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[NFC][SimplifyCFG] Extract CloneInstructionsIntoPredecessorBlockAndUpdateSSAUses() out of PerformBranchToCommonDestFolding() 

To be used in PerformValueComparisonIntoPredecessorFolding()
This commit is contained in:
Roman Lebedev 2021-01-24 00:49:27 +03:00
parent 67f9c87a65
commit 6f2753273e
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GPG Key ID: 083C3EBB4A1689E0
1 changed files with 50 additions and 43 deletions
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93
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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@ -1049,6 +1049,55 @@ static void FitWeights(MutableArrayRef<uint64_t> Weights) {
}
}
static void CloneInstructionsIntoPredecessorBlockAndUpdateSSAUses(
BasicBlock *BB, BasicBlock *PredBlock, ValueToValueMapTy &VMap) {
Instruction *PTI = PredBlock->getTerminator();
// If we have bonus instructions, clone them into the predecessor block.
// Note that there may be multiple predecessor blocks, so we cannot move
// bonus instructions to a predecessor block.
for (Instruction &BonusInst : *BB) {
if (isa<DbgInfoIntrinsic>(BonusInst) || BonusInst.isTerminator())
continue;
Instruction *NewBonusInst = BonusInst.clone();
if (PTI->getDebugLoc() != NewBonusInst->getDebugLoc()) {
// Unless the instruction has the same !dbg location as the original
// branch, drop it. When we fold the bonus instructions we want to make
// sure we reset their debug locations in order to avoid stepping on
// dead code caused by folding dead branches.
NewBonusInst->setDebugLoc(DebugLoc());
}
RemapInstruction(NewBonusInst, VMap,
RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
VMap[&BonusInst] = NewBonusInst;
// If we moved a load, we cannot any longer claim any knowledge about
// its potential value. The previous information might have been valid
// only given the branch precondition.
// For an analogous reason, we must also drop all the metadata whose
// semantics we don't understand. We *can* preserve !annotation, because
// it is tied to the instruction itself, not the value or position.
NewBonusInst->dropUnknownNonDebugMetadata(LLVMContext::MD_annotation);
PredBlock->getInstList().insert(PTI->getIterator(), NewBonusInst);
NewBonusInst->takeName(&BonusInst);
BonusInst.setName(NewBonusInst->getName() + ".old");
// Update (liveout) uses of bonus instructions,
// now that the bonus instruction has been cloned into predecessor.
SSAUpdater SSAUpdate;
SSAUpdate.Initialize(BonusInst.getType(),
(NewBonusInst->getName() + ".merge").str());
SSAUpdate.AddAvailableValue(BB, &BonusInst);
SSAUpdate.AddAvailableValue(PredBlock, NewBonusInst);
for (Use &U : make_early_inc_range(BonusInst.uses()))
SSAUpdate.RewriteUseAfterInsertions(U);
}
}
bool SimplifyCFGOpt::PerformValueComparisonIntoPredecessorFolding(
Instruction *TI, Value *&CV, Instruction *PTI, IRBuilder<> &Builder) {
BasicBlock *BB = TI->getParent();
@ -2890,50 +2939,8 @@ static bool PerformBranchToCommonDestFolding(BranchInst *BI, BranchInst *PBI,
if (MDNode *LoopMD = BI->getMetadata(LLVMContext::MD_loop))
PBI->setMetadata(LLVMContext::MD_loop, LoopMD);
// If we have bonus instructions, clone them into the predecessor block.
// Note that there may be multiple predecessor blocks, so we cannot move
// bonus instructions to a predecessor block.
ValueToValueMapTy VMap; // maps original values to cloned values
for (Instruction &BonusInst : *BB) {
if (isa<DbgInfoIntrinsic>(BonusInst) || isa<BranchInst>(BonusInst))
continue;
Instruction *NewBonusInst = BonusInst.clone();
if (PBI->getDebugLoc() != NewBonusInst->getDebugLoc()) {
// Unless the instruction has the same !dbg location as the original
// branch, drop it. When we fold the bonus instructions we want to make
// sure we reset their debug locations in order to avoid stepping on
// dead code caused by folding dead branches.
NewBonusInst->setDebugLoc(DebugLoc());
}
RemapInstruction(NewBonusInst, VMap,
RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
VMap[&BonusInst] = NewBonusInst;
// If we moved a load, we cannot any longer claim any knowledge about
// its potential value. The previous information might have been valid
// only given the branch precondition.
// For an analogous reason, we must also drop all the metadata whose
// semantics we don't understand. We *can* preserve !annotation, because
// it is tied to the instruction itself, not the value or position.
NewBonusInst->dropUnknownNonDebugMetadata(LLVMContext::MD_annotation);
PredBlock->getInstList().insert(PBI->getIterator(), NewBonusInst);
NewBonusInst->takeName(&BonusInst);
BonusInst.setName(NewBonusInst->getName() + ".old");
// Update (liveout) uses of bonus instructions,
// now that the bonus instruction has been cloned into predecessor.
SSAUpdater SSAUpdate;
SSAUpdate.Initialize(BonusInst.getType(),
(NewBonusInst->getName() + ".merge").str());
SSAUpdate.AddAvailableValue(BB, &BonusInst);
SSAUpdate.AddAvailableValue(PredBlock, NewBonusInst);
for (Use &U : make_early_inc_range(BonusInst.uses()))
SSAUpdate.RewriteUseAfterInsertions(U);
}
CloneInstructionsIntoPredecessorBlockAndUpdateSSAUses(BB, PredBlock, VMap);
// Now that the Cond was cloned into the predecessor basic block,
// or/and the two conditions together.