6024e5c395
clang 20.0.0 (based on r547379) from build 12806354. Bug: http://b/379133546 Test: N/A Change-Id: I2eb8938af55d809de674be63cb30cf27e801862b Upstream-Commit: ad834e67b1105d15ef907f6255d4c96e8e733f57
407 lines
14 KiB
C++
407 lines
14 KiB
C++
//===- GVN.h - Eliminate redundant values and loads -------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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/// \file
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/// This file provides the interface for LLVM's Global Value Numbering pass
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/// which eliminates fully redundant instructions. It also does somewhat Ad-Hoc
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/// PRE and dead load elimination.
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_SCALAR_GVN_H
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#define LLVM_TRANSFORMS_SCALAR_GVN_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/MapVector.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/InstrTypes.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/Support/Allocator.h"
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#include "llvm/Support/Compiler.h"
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#include <cstdint>
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#include <optional>
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#include <utility>
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#include <vector>
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namespace llvm {
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class AAResults;
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class AssumeInst;
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class AssumptionCache;
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class BasicBlock;
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class BranchInst;
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class CallInst;
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class ExtractValueInst;
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class Function;
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class FunctionPass;
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class GetElementPtrInst;
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class ImplicitControlFlowTracking;
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class LoadInst;
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class LoopInfo;
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class MemDepResult;
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class MemoryDependenceResults;
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class MemorySSA;
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class MemorySSAUpdater;
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class NonLocalDepResult;
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class OptimizationRemarkEmitter;
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class PHINode;
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class TargetLibraryInfo;
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class Value;
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/// A private "module" namespace for types and utilities used by GVN. These
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/// are implementation details and should not be used by clients.
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namespace LLVM_LIBRARY_VISIBILITY gvn {
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struct AvailableValue;
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struct AvailableValueInBlock;
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class GVNLegacyPass;
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} // end namespace gvn
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/// A set of parameters to control various transforms performed by GVN pass.
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// Each of the optional boolean parameters can be set to:
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/// true - enabling the transformation.
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/// false - disabling the transformation.
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/// None - relying on a global default.
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/// Intended use is to create a default object, modify parameters with
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/// additional setters and then pass it to GVN.
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struct GVNOptions {
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std::optional<bool> AllowPRE;
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std::optional<bool> AllowLoadPRE;
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std::optional<bool> AllowLoadInLoopPRE;
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std::optional<bool> AllowLoadPRESplitBackedge;
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std::optional<bool> AllowMemDep;
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GVNOptions() = default;
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/// Enables or disables PRE in GVN.
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GVNOptions &setPRE(bool PRE) {
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AllowPRE = PRE;
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return *this;
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}
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/// Enables or disables PRE of loads in GVN.
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GVNOptions &setLoadPRE(bool LoadPRE) {
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AllowLoadPRE = LoadPRE;
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return *this;
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}
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GVNOptions &setLoadInLoopPRE(bool LoadInLoopPRE) {
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AllowLoadInLoopPRE = LoadInLoopPRE;
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return *this;
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}
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/// Enables or disables PRE of loads in GVN.
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GVNOptions &setLoadPRESplitBackedge(bool LoadPRESplitBackedge) {
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AllowLoadPRESplitBackedge = LoadPRESplitBackedge;
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return *this;
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}
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/// Enables or disables use of MemDepAnalysis.
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GVNOptions &setMemDep(bool MemDep) {
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AllowMemDep = MemDep;
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return *this;
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}
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};
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/// The core GVN pass object.
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///
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/// FIXME: We should have a good summary of the GVN algorithm implemented by
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/// this particular pass here.
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class GVNPass : public PassInfoMixin<GVNPass> {
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GVNOptions Options;
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public:
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struct Expression;
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GVNPass(GVNOptions Options = {}) : Options(Options) {}
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/// Run the pass over the function.
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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void printPipeline(raw_ostream &OS,
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function_ref<StringRef(StringRef)> MapClassName2PassName);
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/// This removes the specified instruction from
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/// our various maps and marks it for deletion.
