mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84969 91177308-0d34-0410-b5e6-96231b3b80d8
2002 lines
69 KiB
C++
2002 lines
69 KiB
C++
//===- GVN.cpp - Eliminate redundant values and loads ---------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass performs global value numbering to eliminate fully redundant
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// instructions. It also performs simple dead load elimination.
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//
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// Note that this pass does the value numbering itself; it does not use the
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// ValueNumbering analysis passes.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "gvn"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Operator.h"
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#include "llvm/Value.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/MallocHelper.h"
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#include "llvm/Analysis/MemoryDependenceAnalysis.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/GetElementPtrTypeIterator.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Transforms/Utils/SSAUpdater.h"
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#include <cstdio>
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using namespace llvm;
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STATISTIC(NumGVNInstr, "Number of instructions deleted");
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STATISTIC(NumGVNLoad, "Number of loads deleted");
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STATISTIC(NumGVNPRE, "Number of instructions PRE'd");
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STATISTIC(NumGVNBlocks, "Number of blocks merged");
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STATISTIC(NumPRELoad, "Number of loads PRE'd");
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static cl::opt<bool> EnablePRE("enable-pre",
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cl::init(true), cl::Hidden);
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static cl::opt<bool> EnableLoadPRE("enable-load-pre", cl::init(true));
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//===----------------------------------------------------------------------===//
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// ValueTable Class
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//===----------------------------------------------------------------------===//
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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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namespace {
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struct Expression {
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enum ExpressionOpcode { ADD, FADD, SUB, FSUB, MUL, FMUL,
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UDIV, SDIV, FDIV, UREM, SREM,
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FREM, SHL, LSHR, ASHR, AND, OR, XOR, ICMPEQ,
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ICMPNE, ICMPUGT, ICMPUGE, ICMPULT, ICMPULE,
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ICMPSGT, ICMPSGE, ICMPSLT, ICMPSLE, FCMPOEQ,
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FCMPOGT, FCMPOGE, FCMPOLT, FCMPOLE, FCMPONE,
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FCMPORD, FCMPUNO, FCMPUEQ, FCMPUGT, FCMPUGE,
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FCMPULT, FCMPULE, FCMPUNE, EXTRACT, INSERT,
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SHUFFLE, SELECT, TRUNC, ZEXT, SEXT, FPTOUI,
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FPTOSI, UITOFP, SITOFP, FPTRUNC, FPEXT,
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PTRTOINT, INTTOPTR, BITCAST, GEP, CALL, CONSTANT,
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INSERTVALUE, EXTRACTVALUE, EMPTY, TOMBSTONE };
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ExpressionOpcode opcode;
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const Type* type;
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SmallVector<uint32_t, 4> varargs;
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Value *function;
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Expression() { }
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Expression(ExpressionOpcode o) : opcode(o) { }
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bool operator==(const Expression &other) const {
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if (opcode != other.opcode)
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return false;
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else if (opcode == EMPTY || opcode == TOMBSTONE)
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return true;
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else if (type != other.type)
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return false;
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else if (function != other.function)
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return false;
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else {
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if (varargs.size() != other.varargs.size())
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return false;
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for (size_t i = 0; i < varargs.size(); ++i)
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if (varargs[i] != other.varargs[i])
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return false;
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return true;
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}
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}
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bool operator!=(const Expression &other) const {
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return !(*this == other);
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}
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};
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class ValueTable {
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private:
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DenseMap<Value*, uint32_t> valueNumbering;
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DenseMap<Expression, uint32_t> expressionNumbering;
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AliasAnalysis* AA;
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MemoryDependenceAnalysis* MD;
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DominatorTree* DT;
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uint32_t nextValueNumber;
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Expression::ExpressionOpcode getOpcode(BinaryOperator* BO);
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Expression::ExpressionOpcode getOpcode(CmpInst* C);
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Expression::ExpressionOpcode getOpcode(CastInst* C);
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Expression create_expression(BinaryOperator* BO);
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Expression create_expression(CmpInst* C);
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Expression create_expression(ShuffleVectorInst* V);
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Expression create_expression(ExtractElementInst* C);
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Expression create_expression(InsertElementInst* V);
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Expression create_expression(SelectInst* V);
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Expression create_expression(CastInst* C);
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Expression create_expression(GetElementPtrInst* G);
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Expression create_expression(CallInst* C);
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Expression create_expression(Constant* C);
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Expression create_expression(ExtractValueInst* C);
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Expression create_expression(InsertValueInst* C);
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uint32_t lookup_or_add_call(CallInst* C);
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public:
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ValueTable() : nextValueNumber(1) { }
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uint32_t lookup_or_add(Value *V);
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uint32_t lookup(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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unsigned size();
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void setAliasAnalysis(AliasAnalysis* A) { AA = A; }
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AliasAnalysis *getAliasAnalysis() const { return AA; }
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void setMemDep(MemoryDependenceAnalysis* 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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}
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namespace llvm {
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template <> struct DenseMapInfo<Expression> {
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static inline Expression getEmptyKey() {
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return Expression(Expression::EMPTY);
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}
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static inline Expression getTombstoneKey() {
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return Expression(Expression::TOMBSTONE);
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}
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static unsigned getHashValue(const Expression e) {
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unsigned hash = e.opcode;
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hash = ((unsigned)((uintptr_t)e.type >> 4) ^
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(unsigned)((uintptr_t)e.type >> 9));
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for (SmallVector<uint32_t, 4>::const_iterator I = e.varargs.begin(),
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E = e.varargs.end(); I != E; ++I)
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hash = *I + hash * 37;
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hash = ((unsigned)((uintptr_t)e.function >> 4) ^
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(unsigned)((uintptr_t)e.function >> 9)) +
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hash * 37;
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return hash;
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}
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static bool isEqual(const Expression &LHS, const Expression &RHS) {
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return LHS == RHS;
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}
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static bool isPod() { return true; }
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};
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}
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//===----------------------------------------------------------------------===//
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// ValueTable Internal Functions
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//===----------------------------------------------------------------------===//
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Expression::ExpressionOpcode ValueTable::getOpcode(BinaryOperator* BO) {
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switch(BO->getOpcode()) {
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default: // THIS SHOULD NEVER HAPPEN
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llvm_unreachable("Binary operator with unknown opcode?");
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case Instruction::Add: return Expression::ADD;
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case Instruction::FAdd: return Expression::FADD;
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case Instruction::Sub: return Expression::SUB;
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case Instruction::FSub: return Expression::FSUB;
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case Instruction::Mul: return Expression::MUL;
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case Instruction::FMul: return Expression::FMUL;
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case Instruction::UDiv: return Expression::UDIV;
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case Instruction::SDiv: return Expression::SDIV;
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case Instruction::FDiv: return Expression::FDIV;
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case Instruction::URem: return Expression::UREM;
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case Instruction::SRem: return Expression::SREM;
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case Instruction::FRem: return Expression::FREM;
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case Instruction::Shl: return Expression::SHL;
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case Instruction::LShr: return Expression::LSHR;
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case Instruction::AShr: return Expression::ASHR;
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case Instruction::And: return Expression::AND;
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case Instruction::Or: return Expression::OR;
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case Instruction::Xor: return Expression::XOR;
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}
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}
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Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) {
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if (isa<ICmpInst>(C)) {
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switch (C->getPredicate()) {
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default: // THIS SHOULD NEVER HAPPEN
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llvm_unreachable("Comparison with unknown predicate?");
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case ICmpInst::ICMP_EQ: return Expression::ICMPEQ;
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case ICmpInst::ICMP_NE: return Expression::ICMPNE;
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case ICmpInst::ICMP_UGT: return Expression::ICMPUGT;
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case ICmpInst::ICMP_UGE: return Expression::ICMPUGE;
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case ICmpInst::ICMP_ULT: return Expression::ICMPULT;
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case ICmpInst::ICMP_ULE: return Expression::ICMPULE;
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case ICmpInst::ICMP_SGT: return Expression::ICMPSGT;
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case ICmpInst::ICMP_SGE: return Expression::ICMPSGE;
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case ICmpInst::ICMP_SLT: return Expression::ICMPSLT;
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case ICmpInst::ICMP_SLE: return Expression::ICMPSLE;
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}
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} else {
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switch (C->getPredicate()) {
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default: // THIS SHOULD NEVER HAPPEN
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llvm_unreachable("Comparison with unknown predicate?");
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case FCmpInst::FCMP_OEQ: return Expression::FCMPOEQ;
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case FCmpInst::FCMP_OGT: return Expression::FCMPOGT;
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case FCmpInst::FCMP_OGE: return Expression::FCMPOGE;
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case FCmpInst::FCMP_OLT: return Expression::FCMPOLT;
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case FCmpInst::FCMP_OLE: return Expression::FCMPOLE;
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case FCmpInst::FCMP_ONE: return Expression::FCMPONE;
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case FCmpInst::FCMP_ORD: return Expression::FCMPORD;
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case FCmpInst::FCMP_UNO: return Expression::FCMPUNO;
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case FCmpInst::FCMP_UEQ: return Expression::FCMPUEQ;
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case FCmpInst::FCMP_UGT: return Expression::FCMPUGT;
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case FCmpInst::FCMP_UGE: return Expression::FCMPUGE;
