mirror of
https://github.com/c64scene-ar/llvm-6502.git
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If we see that a load depends on the allocation of its memory with no intervening stores, we now return a 'None' depedency instead of "Normal". This tweaks GVN to do its optimization with the new result. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60267 91177308-0d34-0410-b5e6-96231b3b80d8
1377 lines
45 KiB
C++
1377 lines
45 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/Instructions.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/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/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/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.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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static cl::opt<bool> EnablePRE("enable-pre",
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cl::init(true), cl::Hidden);
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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 VISIBILITY_HIDDEN Expression {
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enum ExpressionOpcode { ADD, SUB, MUL, 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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EMPTY, TOMBSTONE };
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ExpressionOpcode opcode;
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const Type* type;
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uint32_t firstVN;
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uint32_t secondVN;
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uint32_t thirdVN;
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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 if (firstVN != other.firstVN)
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return false;
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else if (secondVN != other.secondVN)
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return false;
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else if (thirdVN != other.thirdVN)
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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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if (opcode != other.opcode)
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return true;
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else if (opcode == EMPTY || opcode == TOMBSTONE)
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return false;
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else if (type != other.type)
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return true;
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else if (function != other.function)
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return true;
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else if (firstVN != other.firstVN)
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return true;
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else if (secondVN != other.secondVN)
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return true;
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else if (thirdVN != other.thirdVN)
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return true;
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else {
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if (varargs.size() != other.varargs.size())
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return true;
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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 true;
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return false;
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}
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}
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};
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class VISIBILITY_HIDDEN 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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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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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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};
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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 = e.firstVN + hash * 37;
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hash = e.secondVN + hash * 37;
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hash = e.thirdVN + hash * 37;
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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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hash * 37;
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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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assert(0 && "Binary operator with unknown opcode?");
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case Instruction::Add: return Expression::ADD;
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case Instruction::Sub: return Expression::SUB;
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case Instruction::Mul: return Expression::MUL;
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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) || isa<VICmpInst>(C)) {
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switch (C->getPredicate()) {
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default: // THIS SHOULD NEVER HAPPEN
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assert(0 && "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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}
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assert((isa<FCmpInst>(C) || isa<VFCmpInst>(C)) && "Unknown compare");
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switch (C->getPredicate()) {
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default: // THIS SHOULD NEVER HAPPEN
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assert(0 && "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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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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assert(0 && "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.firstVN = 0;
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e.secondVN = 0;
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e.thirdVN = 0;
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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.firstVN = lookup_or_add(BO->getOperand(0));
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e.secondVN = lookup_or_add(BO->getOperand(1));
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e.thirdVN = 0;
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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.firstVN = lookup_or_add(C->getOperand(0));
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e.secondVN = lookup_or_add(C->getOperand(1));
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e.thirdVN = 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(CastInst* C) {
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Expression e;
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e.firstVN = lookup_or_add(C->getOperand(0));
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e.secondVN = 0;
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e.thirdVN = 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.firstVN = lookup_or_add(S->getOperand(0));
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e.secondVN = lookup_or_add(S->getOperand(1));
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e.thirdVN = 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.firstVN = lookup_or_add(E->getOperand(0));
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e.secondVN = lookup_or_add(E->getOperand(1));
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e.thirdVN = 0;
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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.firstVN = lookup_or_add(I->getOperand(0));
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e.secondVN = lookup_or_add(I->getOperand(1));
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e.thirdVN = 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.firstVN = lookup_or_add(I->getCondition());
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e.secondVN = lookup_or_add(I->getTrueValue());
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e.thirdVN = 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.firstVN = lookup_or_add(G->getPointerOperand());
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e.secondVN = 0;
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e.thirdVN = 0;
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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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//===----------------------------------------------------------------------===//
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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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/// lookup_or_add - Returns the value number for the specified value, assigning
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/// it a new number if it did not have one before.
