--- /dev/null
+//===- JumpThreading.h - thread control through conditional BBs -*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// See the comments on JumpThreadingPass.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_SCALAR_JUMPTHREADING_H
+#define LLVM_TRANSFORMS_SCALAR_JUMPTHREADING_H
+
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/Analysis/BlockFrequencyInfo.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/Analysis/LazyValueInfo.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/ValueHandle.h"
+
+namespace llvm {
+
+/// A private "module" namespace for types and utilities used by
+/// JumpThreading.
+/// These are implementation details and should not be used by clients.
+namespace jumpthreading {
+// These are at global scope so static functions can use them too.
+typedef SmallVectorImpl<std::pair<Constant *, BasicBlock *>> PredValueInfo;
+typedef SmallVector<std::pair<Constant *, BasicBlock *>, 8> PredValueInfoTy;
+
+// This is used to keep track of what kind of constant we're currently hoping
+// to find.
+enum ConstantPreference { WantInteger, WantBlockAddress };
+}
+
+/// This pass performs 'jump threading', which looks at blocks that have
+/// multiple predecessors and multiple successors. If one or more of the
+/// predecessors of the block can be proven to always jump to one of the
+/// successors, we forward the edge from the predecessor to the successor by
+/// duplicating the contents of this block.
+///
+/// An example of when this can occur is code like this:
+///
+/// if () { ...
+/// X = 4;
+/// }
+/// if (X < 3) {
+///
+/// In this case, the unconditional branch at the end of the first if can be
+/// revectored to the false side of the second if.
+///
+class JumpThreadingPass : public PassInfoMixin<JumpThreadingPass> {
+ TargetLibraryInfo *TLI;
+ LazyValueInfo *LVI;
+ std::unique_ptr<BlockFrequencyInfo> BFI;
+ std::unique_ptr<BranchProbabilityInfo> BPI;
+ bool HasProfileData;
+#ifdef NDEBUG
+ SmallPtrSet<const BasicBlock *, 16> LoopHeaders;
+#else
+ SmallSet<AssertingVH<const BasicBlock>, 16> LoopHeaders;
+#endif
+ DenseSet<std::pair<Value *, BasicBlock *>> RecursionSet;
+
+ unsigned BBDupThreshold;
+
+ // RAII helper for updating the recursion stack.
+ struct RecursionSetRemover {
+ DenseSet<std::pair<Value *, BasicBlock *>> &TheSet;
+ std::pair<Value *, BasicBlock *> ThePair;
+
+ RecursionSetRemover(DenseSet<std::pair<Value *, BasicBlock *>> &S,
+ std::pair<Value *, BasicBlock *> P)
+ : TheSet(S), ThePair(P) {}
+
+ ~RecursionSetRemover() { TheSet.erase(ThePair); }
+ };
+
+public:
+ JumpThreadingPass(int T = -1);
+
+ // Glue for old PM.
+ bool runImpl(Function &F, TargetLibraryInfo *TLI_, LazyValueInfo *LVI_,
+ bool HasProfileData_, std::unique_ptr<BlockFrequencyInfo> BFI_,
+ std::unique_ptr<BranchProbabilityInfo> BPI_);
+
+ PreservedAnalyses run(Function &F, AnalysisManager<Function> &AM);
+
+ void releaseMemory() {
+ BFI.reset();
+ BPI.reset();
+ }
+
+ void FindLoopHeaders(Function &F);
+ bool ProcessBlock(BasicBlock *BB);
+ bool ThreadEdge(BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs,
+ BasicBlock *SuccBB);
+ bool DuplicateCondBranchOnPHIIntoPred(
+ BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs);
+
+ bool
+ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,
+ jumpthreading::PredValueInfo &Result,
+ jumpthreading::ConstantPreference Preference,
+ Instruction *CxtI = nullptr);
+ bool ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
+ jumpthreading::ConstantPreference Preference,
+ Instruction *CxtI = nullptr);
+
+ bool ProcessBranchOnPHI(PHINode *PN);
+ bool ProcessBranchOnXOR(BinaryOperator *BO);
+ bool ProcessImpliedCondition(BasicBlock *BB);
+
+ bool SimplifyPartiallyRedundantLoad(LoadInst *LI);
+ bool TryToUnfoldSelect(CmpInst *CondCmp, BasicBlock *BB);
+ bool TryToUnfoldSelectInCurrBB(BasicBlock *BB);
+
+private:
+ BasicBlock *SplitBlockPreds(BasicBlock *BB, ArrayRef<BasicBlock *> Preds,
+ const char *Suffix);
+ void UpdateBlockFreqAndEdgeWeight(BasicBlock *PredBB, BasicBlock *BB,
+ BasicBlock *NewBB, BasicBlock *SuccBB);
+};
+
+} // end namespace llvm
+
+#endif
//
//===----------------------------------------------------------------------===//
+#include "llvm/Transforms/Scalar/JumpThreading.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/CFG.h"
-#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
-#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
-#include "llvm/Analysis/LazyValueInfo.h"
#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Metadata.h"
-#include "llvm/IR/ValueHandle.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include <algorithm>
#include <memory>
using namespace llvm;
+using namespace jumpthreading;
#define DEBUG_TYPE "jump-threading"
cl::init(3), cl::Hidden);
namespace {
- // These are at global scope so static functions can use them too.
