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llvm-6502/lib/Transforms/Scalar/SCCVN.cpp
Dan Gohman 321a813c53 Use do+while instead of while for loops which obviously have a 
non-zero trip count. Use SmallVector's pop_back_val().


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92734 91177308-0d34-0410-b5e6-96231b3b80d8
2010-01-05 16:27:25 +00:00

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//===- SCCVN.cpp - Eliminate redundant values -----------------------------===//
//
// 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. This is based on the paper "SCC-based Value Numbering"
// by Cooper, et al.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "sccvn"
#include "llvm/Transforms/Scalar.h"
#include "llvm/BasicBlock.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Operator.h"
#include "llvm/Value.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/PostOrderIterator.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/Support/CFG.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
using namespace llvm;
STATISTIC(NumSCCVNInstr, "Number of instructions deleted by SCCVN");
STATISTIC(NumSCCVNPhi, "Number of phis deleted by SCCVN");
//===----------------------------------------------------------------------===//
// 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 Expression {
enum ExpressionOpcode { ADD, FADD, SUB, FSUB, MUL, FMUL,
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,
INSERTVALUE, EXTRACTVALUE, EMPTY, TOMBSTONE };
ExpressionOpcode opcode;
const Type* type;
SmallVector<uint32_t, 4> varargs;
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 (varargs.size() != other.varargs.size())
return false;
for (size_t i = 0; i < varargs.size(); ++i)
if (varargs[i] != other.varargs[i])
return false;
return true;
}
}
bool operator!=(const Expression &other) const {
return !(*this == other);
}
};
class ValueTable {
private:
DenseMap<Value*, uint32_t> valueNumbering;
DenseMap<Expression, uint32_t> expressionNumbering;
DenseMap<Value*, uint32_t> constantsNumbering;
uint32_t nextValueNumber;
Expression::ExpressionOpcode getOpcode(BinaryOperator* BO);
Expression::ExpressionOpcode getOpcode(CmpInst* C);
Expression::ExpressionOpcode getOpcode(CastInst* C);
Expression create_expression(BinaryOperator* BO);
Expression create_expression(CmpInst* C);
Expression create_expression(ShuffleVectorInst* V);
Expression create_expression(ExtractElementInst* C);
Expression create_expression(InsertElementInst* V);
Expression create_expression(SelectInst* V);
Expression create_expression(CastInst* C);
Expression create_expression(GetElementPtrInst* G);
Expression create_expression(CallInst* C);
Expression create_expression(Constant* C);
Expression create_expression(ExtractValueInst* C);
Expression create_expression(InsertValueInst* C);
public:
ValueTable() : nextValueNumber(1) { }
uint32_t computeNumber(Value *V);
uint32_t lookup(Value *V);
void add(Value *V, uint32_t num);
void clear();
void clearExpressions();
void erase(Value *v);
unsigned size();
void verifyRemoved(const Value *) const;
};
}
namespace llvm {
template <> struct DenseMapInfo<Expression> {
static inline Expression getEmptyKey() {
return Expression(Expression::EMPTY);
}
static inline Expression getTombstoneKey() {
return Expression(Expression::TOMBSTONE);
}
static unsigned getHashValue(const Expression e) {
unsigned hash = e.opcode;
hash = ((unsigned)((uintptr_t)e.type >> 4) ^
(unsigned)((uintptr_t)e.type >> 9));
for (SmallVector<uint32_t, 4>::const_iterator I = e.varargs.begin(),
E = e.varargs.end(); I != E; ++I)
hash = *I + hash * 37;
return hash;
}
static bool isEqual(const Expression &LHS, const Expression &RHS) {