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uint32_t ValueTable::lookup_or_add(Value* V) {
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DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
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if (VI != valueNumbering.end())
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return VI->second;
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if (CallInst* C = dyn_cast<CallInst>(V)) {
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if (AA->doesNotAccessMemory(C)) {
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Expression e = create_expression(C);
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DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
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if (EI != expressionNumbering.end()) {
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valueNumbering.insert(std::make_pair(V, EI->second));
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return EI->second;
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} else {
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expressionNumbering.insert(std::make_pair(e, nextValueNumber));
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valueNumbering.insert(std::make_pair(V, nextValueNumber));
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return nextValueNumber++;
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}
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} else if (AA->onlyReadsMemory(C)) {
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Expression e = create_expression(C);
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if (expressionNumbering.find(e) == expressionNumbering.end()) {
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expressionNumbering.insert(std::make_pair(e, nextValueNumber));
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valueNumbering.insert(std::make_pair(V, nextValueNumber));
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return nextValueNumber++;
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}
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MemDepResult local_dep = MD->getDependency(C);
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if (local_dep.isNone()) {
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valueNumbering.insert(std::make_pair(V, nextValueNumber));
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return nextValueNumber++;
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} else if (Instruction *LocalDepInst = local_dep.getInst()) {
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// FIXME: INDENT PROPERLY!
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if (!isa<CallInst>(LocalDepInst)) {
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valueNumbering.insert(std::make_pair(V, nextValueNumber));
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return nextValueNumber++;
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}
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CallInst* local_cdep = cast<CallInst>(LocalDepInst);
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// FIXME: INDENT PROPERLY.
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if (local_cdep->getCalledFunction() != C->getCalledFunction() ||
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local_cdep->getNumOperands() != C->getNumOperands()) {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
} else if (!C->getCalledFunction()) {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
} else {
|
|
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(local_cdep->getOperand(i));
|
|
if (c_vn != cd_vn) {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
}
|
|
}
|
|
|
|
uint32_t v = lookup_or_add(local_cdep);
|
|
valueNumbering.insert(std::make_pair(V, v));
|
|
return v;
|
|
}
|
|
}
|
|
|
|
|
|
SmallVector<std::pair<BasicBlock*, MemDepResult>, 32> deps;
|
|
MD->getNonLocalDependency(C, deps);
|
|
CallInst* cdep = 0;
|
|
|
|
for (SmallVector<std::pair<BasicBlock*, MemDepResult>, 32>
|
|
::iterator I = deps.begin(), E = deps.end(); I != E; ++I) {
|
|
if (I->second.isNone()) {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
|
|
return nextValueNumber++;
|
|
} else if (Instruction *NonLocalDepInst = I->second.getInst()) {
|
|
// FIXME: INDENT PROPERLY
|
|
// FIXME: All duplicated with non-local case.
|
|
if (cdep == 0 && DT->properlyDominates(I->first, C->getParent())) {
|
|
if (CallInst* CD = dyn_cast<CallInst>(NonLocalDepInst))
|
|
cdep = CD;
|
|
else {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
}
|
|
} else {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!cdep) {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
}
|
|
|
|
// FIXME: THIS ISN'T SAFE: CONSIDER:
|
|
// X = strlen(str)
|
|
// if (C)
|
|
// str[0] = 1;
|
|
// Y = strlen(str)
|
|
// This doesn't guarantee all-paths availability!
