mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-12-13 20:32:21 +00:00
Add a GVN pass, using the value numbering code I developed for GVNPRE and the
load elimination code from RedundantLoadElimination. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40469 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
parent
bb862c042f
commit
1ad2cb7555
@ -114,6 +114,7 @@ namespace {
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(void) llvm::createInstCountPass();
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(void) llvm::createPredicateSimplifierPass();
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(void) llvm::createCodeGenPreparePass();
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(void) llvm::createGVNPass();
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(void)new llvm::IntervalPartition();
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(void)new llvm::FindUsedTypes();
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@ -337,6 +337,13 @@ FunctionPass *createFastDeadStoreEliminationPass();
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//
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FunctionPass *createRedundantLoadEliminationPass();
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//===----------------------------------------------------------------------===//
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//
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// GVN - This pass performs global value numbering and redundant load
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// elimination cotemporaneously.
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//
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FunctionPass *createGVNPass();
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//===----------------------------------------------------------------------===//
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//
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// CodeGenPrepare - This pass prepares a function for instruction selection.
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816
lib/Transforms/Scalar/GVN.cpp
Normal file
816
lib/Transforms/Scalar/GVN.cpp
Normal file
@ -0,0 +1,816 @@
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//===- 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 was developed by the Owen Anderson and is distributed under
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// the University of Illinois Open Source 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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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "gvn"
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#include "llvm/Value.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Instructions.h"
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#include "llvm/Function.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/ADT/BitVector.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/MemoryDependenceAnalysis.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Compiler.h"
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using namespace llvm;
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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, EMPTY,
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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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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 (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 (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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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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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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};
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}
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namespace llvm {
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template <> struct DenseMapKeyInfo<Expression> {
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static inline Expression getEmptyKey() { return Expression(Expression::EMPTY); }
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static inline Expression getTombstoneKey() { return Expression(Expression::TOMBSTONE); }
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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(), E = e.varargs.end();
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I != E; ++I)
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hash = *I + hash * 37;
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return hash;
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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
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ValueTable::getOpcode(BinaryOperator* BO) {
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switch(BO->getOpcode()) {
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case Instruction::Add:
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return Expression::ADD;
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case Instruction::Sub:
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return Expression::SUB;
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case Instruction::Mul:
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return Expression::MUL;
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case Instruction::UDiv:
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return Expression::UDIV;
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case Instruction::SDiv:
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return Expression::SDIV;
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case Instruction::FDiv:
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return Expression::FDIV;
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case Instruction::URem:
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return Expression::UREM;
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case Instruction::SRem:
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return Expression::SREM;