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case FCmpInst::FCMP_ULT: return Expression::FCMPULT;
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case FCmpInst::FCMP_ULE: return Expression::FCMPULE;
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case FCmpInst::FCMP_UNE: return Expression::FCMPUNE;
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}
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}
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}
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Expression::ExpressionOpcode ValueTable::getOpcode(CastInst* C) {
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switch(C->getOpcode()) {
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default: // THIS SHOULD NEVER HAPPEN
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llvm_unreachable("Cast operator with unknown opcode?");
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case Instruction::Trunc: return Expression::TRUNC;
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case Instruction::ZExt: return Expression::ZEXT;
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case Instruction::SExt: return Expression::SEXT;
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case Instruction::FPToUI: return Expression::FPTOUI;
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case Instruction::FPToSI: return Expression::FPTOSI;
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case Instruction::UIToFP: return Expression::UITOFP;
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case Instruction::SIToFP: return Expression::SITOFP;
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case Instruction::FPTrunc: return Expression::FPTRUNC;
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case Instruction::FPExt: return Expression::FPEXT;
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case Instruction::PtrToInt: return Expression::PTRTOINT;
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case Instruction::IntToPtr: return Expression::INTTOPTR;
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case Instruction::BitCast: return Expression::BITCAST;
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}
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}
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Expression ValueTable::create_expression(CallInst* C) {
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Expression e;
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e.type = C->getType();
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e.function = C->getCalledFunction();
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e.opcode = Expression::CALL;
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for (CallInst::op_iterator I = C->op_begin()+1, E = C->op_end();
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I != E; ++I)
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e.varargs.push_back(lookup_or_add(*I));
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return e;
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}
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Expression ValueTable::create_expression(BinaryOperator* BO) {
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Expression e;
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e.varargs.push_back(lookup_or_add(BO->getOperand(0)));
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e.varargs.push_back(lookup_or_add(BO->getOperand(1)));
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e.function = 0;
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e.type = BO->getType();
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e.opcode = getOpcode(BO);
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return e;
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}
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Expression ValueTable::create_expression(CmpInst* C) {
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Expression e;
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e.varargs.push_back(lookup_or_add(C->getOperand(0)));
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e.varargs.push_back(lookup_or_add(C->getOperand(1)));
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e.function = 0;
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e.type = C->getType();
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e.opcode = getOpcode(C);
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return e;
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}
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Expression ValueTable::create_expression(CastInst* C) {
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Expression e;
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e.varargs.push_back(lookup_or_add(C->getOperand(0)));
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e.function = 0;
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e.type = C->getType();
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e.opcode = getOpcode(C);
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return e;
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}
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Expression ValueTable::create_expression(ShuffleVectorInst* S) {
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Expression e;
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e.varargs.push_back(lookup_or_add(S->getOperand(0)));
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e.varargs.push_back(lookup_or_add(S->getOperand(1)));
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e.varargs.push_back(lookup_or_add(S->getOperand(2)));
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e.function = 0;
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e.type = S->getType();
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e.opcode = Expression::SHUFFLE;
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return e;
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}
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Expression ValueTable::create_expression(ExtractElementInst* E) {
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Expression e;
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e.varargs.push_back(lookup_or_add(E->getOperand(0)));
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e.varargs.push_back(lookup_or_add(E->getOperand(1)));
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e.function = 0;
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e.type = E->getType();
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e.opcode = Expression::EXTRACT;
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return e;
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}
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Expression ValueTable::create_expression(InsertElementInst* I) {
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Expression e;
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e.varargs.push_back(lookup_or_add(I->getOperand(0)));
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e.varargs.push_back(lookup_or_add(I->getOperand(1)));
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e.varargs.push_back(lookup_or_add(I->getOperand(2)));
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e.function = 0;
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e.type = I->getType();
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e.opcode = Expression::INSERT;
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return e;
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}
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Expression ValueTable::create_expression(SelectInst* I) {
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Expression e;
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e.varargs.push_back(lookup_or_add(I->getCondition()));
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e.varargs.push_back(lookup_or_add(I->getTrueValue()));
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e.varargs.push_back(lookup_or_add(I->getFalseValue()));
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e.function = 0;
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e.type = I->getType();
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e.opcode = Expression::SELECT;
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return e;
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}
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Expression ValueTable::create_expression(GetElementPtrInst* G) {
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Expression e;
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e.varargs.push_back(lookup_or_add(G->getPointerOperand()));
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e.function = 0;
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e.type = G->getType();
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e.opcode = Expression::GEP;
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for (GetElementPtrInst::op_iterator I = G->idx_begin(), E = G->idx_end();
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I != E; ++I)
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e.varargs.push_back(lookup_or_add(*I));
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return e;
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}
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Expression ValueTable::create_expression(ExtractValueInst* E) {
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Expression e;
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e.varargs.push_back(lookup_or_add(E->getAggregateOperand()));
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for (ExtractValueInst::idx_iterator II = E->idx_begin(), IE = E->idx_end();
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II != IE; ++II)
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e.varargs.push_back(*II);
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e.function = 0;
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e.type = E->getType();
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e.opcode = Expression::EXTRACTVALUE;
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return e;
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}
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Expression ValueTable::create_expression(InsertValueInst* E) {
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Expression e;
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e.varargs.push_back(lookup_or_add(E->getAggregateOperand()));
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e.varargs.push_back(lookup_or_add(E->getInsertedValueOperand()));
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for (InsertValueInst::idx_iterator II = E->idx_begin(), IE = E->idx_end();
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II != IE; ++II)
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e.varargs.push_back(*II);
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e.function = 0;
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e.type = E->getType();
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e.opcode = Expression::INSERTVALUE;
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return e;
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}
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//===----------------------------------------------------------------------===//
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// ValueTable External Functions
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//===----------------------------------------------------------------------===//
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/// add - Insert a value into the table with a specified value number.
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void ValueTable::add(Value *V, uint32_t num) {
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valueNumbering.insert(std::make_pair(V, num));
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}
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uint32_t ValueTable::lookup_or_add_call(CallInst* C) {
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if (AA->doesNotAccessMemory(C)) {
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Expression exp = create_expression(C);
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uint32_t& e = expressionNumbering[exp];
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if (!e) e = nextValueNumber++;
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valueNumbering[C] = e;
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return e;
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} else if (AA->onlyReadsMemory(C)) {
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Expression exp = create_expression(C);
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uint32_t& e = expressionNumbering[exp];
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if (!e) {
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e = nextValueNumber++;
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valueNumbering[C] = e;
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return e;
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}
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MemDepResult local_dep = MD->getDependency(C);
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if (!local_dep.isDef() && !local_dep.isNonLocal()) {
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valueNumbering[C] = nextValueNumber;
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return nextValueNumber++;
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}
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if (local_dep.isDef()) {
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CallInst* local_cdep = cast<CallInst>(local_dep.getInst());
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if (local_cdep->getNumOperands() != C->getNumOperands()) {
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valueNumbering[C] = nextValueNumber;
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return nextValueNumber++;
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}
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for (unsigned i = 1; i < C->getNumOperands(); ++i) {
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uint32_t c_vn = lookup_or_add(C->getOperand(i));
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uint32_t cd_vn = lookup_or_add(local_cdep->getOperand(i));
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if (c_vn != cd_vn) {
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valueNumbering[C] = nextValueNumber;
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return nextValueNumber++;
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}
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}
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uint32_t v = lookup_or_add(local_cdep);
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valueNumbering[C] = v;
|
|
return v;
|
|
}
|
|
|
|
// Non-local case.
|
|
const MemoryDependenceAnalysis::NonLocalDepInfo &deps =
|
|
MD->getNonLocalCallDependency(CallSite(C));
|
|
// FIXME: call/call dependencies for readonly calls should return def, not
|
|
// clobber! Move the checking logic to MemDep!
|
|
CallInst* cdep = 0;
|
|
|
|
// Check to see if we have a single dominating call instruction that is
|
|
// identical to C.
|
|
for (unsigned i = 0, e = deps.size(); i != e; ++i) {
|
|
const MemoryDependenceAnalysis::NonLocalDepEntry *I = &deps[i];
|
|
// Ignore non-local dependencies.
|
|
if (I->second.isNonLocal())
|
|
continue;
|
|
|
|
// We don't handle non-depedencies. If we already have a call, reject
|
|
// instruction dependencies.
|
|
if (I->second.isClobber() || cdep != 0) {
|
|
cdep = 0;
|
|
break;
|
|
}
|
|
|
|
CallInst *NonLocalDepCall = dyn_cast<CallInst>(I->second.getInst());
|
|
// FIXME: All duplicated with non-local case.
|
|
if (NonLocalDepCall && DT->properlyDominates(I->first, C->getParent())){
|
|
cdep = NonLocalDepCall;
|
|
continue;
|
|
}
|
|
|
|
cdep = 0;
|
|
break;
|
|
}
|
|
|
|
if (!cdep) {
|
|
valueNumbering[C] = nextValueNumber;
|
|
return nextValueNumber++;
|
|
}
|
|
|
|
if (cdep->getNumOperands() != C->getNumOperands()) {
|
|
valueNumbering[C] = nextValueNumber;
|
|
return nextValueNumber++;
|
|
}
|
|
for (unsigned i = 1; i < C->getNumOperands(); ++i) {
|
|
uint32_t c_vn = lookup_or_add(C->getOperand(i));
|
|
uint32_t cd_vn = lookup_or_add(cdep->getOperand(i));
|
|
if (c_vn != cd_vn) {
|
|
valueNumbering[C] = nextValueNumber;
|
|
return nextValueNumber++;
|
|
}
|
|
}
|
|
|
|
uint32_t v = lookup_or_add(cdep);
|
|
valueNumbering[C] = v;
|
|
return v;
|
|
|
|
} else {
|
|
valueNumbering[C] = nextValueNumber;
|
|
return nextValueNumber++;
|
|
}
|
|
}
|
|
|
|
/// lookup_or_add - Returns the value number for the specified value, assigning
|
|
/// it a new number if it did not have one before.