- typedef SmallVectorImpl<std::pair<Constant*, BasicBlock*> > PredValueInfo;
- typedef SmallVector<std::pair<Constant*, BasicBlock*>, 8> PredValueInfoTy;
-
- // This is used to keep track of what kind of constant we're currently hoping
- // to find.
- enum ConstantPreference {
- WantInteger,
- WantBlockAddress
- };
-
/// This pass performs 'jump threading', which looks at blocks that have
/// multiple predecessors and multiple successors. If one or more of the
/// predecessors of the block can be proven to always jump to one of the
/// revectored to the false side of the second if.
///
class JumpThreading : public FunctionPass {
- TargetLibraryInfo *TLI;
- LazyValueInfo *LVI;
- std::unique_ptr<BlockFrequencyInfo> BFI;
- std::unique_ptr<BranchProbabilityInfo> BPI;
- bool HasProfileData;
-#ifdef NDEBUG
- SmallPtrSet<const BasicBlock *, 16> LoopHeaders;
-#else
- SmallSet<AssertingVH<const BasicBlock>, 16> LoopHeaders;
-#endif
- DenseSet<std::pair<Value*, BasicBlock*> > RecursionSet;
-
- unsigned BBDupThreshold;
-
- // RAII helper for updating the recursion stack.
- struct RecursionSetRemover {
- DenseSet<std::pair<Value*, BasicBlock*> > &TheSet;
- std::pair<Value*, BasicBlock*> ThePair;
-
- RecursionSetRemover(DenseSet<std::pair<Value*, BasicBlock*> > &S,
- std::pair<Value*, BasicBlock*> P)
- : TheSet(S), ThePair(P) { }
-
- ~RecursionSetRemover() {
- TheSet.erase(ThePair);
- }
- };
+ JumpThreadingPass Impl;
+
public:
static char ID; // Pass identification
- JumpThreading(int T = -1) : FunctionPass(ID) {
- BBDupThreshold = (T == -1) ? BBDuplicateThreshold : unsigned(T);
+ JumpThreading(int T = -1) : FunctionPass(ID), Impl(T) {
initializeJumpThreadingPass(*PassRegistry::getPassRegistry());
}
AU.addRequired<TargetLibraryInfoWrapperPass>();
}
- void releaseMemory() override {
- BFI.reset();
- BPI.reset();
- }
-
- void FindLoopHeaders(Function &F);
- bool ProcessBlock(BasicBlock *BB);
- bool ThreadEdge(BasicBlock *BB, const SmallVectorImpl<BasicBlock*> &PredBBs,
- BasicBlock *SuccBB);
- bool DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB,
- const SmallVectorImpl<BasicBlock *> &PredBBs);
-
- bool ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,
- PredValueInfo &Result,
- ConstantPreference Preference,
- Instruction *CxtI = nullptr);
- bool ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
- ConstantPreference Preference,
- Instruction *CxtI = nullptr);
-
- bool ProcessBranchOnPHI(PHINode *PN);
- bool ProcessBranchOnXOR(BinaryOperator *BO);
- bool ProcessImpliedCondition(BasicBlock *BB);
-
- bool SimplifyPartiallyRedundantLoad(LoadInst *LI);
- bool TryToUnfoldSelect(CmpInst *CondCmp, BasicBlock *BB);
- bool TryToUnfoldSelectInCurrBB(BasicBlock *BB);
-
- private:
- BasicBlock *SplitBlockPreds(BasicBlock *BB, ArrayRef<BasicBlock *> Preds,
- const char *Suffix);
- void UpdateBlockFreqAndEdgeWeight(BasicBlock *PredBB, BasicBlock *BB,
- BasicBlock *NewBB, BasicBlock *SuccBB);
+ void releaseMemory() override { Impl.releaseMemory(); }
};
}
// Public interface to the Jump Threading pass
FunctionPass *llvm::createJumpThreadingPass(int Threshold) { return new JumpThreading(Threshold); }
+JumpThreadingPass::JumpThreadingPass(int T) {
+ BBDupThreshold = (T == -1) ? BBDuplicateThreshold : unsigned(T);
+}
+
/// runOnFunction - Top level algorithm.