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case Instruction::FRem:
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return Expression::FREM;
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case Instruction::Shl:
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return Expression::SHL;
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case Instruction::LShr:
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return Expression::LSHR;
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case Instruction::AShr:
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return Expression::ASHR;
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case Instruction::And:
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return Expression::AND;
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case Instruction::Or:
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return Expression::OR;
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case Instruction::Xor:
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return Expression::XOR;
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// THIS SHOULD NEVER HAPPEN
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default:
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assert(0 && "Binary operator with unknown opcode?");
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return Expression::ADD;
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}
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}
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Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) {
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if (C->getOpcode() == Instruction::ICmp) {
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switch (C->getPredicate()) {
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case ICmpInst::ICMP_EQ:
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return Expression::ICMPEQ;
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case ICmpInst::ICMP_NE:
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return Expression::ICMPNE;
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case ICmpInst::ICMP_UGT:
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return Expression::ICMPUGT;
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case ICmpInst::ICMP_UGE:
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return Expression::ICMPUGE;
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case ICmpInst::ICMP_ULT:
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return Expression::ICMPULT;
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case ICmpInst::ICMP_ULE:
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return Expression::ICMPULE;
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case ICmpInst::ICMP_SGT:
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return Expression::ICMPSGT;
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case ICmpInst::ICMP_SGE:
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return Expression::ICMPSGE;
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case ICmpInst::ICMP_SLT:
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return Expression::ICMPSLT;
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case ICmpInst::ICMP_SLE:
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return Expression::ICMPSLE;
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// THIS SHOULD NEVER HAPPEN
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default:
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assert(0 && "Comparison with unknown predicate?");
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return Expression::ICMPEQ;
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}
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} else {
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switch (C->getPredicate()) {
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case FCmpInst::FCMP_OEQ:
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return Expression::FCMPOEQ;
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case FCmpInst::FCMP_OGT:
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return Expression::FCMPOGT;
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case FCmpInst::FCMP_OGE:
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return Expression::FCMPOGE;
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case FCmpInst::FCMP_OLT:
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return Expression::FCMPOLT;
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case FCmpInst::FCMP_OLE:
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return Expression::FCMPOLE;
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case FCmpInst::FCMP_ONE:
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return Expression::FCMPONE;
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case FCmpInst::FCMP_ORD:
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return Expression::FCMPORD;
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case FCmpInst::FCMP_UNO:
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return Expression::FCMPUNO;
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case FCmpInst::FCMP_UEQ:
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return Expression::FCMPUEQ;
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case FCmpInst::FCMP_UGT:
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return Expression::FCMPUGT;
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case FCmpInst::FCMP_UGE:
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return Expression::FCMPUGE;
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case FCmpInst::FCMP_ULT:
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return Expression::FCMPULT;
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case FCmpInst::FCMP_ULE:
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return Expression::FCMPULE;
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case FCmpInst::FCMP_UNE:
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return Expression::FCMPUNE;
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// THIS SHOULD NEVER HAPPEN