|
|
uint32_t ValueTable::lookup_or_add(Value *V) {
|
|
DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
|
|
if (VI != valueNumbering.end())
|
|
return VI->second;
|
|
|
|
if (!isa<Instruction>(V)) {
|
|
valueNumbering[V] = nextValueNumber;
|
|
return nextValueNumber++;
|
|
}
|
|
|
|
Instruction* I = cast<Instruction>(V);
|
|
Expression exp;
|
|
switch (I->getOpcode()) {
|
|
case Instruction::Call:
|
|
return lookup_or_add_call(cast<CallInst>(I));
|
|
case Instruction::Add:
|
|
case Instruction::FAdd:
|
|
case Instruction::Sub:
|
|
case Instruction::FSub:
|
|
case Instruction::Mul:
|
|
case Instruction::FMul:
|
|
case Instruction::UDiv:
|
|
case Instruction::SDiv:
|
|
case Instruction::FDiv:
|
|
case Instruction::URem:
|
|
case Instruction::SRem:
|
|
case Instruction::FRem:
|
|
case Instruction::Shl:
|
|
case Instruction::LShr:
|
|
case Instruction::AShr:
|
|
case Instruction::And:
|
|
case Instruction::Or :
|
|
case Instruction::Xor:
|
|
exp = create_expression(cast<BinaryOperator>(I));
|
|
break;
|
|
case Instruction::ICmp:
|
|
case Instruction::FCmp:
|
|
exp = create_expression(cast<CmpInst>(I));
|
|
break;
|
|
case Instruction::Trunc:
|
|
case Instruction::ZExt:
|
|
case Instruction::SExt:
|
|
case Instruction::FPToUI:
|
|
case Instruction::FPToSI:
|
|
case Instruction::UIToFP:
|
|
case Instruction::SIToFP:
|
|
case Instruction::FPTrunc:
|
|
case Instruction::FPExt:
|
|
case Instruction::PtrToInt:
|
|
case Instruction::IntToPtr:
|
|
case Instruction::BitCast:
|
|
exp = create_expression(cast<CastInst>(I));
|
|
break;
|
|
case Instruction::Select:
|
|
exp = create_expression(cast<SelectInst>(I));
|
|
break;
|
|
case Instruction::ExtractElement:
|
|
exp = create_expression(cast<ExtractElementInst>(I));
|
|
break;
|
|
case Instruction::InsertElement:
|
|
exp = create_expression(cast<InsertElementInst>(I));
|
|
break;
|
|
case Instruction::ShuffleVector:
|
|
exp = create_expression(cast<ShuffleVectorInst>(I));
|
|
break;
|
|
case Instruction::ExtractValue:
|
|
exp = create_expression(cast<ExtractValueInst>(I));
|
|
break;
|
|
case Instruction::InsertValue:
|
|
exp = create_expression(cast<InsertValueInst>(I));
|
|
break;
|
|
case Instruction::GetElementPtr:
|
|
exp = create_expression(cast<GetElementPtrInst>(I));
|
|
break;
|
|
default:
|
|
valueNumbering[V] = nextValueNumber;
|
|
return nextValueNumber++;
|
|
}
|
|
|
|
uint32_t& e = expressionNumbering[exp];
|
|
if (!e) e = nextValueNumber++;
|
|
valueNumbering[V] = e;
|
|
return e;
|
|
}
|
|
|
|
/// lookup - Returns the value number of the specified value. Fails if
|
|
/// the value has not yet been numbered.
|
|
uint32_t ValueTable::lookup(Value *V) const {
|
|
DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
|
|
assert(VI != valueNumbering.end() && "Value not numbered?");
|
|
return VI->second;
|
|
}
|
|
|
|
/// clear - Remove all entries from the ValueTable
|
|
void ValueTable::clear() {
|
|
valueNumbering.clear();
|
|
expressionNumbering.clear();
|
|
nextValueNumber = 1;
|
|
}
|
|
|
|
/// erase - Remove a value from the value numbering
|
|
void ValueTable::erase(Value *V) {
|
|
valueNumbering.erase(V);
|
|
}
|
|
|
|
/// verifyRemoved - Verify that the value is removed from all internal data
|
|
/// structures.
|
|
void ValueTable::verifyRemoved(const Value *V) const {
|
|
for (DenseMap<Value*, uint32_t>::iterator
|
|
I = valueNumbering.begin(), E = valueNumbering.end(); I != E; ++I) {
|
|
assert(I->first != V && "Inst still occurs in value numbering map!");
|
|
}
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// GVN Pass
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
namespace {
|
|
struct ValueNumberScope {
|
|
ValueNumberScope* parent;
|
|
DenseMap<uint32_t, Value*> table;
|
|
|
|
ValueNumberScope(ValueNumberScope* p) : parent(p) { }
|
|
};
|
|
}
|
|
|
|
namespace {
|
|
|
|
class GVN : public FunctionPass {
|
|
bool runOnFunction(Function &F);
|
|
public:
|
|
static char ID; // Pass identification, replacement for typeid
|
|
GVN() : FunctionPass(&ID) { }
|
|
|
|
private:
|
|
MemoryDependenceAnalysis *MD;
|
|
DominatorTree *DT;
|
|
|
|
ValueTable VN;
|
|
DenseMap<BasicBlock*, ValueNumberScope*> localAvail;
|
|
|
|
// This transformation requires dominator postdominator info
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.addRequired<DominatorTree>();
|
|
AU.addRequired<MemoryDependenceAnalysis>();
|
|
AU.addRequired<AliasAnalysis>();
|
|
|
|
AU.addPreserved<DominatorTree>();
|
|
AU.addPreserved<AliasAnalysis>();
|
|
}
|
|
|
|
// Helper fuctions
|
|
// FIXME: eliminate or document these better
|
|
bool processLoad(LoadInst* L,
|
|
SmallVectorImpl<Instruction*> &toErase);
|
|
bool processInstruction(Instruction *I,
|
|
SmallVectorImpl<Instruction*> &toErase);
|
|
bool processNonLocalLoad(LoadInst* L,
|
|
SmallVectorImpl<Instruction*> &toErase);
|
|
bool processBlock(BasicBlock *BB);
|
|
void dump(DenseMap<uint32_t, Value*>& d);
|
|
bool iterateOnFunction(Function &F);
|
|
Value *CollapsePhi(PHINode* p);
|
|
bool performPRE(Function& F);
|
|
Value *lookupNumber(BasicBlock *BB, uint32_t num);
|
|
void cleanupGlobalSets();
|
|
void verifyRemoved(const Instruction *I) const;
|
|
};
|
|
|
|
char GVN::ID = 0;
|
|
}
|
|
|
|
// createGVNPass - The public interface to this file...
|
|
FunctionPass *llvm::createGVNPass() { return new GVN(); }
|
|
|
|
static RegisterPass<GVN> X("gvn",
|
|
"Global Value Numbering");
|
|
|
|
void GVN::dump(DenseMap<uint32_t, Value*>& d) {
|
|
printf("{\n");
|
|
for (DenseMap<uint32_t, Value*>::iterator I = d.begin(),
|
|
E = d.end(); I != E; ++I) {
|
|
printf("%d\n", I->first);
|
|
I->second->dump();
|
|
}
|
|
printf("}\n");
|
|
}
|
|
|
|
static bool isSafeReplacement(PHINode* p, Instruction *inst) {
|
|
if (!isa<PHINode>(inst))
|
|
return true;
|
|
|
|
for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end();
|
|
UI != E; ++UI)
|
|
if (PHINode* use_phi = dyn_cast<PHINode>(UI))
|
|
if (use_phi->getParent() == inst->getParent())
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
Value *GVN::CollapsePhi(PHINode *PN) {
|
|
Value *ConstVal = PN->hasConstantValue(DT);
|
|
if (!ConstVal) return 0;
|
|
|
|
Instruction *Inst = dyn_cast<Instruction>(ConstVal);
|
|
if (!Inst)
|
|
return ConstVal;
|
|
|
|
if (DT->dominates(Inst, PN))
|
|
if (isSafeReplacement(PN, Inst))
|
|
return Inst;
|
|
return 0;
|
|
}
|
|
|
|
/// IsValueFullyAvailableInBlock - Return true if we can prove that the value
|
|
/// we're analyzing is fully available in the specified block. As we go, keep
|
|
/// track of which blocks we know are fully alive in FullyAvailableBlocks. This
|
|
/// map is actually a tri-state map with the following values:
|
|
/// 0) we know the block *is not* fully available.
|
|
/// 1) we know the block *is* fully available.
|
|
/// 2) we do not know whether the block is fully available or not, but we are
|
|
/// currently speculating that it will be.
|
|
/// 3) we are speculating for this block and have used that to speculate for
|
|
/// other blocks.
|
|
static bool IsValueFullyAvailableInBlock(BasicBlock *BB,
|
|
DenseMap<BasicBlock*, char> &FullyAvailableBlocks) {
|
|
// Optimistically assume that the block is fully available and check to see
|
|
// if we already know about this block in one lookup.
|
|
std::pair<DenseMap<BasicBlock*, char>::iterator, char> IV =
|
|
FullyAvailableBlocks.insert(std::make_pair(BB, 2));
|
|
|
|
// If the entry already existed for this block, return the precomputed value.
|
|
if (!IV.second) {
|
|
// If this is a speculative "available" value, mark it as being used for
|
|
// speculation of other blocks.
|
|
if (IV.first->second == 2)
|
|
IV.first->second = 3;
|
|
return IV.first->second != 0;
|
|
}
|
|
|
|
// Otherwise, see if it is fully available in all predecessors.
|
|
pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
|
|
|
|
// If this block has no predecessors, it isn't live-in here.
|
|
if (PI == PE)
|
|
goto SpeculationFailure;
|
|
|
|
for (; PI != PE; ++PI)
|
|
// If the value isn't fully available in one of our predecessors, then it
|
|
// isn't fully available in this block either. Undo our previous
|
|
// optimistic assumption and bail out.
|
|
if (!IsValueFullyAvailableInBlock(*PI, FullyAvailableBlocks))
|
|
goto SpeculationFailure;
|
|
|
|
return true;
|
|
|
|
// SpeculationFailure - If we get here, we found out that this is not, after
|
|
// all, a fully-available block. We have a problem if we speculated on this and
|
|
// used the speculation to mark other blocks as available.
|
|
SpeculationFailure:
|
|
char &BBVal = FullyAvailableBlocks[BB];
|
|
|
|
// If we didn't speculate on this, just return with it set to false.
|
|
if (BBVal == 2) {
|
|
BBVal = 0;
|
|
return false;
|
|
}
|
|
|
|
// If we did speculate on this value, we could have blocks set to 1 that are
|
|
// incorrect. Walk the (transitive) successors of this block and mark them as
|
|
// 0 if set to one.
|
|
SmallVector<BasicBlock*, 32> BBWorklist;
|
|
BBWorklist.push_back(BB);
|
|
|
|
while (!BBWorklist.empty()) {
|
|
BasicBlock *Entry = BBWorklist.pop_back_val();
|
|
// Note that this sets blocks to 0 (unavailable) if they happen to not
|
|
// already be in FullyAvailableBlocks. This is safe.
|
|
char &EntryVal = FullyAvailableBlocks[Entry];
|
|
if (EntryVal == 0) continue; // Already unavailable.
|
|
|
|
// Mark as unavailable.
|
|
EntryVal = 0;
|
|
|
|
for (succ_iterator I = succ_begin(Entry), E = succ_end(Entry); I != E; ++I)
|
|
BBWorklist.push_back(*I);
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
|
|
/// CanCoerceMustAliasedValueToLoad - Return true if
|
|
/// CoerceAvailableValueToLoadType will succeed.
|
|
static bool CanCoerceMustAliasedValueToLoad(Value *StoredVal,
|
|
const Type *LoadTy,
|
|
const TargetData &TD) {
|
|
// If the loaded or stored value is an first class array or struct, don't try
|
|
// to transform them. We need to be able to bitcast to integer.
