've
// eliminated this loop.
LPM.deleteLoopFromQueue(L);
NumDeleted++;