path: root/lib/Transforms/Scalar/GVN.cpp

//===- GVN.cpp - Eliminate redundant values and loads ------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass performs global value numbering to eliminate fully redundant
// instructions.  It also performs simple dead load elimination.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "gvn"
#include "llvm/Transforms/Scalar.h"
#include "llvm/BasicBlock.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/Value.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/SparseBitVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
using namespace llvm;

STATISTIC(NumGVNInstr, "Number of instructions deleted");
STATISTIC(NumGVNLoad, "Number of loads deleted");

//===----------------------------------------------------------------------===//
//                         ValueTable Class
//===----------------------------------------------------------------------===//

/// This class holds the mapping between values and value numbers.  It is used
/// as an efficient mechanism to determine the expression-wise equivalence of
/// two values.
namespace {
  struct VISIBILITY_HIDDEN Expression {
    enum ExpressionOpcode { ADD, SUB, MUL, UDIV, SDIV, FDIV, UREM, SREM, 
                            FREM, SHL, LSHR, ASHR, AND, OR, XOR, ICMPEQ, 
                            ICMPNE, ICMPUGT, ICMPUGE, ICMPULT, ICMPULE, 
                            ICMPSGT, ICMPSGE, ICMPSLT, ICMPSLE, FCMPOEQ, 
                            FCMPOGT, FCMPOGE, FCMPOLT, FCMPOLE, FCMPONE, 
                            FCMPORD, FCMPUNO, FCMPUEQ, FCMPUGT, FCMPUGE, 
                            FCMPULT, FCMPULE, FCMPUNE, EXTRACT, INSERT,
                            SHUFFLE, SELECT, TRUNC, ZEXT, SEXT, FPTOUI,
                            FPTOSI, UITOFP, SITOFP, FPTRUNC, FPEXT, 
                            PTRTOINT, INTTOPTR, BITCAST, GEP, CALL, CONSTANT,
                            EMPTY, TOMBSTONE };

    ExpressionOpcode opcode;
    const Type* type;
    uint32_t firstVN;
    uint32_t secondVN;
    uint32_t thirdVN;
    SmallVector<uint32_t, 4> varargs;
    Value* function;
  
    Expression() { }
    Expression(ExpressionOpcode o) : opcode(o) { }
  
    bool operator==(const Expression &other) const {
      if (opcode != other.opcode)
        return false;
      else if (opcode == EMPTY || opcode == TOMBSTONE)
        return true;
      else if (type != other.type)
        return false;
      else if (function != other.function)
        return false;
      else if (firstVN