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void markInstructionForDeletion(Instruction *I) {
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VN.erase(I);
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InstrsToErase.push_back(I);
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}
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DominatorTree &getDominatorTree() const { return *DT; }
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AAResults *getAliasAnalysis() const { return VN.getAliasAnalysis(); }
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MemoryDependenceResults &getMemDep() const { return *MD; }
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bool isPREEnabled() const;
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bool isLoadPREEnabled() const;
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bool isLoadInLoopPREEnabled() const;
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bool isLoadPRESplitBackedgeEnabled() const;
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bool isMemDepEnabled() const;
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/// This class holds the mapping between values and value numbers. It is used
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/// as an efficient mechanism to determine the expression-wise equivalence of
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/// two values.
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class ValueTable {
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DenseMap<Value *, uint32_t> valueNumbering;
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DenseMap<Expression, uint32_t> expressionNumbering;
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// Expressions is the vector of Expression. ExprIdx is the mapping from
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// value number to the index of Expression in Expressions. We use it
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// instead of a DenseMap because filling such mapping is faster than
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// filling a DenseMap and the compile time is a little better.
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uint32_t nextExprNumber = 0;
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std::vector<Expression> Expressions;
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std::vector<uint32_t> ExprIdx;
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// Value number to PHINode mapping. Used for phi-translate in scalarpre.
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DenseMap<uint32_t, PHINode *> NumberingPhi;
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// Cache for phi-translate in scalarpre.
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using PhiTranslateMap =
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DenseMap<std::pair<uint32_t, const BasicBlock *>, uint32_t>;
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PhiTranslateMap PhiTranslateTable;
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AAResults *AA = nullptr;
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MemoryDependenceResults *MD = nullptr;
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DominatorTree *DT = nullptr;
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uint32_t nextValueNumber = 1;
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Expression createExpr(Instruction *I);
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Expression createCmpExpr(unsigned Opcode, CmpInst::Predicate Predicate,
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Value *LHS, Value *RHS);
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Expression createExtractvalueExpr(ExtractValueInst *EI);
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Expression createGEPExpr(GetElementPtrInst *GEP);
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uint32_t lookupOrAddCall(CallInst *C);
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uint32_t phiTranslateImpl(const BasicBlock *BB, const BasicBlock *PhiBlock,
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uint32_t Num, GVNPass &Gvn);
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bool areCallValsEqual(uint32_t Num, uint32_t NewNum, const BasicBlock *Pred,
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const BasicBlock *PhiBlock, GVNPass &Gvn);
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std::pair<uint32_t, bool> assignExpNewValueNum(Expression &exp);
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bool areAllValsInBB(uint32_t num, const BasicBlock *BB, GVNPass &Gvn);
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public:
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ValueTable();
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ValueTable(const ValueTable &Arg);
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ValueTable(ValueTable &&Arg);
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~ValueTable();
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ValueTable &operator=(const ValueTable &Arg);
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uint32_t lookupOrAdd(Value *V);
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uint32_t lookup(Value *V, bool Verify = true) const;
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uint32_t lookupOrAddCmp(unsigned Opcode, CmpInst::Predicate Pred,
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Value *LHS, Value *RHS);
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uint32_t phiTranslate(const BasicBlock *BB, const BasicBlock *PhiBlock,
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uint32_t Num, GVNPass &Gvn);
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void eraseTranslateCacheEntry(uint32_t Num, const BasicBlock &CurrBlock);
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bool exists(Value *V) const;
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void add(Value *V, uint32_t num);
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void clear();
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void erase(Value *v);
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void setAliasAnalysis(AAResults *A) { AA = A; }
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AAResults *getAliasAnalysis() const { return AA; }
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void setMemDep(MemoryDependenceResults *M) { MD = M; }
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void setDomTree(DominatorTree *D) { DT = D; }
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uint32_t getNextUnusedValueNumber() { return nextValueNumber; }
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void verifyRemoved(const Value *) const;
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};
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private:
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friend class gvn::GVNLegacyPass;
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friend struct DenseMapInfo<Expression>;
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MemoryDependenceResults *MD = nullptr;
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DominatorTree *DT = nullptr;
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const TargetLibraryInfo *TLI = nullptr;
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AssumptionCache *AC = nullptr;
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SetVector<BasicBlock *> DeadBlocks;
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OptimizationRemarkEmitter *ORE = nullptr;
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ImplicitControlFlowTracking *ICF = nullptr;
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LoopInfo *LI = nullptr;
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MemorySSAUpdater *MSSAU = nullptr;
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ValueTable VN;
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/// A mapping from value numbers to lists of Value*'s that
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/// have that value number. Use findLeader to query it.
