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[NFC][SimplifyCFG] FoldBranchToCommonDest(): pull out 'common successor' into a variable

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Makes it easier to use it elsewhere
This commit is contained in:
Roman Lebedev 2020-12-14 16:37:43 +03:00
parent aef5ea6d96
commit 4292a82bd2
1 changed files with 14 additions and 10 deletions
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24
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -2944,12 +2944,16 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
// and non-PHI uses will become invalid.
FormTrivialSSAPHI(BB);
BasicBlock *UniqueSucc =
BI->isConditional()
? (PBI->getSuccessor(0) == BB ? TrueDest : FalseDest)
: TrueDest;
// Before cloning instructions, notify the successor basic block that it
// is about to have a new predecessor. This will update PHI nodes,
// which will allow us to update live-out uses of bonus instructions.
if (BI->isConditional())
AddPredecessorToBlock(PBI->getSuccessor(0) == BB ? TrueDest : FalseDest,
PredBlock, BB, MSSAU);
AddPredecessorToBlock(UniqueSucc, PredBlock, BB, MSSAU);
// If we have bonus instructions, clone them into the predecessor block.
// Note that there may be multiple predecessor blocks, so we cannot move
@ -3011,7 +3015,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
if (PBI->getSuccessor(0) == BB) {
if (HasWeights) {
// PBI: br i1 %x, BB, FalseDest
// BI: br i1 %y, TrueDest, FalseDest
// BI: br i1 %y, UniqueSucc, FalseDest
// TrueWeight is TrueWeight for PBI * TrueWeight for BI.
NewWeights.push_back(PredTrueWeight * SuccTrueWeight);
// FalseWeight is FalseWeight for PBI * TotalWeight for BI +
@ -3022,12 +3026,12 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
(SuccFalseWeight + SuccTrueWeight) +
PredTrueWeight * SuccFalseWeight);
}
PBI->setSuccessor(0, TrueDest);
PBI->setSuccessor(0, UniqueSucc);
}
if (PBI->getSuccessor(1) == BB) {
if (HasWeights) {
// PBI: br i1 %x, TrueDest, BB
// BI: br i1 %y, TrueDest, FalseDest
// BI: br i1 %y, TrueDest, UniqueSucc
// TrueWeight is TrueWeight for PBI * TotalWeight for BI +
// FalseWeight for PBI * TrueWeight for BI.
NewWeights.push_back(PredTrueWeight *
@ -3036,7 +3040,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
// FalseWeight is FalseWeight for PBI * FalseWeight for BI.
NewWeights.push_back(PredFalseWeight * SuccFalseWeight);
}
PBI->setSuccessor(1, FalseDest);
PBI->setSuccessor(1, UniqueSucc);
}
if (NewWeights.size() == 2) {
// Halve the weights if any of them cannot fit in an uint32_t
@ -3054,7 +3058,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
PHIs[i]->getIncomingValueForBlock(PBI->getParent()));
assert(PBI_C->getType()->isIntegerTy(1));
Instruction *MergedCond = nullptr;
if (PBI->getSuccessor(0) == TrueDest) {
if (PBI->getSuccessor(0) == UniqueSucc) {
// Create (PBI_Cond and PBI_C) or (!PBI_Cond and BI_Value)
// PBI_C is true: PBI_Cond or (!PBI_Cond and BI_Value)
// is false: !PBI_Cond and BI_Value
@ -3083,13 +3087,13 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
PHIs[i]->setIncomingValueForBlock(PBI->getParent(), MergedCond);
}
// PBI is changed to branch to TrueDest below. Remove itself from
// PBI is changed to branch to UniqueSucc below. Remove itself from
// potential phis from all other successors.
if (MSSAU)
MSSAU->changeCondBranchToUnconditionalTo(PBI, TrueDest);
MSSAU->changeCondBranchToUnconditionalTo(PBI, UniqueSucc);
// Change PBI from Conditional to Unconditional.
BranchInst *New_PBI = BranchInst::Create(TrueDest, PBI);
BranchInst *New_PBI = BranchInst::Create(UniqueSucc, PBI);
EraseTerminatorAndDCECond(PBI, MSSAU);
PBI = New_PBI;
}