|
|
if (cdep->getCalledFunction() != C->getCalledFunction() ||
|
|
cdep->getNumOperands() != C->getNumOperands()) {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
} else if (!C->getCalledFunction()) {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
} else {
|
|
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.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
}
|
|
}
|
|
|
|
uint32_t v = lookup_or_add(cdep);
|
|
valueNumbering.insert(std::make_pair(V, v));
|
|
return v;
|
|
}
|
|
|
|
} else {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
}
|
|
} else if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) {
|
|
Expression e = create_expression(BO);
|
|
|
|
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
|
|
if (EI != expressionNumbering.end()) {
|
|
valueNumbering.insert(std::make_pair(V, EI->second));
|
|
return EI->second;
|
|
} else {
|
|
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
|
|
return nextValueNumber++;
|
|
}
|
|
} else if (CmpInst* C = dyn_cast<CmpInst>(V)) {
|
|
Expression e = create_expression(C);
|
|
|
|
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
|
|
if (EI != expressionNumbering.end()) {
|
|
valueNumbering.insert(std::make_pair(V, EI->second));
|
|
return EI->second;
|
|
} else {
|
|
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
|
|
return nextValueNumber++;
|
|
}
|
|
} else if (ShuffleVectorInst* U = dyn_cast<ShuffleVectorInst>(V)) {
|
|
Expression e = create_expression(U);
|
|
|
|
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
|
|
if (EI != expressionNumbering.end()) {
|
|
valueNumbering.insert(std::make_pair(V, EI->second));
|
|
return EI->second;
|
|
} else {
|
|
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
|
|
return nextValueNumber++;
|
|
}
|
|
} else if (ExtractElementInst* U = dyn_cast<ExtractElementInst>(V)) {
|
|
Expression e = create_expression(U);
|
|
|
|
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
|
|
if (EI != expressionNumbering.end()) {
|
|
valueNumbering.insert(std::make_pair(V, EI->second));
|
|
return EI->second;
|
|
} else {
|
|
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
|
|
return nextValueNumber++;
|
|
}
|
|
} else if (InsertElementInst* U = dyn_cast<InsertElementInst>(V)) {
|
|
Expression e = create_expression(U);
|
|
|
|
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
|
|
if (EI != expressionNumbering.end()) {
|
|
valueNumbering.insert(std::make_pair(V, EI->second));
|
|
return EI->second;
|
|
} else {
|
|
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
|
|
return nextValueNumber++;
|
|
}
|
|
} else if (SelectInst* U = dyn_cast<SelectInst>(V)) {
|
|
Expression e = create_expression(U);
|
|
|
|
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
|
|
if (EI != expressionNumbering.end()) {
|
|
valueNumbering.insert(std::make_pair(V, EI->second));
|
|
return EI->second;
|
|
} else {
|
|
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
|
|
return nextValueNumber++;
|
|
}
|
|
} else if (CastInst* U = dyn_cast<CastInst>(V)) {
|
|
Expression e = create_expression(U);
|
|
|
|
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
|
|
if (EI != expressionNumbering.end()) {
|
|
valueNumbering.insert(std::make_pair(V, EI->second));
|
|
return EI->second;
|
|
} else {
|
|
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
|
|
return nextValueNumber++;
|
|
}
|
|
} else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(V)) {
|
|
Expression e = create_expression(U);
|
|
|
|
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
|
|
if (EI != expressionNumbering.end()) {
|
|
valueNumbering.insert(std::make_pair(V, EI->second));
|
|
return EI->second;
|
|
} else {
|
|
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
|
|
return nextValueNumber++;
|
|
}
|
|
} else {
|
|
valueNumbering.insert(std::make_pair(V, nextValueNumber));
|
|
return nextValueNumber++;
|
|
}
|
|
}
|
|
|
|
/// 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);
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// GVN Pass
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
namespace {
|
|
struct VISIBILITY_HIDDEN ValueNumberScope {
|
|
ValueNumberScope* parent;
|
|
DenseMap<uint32_t, Value*> table;
|
|
|