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class LeaderMap {
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public:
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struct LeaderTableEntry {
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Value *Val;
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const BasicBlock *BB;
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};
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private:
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struct LeaderListNode {
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LeaderTableEntry Entry;
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LeaderListNode *Next;
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};
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DenseMap<uint32_t, LeaderListNode> NumToLeaders;
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BumpPtrAllocator TableAllocator;
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public:
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class leader_iterator {
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const LeaderListNode *Current;
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public:
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using iterator_category = std::forward_iterator_tag;
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using value_type = const LeaderTableEntry;
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using difference_type = std::ptrdiff_t;
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using pointer = value_type *;
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using reference = value_type &;
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leader_iterator(const LeaderListNode *C) : Current(C) {}
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leader_iterator &operator++() {
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assert(Current && "Dereferenced end of leader list!");
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Current = Current->Next;
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return *this;
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}
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bool operator==(const leader_iterator &Other) const {
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return Current == Other.Current;
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}
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bool operator!=(const leader_iterator &Other) const {
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return Current != Other.Current;
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}
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reference operator*() const { return Current->Entry; }
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};
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iterator_range<leader_iterator> getLeaders(uint32_t N) {
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auto I = NumToLeaders.find(N);
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if (I == NumToLeaders.end()) {
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return iterator_range(leader_iterator(nullptr),
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leader_iterator(nullptr));
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}
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return iterator_range(leader_iterator(&I->second),
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leader_iterator(nullptr));
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}
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void insert(uint32_t N, Value *V, const BasicBlock *BB);
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void erase(uint32_t N, Instruction *I, const BasicBlock *BB);
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void verifyRemoved(const Value *Inst) const;
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void clear() {
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NumToLeaders.clear();
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TableAllocator.Reset();
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}
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};
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LeaderMap LeaderTable;
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// Block-local map of equivalent values to their leader, does not
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// propagate to any successors. Entries added mid-block are applied
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// to the remaining instructions in the block.
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SmallMapVector<Value *, Value *, 4> ReplaceOperandsWithMap;
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SmallVector<Instruction *, 8> InstrsToErase;
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// Map the block to reversed postorder traversal number. It is used to
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// find back edge easily.
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DenseMap<AssertingVH<BasicBlock>, uint32_t> BlockRPONumber;
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// This is set 'true' initially and also when new blocks have been added to
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// the function being analyzed. This boolean is used to control the updating
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// of BlockRPONumber prior to accessing the contents of BlockRPONumber.
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bool InvalidBlockRPONumbers = true;
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using LoadDepVect = SmallVector<NonLocalDepResult, 64>;
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using AvailValInBlkVect = SmallVector<gvn::AvailableValueInBlock, 64>;
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using UnavailBlkVect = SmallVector<BasicBlock *, 64>;
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bool runImpl(Function &F, AssumptionCache &RunAC, DominatorTree &RunDT,
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const TargetLibraryInfo &RunTLI, AAResults &RunAA,
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MemoryDependenceResults *RunMD, LoopInfo &LI,
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OptimizationRemarkEmitter *ORE, MemorySSA *MSSA = nullptr);
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// List of critical edges to be split between iterations.
