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Ifcvt triangle: don't ifcvt 'true' BB if it has other predecessors; don't merge 'false' BB if it has other predecessors. 

llvm-svn: 37382
This commit is contained in:
Evan Cheng 2007-06-01 07:41:07 +00:00
parent a2ab4e5feb
commit 6a2cf070cc
1 changed files with 18 additions and 3 deletions
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21
llvm/lib/CodeGen/IfConversion.cpp
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@ -460,14 +460,29 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
if (!TrueBBI.isPredicable)
return false;
// FIXME: Consider duplicating if BB is small.
if (BBI.TrueBB->pred_size() > 1)
return false;
// Predicate the 'true' block after removing its branch.
TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
PredicateBlock(TrueBBI, BBI.BrCond);
// Join the 'true' and 'false' blocks by copying the instructions
// from the 'false' block to the 'true' block.
// If 'true' block has a 'false' successor, add a early exit branch to it.
if (TrueBBI.FalseBB) {
std::vector<MachineOperand> RevCond(TrueBBI.BrCond);
if (TII->ReverseBranchCondition(RevCond))
assert(false && "Unable to reverse branch condition!");
TII->InsertBranch(*BBI.TrueBB, TrueBBI.FalseBB, NULL, RevCond);
}
// Join the 'true' and 'false' blocks if the 'false' block has no other
// predecessors. Otherwise, add a unconditional branch from 'true' to 'false'.
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
MergeBlocks(TrueBBI, FalseBBI);
if (FalseBBI.BB->pred_size() == 2)
MergeBlocks(TrueBBI, FalseBBI);
else
InsertUncondBranch(TrueBBI.BB, FalseBBI.BB, TII);
// Now merge the entry of the triangle with the true block.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);