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[SimplifyCFG] FoldValueComparisonIntoPredecessors(): switch to non-permissive DomTree updates 

... which requires not adding a DomTree edge that we just added.
This commit is contained in:
Roman Lebedev 2021-01-05 16:23:59 +03:00
parent 29ca7d5a1a
commit fc96cb2dad
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GPG Key ID: 083C3EBB4A1689E0
1 changed files with 14 additions and 10 deletions
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24
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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@ -17,6 +17,7 @@
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/Sequence.h"
#include "llvm/ADT/SetOperations.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
@ -1085,7 +1086,6 @@ static void FitWeights(MutableArrayRef<uint64_t> Weights) {
/// (either a switch or a branch on "X == c").
/// See if any of the predecessors of the terminator block are value comparisons
/// on the same value. If so, and if safe to do so, fold them together.
// FIXME: switch to non-permissive DomTreeUpdater::applyUpdates().
bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
IRBuilder<> &Builder) {
BasicBlock *BB = TI->getParent();
@ -1129,7 +1129,7 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
// Based on whether the default edge from PTI goes to BB or not, fill in
// PredCases and PredDefault with the new switch cases we would like to
// build.
SmallVector<BasicBlock *, 8> NewSuccessors;
SmallMapVector<BasicBlock *, int, 8> NewSuccessors;
// Update the branch weight metadata along the way
SmallVector<uint64_t, 8> Weights;
@ -1185,7 +1185,7 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
if (PredDefault != BB)
Updates.push_back({DominatorTree::Delete, Pred, PredDefault});
PredDefault = BBDefault;
NewSuccessors.push_back(BBDefault);
++NewSuccessors[BBDefault];
}
unsigned CasesFromPred = Weights.size();
@ -1194,7 +1194,7 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
if (!PTIHandled.count(BBCases[i].Value) &&
BBCases[i].Dest != BBDefault) {
PredCases.push_back(BBCases[i]);
NewSuccessors.push_back(BBCases[i].Dest);
++NewSuccessors[BBCases[i].Dest];
if (SuccHasWeights || PredHasWeights) {
// The default weight is at index 0, so weight for the ith case
// should be at index i+1. Scale the cases from successor by
@ -1242,7 +1242,7 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
if (PredHasWeights || SuccHasWeights)
Weights.push_back(WeightsForHandled[BBCases[i].Value]);
PredCases.push_back(BBCases[i]);
NewSuccessors.push_back(BBCases[i].Dest);
++NewSuccessors[BBCases[i].Dest];
PTIHandled.erase(
BBCases[i].Value); // This constant is taken care of
}
@ -1253,16 +1253,20 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
if (PredHasWeights || SuccHasWeights)
Weights.push_back(WeightsForHandled[I]);
PredCases.push_back(ValueEqualityComparisonCase(I, BBDefault));
NewSuccessors.push_back(BBDefault);
++NewSuccessors[BBDefault];
}
}
// Okay, at this point, we know which new successor Pred will get. Make
// sure we update the number of entries in the PHI nodes for these
// successors.
for (BasicBlock *NewSuccessor : NewSuccessors) {
AddPredecessorToBlock(NewSuccessor, Pred, BB);
Updates.push_back({DominatorTree::Insert, Pred, NewSuccessor});
for (const std::pair<BasicBlock *, int /*Num*/> &NewSuccessor :
NewSuccessors) {
for (auto I : seq(0, NewSuccessor.second)) {
(void)I;
AddPredecessorToBlock(NewSuccessor.first, Pred, BB);
}
Updates.push_back({DominatorTree::Insert, Pred, NewSuccessor.first});
}
Builder.SetInsertPoint(PTI);
@ -1314,7 +1318,7 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
Updates.push_back({DominatorTree::Delete, Pred, BB});
if (DTU)
DTU->applyUpdatesPermissive(Updates);
DTU->applyUpdates(Updates);
Changed = true;
}