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Final bit of simplification for FoldBranchToCommonDest.

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llvm-svn: 53528
This commit is contained in:
Chris Lattner 2008-07-13 21:20:19 +00:00
parent 3346d311c7
commit 67bf4acd15
1 changed files with 34 additions and 32 deletions
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66
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -1460,13 +1460,25 @@ static bool FoldBranchToCommonDest(BranchInst *BI) {
!SafeToMergeTerminators(BI, PBI))
continue;
// Canonicalize the predecessors condition (inverting it) if needed to allow
// this xform to trigger.
if (PBI->getSuccessor(0) == FalseDest ||
PBI->getSuccessor(1) == TrueDest) {
Instruction::BinaryOps Opc;
bool InvertPredCond = false;
if (PBI->getSuccessor(0) == TrueDest)
Opc = Instruction::Or;
else if (PBI->getSuccessor(1) == FalseDest)
Opc = Instruction::And;
else if (PBI->getSuccessor(0) == FalseDest)
Opc = Instruction::And, InvertPredCond = true;
else if (PBI->getSuccessor(1) == TrueDest)
Opc = Instruction::Or, InvertPredCond = true;
else
continue;
// If we need to invert the condition in the pred block to match, do so now.
if (InvertPredCond) {
Value *NewCond =
BinaryOperator::CreateNot(PBI->getCondition(),
PBI->getCondition()->getName()+".not", PBI);
PBI->getCondition()->getName()+".not", PBI);
PBI->setCondition(NewCond);
BasicBlock *OldTrue = PBI->getSuccessor(0);
BasicBlock *OldFalse = PBI->getSuccessor(1);
@ -1474,34 +1486,25 @@ static bool FoldBranchToCommonDest(BranchInst *BI) {
PBI->setSuccessor(1, OldTrue);
}
Instruction::BinaryOps Opc = Instruction::Shl; // sentinel.
// Clone Cond into the predecessor basic block, and or/and the
// two conditions together.
Instruction *New = Cond->clone();
PredBlock->getInstList().insert(PBI, New);
New->takeName(Cond);
Cond->setName(New->getName()+".old");
if (PBI->getSuccessor(0) == TrueDest && FalseDest != BB)
Opc = Instruction::Or;
else if (PBI->getSuccessor(1) == FalseDest && TrueDest != BB)
Opc = Instruction::And;
if (Opc != Instruction::Shl) {
// Clone Cond into the predecessor basic block, and or/and the
// two conditions together.
Instruction *New = Cond->clone();
PredBlock->getInstList().insert(PBI, New);
New->takeName(Cond);
Cond->setName(New->getName()+".old");
Value *NewCond = BinaryOperator::Create(Opc, PBI->getCondition(),
New, "or.cond", PBI);
PBI->setCondition(NewCond);
if (PBI->getSuccessor(0) == BB) {
AddPredecessorToBlock(TrueDest, PredBlock, BB);
PBI->setSuccessor(0, TrueDest);
}
if (PBI->getSuccessor(1) == BB) {
AddPredecessorToBlock(FalseDest, PredBlock, BB);
PBI->setSuccessor(1, FalseDest);
}
return true;
Value *NewCond = BinaryOperator::Create(Opc, PBI->getCondition(),
New, "or.cond", PBI);
PBI->setCondition(NewCond);
if (PBI->getSuccessor(0) == BB) {
AddPredecessorToBlock(TrueDest, PredBlock, BB);
PBI->setSuccessor(0, TrueDest);
}
if (PBI->getSuccessor(1) == BB) {
AddPredecessorToBlock(FalseDest, PredBlock, BB);
PBI->setSuccessor(1, FalseDest);
}
return true;
}
return false;
}
@ -1742,7 +1745,6 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
if (FoldBranchToCommonDest(BI))
return SimplifyCFG(BB) | 1;
// Scan predessor blocks for conditional branches.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))