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SmallVector<std::pair<Instruction *, unsigned>, 4> toSplit;
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// Helper functions of redundant load elimination
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bool processLoad(LoadInst *L);
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bool processNonLocalLoad(LoadInst *L);
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bool processAssumeIntrinsic(AssumeInst *II);
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/// Given a local dependency (Def or Clobber) determine if a value is
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/// available for the load.
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std::optional<gvn::AvailableValue>
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AnalyzeLoadAvailability(LoadInst *Load, MemDepResult DepInfo, Value *Address);
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/// Given a list of non-local dependencies, determine if a value is
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/// available for the load in each specified block. If it is, add it to
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/// ValuesPerBlock. If not, add it to UnavailableBlocks.
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void AnalyzeLoadAvailability(LoadInst *Load, LoadDepVect &Deps,
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AvailValInBlkVect &ValuesPerBlock,
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UnavailBlkVect &UnavailableBlocks);
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/// Given a critical edge from Pred to LoadBB, find a load instruction
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/// which is identical to Load from another successor of Pred.
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LoadInst *findLoadToHoistIntoPred(BasicBlock *Pred, BasicBlock *LoadBB,
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LoadInst *Load);
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bool PerformLoadPRE(LoadInst *Load, AvailValInBlkVect &ValuesPerBlock,
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UnavailBlkVect &UnavailableBlocks);
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/// Try to replace a load which executes on each loop iteraiton with Phi
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/// translation of load in preheader and load(s) in conditionally executed
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/// paths.
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bool performLoopLoadPRE(LoadInst *Load, AvailValInBlkVect &ValuesPerBlock,
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UnavailBlkVect &UnavailableBlocks);
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/// Eliminates partially redundant \p Load, replacing it with \p
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/// AvailableLoads (connected by Phis if needed).
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void eliminatePartiallyRedundantLoad(
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LoadInst *Load, AvailValInBlkVect &ValuesPerBlock,
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MapVector<BasicBlock *, Value *> &AvailableLoads,
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MapVector<BasicBlock *, LoadInst *> *CriticalEdgePredAndLoad);
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// Other helper routines
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bool processInstruction(Instruction *I);
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bool processBlock(BasicBlock *BB);
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void dump(DenseMap<uint32_t, Value *> &d) const;
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bool iterateOnFunction(Function &F);
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bool performPRE(Function &F);
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bool performScalarPRE(Instruction *I);
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bool performScalarPREInsertion(Instruction *Instr, BasicBlock *Pred,
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BasicBlock *Curr, unsigned int ValNo);
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Value *findLeader(const BasicBlock *BB, uint32_t num);
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void cleanupGlobalSets();
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void removeInstruction(Instruction *I);
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void verifyRemoved(const Instruction *I) const;
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bool splitCriticalEdges();
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BasicBlock *splitCriticalEdges(BasicBlock *Pred, BasicBlock *Succ);
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bool replaceOperandsForInBlockEquality(Instruction *I) const;
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bool propagateEquality(Value *LHS, Value *RHS, const BasicBlockEdge &Root,
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bool DominatesByEdge);
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bool processFoldableCondBr(BranchInst *BI);
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void addDeadBlock(BasicBlock *BB);
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void assignValNumForDeadCode();
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void assignBlockRPONumber(Function &F);
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};
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/// Create a legacy GVN pass. This also allows parameterizing whether or not
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/// MemDep is enabled.
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FunctionPass *createGVNPass(bool NoMemDepAnalysis = false);
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/// A simple and fast domtree-based GVN pass to hoist common expressions
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/// from sibling branches.
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struct GVNHoistPass : PassInfoMixin<GVNHoistPass> {
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/// Run the pass over the function.
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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};
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/// Uses an "inverted" value numbering to decide the similarity of
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/// expressions and sinks similar expressions into successors.
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struct GVNSinkPass : PassInfoMixin<GVNSinkPass> {
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/// Run the pass over the function.
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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};
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} // end namespace llvm
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#endif // LLVM_TRANSFORMS_SCALAR_GVN_H
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