///
bool JumpThreading::runOnFunction(Function &F) {
if (skipFunction(F))
return false;
+ auto TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+ auto LVI = &getAnalysis<LazyValueInfoWrapperPass>().getLVI();
+ std::unique_ptr<BlockFrequencyInfo> BFI;
+ std::unique_ptr<BranchProbabilityInfo> BPI;
+ bool HasProfileData = F.getEntryCount().hasValue();
+ if (HasProfileData) {
+ LoopInfo LI{DominatorTree(F)};
+ BPI.reset(new BranchProbabilityInfo(F, LI));
+ BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
+ }
+ return Impl.runImpl(F, TLI, LVI, HasProfileData, std::move(BFI),
+ std::move(BPI));
+}
+
+PreservedAnalyses JumpThreadingPass::run(Function &F,
+ AnalysisManager<Function> &AM) {
+
+ auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
+ auto &LVI = AM.getResult<LazyValueAnalysis>(F);
+ std::unique_ptr<BlockFrequencyInfo> BFI;
+ std::unique_ptr<BranchProbabilityInfo> BPI;
+ bool HasProfileData = F.getEntryCount().hasValue();
+ if (HasProfileData) {
+ LoopInfo LI{DominatorTree(F)};
+ BPI.reset(new BranchProbabilityInfo(F, LI));
+ BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
+ }
+ bool Changed =
+ runImpl(F, &TLI, &LVI, HasProfileData, std::move(BFI), std::move(BPI));
+ if (!Changed)
+ return PreservedAnalyses::all();
+ PreservedAnalyses PA;
+ PA.preserve<LazyValueAnalysis>();
+ PA.preserve<GlobalsAA>();
+ return PreservedAnalyses::none();
+}
+
+bool JumpThreadingPass::runImpl(Function &F, TargetLibraryInfo *TLI_,
+ LazyValueInfo *LVI_, bool HasProfileData_,
+ std::unique_ptr<BlockFrequencyInfo> BFI_,
+ std::unique_ptr<BranchProbabilityInfo> BPI_) {
DEBUG(dbgs() << "Jump threading on function '" << F.getName() << "'\n");
- TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
- LVI = &getAnalysis<LazyValueInfoWrapperPass>().getLVI();
+ TLI = TLI_;
+ LVI = LVI_;
BFI.reset();
BPI.reset();
// When profile data is available, we need to update edge weights after
// successful jump threading, which requires both BPI and BFI being available.
- HasProfileData = F.getEntryCount().hasValue();
+ HasProfileData = HasProfileData_;
if (HasProfileData) {
- LoopInfo LI{DominatorTree(F)};
- BPI.reset(new BranchProbabilityInfo(F, LI));
- BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
+ BPI = std::move(BPI_);
+ BFI = std::move(BFI_);
}
// Remove unreachable blocks from function as they may result in infinite
/// enough to track all of these properties and keep it up-to-date as the CFG
/// mutates, so we don't allow any of these transformations.
///
-void JumpThreading::FindLoopHeaders(Function &F) {
+void JumpThreadingPass::FindLoopHeaders(Function &F) {
SmallVector<std::pair<const BasicBlock*,const BasicBlock*>, 32> Edges;
FindFunctionBackedges(F, Edges);
///
/// This returns true if there were any known values.
///
-bool JumpThreading::
-ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB, PredValueInfo &Result,
- ConstantPreference Preference,
- Instruction *CxtI) {
+bool JumpThreadingPass::ComputeValueKnownInPredecessors(
+ Value *V, BasicBlock *BB, PredValueInfo &Result,
+ ConstantPreference Preference, Instruction *CxtI) {
// This method walks up use-def chains recursively. Because of this, we could
// get into an infinite loop going around loops in the use-def chain. To
// prevent this, keep track of what (value, block) pairs we've already visited
/// ProcessBlock - If there are any predecessors whose control can be threaded
/// through to a successor, transform them now.
-bool JumpThreading::ProcessBlock(BasicBlock *BB) {
+bool JumpThreadingPass::ProcessBlock(BasicBlock *BB) {
// If the block is trivially dead, just return and let the caller nuke it.
// This simplifies other transformations.
if (pred_empty(BB) &&
return false;
}
-bool JumpThreading::ProcessImpliedCondition(BasicBlock *BB) {
+bool JumpThreadingPass::ProcessImpliedCondition(BasicBlock *BB) {
auto *BI = dyn_cast<BranchInst>(BB->getTerminator());
if (!BI || !BI->isConditional())
return false;
/// load instruction, eliminate it by replacing it with a PHI node. This is an
/// important optimization that encourages jump threading, and needs to be run
/// interlaced with other jump threading tasks.
-bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
+bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
// Don't hack volatile/atomic loads.
if (!LI->isSimple()) return false;
return MostPopularDest;
}
-bool JumpThreading::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
- ConstantPreference Preference,
- Instruction *CxtI) {
+bool JumpThreadingPass::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
+ ConstantPreference Preference,
+ Instruction *CxtI) {
// If threading this would thread across a loop header, don't even try to
// thread the edge.
if (LoopHeaders.count(BB))
/// a PHI node in the current block. See if there are any simplifications we
/// can do based on inputs to the phi node.
///
-bool JumpThreading::ProcessBranchOnPHI(PHINode *PN) {
+bool JumpThreadingPass::ProcessBranchOnPHI(PHINode *PN) {
BasicBlock *BB = PN->getParent();
// TODO: We could make use of this to do it once for blocks with common PHI
/// a xor instruction in the current block. See if there are any
/// simplifications we can do based on inputs to the xor.
///
-bool JumpThreading::ProcessBranchOnXOR(BinaryOperator *BO) {
+bool JumpThreadingPass::ProcessBranchOnXOR(BinaryOperator *BO) {
BasicBlock *BB = BO->getParent();
// If either the LHS or RHS of the xor is a constant, don't do this
/// ThreadEdge - We have decided that it is safe and profitable to factor the
/// blocks in PredBBs to one predecessor, then thread an edge from it to SuccBB
/// across BB. Transform the IR to reflect this change.
-bool JumpThreading::ThreadEdge(BasicBlock *BB,
- const SmallVectorImpl<BasicBlock*> &PredBBs,
- BasicBlock *SuccBB) {
+bool JumpThreadingPass::ThreadEdge(BasicBlock *BB,
+ const SmallVectorImpl<BasicBlock *> &PredBBs,
+ BasicBlock *SuccBB) {
// If threading to the same block as we come from, we would infinite loop.
if (SuccBB == BB) {
DEBUG(dbgs() << " Not threading across BB '" << BB->getName()
/// Create a new basic block that will be the predecessor of BB and successor of
/// all blocks in Preds. When profile data is availble, update the frequency of
/// this new block.
-BasicBlock *JumpThreading::SplitBlockPreds(BasicBlock *BB,
- ArrayRef<BasicBlock *> Preds,
- const char *Suffix) {
+BasicBlock *JumpThreadingPass::SplitBlockPreds(BasicBlock *BB,
+ ArrayRef<BasicBlock *> Preds,
+ const char *Suffix) {
// Collect the frequencies of all predecessors of BB, which will be used to
// update the edge weight on BB->SuccBB.
BlockFrequency PredBBFreq(0);
/// Update the block frequency of BB and branch weight and the metadata on the
/// edge BB->SuccBB. This is done by scaling the weight of BB->SuccBB by 1 -
/// Freq(PredBB->BB) / Freq(BB->SuccBB).
-void JumpThreading::UpdateBlockFreqAndEdgeWeight(BasicBlock *PredBB,
- BasicBlock *BB,
- BasicBlock *NewBB,
- BasicBlock *SuccBB) {
+void JumpThreadingPass::UpdateBlockFreqAndEdgeWeight(BasicBlock *PredBB,
+ BasicBlock *BB,
+ BasicBlock *NewBB,
+ BasicBlock *SuccBB) {
if (!HasProfileData)
return;
/// If we can duplicate the contents of BB up into PredBB do so now, this
/// improves the odds that the branch will be on an analyzable instruction like
/// a compare.
-bool JumpThreading::DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB,
- const SmallVectorImpl<BasicBlock *> &PredBBs) {
+bool JumpThreadingPass::DuplicateCondBranchOnPHIIntoPred(
+ BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs) {
assert(!PredBBs.empty() && "Can't handle an empty set");
// If BB is a loop header, then duplicating this block outside the loop would
///
/// And expand the select into a branch structure if one of its arms allows %c
/// to be folded. This later enables threading from bb1 over bb2.
-bool JumpThreading::TryToUnfoldSelect(CmpInst *CondCmp, BasicBlock *BB) {
+bool JumpThreadingPass::TryToUnfoldSelect(CmpInst *CondCmp, BasicBlock *BB) {
BranchInst *CondBr = dyn_cast<BranchInst>(BB->getTerminator());
PHINode *CondLHS = dyn_cast<PHINode>(CondCmp->getOperand(0));
Constant *CondRHS = cast<Constant>(CondCmp->getOperand(1));
/// select if the associated PHI has at least one constant. If the unfolded
/// select is not jump-threaded, it will be folded again in the later
/// optimizations.
-bool JumpThreading::TryToUnfoldSelectInCurrBB(BasicBlock *BB) {
+bool JumpThreadingPass::TryToUnfoldSelectInCurrBB(BasicBlock *BB) {
// If threading this would thread across a loop header, don't thread the edge.
// See the comments above FindLoopHeaders for justifications and caveats.
if (LoopHeaders.count(BB))
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