return LHS == RHS;
}
};
template <>
struct isPodLike<Expression> { static const bool value = true; };
}
//===----------------------------------------------------------------------===//
// ValueTable Internal Functions
//===----------------------------------------------------------------------===//
Expression::ExpressionOpcode ValueTable::getOpcode(BinaryOperator* BO) {
switch(BO->getOpcode()) {
default: // THIS SHOULD NEVER HAPPEN
llvm_unreachable("Binary operator with unknown opcode?");
case Instruction::Add: return Expression::ADD;
case Instruction::FAdd: return Expression::FADD;
case Instruction::Sub: return Expression::SUB;
case Instruction::FSub: return Expression::FSUB;
case Instruction::Mul: return Expression::MUL;
case Instruction::FMul: return Expression::FMUL;
case Instruction::UDiv: return Expression::UDIV;
case Instruction::SDiv: return Expression::SDIV;
case Instruction::FDiv: return Expression::FDIV;
case Instruction::URem: return Expression::UREM;
case Instruction::SRem: return Expression::SREM;
case Instruction::FRem: return Expression::FREM;
case Instruction::Shl: return Expression::SHL;
case Instruction::LShr: return Expression::LSHR;
case Instruction::AShr: return Expression::ASHR;
case Instruction::And: return Expression::AND;
case Instruction::Or: return Expression::OR;
case Instruction::Xor: return Expression::XOR;
}
}
Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) {
if (isa<ICmpInst>(C)) {
switch (C->getPredicate()) {
default: // THIS SHOULD NEVER HAPPEN
llvm_unreachable("Comparison with unknown predicate?");
case ICmpInst::ICMP_EQ: return Expression::ICMPEQ;
case ICmpInst::ICMP_NE: return Expression::ICMPNE;
case ICmpInst::ICMP_UGT: return Expression::ICMPUGT;
case ICmpInst::ICMP_UGE: return Expression::ICMPUGE;
case ICmpInst::ICMP_ULT: return Expression::ICMPULT;
case ICmpInst::ICMP_ULE: return Expression::ICMPULE;
case ICmpInst::ICMP_SGT: return Expression::ICMPSGT;
case ICmpInst::ICMP_SGE: return Expression::ICMPSGE;
case ICmpInst::ICMP_SLT: return Expression::ICMPSLT;
case ICmpInst::ICMP_SLE: return Expression::ICMPSLE;
}
} else {
switch (C->getPredicate()) {
default: // THIS SHOULD NEVER HAPPEN
llvm_unreachable("Comparison with unknown predicate?");
case FCmpInst::FCMP_OEQ: return Expression::FCMPOEQ;
case FCmpInst::FCMP_OGT: return Expression::FCMPOGT;
case FCmpInst::FCMP_OGE: return Expression::FCMPOGE;
case FCmpInst::FCMP_OLT: return Expression::FCMPOLT;
case FCmpInst::FCMP_OLE: return Expression::FCMPOLE;
case FCmpInst::FCMP_ONE: return Expression::FCMPONE;
case FCmpInst::FCMP_ORD: return Expression::FCMPORD;
case FCmpInst::FCMP_UNO: return Expression::FCMPUNO;
case FCmpInst::FCMP_UEQ: return Expression::FCMPUEQ;
case FCmpInst::FCMP_UGT: return Expression::FCMPUGT;
case FCmpInst::FCMP_UGE: return Expression::FCMPUGE;
case FCmpInst::FCMP_ULT: return Expression::FCMPULT;
case FCmpInst::FCMP_ULE: return Expression::FCMPULE;
case FCmpInst::FCMP_UNE: return Expression::FCMPUNE;
}
}
}
Expression::ExpressionOpcode ValueTable::getOpcode(CastInst* C) {
switch(C->getOpcode()) {
default: // THIS SHOULD NEVER HAPPEN
llvm_unreachable("Cast operator with unknown opcode?");
case Instruction::Trunc: return Expression::TRUNC;
case Instruction::ZExt: return Expression::ZEXT;
case Instruction::SExt: return Expression::SEXT;
case Instruction::FPToUI: return Expression::FPTOUI;
case Instruction::FPToSI: return Expression::FPTOSI;
case Instruction::UIToFP: return Expression::UITOFP;
case Instruction::SIToFP: return Expression::SITOFP;
case Instruction::FPTrunc: return Expression::FPTRUNC;
case Instruction::FPExt: return Expression::FPEXT;