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default:
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assert(0 && "Comparison with unknown predicate?");
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return Expression::FCMPOEQ;
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}
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}
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}
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Expression::ExpressionOpcode
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ValueTable::getOpcode(CastInst* C) {
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switch(C->getOpcode()) {
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case Instruction::Trunc:
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return Expression::TRUNC;
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case Instruction::ZExt:
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return Expression::ZEXT;
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case Instruction::SExt:
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return Expression::SEXT;
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case Instruction::FPToUI:
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return Expression::FPTOUI;
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case Instruction::FPToSI:
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return Expression::FPTOSI;
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case Instruction::UIToFP:
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return Expression::UITOFP;
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case Instruction::SIToFP:
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return Expression::SITOFP;
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case Instruction::FPTrunc:
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return Expression::FPTRUNC;
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case Instruction::FPExt:
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return Expression::FPEXT;
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case Instruction::PtrToInt:
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return Expression::PTRTOINT;
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case Instruction::IntToPtr:
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return Expression::INTTOPTR;
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case Instruction::BitCast:
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return Expression::BITCAST;
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// THIS SHOULD NEVER HAPPEN
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default:
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assert(0 && "Cast operator with unknown opcode?");
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return Expression::BITCAST;
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}
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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.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.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.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.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.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.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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|
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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.type = I->getType();
|
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e.opcode = Expression::SELECT;
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|
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return e;
|
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}
|
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|
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Expression ValueTable::create_expression(GetElementPtrInst* G) {
|
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Expression e;
|
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|
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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.type = G->getType();
|
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e.opcode = Expression::GEP;
|
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|
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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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/// 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);
|
||||
if (VI != valueNumbering.end())
|
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return VI->second;
|
||||
|
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|
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if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) {
|
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Expression e = create_expression(BO);
|
||||
|
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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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|
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return nextValueNumber++;
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}
|
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} else if (CmpInst* C = dyn_cast<CmpInst>(V)) {
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Expression e = create_expression(C);
|
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|
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DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
|
||||
if (EI != expressionNumbering.end()) {
|
||||
valueNumbering.insert(std::make_pair(V, EI->second));
|
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return EI->second;
|
||||
} else {
|
||||
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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}
|
||||
} 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);
|
||||
if (VI != valueNumbering.end())
|
||||
return VI->second;
|
||||
else
|
||||
assert(0 && "Value not numbered?");
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/// clear - Remove all entries from the ValueTable
|
||||