|
|
if (isa<StructType>(LoadTy) || isa<ArrayType>(LoadTy) ||
|
|
isa<StructType>(StoredVal->getType()) ||
|
|
isa<ArrayType>(StoredVal->getType()))
|
|
return false;
|
|
|
|
// The store has to be at least as big as the load.
|
|
if (TD.getTypeSizeInBits(StoredVal->getType()) <
|
|
TD.getTypeSizeInBits(LoadTy))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
/// CoerceAvailableValueToLoadType - If we saw a store of a value to memory, and
|
|
/// then a load from a must-aliased pointer of a different type, try to coerce
|
|
/// the stored value. LoadedTy is the type of the load we want to replace and
|
|
/// InsertPt is the place to insert new instructions.
|
|
///
|
|
/// If we can't do it, return null.
|
|
static Value *CoerceAvailableValueToLoadType(Value *StoredVal,
|
|
const Type *LoadedTy,
|
|
Instruction *InsertPt,
|
|
const TargetData &TD) {
|
|
if (!CanCoerceMustAliasedValueToLoad(StoredVal, LoadedTy, TD))
|
|
return 0;
|
|
|
|
const Type *StoredValTy = StoredVal->getType();
|
|
|
|
uint64_t StoreSize = TD.getTypeSizeInBits(StoredValTy);
|
|
uint64_t LoadSize = TD.getTypeSizeInBits(LoadedTy);
|
|
|
|
// If the store and reload are the same size, we can always reuse it.
|
|
if (StoreSize == LoadSize) {
|
|
if (isa<PointerType>(StoredValTy) && isa<PointerType>(LoadedTy)) {
|
|
// Pointer to Pointer -> use bitcast.
|
|
return new BitCastInst(StoredVal, LoadedTy, "", InsertPt);
|
|
}
|
|
|
|
// Convert source pointers to integers, which can be bitcast.
|
|
if (isa<PointerType>(StoredValTy)) {
|
|
StoredValTy = TD.getIntPtrType(StoredValTy->getContext());
|
|
StoredVal = new PtrToIntInst(StoredVal, StoredValTy, "", InsertPt);
|
|
}
|
|
|
|
const Type *TypeToCastTo = LoadedTy;
|
|
if (isa<PointerType>(TypeToCastTo))
|
|
TypeToCastTo = TD.getIntPtrType(StoredValTy->getContext());
|
|
|
|
if (StoredValTy != TypeToCastTo)
|
|
StoredVal = new BitCastInst(StoredVal, TypeToCastTo, "", InsertPt);
|
|
|
|
// Cast to pointer if the load needs a pointer type.
|
|
if (isa<PointerType>(LoadedTy))
|
|
StoredVal = new IntToPtrInst(StoredVal, LoadedTy, "", InsertPt);
|
|
|
|
return StoredVal;
|
|
}
|
|
|
|
// If the loaded value is smaller than the available value, then we can
|
|
// extract out a piece from it. If the available value is too small, then we
|
|
// can't do anything.
|
|
assert(StoreSize >= LoadSize && "CanCoerceMustAliasedValueToLoad fail");
|
|
|
|
// Convert source pointers to integers, which can be manipulated.
|
|
if (isa<PointerType>(StoredValTy)) {
|
|
StoredValTy = TD.getIntPtrType(StoredValTy->getContext());
|
|
StoredVal = new PtrToIntInst(StoredVal, StoredValTy, "", InsertPt);
|
|
}
|
|
|
|
// Convert vectors and fp to integer, which can be manipulated.
|
|
if (!isa<IntegerType>(StoredValTy)) {
|
|
StoredValTy = IntegerType::get(StoredValTy->getContext(), StoreSize);
|
|
StoredVal = new BitCastInst(StoredVal, StoredValTy, "", InsertPt);
|
|
}
|
|
|
|
// If this is a big-endian system, we need to shift the value down to the low
|
|
// bits so that a truncate will work.
|
|
if (TD.isBigEndian()) {
|
|
Constant *Val = ConstantInt::get(StoredVal->getType(), StoreSize-LoadSize);
|
|
StoredVal = BinaryOperator::CreateLShr(StoredVal, Val, "tmp", InsertPt);
|
|
}
|
|
|
|
// Truncate the integer to the right size now.
|
|
const Type *NewIntTy = IntegerType::get(StoredValTy->getContext(), LoadSize);
|
|
StoredVal = new TruncInst(StoredVal, NewIntTy, "trunc", InsertPt);
|
|
|
|
if (LoadedTy == NewIntTy)
|
|
return StoredVal;
|
|
|
|
// If the result is a pointer, inttoptr.
|
|
if (isa<PointerType>(LoadedTy))
|
|
return new IntToPtrInst(StoredVal, LoadedTy, "inttoptr", InsertPt);
|
|
|
|
// Otherwise, bitcast.
|
|
return new BitCastInst(StoredVal, LoadedTy, "bitcast", InsertPt);
|
|
}
|
|
|
|
/// GetBaseWithConstantOffset - Analyze the specified pointer to see if it can
|
|
/// be expressed as a base pointer plus a constant offset. Return the base and
|
|
/// offset to the caller.
|
|
static Value *GetBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
|
|
const TargetData &TD) {
|
|
Operator *PtrOp = dyn_cast<Operator>(Ptr);
|
|
if (PtrOp == 0) return Ptr;
|
|
|
|
// Just look through bitcasts.
|
|
if (PtrOp->getOpcode() == Instruction::BitCast)
|
|
return GetBaseWithConstantOffset(PtrOp->getOperand(0), Offset, TD);
|
|
|
|
// If this is a GEP with constant indices, we can look through it.
|
|
GEPOperator *GEP = dyn_cast<GEPOperator>(PtrOp);
|
|
if (GEP == 0 || !GEP->hasAllConstantIndices()) return Ptr;
|
|
|
|
gep_type_iterator GTI = gep_type_begin(GEP);
|
|
for (User::op_iterator I = GEP->idx_begin(), E = GEP->idx_end(); I != E;
|
|
++I, ++GTI) {
|
|
ConstantInt *OpC = cast<ConstantInt>(*I);
|
|
if (OpC->isZero()) continue;
|
|
|
|
// Handle a struct and array indices which add their offset to the pointer.
|
|
if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
|
|
Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
|
|
} else {
|
|
uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
|
|
Offset += OpC->getSExtValue()*Size;
|
|
}
|
|
}
|
|
|
|
// Re-sign extend from the pointer size if needed to get overflow edge cases
|
|
// right.
|
|
unsigned PtrSize = TD.getPointerSizeInBits();
|
|
if (PtrSize < 64)
|
|
Offset = (Offset << (64-PtrSize)) >> (64-PtrSize);
|
|
|
|
return GetBaseWithConstantOffset(GEP->getPointerOperand(), Offset, TD);
|
|
}
|
|
|
|
|
|
/// AnalyzeLoadFromClobberingStore - This function is called when we have a
|
|
/// memdep query of a load that ends up being a clobbering store. This means
|
|
/// that the store *may* provide bits used by the load but we can't be sure
|
|
/// because the pointers don't mustalias. Check this case to see if there is
|
|
/// anything more we can do before we give up. This returns -1 if we have to
|
|
/// give up, or a byte number in the stored value of the piece that feeds the
|
|
/// load.
|
|
static int AnalyzeLoadFromClobberingStore(LoadInst *L, StoreInst *DepSI,
|
|
const TargetData &TD) {
|
|
// If the loaded or stored value is an first class array or struct, don't try
|
|
// to transform them. We need to be able to bitcast to integer.
|
|
if (isa<StructType>(L->getType()) || isa<ArrayType>(L->getType()) ||
|
|
isa<StructType>(DepSI->getOperand(0)->getType()) ||
|
|
isa<ArrayType>(DepSI->getOperand(0)->getType()))
|
|
return -1;
|
|
|
|
int64_t StoreOffset = 0, LoadOffset = 0;
|
|
Value *StoreBase =
|
|
GetBaseWithConstantOffset(DepSI->getPointerOperand(), StoreOffset, TD);
|
|
Value *LoadBase =
|
|
GetBaseWithConstantOffset(L->getPointerOperand(), LoadOffset, TD);
|
|
if (StoreBase != LoadBase)
|
|
return -1;
|
|
|
|
// If the load and store are to the exact same address, they should have been
|
|
// a must alias. AA must have gotten confused.
|
|
// FIXME: Study to see if/when this happens.
|
|
if (LoadOffset == StoreOffset) {
|
|
#if 0
|
|
errs() << "STORE/LOAD DEP WITH COMMON POINTER MISSED:\n"
|
|
<< "Base = " << *StoreBase << "\n"
|
|
<< "Store Ptr = " << *DepSI->getPointerOperand() << "\n"
|
|
<< "Store Offs = " << StoreOffset << " - " << *DepSI << "\n"
|
|
<< "Load Ptr = " << *L->getPointerOperand() << "\n"
|
|
<< "Load Offs = " << LoadOffset << " - " << *L << "\n\n";
|
|
errs() << "'" << L->getParent()->getParent()->getName() << "'"
|
|
<< *L->getParent();
|
|
#endif
|
|
return -1;
|
|
}
|
|
|
|
// If the load and store don't overlap at all, the store doesn't provide
|
|
// anything to the load. In this case, they really don't alias at all, AA
|
|
// must have gotten confused.
|
|
// FIXME: Investigate cases where this bails out, e.g. rdar://7238614. Then
|
|
// remove this check, as it is duplicated with what we have below.
|
|
uint64_t StoreSize = TD.getTypeSizeInBits(DepSI->getOperand(0)->getType());
|
|
uint64_t LoadSize = TD.getTypeSizeInBits(L->getType());
|
|
|
|
if ((StoreSize & 7) | (LoadSize & 7))
|
|
return -1;
|
|
StoreSize >>= 3; // Convert to bytes.