case Instruction::PtrToInt: return Expression::PTRTOINT;
case Instruction::IntToPtr: return Expression::INTTOPTR;
case Instruction::BitCast: return Expression::BITCAST;
}
}
Expression ValueTable::create_expression(CallInst* C) {
Expression e;
e.type = C->getType();
e.opcode = Expression::CALL;
e.varargs.push_back(lookup(C->getCalledFunction()));
for (CallInst::op_iterator I = C->op_begin()+1, E = C->op_end();
I != E; ++I)
e.varargs.push_back(lookup(*I));
return e;
}
Expression ValueTable::create_expression(BinaryOperator* BO) {
Expression e;
e.varargs.push_back(lookup(BO->getOperand(0)));
e.varargs.push_back(lookup(BO->getOperand(1)));
e.type = BO->getType();
e.opcode = getOpcode(BO);
return e;
}
Expression ValueTable::create_expression(CmpInst* C) {
Expression e;
e.varargs.push_back(lookup(C->getOperand(0)));
e.varargs.push_back(lookup(C->getOperand(1)));
e.type = C->getType();
e.opcode = getOpcode(C);
return e;
}
Expression ValueTable::create_expression(CastInst* C) {
Expression e;
e.varargs.push_back(lookup(C->getOperand(0)));
e.type = C->getType();
e.opcode = getOpcode(C);
return e;
}
Expression ValueTable::create_expression(ShuffleVectorInst* S) {
Expression e;
e.varargs.push_back(lookup(S->getOperand(0)));
e.varargs.push_back(lookup(S->getOperand(1)));
e.varargs.push_back(lookup(S->getOperand(2)));
e.type = S->getType();
e.opcode = Expression::SHUFFLE;
return e;
}
Expression ValueTable::create_expression(ExtractElementInst* E) {
Expression e;
e.varargs.push_back(lookup(E->getOperand(0)));
e.varargs.push_back(lookup(E->getOperand(1)));
e.type = E->getType();
e.opcode = Expression::EXTRACT;
return e;
}
Expression ValueTable::create_expression(InsertElementInst* I) {
Expression e;
e.varargs.push_back(lookup(I->getOperand(0)));
e.varargs.push_back(lookup(I->getOperand(1)));
e.varargs.push_back(lookup(I->getOperand(2)));
e.type = I->getType();
e.opcode = Expression::INSERT;
return e;
}
Expression ValueTable::create_expression(SelectInst* I) {
Expression e;
e.varargs.push_back(lookup(I->getCondition()));
e.varargs.push_back(lookup(I->getTrueValue()));
e.varargs.push_back(lookup(I->getFalseValue()));
e.type = I->getType();
e.opcode = Expression::SELECT;
return e;
}
Expression ValueTable::create_expression(GetElementPtrInst* G) {
Expression e;
e.varargs.push_back(lookup(G->getPointerOperand()));
e.type = G->getType();
e.opcode = Expression::GEP;
for (GetElementPtrInst::op_iterator I = G->idx_begin(), E = G->idx_end();
I != E; ++I)
e.varargs.push_back(lookup(*I));
return e;
}
Expression ValueTable::create_expression(ExtractValueInst* E) {
Expression e;
e.varargs.push_back(lookup(E->getAggregateOperand()));
for (ExtractValueInst::idx_iterator II = E->idx_begin(), IE = E->idx_end();
II != IE; ++II)
e.varargs.push_back(*II);
e.type = E->getType();
e.opcode = Expression::EXTRACTVALUE;
return e;
}
Expression ValueTable::create_expression(InsertValueInst* E) {
Expression e;
e.varargs.push_back(lookup(E->getAggregateOperand()));
e.varargs.push_back(lookup(E->getInsertedValueOperand()));
for (InsertValueInst::idx_iterator II = E->idx_begin(), IE = E->idx_end();
II != IE; ++II)
e.varargs.push_back(*II);
e.type = E->getType();
e.opcode = Expression::INSERTVALUE;
return e;
}
//===----------------------------------------------------------------------===//
// ValueTable External Functions
//===----------------------------------------------------------------------===//
/// add - Insert a value into the table with a specified value number.
void ValueTable::add(Value *V, uint32_t num) {
valueNumbering[V] = num;
}
/// computeNumber - Returns the value number for the specified value, assigning
/// it a new number if it did not have one before.
