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-rw-r--r--lib/Transforms/Utils/SimplifyCFG.cpp171
1 files changed, 93 insertions, 78 deletions
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 7b0bddbbb831..127a44df5344 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -22,6 +22,7 @@
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/Analysis/InstructionSimplify.h"
@@ -169,6 +170,8 @@ class SimplifyCFGOpt {
unsigned BonusInstThreshold;
AssumptionCache *AC;
SmallPtrSetImpl<BasicBlock *> *LoopHeaders;
+ // See comments in SimplifyCFGOpt::SimplifySwitch.
+ bool LateSimplifyCFG;
Value *isValueEqualityComparison(TerminatorInst *TI);
BasicBlock *GetValueEqualityComparisonCases(
TerminatorInst *TI, std::vector<ValueEqualityComparisonCase> &Cases);
@@ -192,9 +195,10 @@ class SimplifyCFGOpt {
public:
SimplifyCFGOpt(const TargetTransformInfo &TTI, const DataLayout &DL,
unsigned BonusInstThreshold, AssumptionCache *AC,
- SmallPtrSetImpl<BasicBlock *> *LoopHeaders)
+ SmallPtrSetImpl<BasicBlock *> *LoopHeaders,
+ bool LateSimplifyCFG)
: TTI(TTI), DL(DL), BonusInstThreshold(BonusInstThreshold), AC(AC),
- LoopHeaders(LoopHeaders) {}
+ LoopHeaders(LoopHeaders), LateSimplifyCFG(LateSimplifyCFG) {}
bool run(BasicBlock *BB);
};
@@ -710,10 +714,9 @@ BasicBlock *SimplifyCFGOpt::GetValueEqualityComparisonCases(
TerminatorInst *TI, std::vector<ValueEqualityComparisonCase> &Cases) {
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
Cases.reserve(SI->getNumCases());
- for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); i != e;
- ++i)
- Cases.push_back(
- ValueEqualityComparisonCase(i.getCaseValue(), i.getCaseSuccessor()));
+ for (auto Case : SI->cases())
+ Cases.push_back(ValueEqualityComparisonCase(Case.getCaseValue(),
+ Case.getCaseSuccessor()));
return SI->getDefaultDest();
}
@@ -846,12 +849,12 @@ bool SimplifyCFGOpt::SimplifyEqualityComparisonWithOnlyPredecessor(
}
for (SwitchInst::CaseIt i = SI->case_end(), e = SI->case_begin(); i != e;) {
--i;
- if (DeadCases.count(i.getCaseValue())) {
+ if (DeadCases.count(i->getCaseValue())) {
if (HasWeight) {
- std::swap(Weights[i.getCaseIndex() + 1], Weights.back());
+ std::swap(Weights[i->getCaseIndex() + 1], Weights.back());
Weights.pop_back();
}
- i.getCaseSuccessor()->removePredecessor(TI->getParent());
+ i->getCaseSuccessor()->removePredecessor(TI->getParent());
SI->removeCase(i);
}
}
@@ -996,8 +999,7 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
SmallSetVector<BasicBlock*, 4> FailBlocks;
if (!SafeToMergeTerminators(TI, PTI, &FailBlocks)) {
for (auto *Succ : FailBlocks) {
- std::vector<BasicBlock*> Blocks = { TI->getParent() };
- if (!SplitBlockPredecessors(Succ, Blocks, ".fold.split"))
+ if (!SplitBlockPredecessors(Succ, TI->getParent(), ".fold.split"))
return false;
}
}
@@ -1280,7 +1282,7 @@ static bool HoistThenElseCodeToIf(BranchInst *BI,
if (!isa<CallInst>(I1))
I1->setDebugLoc(
DILocation::getMergedLocation(I1->getDebugLoc(), I2->getDebugLoc()));
-
+
I2->eraseFromParent();
Changed = true;
@@ -1472,29 +1474,28 @@ static bool canSinkInstructions(
return false;
}
+ // Because SROA can't handle speculating stores of selects, try not
+ // to sink loads or stores of allocas when we'd have to create a PHI for
+ // the address operand. Also, because it is likely that loads or stores
+ // of allocas will disappear when Mem2Reg/SROA is run, don't sink them.