|
|
LoadSize >>= 3;
|
|
|
|
|
|
bool isAAFailure = false;
|
|
if (StoreOffset < LoadOffset) {
|
|
isAAFailure = StoreOffset+int64_t(StoreSize) <= LoadOffset;
|
|
} else {
|
|
isAAFailure = LoadOffset+int64_t(LoadSize) <= StoreOffset;
|
|
}
|
|
if (isAAFailure) {
|
|
#if 0
|
|
errs() << "STORE LOAD DEP WITH COMMON BASE:\n"
|
|
<< "Base = " << *StoreBase << "\n"
|
|
<< "Store Ptr = " << *DepSI->getPointerOperand() << "\n"
|
|
<< "Store Offs = " << StoreOffset << " - " << *DepSI << "\n"
|
|
<< "Load Ptr = " << *L->getPointerOperand() << "\n"
|
|
<< "Load Offs = " << LoadOffset << " - " << *L << "\n\n";
|
|
errs() << "'" << L->getParent()->getParent()->getName() << "'"
|
|
<< *L->getParent();
|
|
#endif
|
|
return -1;
|
|
}
|
|
|
|
// If the Load isn't completely contained within the stored bits, we don't
|
|
// have all the bits to feed it. We could do something crazy in the future
|
|
// (issue a smaller load then merge the bits in) but this seems unlikely to be
|
|
// valuable.
|
|
if (StoreOffset > LoadOffset ||
|
|
StoreOffset+StoreSize < LoadOffset+LoadSize)
|
|
return -1;
|
|
|
|
// Okay, we can do this transformation. Return the number of bytes into the
|
|
// store that the load is.
|
|
return LoadOffset-StoreOffset;
|
|
}
|
|
|
|
|
|
/// GetStoreValueForLoad - This function is called when we have a
|
|
/// memdep query of a load that ends up being a clobbering store. This means
|
|
/// that the store *may* provide bits used by the load but we can't be sure
|
|
/// because the pointers don't mustalias. Check this case to see if there is
|
|
/// anything more we can do before we give up.
|
|
static Value *GetStoreValueForLoad(Value *SrcVal, unsigned Offset,
|
|
const Type *LoadTy,
|
|
Instruction *InsertPt, const TargetData &TD){
|
|
LLVMContext &Ctx = SrcVal->getType()->getContext();
|
|
|
|
uint64_t StoreSize = TD.getTypeSizeInBits(SrcVal->getType())/8;
|
|
uint64_t LoadSize = TD.getTypeSizeInBits(LoadTy)/8;
|
|
|
|
|
|
// Compute which bits of the stored value are being used by the load. Convert
|
|
// to an integer type to start with.
|
|
if (isa<PointerType>(SrcVal->getType()))
|
|
SrcVal = new PtrToIntInst(SrcVal, TD.getIntPtrType(Ctx), "tmp", InsertPt);
|
|
if (!isa<IntegerType>(SrcVal->getType()))
|
|
SrcVal = new BitCastInst(SrcVal, IntegerType::get(Ctx, StoreSize*8),
|
|
"tmp", InsertPt);
|
|
|
|
// Shift the bits to the least significant depending on endianness.
|
|
unsigned ShiftAmt;
|
|
if (TD.isLittleEndian()) {
|
|
ShiftAmt = Offset*8;
|
|
} else {
|
|
ShiftAmt = (StoreSize-LoadSize-Offset)*8;
|
|
}
|
|
|
|
if (ShiftAmt)
|
|
SrcVal = BinaryOperator::CreateLShr(SrcVal,
|
|
ConstantInt::get(SrcVal->getType(), ShiftAmt), "tmp", InsertPt);
|
|
|
|
if (LoadSize != StoreSize)
|
|
SrcVal = new TruncInst(SrcVal, IntegerType::get(Ctx, LoadSize*8),
|
|
"tmp", InsertPt);
|
|
|
|
return CoerceAvailableValueToLoadType(SrcVal, LoadTy, InsertPt, TD);
|
|
}
|
|
|
|
struct AvailableValueInBlock {
|
|
/// BB - The basic block in question.
|
|
BasicBlock *BB;
|
|
/// V - The value that is live out of the block.
|
|
Value *V;
|
|
/// Offset - The byte offset in V that is interesting for the load query.
|
|
unsigned Offset;
|
|
|
|
static AvailableValueInBlock get(BasicBlock *BB, Value *V,
|
|
unsigned Offset = 0) {
|
|
AvailableValueInBlock Res;
|
|
Res.BB = BB;
|
|
Res.V = V;
|
|
Res.Offset = Offset;
|
|
return Res;
|
|
}
|
|
};
|
|
|
|
/// ConstructSSAForLoadSet - Given a set of loads specified by ValuesPerBlock,
|
|
/// construct SSA form, allowing us to eliminate LI. This returns the value
|
|
/// that should be used at LI's definition site.
|
|
static Value *ConstructSSAForLoadSet(LoadInst *LI,
|
|
SmallVectorImpl<AvailableValueInBlock> &ValuesPerBlock,
|
|
const TargetData *TD,
|
|
AliasAnalysis *AA) {
|
|
SmallVector<PHINode*, 8> NewPHIs;
|
|
SSAUpdater SSAUpdate(&NewPHIs);
|
|
SSAUpdate.Initialize(LI);
|
|
|
|
const Type *LoadTy = LI->getType();
|
|
|
|
for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) {
|
|
BasicBlock *BB = ValuesPerBlock[i].BB;
|
|
Value *AvailableVal = ValuesPerBlock[i].V;
|
|
unsigned Offset = ValuesPerBlock[i].Offset;
|
|
|
|
if (SSAUpdate.HasValueForBlock(BB))
|
|
continue;
|
|
|
|
if (AvailableVal->getType() != LoadTy) {
|
|
assert(TD && "Need target data to handle type mismatch case");
|
|
AvailableVal = GetStoreValueForLoad(AvailableVal, Offset, LoadTy,
|
|
BB->getTerminator(), *TD);
|
|
|
|
if (Offset) {
|
|
DEBUG(errs() << "GVN COERCED NONLOCAL VAL:\n"
|
|
<< *ValuesPerBlock[i].V << '\n'
|
|
<< *AvailableVal << '\n' << "\n\n\n");
|
|
}
|
|
|
|
|
|
DEBUG(errs() << "GVN COERCED NONLOCAL VAL:\n"
|
|
<< *ValuesPerBlock[i].V << '\n'
|
|
<< *AvailableVal << '\n' << "\n\n\n");
|
|
}
|
|
|
|
SSAUpdate.AddAvailableValue(BB, AvailableVal);
|
|
}
|
|
|
|
// Perform PHI construction.
|
|
Value *V = SSAUpdate.GetValueInMiddleOfBlock(LI->getParent());
|
|
|
|
// If new PHI nodes were created, notify alias analysis.
|
|
if (isa<PointerType>(V->getType()))
|
|
for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
|
|
AA->copyValue(LI, NewPHIs[i]);
|
|
|
|
return V;
|
|
}
|
|
|
|
/// processNonLocalLoad - Attempt to eliminate a load whose dependencies are
|
|
/// non-local by performing PHI construction.
|
|
bool GVN::processNonLocalLoad(LoadInst *LI,
|
|
SmallVectorImpl<Instruction*> &toErase) {
|
|
// Find the non-local dependencies of the load.
|
|
SmallVector<MemoryDependenceAnalysis::NonLocalDepEntry, 64> Deps;
|
|
MD->getNonLocalPointerDependency(LI->getOperand(0), true, LI->getParent(),
|
|
Deps);
|
|
//DEBUG(errs() << "INVESTIGATING NONLOCAL LOAD: "
|
|
// << Deps.size() << *LI << '\n');
|
|
|
|
// If we had to process more than one hundred blocks to find the
|
|
// dependencies, this load isn't worth worrying about. Optimizing
|
|
// it will be too expensive.
|
|
if (Deps.size() > 100)
|
|
return false;
|
|
|
|
// If we had a phi translation failure, we'll have a single entry which is a
|
|
// clobber in the current block. Reject this early.
|
|
if (Deps.size() == 1 && Deps[0].second.isClobber()) {
|
|
DEBUG(
|
|
errs() << "GVN: non-local load ";
|
|
WriteAsOperand(errs(), LI);
|
|
errs() << " is clobbered by " << *Deps[0].second.getInst() << '\n';
|
|
);
|
|
return false;
|
|
}
|
|
|
|
// Filter out useless results (non-locals, etc). Keep track of the blocks
|
|
// where we have a value available in repl, also keep track of whether we see
|
|
// dependencies that produce an unknown value for the load (such as a call
|
|
// that could potentially clobber the load).
|
|
SmallVector<AvailableValueInBlock, 16> ValuesPerBlock;
|
|
SmallVector<BasicBlock*, 16> UnavailableBlocks;
|
|
|
|
const TargetData *TD = 0;
|
|
|
|
for (unsigned i = 0, e = Deps.size(); i != e; ++i) {
|
|
BasicBlock *DepBB = Deps[i].first;
|
|
MemDepResult DepInfo = Deps[i].second;
|
|
|
|
if (DepInfo.isClobber()) {
|
|
// If the dependence is to a store that writes to a superset of the bits
|
|
// read by the load, we can extract the bits we need for the load from the
|
|
// stored value.
|
|
if (StoreInst *DepSI = dyn_cast<StoreInst>(DepInfo.getInst())) {
|
|
if (TD == 0)
|
|
TD = getAnalysisIfAvailable<TargetData>();
|
|
if (TD) {
|
|
int Offset = AnalyzeLoadFromClobberingStore(LI, DepSI, *TD);
|
|
if (Offset != -1) {
|
|
ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
|
|
DepSI->getOperand(0),
|
|
Offset));
|
|
continue;
|
|
}
|
|
}
|
|
}
|
|
|
|
// FIXME: Handle memset/memcpy.
|
|
UnavailableBlocks.push_back(DepBB);
|
|
continue;
|
|
}
|
|
|
|
Instruction *DepInst = DepInfo.getInst();
|
|
|
|
// Loading the allocation -> undef.
|
|
if (isa<AllocaInst>(DepInst) || isMalloc(DepInst)) {
|
|
ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
|
|
UndefValue::get(LI->getType())));
|
|
continue;
|
|
}
|
|
|
|
if (StoreInst *S = dyn_cast<StoreInst>(DepInst)) {
|
|
// Reject loads and stores that are to the same address but are of
|
|
// different types if we have to.
|
|
if (S->getOperand(0)->getType() != LI->getType()) {
|
|
if (TD == 0)
|
|
TD = getAnalysisIfAvailable<TargetData>();
|
|
|
|
// If the stored value is larger or equal to the loaded value, we can
|
|
// reuse it.
|
|
if (TD == 0 || !CanCoerceMustAliasedValueToLoad(S->getOperand(0),
|
|
LI->getType(), *TD)) {
|
|
UnavailableBlocks.push_back(DepBB);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
|
|
S->getOperand(0)));
|
|
continue;
|
|
}
|
|
|
|
if (LoadInst *LD = dyn_cast<LoadInst>(DepInst)) {
|
|
// If the types mismatch and we can't handle it, reject reuse of the load.