uint32_t ValueTable::computeNumber(Value *V) {
if (uint32_t v = valueNumbering[V])
return v;
else if (uint32_t v= constantsNumbering[V])
return v;
if (!isa<Instruction>(V)) {
constantsNumbering[V] = nextValueNumber;
return nextValueNumber++;
}
Instruction* I = cast<Instruction>(V);
Expression exp;
switch (I->getOpcode()) {
case Instruction::Add:
case Instruction::FAdd:
case Instruction::Sub:
case Instruction::FSub:
case Instruction::Mul:
case Instruction::FMul:
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::FDiv:
case Instruction::URem:
case Instruction::SRem:
case Instruction::FRem:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::And:
case Instruction::Or :
case Instruction::Xor:
exp = create_expression(cast<BinaryOperator>(I));
break;
case Instruction::ICmp:
case Instruction::FCmp:
exp = create_expression(cast<CmpInst>(I));
break;
case Instruction::Trunc:
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::UIToFP:
case Instruction::SIToFP:
case Instruction::FPTrunc:
case Instruction::FPExt:
case Instruction::PtrToInt:
case Instruction::IntToPtr:
case Instruction::BitCast:
exp = create_expression(cast<CastInst>(I));
break;
case Instruction::Select:
exp = create_expression(cast<SelectInst>(I));
break;
case Instruction::ExtractElement:
exp = create_expression(cast<ExtractElementInst>(I));
break;
case Instruction::InsertElement:
exp = create_expression(cast<InsertElementInst>(I));
break;
case Instruction::ShuffleVector:
exp = create_expression(cast<ShuffleVectorInst>(I));
break;
case Instruction::ExtractValue:
exp = create_expression(cast<ExtractValueInst>(I));
break;
case Instruction::InsertValue:
exp = create_expression(cast<InsertValueInst>(I));
break;
case Instruction::GetElementPtr:
exp = create_expression(cast<GetElementPtrInst>(I));
break;
default:
valueNumbering[V] = nextValueNumber;
return nextValueNumber++;
}
uint32_t& e = expressionNumbering[exp];
if (!e) e = nextValueNumber++;
valueNumbering[V] = e;
return e;
}
/// lookup - Returns the value number of the specified value. Returns 0 if
/// the value has not yet been numbered.
uint32_t ValueTable::lookup(Value *V) {
if (!isa<Instruction>(V)) {
if (!constantsNumbering.count(V))
constantsNumbering[V] = nextValueNumber++;
return constantsNumbering[V];
}
return valueNumbering[V];
}
/// clear - Remove all entries from the ValueTable
void ValueTable::clear() {
valueNumbering.clear();
expressionNumbering.clear();
constantsNumbering.clear();
nextValueNumber = 1;
}
void ValueTable::clearExpressions() {
expressionNumbering.clear();
constantsNumbering.clear();
nextValueNumber = 1;
}
/// erase - Remove a value from the value numbering
void ValueTable::erase(Value *V) {
valueNumbering.erase(V);
}
/// verifyRemoved - Verify that the value is removed from all internal data
/// structures.
void ValueTable::verifyRemoved(const Value *V) const {
for (DenseMap<Value*, uint32_t>::const_iterator
I = valueNumbering.begin(), E = valueNumbering.end(); I != E; ++I) {
assert(I->first != V && "Inst still occurs in value numbering map!");
}
}
//===----------------------------------------------------------------------===//
// SCCVN Pass
//===----------------------------------------------------------------------===//
namespace {
struct ValueNumberScope {
ValueNumberScope* parent;
DenseMap<uint32_t, Value*> table;
SparseBitVector<128> availIn;
SparseBitVector<128> availOut;
ValueNumberScope(ValueNumberScope* p) : parent(p) { }
};
class SCCVN : public FunctionPass {
bool runOnFunction(Function &F);
public:
static char ID; // Pass identification, replacement for typeid
SCCVN() : FunctionPass(&ID) { }
private:
ValueTable VT;
DenseMap<BasicBlock*, ValueNumberScope*> BBMap;
// This transformation requires dominator postdominator info
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DominatorTree>();
AU.addPreserved<DominatorTree>();
AU.setPreservesCFG();
}
};
char SCCVN::ID = 0;
}
// createSCCVNPass - The public interface to this file...