|
ValueNumberScope(ValueNumberScope* p) : parent(p) { }
|
|
};
|
|
}
|
|
|
|
namespace {
|
|
|
|
class VISIBILITY_HIDDEN GVN : public FunctionPass {
|
|
bool runOnFunction(Function &F);
|
|
public:
|
|
static char ID; // Pass identification, replacement for typeid
|
|
GVN() : FunctionPass(&ID) { }
|
|
|
|
private:
|
|
ValueTable VN;
|
|
DenseMap<BasicBlock*, ValueNumberScope*> localAvail;
|
|
|
|
typedef DenseMap<Value*, SmallPtrSet<Instruction*, 4> > PhiMapType;
|
|
PhiMapType phiMap;
|
|
|
|
|
|
// 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,
|
|
DenseMap<Value*, LoadInst*> &lastLoad,
|
|
SmallVectorImpl<Instruction*> &toErase);
|
|
bool processInstruction(Instruction* I,
|
|
DenseMap<Value*, LoadInst*>& lastSeenLoad,
|
|
SmallVectorImpl<Instruction*> &toErase);
|
|
bool processNonLocalLoad(LoadInst* L,
|
|
SmallVectorImpl<Instruction*> &toErase);
|
|
bool processBlock(DomTreeNode* DTN);
|
|
Value *GetValueForBlock(BasicBlock *BB, LoadInst* orig,
|
|
DenseMap<BasicBlock*, Value*> &Phis,
|
|
bool top_level = false);
|
|
void dump(DenseMap<uint32_t, Value*>& d);
|
|
bool iterateOnFunction(Function &F);
|
|
Value* CollapsePhi(PHINode* p);
|
|
bool isSafeReplacement(PHINode* p, Instruction* inst);
|
|
bool performPRE(Function& F);
|
|
Value* lookupNumber(BasicBlock* BB, uint32_t num);
|
|
bool mergeBlockIntoPredecessor(BasicBlock* BB);
|
|
void cleanupGlobalSets();
|
|
};
|
|
|
|
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");
|
|
}
|
|
|
|
Value* GVN::CollapsePhi(PHINode* p) {
|
|
DominatorTree &DT = getAnalysis<DominatorTree>();
|
|
Value* constVal = p->hasConstantValue();
|
|
|
|
if (!constVal) return 0;
|
|
|
|
Instruction* inst = dyn_cast<Instruction>(constVal);
|
|
if (!inst)
|
|
return constVal;
|
|
|
|
if (DT.dominates(inst, p))
|
|
if (isSafeReplacement(p, inst))
|
|
return inst;
|
|
return 0;
|
|
}
|
|
|
|
bool GVN::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;
|
|
}
|
|
|
|
/// GetValueForBlock - Get the value to use within the specified basic block.
|
|
/// available values are in Phis.
|
|
Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig,
|
|
DenseMap<BasicBlock*, Value*> &Phis,
|
|
bool top_level) {
|
|
|
|
// If we have already computed this value, return the previously computed val.
|
|
DenseMap<BasicBlock*, Value*>::iterator V = Phis.find(BB);
|
|
if (V != Phis.end() && !top_level) return V->second;
|
|
|
|
// If the block is unreachable, just return undef, since this path
|
|
// can't actually occur at runtime.
|
|
if (!getAnalysis<DominatorTree>().isReachableFromEntry(BB))
|
|
return Phis[BB] = UndefValue::get(orig->getType());
|
|
|
|
BasicBlock* singlePred = BB->getSinglePredecessor();
|
|
if (singlePred) {
|
|
Value *ret = GetValueForBlock(singlePred, orig, Phis);
|
|
Phis[BB] = ret;
|
|
return ret;
|
|
}
|
|
|
|
// Otherwise, the idom is the loop, so we need to insert a PHI node. Do so
|
|
// now, then get values to fill in the incoming values for the PHI.
|
|
PHINode *PN = PHINode::Create(orig->getType(), orig->getName()+".rle",
|
|
BB->begin());
|
|
PN->reserveOperandSpace(std::distance(pred_begin(BB), pred_end(BB)));
|
|
|
|
if (Phis.count(BB) == 0)
|
|
Phis.insert(std::make_pair(BB, PN));
|
|
|
|
// Fill in the incoming values for the block.
|
|
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
|
|
Value* val = GetValueForBlock(*PI, orig, Phis);
|
|
PN->addIncoming(val, *PI);
|
|
}
|
|
|
|
AliasAnalysis& AA = getAnalysis<AliasAnalysis>();
|
|
AA.copyValue(orig, PN);
|
|
|
|
// Attempt to collapse PHI nodes that are trivially redundant
|
|
Value* v = CollapsePhi(PN);
|
|
if (!v) {
|
|
// Cache our phi construction results
|
|
phiMap[orig->getPointerOperand()].insert(PN);
|
|
return PN;
|
|
}
|
|
|
|
MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
|
|
|
|
MD.removeInstruction(PN);
|
|
PN->replaceAllUsesWith(v);
|
|
|
|
for (DenseMap<BasicBlock*, Value*>::iterator I = Phis.begin(),
|
|
E = Phis.end(); I != E; ++I)
|
|
if (I->second == PN)
|
|
I->second = v;
|
|
|
|
PN->eraseFromParent();
|
|
|
|
Phis[BB] = v;
|
|
return v;
|
|
}
|
|
|
|
/// processNonLocalLoad - Attempt to eliminate a load whose dependencies are
|
|
/// non-local by performing PHI construction.