|
|
if (LD->getType() != LI->getType()) {
|
|
if (TD == 0)
|
|
TD = getAnalysisIfAvailable<TargetData>();
|
|
|
|
// If the stored value is larger or equal to the loaded value, we can
|
|
// reuse it.
|
|
if (TD == 0 || !CanCoerceMustAliasedValueToLoad(LD, LI->getType(),*TD)){
|
|
UnavailableBlocks.push_back(DepBB);
|
|
continue;
|
|
}
|
|
}
|
|
ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB, LD));
|
|
continue;
|
|
}
|
|
|
|
UnavailableBlocks.push_back(DepBB);
|
|
continue;
|
|
}
|
|
|
|
// If we have no predecessors that produce a known value for this load, exit
|
|
// early.
|
|
if (ValuesPerBlock.empty()) return false;
|
|
|
|
// If all of the instructions we depend on produce a known value for this
|
|
// load, then it is fully redundant and we can use PHI insertion to compute
|
|
// its value. Insert PHIs and remove the fully redundant value now.
|
|
if (UnavailableBlocks.empty()) {
|
|
DEBUG(errs() << "GVN REMOVING NONLOCAL LOAD: " << *LI << '\n');
|
|
|
|
// Perform PHI construction.
|
|
Value *V = ConstructSSAForLoadSet(LI, ValuesPerBlock, TD,
|
|
VN.getAliasAnalysis());
|
|
LI->replaceAllUsesWith(V);
|
|
|
|
if (isa<PHINode>(V))
|
|
V->takeName(LI);
|
|
if (isa<PointerType>(V->getType()))
|
|
MD->invalidateCachedPointerInfo(V);
|
|
toErase.push_back(LI);
|
|
NumGVNLoad++;
|
|
return true;
|
|
}
|
|
|
|
if (!EnablePRE || !EnableLoadPRE)
|
|
return false;
|
|
|
|
// Okay, we have *some* definitions of the value. This means that the value
|
|
// is available in some of our (transitive) predecessors. Lets think about
|
|
// doing PRE of this load. This will involve inserting a new load into the
|
|
// predecessor when it's not available. We could do this in general, but
|
|
// prefer to not increase code size. As such, we only do this when we know
|
|
// that we only have to insert *one* load (which means we're basically moving
|
|
// the load, not inserting a new one).
|
|
|
|
SmallPtrSet<BasicBlock *, 4> Blockers;
|
|
for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
|
|
Blockers.insert(UnavailableBlocks[i]);
|
|
|
|
// Lets find first basic block with more than one predecessor. Walk backwards
|
|
// through predecessors if needed.
|
|
BasicBlock *LoadBB = LI->getParent();
|
|
BasicBlock *TmpBB = LoadBB;
|
|
|
|
bool isSinglePred = false;
|
|
bool allSingleSucc = true;
|
|
while (TmpBB->getSinglePredecessor()) {
|
|
isSinglePred = true;
|
|
TmpBB = TmpBB->getSinglePredecessor();
|
|
if (!TmpBB) // If haven't found any, bail now.
|
|
return false;
|
|
if (TmpBB == LoadBB) // Infinite (unreachable) loop.
|
|
return false;
|
|
if (Blockers.count(TmpBB))
|
|
return false;
|
|
if (TmpBB->getTerminator()->getNumSuccessors() != 1)
|
|
allSingleSucc = false;
|
|
}
|
|
|
|
assert(TmpBB);
|
|
LoadBB = TmpBB;
|
|
|
|
// If we have a repl set with LI itself in it, this means we have a loop where
|
|
// at least one of the values is LI. Since this means that we won't be able
|
|
// to eliminate LI even if we insert uses in the other predecessors, we will
|
|
// end up increasing code size. Reject this by scanning for LI.
|
|
for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i)
|
|
if (ValuesPerBlock[i].V == LI)
|
|
return false;
|
|
|
|
if (isSinglePred) {
|
|
bool isHot = false;
|
|
for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i)
|
|
if (Instruction *I = dyn_cast<Instruction>(ValuesPerBlock[i].V))
|
|
// "Hot" Instruction is in some loop (because it dominates its dep.
|
|
// instruction).
|
|
if (DT->dominates(LI, I)) {
|
|
isHot = true;
|
|
break;
|
|
}
|
|
|
|
// We are interested only in "hot" instructions. We don't want to do any
|
|
// mis-optimizations here.
|
|
if (!isHot)
|
|
return false;
|
|
}
|
|
|
|
// Okay, we have some hope :). Check to see if the loaded value is fully
|
|
// available in all but one predecessor.
|
|
// FIXME: If we could restructure the CFG, we could make a common pred with
|
|
// all the preds that don't have an available LI and insert a new load into
|
|
// that one block.
|
|
BasicBlock *UnavailablePred = 0;
|
|
|
|
DenseMap<BasicBlock*, char> FullyAvailableBlocks;
|
|
for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i)
|
|
FullyAvailableBlocks[ValuesPerBlock[i].BB] = true;
|
|
for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
|
|
FullyAvailableBlocks[UnavailableBlocks[i]] = false;
|
|
|
|
for (pred_iterator PI = pred_begin(LoadBB), E = pred_end(LoadBB);
|
|
PI != E; ++PI) {
|
|
if (IsValueFullyAvailableInBlock(*PI, FullyAvailableBlocks))
|
|
continue;
|
|
|
|
// If this load is not available in multiple predecessors, reject it.
|
|
if (UnavailablePred && UnavailablePred != *PI)
|
|
return false;
|
|
UnavailablePred = *PI;
|
|
}
|
|
|
|
assert(UnavailablePred != 0 &&
|
|
"Fully available value should be eliminated above!");
|
|
|
|
// If the loaded pointer is PHI node defined in this block, do PHI translation
|
|
// to get its value in the predecessor.
|
|
Value *LoadPtr = LI->getOperand(0)->DoPHITranslation(LoadBB, UnavailablePred);
|
|
|
|
// Make sure the value is live in the predecessor. If it was defined by a
|
|
// non-PHI instruction in this block, we don't know how to recompute it above.
|
|
if (Instruction *LPInst = dyn_cast<Instruction>(LoadPtr))
|
|
if (!DT->dominates(LPInst->getParent(), UnavailablePred)) {
|
|
DEBUG(errs() << "COULDN'T PRE LOAD BECAUSE PTR IS UNAVAILABLE IN PRED: "
|
|
<< *LPInst << '\n' << *LI << "\n");
|
|
return false;
|
|
}
|
|
|
|
// We don't currently handle critical edges :(
|
|
if (UnavailablePred->getTerminator()->getNumSuccessors() != 1) {
|
|
DEBUG(errs() << "COULD NOT PRE LOAD BECAUSE OF CRITICAL EDGE '"
|
|
<< UnavailablePred->getName() << "': " << *LI << '\n');
|
|
return false;
|
|
}
|
|
|
|
// Make sure it is valid to move this load here. We have to watch out for:
|
|
// @1 = getelementptr (i8* p, ...
|
|
// test p and branch if == 0
|
|
// load @1
|
|
// It is valid to have the getelementptr before the test, even if p can be 0,
|
|
// as getelementptr only does address arithmetic.
|
|
// If we are not pushing the value through any multiple-successor blocks
|
|
// we do not have this case. Otherwise, check that the load is safe to
|
|
// put anywhere; this can be improved, but should be conservatively safe.
|
|
if (!allSingleSucc &&
|
|
!isSafeToLoadUnconditionally(LoadPtr, UnavailablePred->getTerminator()))
|
|
return false;
|
|
|
|
// Okay, we can eliminate this load by inserting a reload in the predecessor
|
|
// and using PHI construction to get the value in the other predecessors, do
|
|
// it.
|
|
DEBUG(errs() << "GVN REMOVING PRE LOAD: " << *LI << '\n');
|
|
|
|
Value *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre", false,
|
|
LI->getAlignment(),
|
|
UnavailablePred->getTerminator());
|
|
|
|
// Add the newly created load.
|
|
ValuesPerBlock.push_back(AvailableValueInBlock::get(UnavailablePred,NewLoad));
|
|
|
|
// Perform PHI construction.
|
|
Value *V = ConstructSSAForLoadSet(LI, ValuesPerBlock, TD,
|
|
VN.getAliasAnalysis());
|
|
LI->replaceAllUsesWith(V);
|
|
if (isa<PHINode>(V))
|
|
V->takeName(LI);
|
|
if (isa<PointerType>(V->getType()))
|
|
MD->invalidateCachedPointerInfo(V);
|
|
toErase.push_back(LI);
|
|
NumPRELoad++;
|
|
return true;
|
|
}
|
|
|
|
/// processLoad - Attempt to eliminate a load, first by eliminating it
|
|
/// locally, and then attempting non-local elimination if that fails.
|
|
bool GVN::processLoad(LoadInst *L, SmallVectorImpl<Instruction*> &toErase) {
|
|
if (L->isVolatile())
|
|
return false;
|
|
|
|
// ... to a pointer that has been loaded from before...
|
|
MemDepResult Dep = MD->getDependency(L);
|
|
|
|
// If the value isn't available, don't do anything!
|
|
if (Dep.isClobber()) {
|
|
// FIXME: We should handle memset/memcpy/memmove as dependent instructions
|
|
// to forward the value if available.
|
|
//if (isa<MemIntrinsic>(Dep.getInst()))
|
|
//errs() << "LOAD DEPENDS ON MEM: " << *L << "\n" << *Dep.getInst()<<"\n\n";
|
|
|
|
// Check to see if we have something like this:
|
|
// store i32 123, i32* %P
|
|
// %A = bitcast i32* %P to i8*
|
|
// %B = gep i8* %A, i32 1
|
|
// %C = load i8* %B
|
|
//
|
|
// We could do that by recognizing if the clobber instructions are obviously
|
|
// a common base + constant offset, and if the previous store (or memset)
|
|
// completely covers this load. This sort of thing can happen in bitfield
|
|
// access code.
|
|
if (StoreInst *DepSI = dyn_cast<StoreInst>(Dep.getInst()))
|
|
if (const TargetData *TD = getAnalysisIfAvailable<TargetData>()) {
|
|
int Offset = AnalyzeLoadFromClobberingStore(L, DepSI, *TD);
|
|
if (Offset != -1) {
|
|
Value *AvailVal = GetStoreValueForLoad(DepSI->getOperand(0), Offset,
|
|
L->getType(), L, *TD);
|
|
DEBUG(errs() << "GVN COERCED STORE BITS:\n" << *DepSI << '\n'
|
|
<< *AvailVal << '\n' << *L << "\n\n\n");
|
|
|
|
// Replace the load!