FunctionPass *llvm::createSCCVNPass() { return new SCCVN(); }
static RegisterPass<SCCVN> X("sccvn",
"SCC Value Numbering");
static Value *lookupNumber(ValueNumberScope *Locals, uint32_t num) {
while (Locals) {
DenseMap<uint32_t, Value*>::iterator I = Locals->table.find(num);
if (I != Locals->table.end())
return I->second;
Locals = Locals->parent;
}
return 0;
}
bool SCCVN::runOnFunction(Function& F) {
// Implement the RPO version of the SCCVN algorithm. Conceptually,
// we optimisitically assume that all instructions with the same opcode have
// the same VN. Then we deepen our comparison by one level, to all
// instructions whose operands have the same opcodes get the same VN. We
// iterate this process until the partitioning stops changing, at which
// point we have computed a full numbering.
ReversePostOrderTraversal<Function*> RPOT(&F);
bool done = false;
while (!done) {
done = true;
VT.clearExpressions();
for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(),
E = RPOT.end(); I != E; ++I) {
BasicBlock* BB = *I;
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
BI != BE; ++BI) {
uint32_t origVN = VT.lookup(BI);
uint32_t newVN = VT.computeNumber(BI);
if (origVN != newVN)
done = false;
}
}
}
// Now, do a dominator walk, eliminating simple, dominated redundancies as we
// go. Also, build the ValueNumberScope structure that will be used for
// computing full availability.
DominatorTree& DT = getAnalysis<DominatorTree>();
bool changed = false;
for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
DE = df_end(DT.getRootNode()); DI != DE; ++DI) {
BasicBlock* BB = DI->getBlock();
if (DI->getIDom())
BBMap[BB] = new ValueNumberScope(BBMap[DI->getIDom()->getBlock()]);
else
BBMap[BB] = new ValueNumberScope(0);
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
uint32_t num = VT.lookup(I);
Value* repl = lookupNumber(BBMap[BB], num);
if (repl) {
if (isa<PHINode>(I))
++NumSCCVNPhi;
else
++NumSCCVNInstr;
I->replaceAllUsesWith(repl);
Instruction* OldInst = I;
++I;
BBMap[BB]->table[num] = repl;
OldInst->eraseFromParent();
changed = true;
} else {
BBMap[BB]->table[num] = I;
BBMap[BB]->availOut.set(num);
++I;
}
}
}
// Perform a forward data-flow to compute availability at all points on
// the CFG.
do {
changed = false;
for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(),
E = RPOT.end(); I != E; ++I) {
BasicBlock* BB = *I;
ValueNumberScope *VNS = BBMap[BB];
SparseBitVector<128> preds;
bool first = true;
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
PI != PE; ++PI) {
if (first) {
preds = BBMap[*PI]->availOut;
first = false;
} else {
preds &= BBMap[*PI]->availOut;
}
}
changed |= (VNS->availIn |= preds);
changed |= (VNS->availOut |= preds);
}
} while (changed);
// Use full availability information to perform non-dominated replacements.
SSAUpdater SSU;
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
if (!BBMap.count(FI)) continue;
for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
BI != BE; ) {
uint32_t num = VT.lookup(BI);
if (!BBMap[FI]->availIn.test(num)) {
++BI;
continue;
}
SSU.Initialize(BI);
SmallPtrSet<BasicBlock*, 8> visited;
SmallVector<BasicBlock*, 8> stack;
visited.insert(FI);
for (pred_iterator PI = pred_begin(FI), PE = pred_end(FI);
PI != PE; ++PI)
if (!visited.count(*PI))
stack.push_back(*PI);
while (!stack.empty()) {
BasicBlock* CurrBB = stack.pop_back_val();
visited.insert(CurrBB);
ValueNumberScope* S = BBMap[CurrBB];
if (S->table.count(num)) {
SSU.AddAvailableValue(CurrBB, S->table[num]);
} else {
for (pred_iterator PI = pred_begin(CurrBB), PE = pred_end(CurrBB);
PI != PE; ++PI)
if (!visited.count(*PI))
stack.push_back(*PI);
}
}
Value* repl = SSU.GetValueInMiddleOfBlock(FI);
BI->replaceAllUsesWith(repl);
Instruction* CurInst = BI;
++BI;
BBMap[FI]->table[num] = repl;
if (isa<PHINode>(CurInst))
++NumSCCVNPhi;
else
++NumSCCVNInstr;
CurInst->eraseFromParent();
}
}
VT.clear();
for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator
I = BBMap.begin(), E = BBMap.end(); I != E; ++I)
delete I->second;
BBMap.clear();
return changed;
}
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