+ // This can cause code churn which can have unintended consequences down
+ // the line - see https://llvm.org/bugs/show_bug.cgi?id=30244.
+ // FIXME: This is a workaround for a deficiency in SROA - see
+ // https://llvm.org/bugs/show_bug.cgi?id=30188
+ if (isa<StoreInst>(I0) && any_of(Insts, [](const Instruction *I) {
+ return isa<AllocaInst>(I->getOperand(1));
+ }))
+ return false;
+ if (isa<LoadInst>(I0) && any_of(Insts, [](const Instruction *I) {
+ return isa<AllocaInst>(I->getOperand(0));
+ }))
+ return false;
+
for (unsigned OI = 0, OE = I0->getNumOperands(); OI != OE; ++OI) {
if (I0->getOperand(OI)->getType()->isTokenTy())
// Don't touch any operand of token type.
return false;
- // Because SROA can't handle speculating stores of selects, try not
- // to sink loads or stores of allocas when we'd have to create a PHI for
- // the address operand. Also, because it is likely that loads or stores
- // of allocas will disappear when Mem2Reg/SROA is run, don't sink them.
- // This can cause code churn which can have unintended consequences down
- // the line - see https://llvm.org/bugs/show_bug.cgi?id=30244.
- // FIXME: This is a workaround for a deficiency in SROA - see
- // https://llvm.org/bugs/show_bug.cgi?id=30188
- if (OI == 1 && isa<StoreInst>(I0) &&
- any_of(Insts, [](const Instruction *I) {
- return isa<AllocaInst>(I->getOperand(1));
- }))
- return false;
- if (OI == 0 && isa<LoadInst>(I0) && any_of(Insts, [](const Instruction *I) {
- return isa<AllocaInst>(I->getOperand(0));
- }))
- return false;
-
auto SameAsI0 = [&I0, OI](const Instruction *I) {
assert(I->getNumOperands() == I0->getNumOperands());
return I->getOperand(OI) == I0->getOperand(OI);
@@ -1546,7 +1547,7 @@ static bool sinkLastInstruction(ArrayRef<BasicBlock*> Blocks) {
}))
return false;
}
-
+
// We don't need to do any more checking here; canSinkLastInstruction should
// have done it all for us.
SmallVector<Value*, 4> NewOperands;
@@ -1653,7 +1654,7 @@ namespace {
bool isValid() const {
return !Fail;
}
-
+
void operator -- () {
if (Fail)
return;
@@ -1699,7 +1700,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
// / \
// [f(1)] [if]
// | | \
- // | | \
+ // | | |
// | [f(2)]|
// \ | /
// [ end ]
@@ -1737,7 +1738,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
}
if (UnconditionalPreds.size() < 2)
return false;
-
+
bool Changed = false;
// We take a two-step approach to tail sinking. First we scan from the end of
// each block upwards in lockstep. If the n'th instruction from the end of each
@@ -1767,7 +1768,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
unsigned NumPHIInsts = NumPHIdValues / UnconditionalPreds.size();
if ((NumPHIdValues % UnconditionalPreds.size()) != 0)
NumPHIInsts++;
-
+
return NumPHIInsts <= 1;
};
@@ -1790,7 +1791,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
}
if (!Profitable)
return false;
-
+
DEBUG(dbgs() << "SINK: Splitting edge\n");
// We have a conditional edge and we're going to sink some instructions.
// Insert a new block postdominating all blocks we're going to sink from.