|
|
L->replaceAllUsesWith(AvailVal);
|
|
if (isa<PointerType>(AvailVal->getType()))
|
|
MD->invalidateCachedPointerInfo(AvailVal);
|
|
toErase.push_back(L);
|
|
NumGVNLoad++;
|
|
return true;
|
|
}
|
|
}
|
|
|
|
DEBUG(
|
|
// fast print dep, using operator<< on instruction would be too slow
|
|
errs() << "GVN: load ";
|
|
WriteAsOperand(errs(), L);
|
|
Instruction *I = Dep.getInst();
|
|
errs() << " is clobbered by " << *I << '\n';
|
|
);
|
|
return false;
|
|
}
|
|
|
|
// If it is defined in another block, try harder.
|
|
if (Dep.isNonLocal())
|
|
return processNonLocalLoad(L, toErase);
|
|
|
|
Instruction *DepInst = Dep.getInst();
|
|
if (StoreInst *DepSI = dyn_cast<StoreInst>(DepInst)) {
|
|
Value *StoredVal = DepSI->getOperand(0);
|
|
|
|
// The store and load are to a must-aliased pointer, but they may not
|
|
// actually have the same type. See if we know how to reuse the stored
|
|
// value (depending on its type).
|
|
const TargetData *TD = 0;
|
|
if (StoredVal->getType() != L->getType()) {
|
|
if ((TD = getAnalysisIfAvailable<TargetData>())) {
|
|
StoredVal = CoerceAvailableValueToLoadType(StoredVal, L->getType(),
|
|
L, *TD);
|
|
if (StoredVal == 0)
|
|
return false;
|
|
|
|
DEBUG(errs() << "GVN COERCED STORE:\n" << *DepSI << '\n' << *StoredVal
|
|
<< '\n' << *L << "\n\n\n");
|
|
}
|
|
else
|
|
return false;
|
|
}
|
|
|
|
// Remove it!
|
|
L->replaceAllUsesWith(StoredVal);
|
|
if (isa<PointerType>(StoredVal->getType()))
|
|
MD->invalidateCachedPointerInfo(StoredVal);
|
|
toErase.push_back(L);
|
|
NumGVNLoad++;
|
|
return true;
|
|
}
|
|
|
|
if (LoadInst *DepLI = dyn_cast<LoadInst>(DepInst)) {
|
|
Value *AvailableVal = DepLI;
|
|
|
|
// The loads are of a must-aliased pointer, but they may not actually have
|
|
// the same type. See if we know how to reuse the previously loaded value
|
|
// (depending on its type).
|
|
const TargetData *TD = 0;
|
|
if (DepLI->getType() != L->getType()) {
|
|
if ((TD = getAnalysisIfAvailable<TargetData>())) {
|
|
AvailableVal = CoerceAvailableValueToLoadType(DepLI, L->getType(), L,*TD);
|
|
if (AvailableVal == 0)
|
|
return false;
|
|
|
|
DEBUG(errs() << "GVN COERCED LOAD:\n" << *DepLI << "\n" << *AvailableVal
|
|
<< "\n" << *L << "\n\n\n");
|
|
}
|
|
else
|
|
return false;
|
|
}
|
|
|
|
// Remove it!
|
|
L->replaceAllUsesWith(AvailableVal);
|
|
if (isa<PointerType>(DepLI->getType()))
|
|
MD->invalidateCachedPointerInfo(DepLI);
|
|
toErase.push_back(L);
|
|
NumGVNLoad++;
|
|
return true;
|
|
}
|
|
|
|
// If this load really doesn't depend on anything, then we must be loading an
|
|
// undef value. This can happen when loading for a fresh allocation with no
|
|
// intervening stores, for example.
|
|
if (isa<AllocaInst>(DepInst) || isMalloc(DepInst)) {
|
|
L->replaceAllUsesWith(UndefValue::get(L->getType()));
|
|
toErase.push_back(L);
|
|
NumGVNLoad++;
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
Value *GVN::lookupNumber(BasicBlock *BB, uint32_t num) {
|
|
DenseMap<BasicBlock*, ValueNumberScope*>::iterator I = localAvail.find(BB);
|
|
if (I == localAvail.end())
|
|
return 0;
|
|
|
|
ValueNumberScope *Locals = I->second;
|
|
while (Locals) {
|
|
DenseMap<uint32_t, Value*>::iterator I = Locals->table.find(num);
|
|
if (I != Locals->table.end())
|
|
return I->second;
|
|
Locals = Locals->parent;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
/// processInstruction - When calculating availability, handle an instruction
|
|
/// by inserting it into the appropriate sets
|
|
bool GVN::processInstruction(Instruction *I,
|
|
SmallVectorImpl<Instruction*> &toErase) {
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
|
|
bool Changed = processLoad(LI, toErase);
|
|
|
|
if (!Changed) {
|
|
unsigned Num = VN.lookup_or_add(LI);
|
|
localAvail[I->getParent()]->table.insert(std::make_pair(Num, LI));
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
uint32_t NextNum = VN.getNextUnusedValueNumber();
|
|
unsigned Num = VN.lookup_or_add(I);
|
|
|
|
if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
|
|
localAvail[I->getParent()]->table.insert(std::make_pair(Num, I));
|
|
|
|
if (!BI->isConditional() || isa<Constant>(BI->getCondition()))
|
|
return false;
|
|
|
|
Value *BranchCond = BI->getCondition();
|
|
uint32_t CondVN = VN.lookup_or_add(BranchCond);
|
|
|
|
BasicBlock *TrueSucc = BI->getSuccessor(0);
|
|
BasicBlock *FalseSucc = BI->getSuccessor(1);
|
|
|
|
if (TrueSucc->getSinglePredecessor())
|
|
localAvail[TrueSucc]->table[CondVN] =
|
|
ConstantInt::getTrue(TrueSucc->getContext());
|
|
if (FalseSucc->getSinglePredecessor())
|
|
localAvail[FalseSucc]->table[CondVN] =
|
|
ConstantInt::getFalse(TrueSucc->getContext());
|
|
|
|
return false;
|
|
|
|
// Allocations are always uniquely numbered, so we can save time and memory
|
|
// by fast failing them.
|
|
} else if (isa<AllocaInst>(I) || isa<TerminatorInst>(I)) {
|
|
localAvail[I->getParent()]->table.insert(std::make_pair(Num, I));
|
|
return false;
|
|
}
|
|
|
|
// Collapse PHI nodes
|
|
if (PHINode* p = dyn_cast<PHINode>(I)) {
|
|
Value *constVal = CollapsePhi(p);
|
|
|
|
if (constVal) {
|
|
p->replaceAllUsesWith(constVal);
|
|
if (isa<PointerType>(constVal->getType()))
|
|
MD->invalidateCachedPointerInfo(constVal);
|
|
VN.erase(p);
|
|
|
|
toErase.push_back(p);
|
|
} else {
|
|
localAvail[I->getParent()]->table.insert(std::make_pair(Num, I));
|
|
}
|
|
|
|
// If the number we were assigned was a brand new VN, then we don't
|
|
// need to do a lookup to see if the number already exists
|
|
// somewhere in the domtree: it can't!
|
|
} else if (Num == NextNum) {
|
|
localAvail[I->getParent()]->table.insert(std::make_pair(Num, I));
|
|
|
|
// Perform fast-path value-number based elimination of values inherited from
|
|
// dominators.
|
|
} else if (Value *repl = lookupNumber(I->getParent(), Num)) {
|
|
// Remove it!
|
|
VN.erase(I);
|
|
I->replaceAllUsesWith(repl);
|
|
if (isa<PointerType>(repl->getType()))
|
|
MD->invalidateCachedPointerInfo(repl);
|
|
toErase.push_back(I);
|
|
return true;
|
|
|
|
} else {
|
|
localAvail[I->getParent()]->table.insert(std::make_pair(Num, I));
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// runOnFunction - This is the main transformation entry point for a function.
|
|
bool GVN::runOnFunction(Function& F) {
|
|
MD = &getAnalysis<MemoryDependenceAnalysis>();
|
|
DT = &getAnalysis<DominatorTree>();
|
|
VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>());
|
|
VN.setMemDep(MD);
|
|
VN.setDomTree(DT);
|
|
|
|
bool Changed = false;
|
|
bool ShouldContinue = true;
|
|
|
|
// Merge unconditional branches, allowing PRE to catch more
|
|
// optimization opportunities.
|
|
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ) {
|
|
BasicBlock *BB = FI;
|
|
++FI;
|
|
bool removedBlock = MergeBlockIntoPredecessor(BB, this);
|
|
if (removedBlock) NumGVNBlocks++;
|
|
|
|
Changed |= removedBlock;
|
|
}
|
|
|
|
unsigned Iteration = 0;
|
|
|
|
while (ShouldContinue) {
|
|
DEBUG(errs() << "GVN iteration: " << Iteration << "\n");
|
|
ShouldContinue = iterateOnFunction(F);
|
|
Changed |= ShouldContinue;
|
|
++Iteration;
|
|
}
|
|
|
|
if (EnablePRE) {
|
|
bool PREChanged = true;
|
|
while (PREChanged) {
|
|
PREChanged = performPRE(F);
|
|
Changed |= PREChanged;
|
|
}
|
|
}
|
|
// FIXME: Should perform GVN again after PRE does something. PRE can move
|
|
// computations into blocks where they become fully redundant. Note that
|
|
// we can't do this until PRE's critical edge splitting updates memdep.
|
|
// Actually, when this happens, we should just fully integrate PRE into GVN.
|
|
|
|
cleanupGlobalSets();
|
|
|
|
return Changed;
|
|
}
|
|
|
|
|
|
bool GVN::processBlock(BasicBlock *BB) {
|
|
// FIXME: Kill off toErase by doing erasing eagerly in a helper function (and
|
|
// incrementing BI before processing an instruction).
|
|
SmallVector<Instruction*, 8> toErase;
|
|
bool ChangedFunction = false;
|
|
|
|
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
|
|
BI != BE;) {
|
|
ChangedFunction |= processInstruction(BI, toErase);
|
|
if (toErase.empty()) {
|
|
++BI;
|
|
continue;
|
|
}
|
|
|
|
// If we need some instructions deleted, do it now.
