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Re-apply r80926, with fixes: keep the domtree informed of new blocks

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that get created during loop unswitching, and fix SplitBlockPredecessors'
LCSSA updating code to create new PHIs instead of trying to just move
existing ones.

Also, optimize Loop::verifyLoop, since it gets called a lot. Use
searches on a sorted list of blocks instead of calling the "contains"
function, as is done in other places in the Loop class, since "contains"
does a linear search. Also, don't call verifyLoop from LoopSimplify or
LCSSA, as the PassManager is already calling verifyLoop as part of
LoopInfo's verifyAnalysis.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81221 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-09-08 15:45:00 +00:00
parent 6ca0b9e722
commit 5c89b5240c
12 changed files with 959 additions and 197 deletions
Download Patch File Download Diff File Expand all files Collapse all files

105
lib/Transforms/Scalar/LoopUnswitch.cpp
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@ -112,6 +112,10 @@ namespace {
private:
virtual void releaseMemory() {
UnswitchedVals.clear();
}
/// RemoveLoopFromWorklist - If the specified loop is on the loop worklist,
/// remove it.
void RemoveLoopFromWorklist(Loop *L) {
@ -518,7 +522,12 @@ void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
std::swap(TrueDest, FalseDest);
// Insert the new branch.
BranchInst::Create(TrueDest, FalseDest, BranchVal, InsertPt);
BranchInst *BI = BranchInst::Create(TrueDest, FalseDest, BranchVal, InsertPt);
// If either edge is critical, split it. This helps preserve LoopSimplify
// form for enclosing loops.
SplitCriticalEdge(BI, 0, this);
SplitCriticalEdge(BI, 1, this);
}
/// UnswitchTrivialCondition - Given a loop that has a trivial unswitchable
@ -575,47 +584,11 @@ void LoopUnswitch::SplitExitEdges(Loop *L,
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
BasicBlock *ExitBlock = ExitBlocks[i];
std::vector<BasicBlock*> Preds(pred_begin(ExitBlock), pred_end(ExitBlock));
for (unsigned j = 0, e = Preds.size(); j != e; ++j) {
BasicBlock* NewExitBlock = SplitEdge(Preds[j], ExitBlock, this);
BasicBlock* StartBlock = Preds[j];
BasicBlock* EndBlock;
if (NewExitBlock->getSinglePredecessor() == ExitBlock) {
EndBlock = NewExitBlock;
NewExitBlock = EndBlock->getSinglePredecessor();
} else {
EndBlock = ExitBlock;
}
std::set<PHINode*> InsertedPHIs;
PHINode* OldLCSSA = 0;
for (BasicBlock::iterator I = EndBlock->begin();
(OldLCSSA = dyn_cast<PHINode>(I)); ++I) {
Value* OldValue = OldLCSSA->getIncomingValueForBlock(NewExitBlock);
PHINode* NewLCSSA = PHINode::Create(OldLCSSA->getType(),
OldLCSSA->getName() + ".us-lcssa",
NewExitBlock->getTerminator());
NewLCSSA->addIncoming(OldValue, StartBlock);
OldLCSSA->setIncomingValue(OldLCSSA->getBasicBlockIndex(NewExitBlock),
NewLCSSA);
InsertedPHIs.insert(NewLCSSA);
}
BasicBlock::iterator InsertPt = EndBlock->getFirstNonPHI();
for (BasicBlock::iterator I = NewExitBlock->begin();
(OldLCSSA = dyn_cast<PHINode>(I)) && InsertedPHIs.count(OldLCSSA) == 0;
++I) {
PHINode *NewLCSSA = PHINode::Create(OldLCSSA->getType(),
OldLCSSA->getName() + ".us-lcssa",
InsertPt);
OldLCSSA->replaceAllUsesWith(NewLCSSA);
NewLCSSA->addIncoming(OldLCSSA, NewExitBlock);
}
}
SmallVector<BasicBlock *, 4> Preds(pred_begin(ExitBlock),
pred_end(ExitBlock));
SplitBlockPredecessors(ExitBlock, Preds.data(), Preds.size(),
".us-lcssa", this);
}
}
/// UnswitchNontrivialCondition - We determined that the loop is profitable
@ -945,27 +918,35 @@ void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
// FIXME: This is a hack. We need to keep the successor around
// and hooked up so as to preserve the loop structure, because
// trying to update it is complicated. So instead we preserve the
// loop structure and put the block on an dead code path.
BasicBlock *SISucc = SI->getSuccessor(i);
BasicBlock* Old = SI->getParent();
BasicBlock* Split = SplitBlock(Old, SI, this);
Instruction* OldTerm = Old->getTerminator();
BranchInst::Create(Split, SISucc,
ConstantInt::getTrue(Context), OldTerm);
LPM->deleteSimpleAnalysisValue(Old->getTerminator(), L);
Old->getTerminator()->eraseFromParent();
PHINode *PN;
for (BasicBlock::iterator II = SISucc->begin();
(PN = dyn_cast<PHINode>(II)); ++II) {
Value *InVal = PN->removeIncomingValue(Split, false);
PN->addIncoming(InVal, Old);
}
SI->removeCase(i);
// loop structure and put the block on a dead code path.
BasicBlock *Switch = SI->getParent();
SplitEdge(Switch, SI->getSuccessor(i), this);
// Compute the successors instead of relying on the return value
// of SplitEdge, since it may have split the switch successor
// after PHI nodes.
BasicBlock *NewSISucc = SI->getSuccessor(i);
BasicBlock *OldSISucc = *succ_begin(NewSISucc);
// Create an "unreachable" destination.
BasicBlock *Abort = BasicBlock::Create(Context, "us-unreachable",
Switch->getParent(),
OldSISucc);
new UnreachableInst(Context, Abort);
// Force the new case destination to branch to the "unreachable"
// block while maintaining a (dead) CFG edge to the old block.
NewSISucc->getTerminator()->eraseFromParent();
BranchInst::Create(Abort, OldSISucc,
ConstantInt::getTrue(Context), NewSISucc);
// Release the PHI operands for this edge.
for (BasicBlock::iterator II = NewSISucc->begin();
PHINode *PN = dyn_cast<PHINode>(II); ++II)
PN->setIncomingValue(PN->getBasicBlockIndex(Switch),
UndefValue::get(PN->getType()));
// Tell the domtree about the new block. We don't fully update
// the domtree here -- instead we force it to do a full recomputation
// after the pass is complete -- but we do need to inform it of
// new blocks.
if (DT)
DT->addNewBlock(Abort, NewSISucc);
break;
}
}