@@ -1800,7 +1801,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
return false;
Changed = true;
}
-
+
// Now that we've analyzed all potential sinking candidates, perform the
// actual sink. We iteratively sink the last non-terminator of the source
// blocks into their common successor unless doing so would require too
@@ -1826,7 +1827,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
DEBUG(dbgs() << "SINK: stopping here, too many PHIs would be created!\n");
break;
}
-
+
if (!sinkLastInstruction(UnconditionalPreds))
return Changed;
NumSinkCommons++;
@@ -2078,6 +2079,9 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
Value *S = Builder.CreateSelect(
BrCond, TrueV, FalseV, TrueV->getName() + "." + FalseV->getName(), BI);
SpeculatedStore->setOperand(0, S);
+ SpeculatedStore->setDebugLoc(
+ DILocation::getMergedLocation(
+ BI->getDebugLoc(), SpeculatedStore->getDebugLoc()));
}
// Metadata can be dependent on the condition we are hoisting above.
@@ -2147,7 +2151,8 @@ static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) {
/// If we have a conditional branch on a PHI node value that is defined in the
/// same block as the branch and if any PHI entries are constants, thread edges
/// corresponding to that entry to be branches to their ultimate destination.
-static bool FoldCondBranchOnPHI(BranchInst *BI, const DataLayout &DL) {
+static bool FoldCondBranchOnPHI(BranchInst *BI, const DataLayout &DL,
+ AssumptionCache *AC) {
BasicBlock *BB = BI->getParent();
PHINode *PN = dyn_cast<PHINode>(BI->getCondition());
// NOTE: we currently cannot transform this case if the PHI node is used
@@ -2239,6 +2244,11 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const DataLayout &DL) {
// Insert the new instruction into its new home.
if (N)
EdgeBB->getInstList().insert(InsertPt, N);
+
+ // Register the new instruction with the assumption cache if necessary.
+ if (auto *II = dyn_cast_or_null<IntrinsicInst>(N))
+ if (II->getIntrinsicID() == Intrinsic::assume)
+ AC->registerAssumption(II);
}
// Loop over all of the edges from PredBB to BB, changing them to branch
@@ -2251,7 +2261,7 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const DataLayout &DL) {
}
// Recurse, simplifying any other constants.
- return FoldCondBranchOnPHI(BI, DL) | true;
+ return FoldCondBranchOnPHI(BI, DL, AC) | true;
}
return false;
@@ -3433,8 +3443,8 @@ static bool SimplifySwitchOnSelect(SwitchInst *SI, SelectInst *Select) {
// Find the relevant condition and destinations.
Value *Condition = Select->getCondition();
- BasicBlock *TrueBB = SI->findCaseValue(TrueVal).getCaseSuccessor();
- BasicBlock *FalseBB = SI->findCaseValue(FalseVal).getCaseSuccessor();
+ BasicBlock *TrueBB = SI->findCaseValue(TrueVal)->getCaseSuccessor();
+ BasicBlock *FalseBB = SI->findCaseValue(FalseVal)->getCaseSuccessor();
// Get weight for TrueBB and FalseBB.