|
|
NumGVNInstr += toErase.size();
|
|
|
|
// Avoid iterator invalidation.
|
|
bool AtStart = BI == BB->begin();
|
|
if (!AtStart)
|
|
--BI;
|
|
|
|
for (SmallVector<Instruction*, 4>::iterator I = toErase.begin(),
|
|
E = toErase.end(); I != E; ++I) {
|
|
DEBUG(errs() << "GVN removed: " << **I << '\n');
|
|
MD->removeInstruction(*I);
|
|
(*I)->eraseFromParent();
|
|
DEBUG(verifyRemoved(*I));
|
|
}
|
|
toErase.clear();
|
|
|
|
if (AtStart)
|
|
BI = BB->begin();
|
|
else
|
|
++BI;
|
|
}
|
|
|
|
return ChangedFunction;
|
|
}
|
|
|
|
/// performPRE - Perform a purely local form of PRE that looks for diamond
|
|
/// control flow patterns and attempts to perform simple PRE at the join point.
|
|
bool GVN::performPRE(Function& F) {
|
|
bool Changed = false;
|
|
SmallVector<std::pair<TerminatorInst*, unsigned>, 4> toSplit;
|
|
DenseMap<BasicBlock*, Value*> predMap;
|
|
for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
|
|
DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) {
|
|
BasicBlock *CurrentBlock = *DI;
|
|
|
|
// Nothing to PRE in the entry block.
|
|
if (CurrentBlock == &F.getEntryBlock()) continue;
|
|
|
|
for (BasicBlock::iterator BI = CurrentBlock->begin(),
|
|
BE = CurrentBlock->end(); BI != BE; ) {
|
|
Instruction *CurInst = BI++;
|
|
|
|
if (isa<AllocaInst>(CurInst) ||
|
|
isa<TerminatorInst>(CurInst) || isa<PHINode>(CurInst) ||
|
|
CurInst->getType()->isVoidTy() ||
|
|
CurInst->mayReadFromMemory() || CurInst->mayHaveSideEffects() ||
|
|
isa<DbgInfoIntrinsic>(CurInst))
|
|
continue;
|
|
|
|
uint32_t ValNo = VN.lookup(CurInst);
|
|
|
|
// Look for the predecessors for PRE opportunities. We're
|
|
// only trying to solve the basic diamond case, where
|
|
// a value is computed in the successor and one predecessor,
|
|
// but not the other. We also explicitly disallow cases
|
|
// where the successor is its own predecessor, because they're
|
|
// more complicated to get right.
|
|
unsigned NumWith = 0;
|
|
unsigned NumWithout = 0;
|
|
BasicBlock *PREPred = 0;
|
|
predMap.clear();
|
|
|
|
for (pred_iterator PI = pred_begin(CurrentBlock),
|
|
PE = pred_end(CurrentBlock); PI != PE; ++PI) {
|
|
// We're not interested in PRE where the block is its
|
|
// own predecessor, on in blocks with predecessors
|
|
// that are not reachable.
|
|
if (*PI == CurrentBlock) {
|
|
NumWithout = 2;
|
|
break;
|
|
} else if (!localAvail.count(*PI)) {
|
|
NumWithout = 2;
|
|
break;
|
|
}
|
|
|
|
DenseMap<uint32_t, Value*>::iterator predV =
|
|
localAvail[*PI]->table.find(ValNo);
|
|
if (predV == localAvail[*PI]->table.end()) {
|
|
PREPred = *PI;
|
|
NumWithout++;
|
|
} else if (predV->second == CurInst) {
|
|
NumWithout = 2;
|
|
} else {
|
|
predMap[*PI] = predV->second;
|
|
NumWith++;
|
|
}
|
|
}
|
|
|
|
// Don't do PRE when it might increase code size, i.e. when
|
|
// we would need to insert instructions in more than one pred.
|
|
if (NumWithout != 1 || NumWith == 0)
|
|
continue;
|
|
|
|
// We can't do PRE safely on a critical edge, so instead we schedule
|
|
// the edge to be split and perform the PRE the next time we iterate
|
|
// on the function.
|
|
unsigned SuccNum = 0;
|
|
for (unsigned i = 0, e = PREPred->getTerminator()->getNumSuccessors();
|
|
i != e; ++i)
|
|
if (PREPred->getTerminator()->getSuccessor(i) == CurrentBlock) {
|
|
SuccNum = i;
|
|
break;
|
|
}
|
|
|
|
if (isCriticalEdge(PREPred->getTerminator(), SuccNum)) {
|
|
toSplit.push_back(std::make_pair(PREPred->getTerminator(), SuccNum));
|
|
continue;
|
|
}
|
|
|
|
// Instantiate the expression the in predecessor that lacked it.
|
|
// Because we are going top-down through the block, all value numbers
|
|
// will be available in the predecessor by the time we need them. Any
|
|
// that weren't original present will have been instantiated earlier
|
|
// in this loop.
|
|
Instruction *PREInstr = CurInst->clone();
|
|
bool success = true;
|
|
for (unsigned i = 0, e = CurInst->getNumOperands(); i != e; ++i) {
|
|
Value *Op = PREInstr->getOperand(i);
|
|
if (isa<Argument>(Op) || isa<Constant>(Op) || isa<GlobalValue>(Op))
|
|
continue;
|
|
|
|
if (Value *V = lookupNumber(PREPred, VN.lookup(Op))) {
|
|
PREInstr->setOperand(i, V);
|
|
} else {
|
|
success = false;
|
|
break;
|
|
}
|
|
}
|
|
|
|
// Fail out if we encounter an operand that is not available in
|
|
// the PRE predecessor. This is typically because of loads which
|
|
// are not value numbered precisely.
|
|
if (!success) {
|
|
delete PREInstr;
|
|
DEBUG(verifyRemoved(PREInstr));
|
|
continue;
|
|
}
|
|
|
|
PREInstr->insertBefore(PREPred->getTerminator());
|
|
PREInstr->setName(CurInst->getName() + ".pre");
|
|
predMap[PREPred] = PREInstr;
|
|
VN.add(PREInstr, ValNo);
|
|
NumGVNPRE++;
|
|
|
|
// Update the availability map to include the new instruction.
|
|
localAvail[PREPred]->table.insert(std::make_pair(ValNo, PREInstr));
|
|
|
|
// Create a PHI to make the value available in this block.
|
|
PHINode* Phi = PHINode::Create(CurInst->getType(),
|
|
CurInst->getName() + ".pre-phi",
|
|
CurrentBlock->begin());
|
|
for (pred_iterator PI = pred_begin(CurrentBlock),
|
|
PE = pred_end(CurrentBlock); PI != PE; ++PI)
|
|
Phi->addIncoming(predMap[*PI], *PI);
|
|
|
|
VN.add(Phi, ValNo);
|
|
localAvail[CurrentBlock]->table[ValNo] = Phi;
|
|
|
|
CurInst->replaceAllUsesWith(Phi);
|
|
if (isa<PointerType>(Phi->getType()))
|
|
MD->invalidateCachedPointerInfo(Phi);
|
|
VN.erase(CurInst);
|
|
|
|
DEBUG(errs() << "GVN PRE removed: " << *CurInst << '\n');
|
|
MD->removeInstruction(CurInst);
|
|
CurInst->eraseFromParent();
|
|
DEBUG(verifyRemoved(CurInst));
|
|
Changed = true;
|
|
}
|
|
}
|
|
|
|
for (SmallVector<std::pair<TerminatorInst*, unsigned>, 4>::iterator
|
|
I = toSplit.begin(), E = toSplit.end(); I != E; ++I)
|
|
SplitCriticalEdge(I->first, I->second, this);
|
|
|
|
return Changed || toSplit.size();
|
|
}
|
|
|
|
/// iterateOnFunction - Executes one iteration of GVN
|
|
bool GVN::iterateOnFunction(Function &F) {
|
|
cleanupGlobalSets();
|
|
|
|
for (df_iterator<DomTreeNode*> DI = df_begin(DT->getRootNode()),
|
|
DE = df_end(DT->getRootNode()); DI != DE; ++DI) {
|
|
if (DI->getIDom())
|
|
localAvail[DI->getBlock()] =
|
|
new ValueNumberScope(localAvail[DI->getIDom()->getBlock()]);
|
|
else
|
|
localAvail[DI->getBlock()] = new ValueNumberScope(0);
|
|
}
|
|
|
|
// Top-down walk of the dominator tree
|
|
bool Changed = false;
|
|
#if 0
|
|
// Needed for value numbering with phi construction to work.
|
|
ReversePostOrderTraversal<Function*> RPOT(&F);
|
|
for (ReversePostOrderTraversal<Function*>::rpo_iterator RI = RPOT.begin(),
|
|
RE = RPOT.end(); RI != RE; ++RI)
|
|
Changed |= processBlock(*RI);
|
|
#else
|
|
for (df_iterator<DomTreeNode*> DI = df_begin(DT->getRootNode()),
|
|
DE = df_end(DT->getRootNode()); DI != DE; ++DI)
|
|
Changed |= processBlock(DI->getBlock());
|
|
#endif
|
|
|
|
return Changed;
|
|
}
|
|
|
|
void GVN::cleanupGlobalSets() {
|
|
VN.clear();
|
|
|
|
for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator
|
|
I = localAvail.begin(), E = localAvail.end(); I != E; ++I)
|
|
delete I->second;
|
|
localAvail.clear();
|
|
}
|
|
|
|
/// verifyRemoved - Verify that the specified instruction does not occur in our
|
|
/// internal data structures.
|
|
void GVN::verifyRemoved(const Instruction *Inst) const {
|
|
VN.verifyRemoved(Inst);
|
|
|
|
// Walk through the value number scope to make sure the instruction isn't
|
|
// ferreted away in it.
|
|
for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator
|
|
I = localAvail.begin(), E = localAvail.end(); I != E; ++I) {
|
|
const ValueNumberScope *VNS = I->second;
|
|
|
|
while (VNS) {
|
|
for (DenseMap<uint32_t, Value*>::iterator
|
|
II = VNS->table.begin(), IE = VNS->table.end(); II != IE; ++II) {
|
|
assert(II->second != Inst && "Inst still in value numbering scope!");
|
|
}
|
|
|
|
VNS = VNS->parent;
|
|
}
|
|
}
|
|
}
|