void ValueTable::clear() {
|
||||
valueNumbering.clear();
|
||||
expressionNumbering.clear();
|
||||
nextValueNumber = 1;
|
||||
}
|
||||
|
||||
//===----------------------------------------------------------------------===//
|
||||
// ValueNumberedSet Class
|
||||
//===----------------------------------------------------------------------===//
|
||||
namespace {
|
||||
class ValueNumberedSet {
|
||||
private:
|
||||
SmallPtrSet<Value*, 8> contents;
|
||||
BitVector numbers;
|
||||
public:
|
||||
ValueNumberedSet() { numbers.resize(1); }
|
||||
ValueNumberedSet(const ValueNumberedSet& other) {
|
||||
numbers = other.numbers;
|
||||
contents = other.contents;
|
||||
}
|
||||
|
||||
typedef SmallPtrSet<Value*, 8>::iterator iterator;
|
||||
|
||||
iterator begin() { return contents.begin(); }
|
||||
iterator end() { return contents.end(); }
|
||||
|
||||
bool insert(Value* v) { return contents.insert(v); }
|
||||
void insert(iterator I, iterator E) { contents.insert(I, E); }
|
||||
void erase(Value* v) { contents.erase(v); }
|
||||
unsigned count(Value* v) { return contents.count(v); }
|
||||
size_t size() { return contents.size(); }
|
||||
|
||||
void set(unsigned i) {
|
||||
if (i >= numbers.size())
|
||||
numbers.resize(i+1);
|
||||
|
||||
numbers.set(i);
|
||||
}
|
||||
|
||||
void operator=(const ValueNumberedSet& other) {
|
||||
contents = other.contents;
|
||||
numbers = other.numbers;
|
||||
}
|
||||
|
||||
void reset(unsigned i) {
|
||||
if (i < numbers.size())
|
||||
numbers.reset(i);
|
||||
}
|
||||
|
||||
bool test(unsigned i) {
|
||||
if (i >= numbers.size())
|
||||
return false;
|
||||
|
||||
return numbers.test(i);
|
||||
}
|
||||
|
||||
void clear() {
|
||||
contents.clear();
|
||||
numbers.clear();
|
||||
}
|
||||
};
|
||||
}
|
||||
|
||||
//===----------------------------------------------------------------------===//
|
||||
// GVN Pass
|
||||
//===----------------------------------------------------------------------===//
|
||||
|
||||
namespace {
|
||||
|
||||
class VISIBILITY_HIDDEN GVN : public FunctionPass {
|
||||
bool runOnFunction(Function &F);
|
||||
public:
|
||||
static char ID; // Pass identification, replacement for typeid
|
||||
GVN() : FunctionPass((intptr_t)&ID) { }
|
||||
|
||||
private:
|
||||
ValueTable VN;
|
||||
|
||||
DenseMap<BasicBlock*, ValueNumberedSet> availableOut;
|
||||
|
||||
// This transformation requires dominator postdominator info
|
||||
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
|
||||
AU.setPreservesCFG();
|
||||
AU.addRequired<DominatorTree>();
|
||||
AU.addRequired<MemoryDependenceAnalysis>();
|
||||
AU.addPreserved<MemoryDependenceAnalysis>();
|
||||
}
|
||||
|
||||
// Helper fuctions
|
||||
// FIXME: eliminate or document these better
|
||||
Value* find_leader(ValueNumberedSet& vals, uint32_t v) ;
|
||||
void val_insert(ValueNumberedSet& s, Value* v);
|
||||
bool processLoad(LoadInst* L,
|
||||
DenseMap<Value*, LoadInst*>& lastLoad,
|
||||
SmallVector<Instruction*, 4>& toErase);
|
||||
bool processInstruction(Instruction* I,
|
||||
ValueNumberedSet& currAvail,
|
||||
DenseMap<Value*, LoadInst*>& lastSeenLoad,
|
||||
SmallVector<Instruction*, 4>& toErase);
|
||||
};
|
||||
|
||||
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");
|
||||
|
||||
STATISTIC(NumGVNInstr, "Number of instructions deleted");
|
||||
STATISTIC(NumGVNLoad, "Number of loads deleted");
|
||||
|
||||
/// find_leader - Given a set and a value number, return the first
|
||||
/// element of the set with that value number, or 0 if no such element
|
||||
/// is present
|
||||
Value* GVN::find_leader(ValueNumberedSet& vals, uint32_t v) {
|
||||
if (!vals.test(v))
|
||||
return 0;
|
||||
|
||||
for (ValueNumberedSet::iterator I = vals.begin(), E = vals.end();
|
||||
I != E; ++I)
|
||||
if (v == VN.lookup(*I))
|
||||
return *I;
|
||||
|
||||
assert(0 && "No leader found, but present bit is set?");
|
||||
return 0;
|
||||
}
|
||||
|
||||
/// val_insert - Insert a value into a set only if there is not a value
|
||||
/// with the same value number already in the set
|
||||
void GVN::val_insert(ValueNumberedSet& s, Value* v) {
|
||||
uint32_t num = VN.lookup(v);
|
||||
if (!s.test(num))
|
||||
s.insert(v);
|
||||
}
|
||||
|
||||
bool GVN::processLoad(LoadInst* L,
|
||||
DenseMap<Value*, LoadInst*>& lastLoad,
|
||||
SmallVector<Instruction*, 4>& 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>();
|
||||
Instruction* dep = MD.getDependency(L);
|
||||
bool deletedLoad = false;
|
||||
|
||||
while (dep != MemoryDependenceAnalysis::None &&
|
||||
dep != MemoryDependenceAnalysis::NonLocal &&
|
||||
(isa<LoadInst>(dep) || isa<StoreInst>(dep))) {
|
||||
// ... that depends on a store ...
|
||||
if (StoreInst* S = dyn_cast<StoreInst>(dep)) {
|
||||
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 (!last) {
|
||||
// If we don't depend on a store, and we haven't
|
||||
// been loaded before, bail.
|
||||
break;
|
||||
} else if (dep == last) {
|
||||
// Remove it!
|
||||
MD.removeInstruction(L);
|
||||
|
||||
L->replaceAllUsesWith(last);
|
||||
toErase.push_back(L);
|
||||
deletedLoad = true;
|
||||
NumGVNLoad++;
|
||||
|
||||
break;
|
||||
} else {
|
||||
dep = MD.getDependency(L, dep);
|
||||
}
|
||||
}
|
||||
|
||||
if (!deletedLoad)
|
||||
last = L;
|
||||
|
||||
return deletedLoad;
|
||||
}
|
||||
|
||||
/// buildsets_availout - When calculating availability, handle an instruction
|
||||
/// by inserting it into the appropriate sets
|
||||
bool GVN::processInstruction(Instruction* I,
|
||||
ValueNumberedSet& currAvail,
|
||||
DenseMap<Value*, LoadInst*>& lastSeenLoad,
|
||||
SmallVector<Instruction*, 4>& toErase) {
|
||||
if (LoadInst* L = dyn_cast<LoadInst>(I)) {
|
||||
return processLoad(L, lastSeenLoad, toErase);
|
||||
}
|
||||
|
||||
unsigned num = VN.lookup_or_add(I);
|
||||
|
||||
if (currAvail.test(num)) {
|
||||
Value* repl = find_leader(currAvail, num);
|
||||
|
||||
I->replaceAllUsesWith(repl);
|
||||
toErase.push_back(I);
|
||||
return true;
|
||||
} else if (!I->isTerminator()) {
|
||||
currAvail.set(num);
|
||||
currAvail.insert(I);
|
||||
}
|
||||
|
||||
return false;
|
||||
}
|
||||
|
||||
// GVN::runOnFunction - This is the main transformation entry point for a
|
||||
// function.