uint32_t TrueWeight = 0, FalseWeight = 0;
@@ -3444,9 +3454,9 @@ static bool SimplifySwitchOnSelect(SwitchInst *SI, SelectInst *Select) {
GetBranchWeights(SI, Weights);
if (Weights.size() == 1 + SI->getNumCases()) {
TrueWeight =
- (uint32_t)Weights[SI->findCaseValue(TrueVal).getSuccessorIndex()];
+ (uint32_t)Weights[SI->findCaseValue(TrueVal)->getSuccessorIndex()];
FalseWeight =
- (uint32_t)Weights[SI->findCaseValue(FalseVal).getSuccessorIndex()];
+ (uint32_t)Weights[SI->findCaseValue(FalseVal)->getSuccessorIndex()];
}
}
@@ -4148,15 +4158,16 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) {
}
}
} else if (auto *SI = dyn_cast<SwitchInst>(TI)) {
- for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); i != e;
- ++i)
- if (i.getCaseSuccessor() == BB) {
- BB->removePredecessor(SI->getParent());
- SI->removeCase(i);
- --i;
- --e;
- Changed = true;
+ for (auto i = SI->case_begin(), e = SI->case_end(); i != e;) {
+ if (i->getCaseSuccessor() != BB) {
+ ++i;
+ continue;
}
+ BB->removePredecessor(SI->getParent());
+ i = SI->removeCase(i);
+ e = SI->case_end();
+ Changed = true;
+ }
} else if (auto *II = dyn_cast<InvokeInst>(TI)) {
if (II->getUnwindDest() == BB) {
removeUnwindEdge(TI->getParent());
@@ -4239,18 +4250,18 @@ static bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder) {
SmallVector<ConstantInt *, 16> CasesA;
SmallVector<ConstantInt *, 16> CasesB;
- for (SwitchInst::CaseIt I : SI->cases()) {
- BasicBlock *Dest = I.getCaseSuccessor();
+ for (auto Case : SI->cases()) {
+ BasicBlock *Dest = Case.getCaseSuccessor();
if (!DestA)
DestA = Dest;
if (Dest == DestA) {
- CasesA.push_back(I.getCaseValue());
+ CasesA.push_back(Case.getCaseValue());
continue;
}
if (!DestB)
DestB = Dest;
if (Dest == DestB) {
- CasesB.push_back(I.getCaseValue());
+ CasesB.push_back(Case.getCaseValue());
continue;
}
return false; // More than two destinations.
@@ -4375,7 +4386,7 @@ static bool EliminateDeadSwitchCases(SwitchInst *SI, AssumptionCache *AC,
bool HasDefault =
!isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg());
const unsigned NumUnknownBits =
- Bits - (KnownZero.Or(KnownOne)).countPopulation();
+ Bits - (KnownZero | KnownOne).countPopulation();
assert(NumUnknownBits <= Bits);
if (HasDefault && DeadCases.empty() &&
NumUnknownBits < 64 /* avoid overflow */ &&
@@ -4400,17 +4411,17 @@ static bool EliminateDeadSwitchCases(SwitchInst *SI, AssumptionCache *AC,
// Remove dead cases from the switch.
for (ConstantInt *DeadCase : DeadCases) {
- SwitchInst::CaseIt Case = SI->findCaseValue(DeadCase);
- assert(Case != SI->case_default() &&
+ SwitchInst::CaseIt CaseI = SI->findCaseValue(DeadCase);
+ assert(CaseI != SI->case_default() &&
"Case was not found. Probably mistake in DeadCases forming.");
if (HasWeight) {
- std::swap(Weights[Case.getCaseIndex() + 1], Weights.back());
+ std::swap(Weights[CaseI->getCaseIndex() + 1], Weights.back());
Weights.pop_back();
}
// Prune unused values from PHI nodes.
- Case.getCaseSuccessor()->removePredecessor(SI->getParent());
- SI->removeCase(Case);
+ CaseI->getCaseSuccessor()->removePredecessor(SI->getParent());
+ SI->removeCase(CaseI);
}
if (HasWeight && Weights.size() >= 2) {
SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());
@@ -4464,10 +4475,9 @@ static bool ForwardSwitchConditionToPHI(SwitchInst *SI) {
typedef DenseMap<PHINode *, SmallVector<int, 4>> ForwardingNodesMap;
ForwardingNodesMap ForwardingNodes;
- for (SwitchInst::CaseIt I = SI->case_begin(), E = SI->case_end(); I != E;
- ++I) {
- ConstantInt *CaseValue = I.getCaseValue();
- BasicBlock *CaseDest = I.getCaseSuccessor();
+ for (auto Case : SI->cases()) {
+ ConstantInt *CaseValue = Case.getCaseValue();
+ BasicBlock *CaseDest = Case.getCaseSuccessor();
int PhiIndex;
PHINode *PHI =
@@ -5202,8 +5212,8 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
// common destination, as well as the min and max case values.