|
|
bool GVN::processNonLocalLoad(LoadInst* L,
|
|
SmallVectorImpl<Instruction*> &toErase) {
|
|
MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
|
|
|
|
// Find the non-local dependencies of the load
|
|
SmallVector<std::pair<BasicBlock*, MemDepResult>, 32> deps;
|
|
MD.getNonLocalDependency(L, deps);
|
|
|
|
// 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;
|
|
|
|
BasicBlock *EntryBlock = &L->getParent()->getParent()->getEntryBlock();
|
|
|
|
DenseMap<BasicBlock*, Value*> repl;
|
|
|
|
// Filter out useless results (non-locals, etc)
|
|
for (SmallVector<std::pair<BasicBlock*, MemDepResult>, 32>::iterator
|
|
I = deps.begin(), E = deps.end(); I != E; ++I) {
|
|
if (I->second.isNone()) {
|
|
repl[I->first] = UndefValue::get(L->getType());
|
|
continue;
|
|
}
|
|
|
|
if (I->second.isNonLocal()) {
|
|
// If this is a non-local dependency in the entry block, then we depend on
|
|
// the value live-in at the start of the function. We could insert a load
|
|
// in the entry block to get this, but for now we'll just bail out.
|
|
// FIXME: Consider emitting a load in the entry block to catch this case!
|
|
if (I->first == EntryBlock)
|
|
return false;
|
|
continue;
|
|
}
|
|
|
|
if (StoreInst* S = dyn_cast<StoreInst>(I->second.getInst())) {
|
|
if (S->getPointerOperand() != L->getPointerOperand())
|
|
return false;
|
|
repl[I->first] = S->getOperand(0);
|
|
} else if (LoadInst* LD = dyn_cast<LoadInst>(I->second.getInst())) {
|
|
if (LD->getPointerOperand() != L->getPointerOperand())
|
|
return false;
|
|
repl[I->first] = LD;
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// Use cached PHI construction information from previous runs
|
|
SmallPtrSet<Instruction*, 4>& p = phiMap[L->getPointerOperand()];
|
|
for (SmallPtrSet<Instruction*, 4>::iterator I = p.begin(), E = p.end();
|
|
I != E; ++I) {
|
|
if ((*I)->getParent() == L->getParent()) {
|
|
MD.removeInstruction(L);
|
|
L->replaceAllUsesWith(*I);
|
|
toErase.push_back(L);
|
|
NumGVNLoad++;
|
|
return true;
|
|
}
|
|
|
|
repl.insert(std::make_pair((*I)->getParent(), *I));
|
|
}
|
|
|
|
// Perform PHI construction
|
|
SmallPtrSet<BasicBlock*, 4> visited;
|
|
Value* v = GetValueForBlock(L->getParent(), L, repl, true);
|
|
|
|
MD.removeInstruction(L);
|
|
L->replaceAllUsesWith(v);
|
|
toErase.push_back(L);
|
|
NumGVNLoad++;
|
|
|
|
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, DenseMap<Value*, LoadInst*> &lastLoad,
|
|
SmallVectorImpl<Instruction*> &toErase) {
|
|
if (L->isVolatile()) {
|
|
lastLoad[L->getPointerOperand()] = L;
|
|
return false;
|
|
}
|
|
|
|
Value* pointer = L->getPointerOperand();
|
|
LoadInst*& last = lastLoad[pointer];
|
|
|
|
// ... to a pointer that has been loaded from before...
|
|
MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
|
|
bool removedNonLocal = false;
|
|
MemDepResult dep = MD.getDependency(L);
|
|
if (dep.isNonLocal() &&
|
|
L->getParent() != &L->getParent()->getParent()->getEntryBlock()) {
|
|
removedNonLocal = processNonLocalLoad(L, toErase);
|
|
|
|
if (!removedNonLocal)
|
|
last = L;
|
|
|
|
return removedNonLocal;
|
|
}
|
|
|
|
|
|
bool deletedLoad = false;
|
|
|
|
// Walk up the dependency chain until we either find
|
|
// a dependency we can use, or we can't walk any further
|
|
while (Instruction *DepInst = dep.getInst()) {
|
|
// ... that depends on a store ...