|
||||
//
|
||||
bool GVN::runOnFunction(Function &F) {
|
||||
// Clean out global sets from any previous functions
|
||||
VN.clear();
|
||||
availableOut.clear();
|
||||
|
||||
bool changed_function = false;
|
||||
|
||||
DominatorTree &DT = getAnalysis<DominatorTree>();
|
||||
|
||||
SmallVector<Instruction*, 4> toErase;
|
||||
|
||||
// Top-down walk of the dominator tree
|
||||
for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
|
||||
E = df_end(DT.getRootNode()); DI != E; ++DI) {
|
||||
|
||||
// Get the set to update for this block
|
||||
ValueNumberedSet& currAvail = availableOut[DI->getBlock()];
|
||||
DenseMap<Value*, LoadInst*> lastSeenLoad;
|
||||
|
||||
BasicBlock* BB = DI->getBlock();
|
||||
|
||||
// A block inherits AVAIL_OUT from its dominator
|
||||
if (DI->getIDom() != 0)
|
||||
currAvail = availableOut[DI->getIDom()->getBlock()];
|
||||
|
||||
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
|
||||
BI != BE; ++BI) {
|
||||
processInstruction(BI, currAvail, lastSeenLoad, toErase);
|
||||
}
|
||||
}
|
||||
|
||||
NumGVNInstr = toErase.size();
|
||||
|
||||
for (SmallVector<Instruction*, 4>::iterator I = toErase.begin(),
|
||||
E = toErase.end(); I != E; ++I)
|
||||
(*I)->eraseFromParent();
|
||||
|
||||
return changed_function;
|
||||
}
|
||||
10
test/Transforms/GVN/basic.ll
Normal file
10
test/Transforms/GVN/basic.ll
Normal file
@ -0,0 +1,10 @@
|
||||
; RUN: llvm-as < %s | opt -gvn | llvm-dis | not grep {%z2 =}
|
||||
|
||||
define i32 @main() {
|
||||
block1:
|
||||
%z1 = bitcast i32 0 to i32
|
||||
br label %block2
|
||||
block2:
|
||||
%z2 = bitcast i32 0 to i32
|
||||
ret i32 %z2
|
||||
}
|
||||
3
test/Transforms/GVN/dg.exp
Normal file
3
test/Transforms/GVN/dg.exp
Normal file
@ -0,0 +1,3 @@
|
||||
load_lib llvm.exp
|
||||
|
||||
RunLLVMTests [lsort [glob -nocomplain $srcdir/$subdir/*.{ll,llx,c,cpp,tr}]]
|
||||
13
test/Transforms/GVN/mixed.ll
Normal file
13
test/Transforms/GVN/mixed.ll
Normal file
@ -0,0 +1,13 @@
|
||||
; RUN: llvm-as < %s | opt -gvn | llvm-dis | not grep DEADLOAD
|
||||
; RUN: llvm-as < %s | opt -gvn | llvm-dis | not grep DEADGEP
|
||||
|
||||
define i32 @main(i32** %p) {
|
||||
block1:
|
||||
%z1 = load i32** %p
|
||||
%z2 = getelementptr i32* %z1, i32 0
|
||||
%z3 = load i32* %z2
|
||||
%DEADLOAD = load i32** %p
|
||||
%DEADGEP = getelementptr i32* %DEADLOAD, i32 0
|
||||
%DEADLOAD2 = load i32* %DEADGEP
|
||||
ret i32 %DEADLOAD2
|
||||
}
|
||||
Loading…
Reference in New Issue
Block a user