assert(SI->case_begin() != SI->case_end());
SwitchInst::CaseIt CI = SI->case_begin();
- ConstantInt *MinCaseVal = CI.getCaseValue();
- ConstantInt *MaxCaseVal = CI.getCaseValue();
+ ConstantInt *MinCaseVal = CI->getCaseValue();
+ ConstantInt *MaxCaseVal = CI->getCaseValue();
BasicBlock *CommonDest = nullptr;
typedef SmallVector<std::pair<ConstantInt *, Constant *>, 4> ResultListTy;
@@ -5213,7 +5223,7 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
SmallVector<PHINode *, 4> PHIs;
for (SwitchInst::CaseIt E = SI->case_end(); CI != E; ++CI) {
- ConstantInt *CaseVal = CI.getCaseValue();
+ ConstantInt *CaseVal = CI->getCaseValue();
if (CaseVal->getValue().slt(MinCaseVal->getValue()))
MinCaseVal = CaseVal;
if (CaseVal->getValue().sgt(MaxCaseVal->getValue()))
@@ -5222,7 +5232,7 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
// Resulting value at phi nodes for this case value.
typedef SmallVector<std::pair<PHINode *, Constant *>, 4> ResultsTy;
ResultsTy Results;
- if (!GetCaseResults(SI, CaseVal, CI.getCaseSuccessor(), &CommonDest,
+ if (!GetCaseResults(SI, CaseVal, CI->getCaseSuccessor(), &CommonDest,
Results, DL, TTI))
return false;
@@ -5503,11 +5513,10 @@ static bool ReduceSwitchRange(SwitchInst *SI, IRBuilder<> &Builder,
auto *Rot = Builder.CreateOr(LShr, Shl);
SI->replaceUsesOfWith(SI->getCondition(), Rot);
- for (SwitchInst::CaseIt C = SI->case_begin(), E = SI->case_end(); C != E;
- ++C) {
- auto *Orig = C.getCaseValue();
+ for (auto Case : SI->cases()) {
+ auto *Orig = Case.getCaseValue();
auto Sub = Orig->getValue() - APInt(Ty->getBitWidth(), Base);
- C.setValue(
+ Case.setValue(
cast<ConstantInt>(ConstantInt::get(Ty, Sub.lshr(ShiftC->getValue()))));
}
return true;
@@ -5553,7 +5562,12 @@ bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) {
if (ForwardSwitchConditionToPHI(SI))
return SimplifyCFG(BB, TTI, BonusInstThreshold, AC) | true;
- if (SwitchToLookupTable(SI, Builder, DL, TTI))
+ // The conversion from switch to lookup tables results in difficult
+ // to analyze code and makes pruning branches much harder.
+ // This is a problem of the switch expression itself can still be
+ // restricted as a result of inlining or CVP. There only apply this
+ // transformation during late steps of the optimisation chain.
+ if (LateSimplifyCFG && SwitchToLookupTable(SI, Builder, DL, TTI))
return SimplifyCFG(BB, TTI, BonusInstThreshold, AC) | true;
if (ReduceSwitchRange(SI, Builder, DL, TTI))
@@ -5833,7 +5847,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
// through this block if any PHI node entries are constants.
if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition()))
if (PN->getParent() == BI->getParent())
- if (FoldCondBranchOnPHI(BI, DL))
+ if (FoldCondBranchOnPHI(BI, DL, AC))
return SimplifyCFG(BB, TTI, BonusInstThreshold, AC) | true;
// Scan predecessor blocks for conditional branches.
@@ -6012,8 +6026,9 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
///
bool llvm::SimplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
unsigned BonusInstThreshold, AssumptionCache *AC,
- SmallPtrSetImpl<BasicBlock *> *LoopHeaders) {
+ SmallPtrSetImpl<BasicBlock *> *LoopHeaders,
+ bool LateSimplifyCFG) {
return SimplifyCFGOpt(TTI, BB->getModule()->getDataLayout(),
- BonusInstThreshold, AC, LoopHeaders)
+ BonusInstThreshold, AC, LoopHeaders, LateSimplifyCFG)
.run(BB);
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-08-10 10:51:01 +0000