|
|
if (StoreInst* S = dyn_cast<StoreInst>(DepInst)) {
|
|
if (S->getPointerOperand() == pointer) {
|
|
// Remove it!
|
|
MD.removeInstruction(L);
|
|
|
|
L->replaceAllUsesWith(S->getOperand(0));
|
|
toErase.push_back(L);
|
|
deletedLoad = true;
|
|
NumGVNLoad++;
|
|
}
|
|
|
|
// Whether we removed it or not, we can't
|
|
// go any further
|
|
break;
|
|
} else if (!isa<LoadInst>(DepInst)) {
|
|
// Only want to handle loads below.
|
|
break;
|
|
} else if (!last) {
|
|
// If we don't depend on a store, and we haven't
|
|
// been loaded before, bail.
|
|
break;
|
|
} else if (DepInst == last) {
|
|
// Remove it!
|
|
MD.removeInstruction(L);
|
|
|
|
L->replaceAllUsesWith(last);
|
|
toErase.push_back(L);
|
|
deletedLoad = true;
|
|
NumGVNLoad++;
|
|
break;
|
|
} else {
|
|
dep = MD.getDependencyFrom(L, DepInst, DepInst->getParent());
|
|
}
|
|
}
|
|
|
|
// 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 (dep.isNone()) {
|
|
// If this load depends directly on an allocation, there isn't
|
|
// anything stored there; therefore, we can optimize this load
|
|
// to undef.
|
|
MD.removeInstruction(L);
|
|
L->replaceAllUsesWith(UndefValue::get(L->getType()));
|
|
toErase.push_back(L);
|
|
deletedLoad = true;
|
|
NumGVNLoad++;
|
|
}
|
|
|
|
if (!deletedLoad)
|
|
last = L;
|
|
|
|
return deletedLoad;
|
|
}
|
|
|
|
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;
|
|
else
|
|
locals = locals->parent;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/// processInstruction - When calculating availability, handle an instruction
|
|
/// by inserting it into the appropriate sets
|
|
bool GVN::processInstruction(Instruction *I,
|
|
DenseMap<Value*, LoadInst*> &lastSeenLoad,
|
|
SmallVectorImpl<Instruction*> &toErase) {
|
|
if (LoadInst* L = dyn_cast<LoadInst>(I)) {
|
|
bool changed = processLoad(L, lastSeenLoad, toErase);
|
|
|
|
if (!changed) {
|
|
unsigned num = VN.lookup_or_add(L);
|
|
localAvail[I->getParent()]->table.insert(std::make_pair(num, L));
|
|
}
|
|
|
|
return changed;
|
|
}
|
|
|
|
uint32_t nextNum = VN.getNextUnusedValueNumber();
|
|
unsigned num = VN.lookup_or_add(I);
|
|
|
|
// Allocations are always uniquely numbered, so we can save time and memory
|
|
// by fast failing them.
|
|
if (isa<AllocationInst>(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) {
|
|
for (PhiMapType::iterator PI = phiMap.begin(), PE = phiMap.end();
|
|
PI != PE; ++PI)
|
|
if (PI->second.count(p))
|
|
PI->second.erase(p);
|
|
|
|
p->replaceAllUsesWith(constVal);
|
|
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 value-number based elimination
|
|
} else if (Value* repl = lookupNumber(I->getParent(), num)) {
|
|
// Remove it!
|
|
MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
|
|
MD.removeInstruction(I);
|
|
|
|
VN.erase(I);
|
|
I->replaceAllUsesWith(repl);
|
|
toErase.push_back(I);
|
|
return true;
|
|
} else {
|
|
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
// GVN::runOnFunction - This is the main transformation entry point for a
|
|
// function.
|
|
//
|
|
bool GVN::runOnFunction(Function& F) {
|
|
VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>());
|
|
VN.setMemDep(&getAnalysis<MemoryDependenceAnalysis>());
|
|
VN.setDomTree(&getAnalysis<DominatorTree>());
|
|
|
|
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;
|
|
}
|
|
|
|
while (shouldContinue) {
|
|
shouldContinue = iterateOnFunction(F);
|
|
changed |= shouldContinue;
|
|
}
|
|
|
|
if (EnablePRE) {
|
|
bool PREChanged = true;
|
|
while (PREChanged) {
|
|
PREChanged = performPRE(F);
|
|
changed |= PREChanged;
|
|
}
|
|
}
|
|
|
|
cleanupGlobalSets();
|
|
|
|
return changed;
|
|
}
|
|
|
|
|
|
bool GVN::processBlock(DomTreeNode* DTN) {
|
|
BasicBlock* BB = DTN->getBlock();
|
|
|
|
SmallVector<Instruction*, 8> toErase;
|
|
DenseMap<Value*, LoadInst*> lastSeenLoad;
|
|
bool changed_function = false;
|
|
|
|
if (DTN->getIDom())
|
|
localAvail[BB] =
|
|
new ValueNumberScope(localAvail[DTN->getIDom()->getBlock()]);
|
|
else
|
|
localAvail[BB] = new ValueNumberScope(0);
|
|
|
|
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
|
|
BI != BE;) {
|
|
changed_function |= processInstruction(BI, lastSeenLoad, 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)
|
|
(*I)->eraseFromParent();
|
|
|
|
if (AtStart)
|
|
BI = BB->begin();
|
|
else
|
|
++BI;
|
|
|
|
toErase.clear();
|
|
}
|
|
|
|
return changed_function;
|
|
}
|
|
|
|
/// 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;
|
|
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; ) {
|
|
if (isa<AllocationInst>(BI) || isa<TerminatorInst>(BI) ||
|
|
isa<PHINode>(BI) || BI->mayReadFromMemory() ||
|
|
BI->mayWriteToMemory()) {
|
|
BI++;
|
|
continue;
|
|
}
|
|
|
|
uint32_t valno = VN.lookup(BI);
|
|
|
|
// 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;
|
|
DenseMap<BasicBlock*, Value*> predMap;
|
|
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 == BI) {
|
|
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) {
|
|
BI++;
|
|
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));
|
|
changed = true;
|
|
BI++;
|
|
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 = BI->clone();
|
|
bool success = true;
|
|
for (unsigned i = 0; i < BI->getNumOperands(); ++i) {
|
|
Value* op = BI->getOperand(i);
|
|
if (isa<Argument>(op) || isa<Constant>(op) || isa<GlobalValue>(op))
|
|
PREInstr->setOperand(i, op);
|
|
else {
|
|
Value* V = lookupNumber(PREPred, VN.lookup(op));
|
|
if (!V) {
|
|
success = false;
|
|
break;
|
|
} else
|
|
PREInstr->setOperand(i, V);
|
|
}
|
|
}
|
|
|
|
// 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;
|
|
BI++;
|
|
continue;
|
|
}
|
|
|
|
PREInstr->insertBefore(PREPred->getTerminator());
|
|
PREInstr->setName(BI->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(BI->getType(),
|
|
BI->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;
|
|
|
|
BI->replaceAllUsesWith(Phi);
|
|
VN.erase(BI);
|
|
|
|
Instruction* erase = BI;
|
|
BI++;
|
|
erase->eraseFromParent();
|
|
|
|
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) {
|
|
DominatorTree &DT = getAnalysis<DominatorTree>();
|
|
|
|
cleanupGlobalSets();
|
|
|
|
// Top-down walk of the dominator tree
|
|
bool changed = false;
|
|
for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
|
|
DE = df_end(DT.getRootNode()); DI != DE; ++DI)
|
|
changed |= processBlock(*DI);
|
|
|
|
return changed;
|
|
}
|
|
|
|
void GVN::cleanupGlobalSets() {
|
|
VN.clear();
|
|
phiMap.clear();
|
|
|
|
for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator
|
|
I = localAvail.begin(), E = localAvail.end(); I != E; ++I)
|
|
delete I->second;
|
|
localAvail.clear();
|
|
}
|