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llvm-project/llvm/lib/Transforms/Scalar/GVNPRE.cpp

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//===- GVNPRE.cpp - Eliminate redundant values and expressions ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the Owen Anderson and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass performs a hybrid of global value numbering and partial redundancy
// elimination, known as GVN-PRE. It performs partial redundancy elimination on
// values, rather than lexical expressions, allowing a more comprehensive view
// the optimization. It replaces redundant values with uses of earlier
// occurences of the same value. While this is beneficial in that it eliminates
// unneeded computation, it also increases register pressure by creating large
// live ranges, and should be used with caution on platforms that are very
// sensitive to register pressure.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "gvnpre"
#include "llvm/Value.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Instructions.h"
#include "llvm/Function.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include <algorithm>
#include <deque>
#include <map>
#include <vector>
#include <set>
using namespace llvm;
//===----------------------------------------------------------------------===//
// 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 {
class VISIBILITY_HIDDEN ValueTable {
public:
struct 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 };
ExpressionOpcode opcode;
uint32_t leftVN;
uint32_t rightVN;
bool operator< (const Expression& other) const {
if (opcode < other.opcode)
return true;
else if (opcode > other.opcode)
return false;
else if (leftVN < other.leftVN)
return true;
else if (leftVN > other.leftVN)
return false;
else if (rightVN < other.rightVN)
return true;
else if (rightVN > other.rightVN)
return false;
else
return false;
}
};
private:
DenseMap<Value*, uint32_t> valueNumbering;
std::map<Expression, uint32_t> expressionNumbering;
std::set<Expression> maximalExpressions;
std::set<Value*> maximalValues;
uint32_t nextValueNumber;
Expression::ExpressionOpcode getOpcode(BinaryOperator* BO);
Expression::ExpressionOpcode getOpcode(CmpInst* C);
Expression create_expression(BinaryOperator* BO);
Expression create_expression(CmpInst* C);
public:
ValueTable() { nextValueNumber = 1; }
uint32_t lookup_or_add(Value* V);
uint32_t lookup(Value* V);
void add(Value* V, uint32_t num);
void clear();
std::set<Expression>& getMaximalExpressions() {
return maximalExpressions;
}
std::set<Value*>& getMaximalValues() { return maximalValues; }
void erase(Value* v);
};
}
//===----------------------------------------------------------------------===//
// ValueTable Internal Functions
//===----------------------------------------------------------------------===//
ValueTable::Expression::ExpressionOpcode
ValueTable::getOpcode(BinaryOperator* BO) {
switch(BO->getOpcode()) {
case Instruction::Add:
return Expression::ADD;
case Instruction::Sub:
return Expression::SUB;
case Instruction::Mul:
return Expression::MUL;
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;
// THIS SHOULD NEVER HAPPEN
default:
assert(0 && "Binary operator with unknown opcode?");
return Expression::ADD;
}
}
ValueTable::Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) {
if (C->getOpcode() == Instruction::ICmp) {
switch (C->getPredicate()) {
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;
// THIS SHOULD NEVER HAPPEN
default:
assert(0 && "Comparison with unknown predicate?");
return Expression::ICMPEQ;
}
} else {
switch (C->getPredicate()) {
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;
// THIS SHOULD NEVER HAPPEN
default:
assert(0 && "Comparison with unknown predicate?");
return Expression::FCMPOEQ;
}
}
}
ValueTable::Expression ValueTable::create_expression(BinaryOperator* BO) {
Expression e;
e.leftVN = lookup_or_add(BO->getOperand(0));
e.rightVN = lookup_or_add(BO->getOperand(1));
e.opcode = getOpcode(BO);
maximalExpressions.insert(e);
return e;
}
ValueTable::Expression ValueTable::create_expression(CmpInst* C) {
Expression e;
e.leftVN = lookup_or_add(C->getOperand(0));
e.rightVN = lookup_or_add(C->getOperand(1));
e.opcode = getOpcode(C);
maximalExpressions.insert(e);
return e;
}
//===----------------------------------------------------------------------===//
// ValueTable External Functions
//===----------------------------------------------------------------------===//
/// lookup_or_add - Returns the value number for the specified value, assigning
/// it a new number if it did not have one before.
uint32_t ValueTable::lookup_or_add(Value* V) {
maximalValues.insert(V);
DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
if (VI != valueNumbering.end())
return VI->second;
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) {
Expression e = create_expression(BO);
std::map<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);
std::map<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) {
DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
if (VI != valueNumbering.end())
return VI->second;
else
assert(0 && "Value not numbered?");
return 0;
}
/// add - Add the specified value with the given value number, removing
/// its old number, if any
void ValueTable::add(Value* V, uint32_t num) {
DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
if (VI != valueNumbering.end())
valueNumbering.erase(VI);
valueNumbering.insert(std::make_pair(V, num));
}
/// clear - Remove all entries from the ValueTable and the maximal sets
void ValueTable::clear() {
valueNumbering.clear();
expressionNumbering.clear();
maximalExpressions.clear();
maximalValues.clear();
nextValueNumber = 1;
}
/// erase - Remove a value from the value numbering and maximal sets
void ValueTable::erase(Value* V) {
maximalValues.erase(V);
valueNumbering.erase(V);
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V))
maximalExpressions.erase(create_expression(BO));
else if (CmpInst* C = dyn_cast<CmpInst>(V))
maximalExpressions.erase(create_expression(C));
}
//===----------------------------------------------------------------------===//
// GVNPRE Pass
//===----------------------------------------------------------------------===//
namespace {
class VISIBILITY_HIDDEN GVNPRE : public FunctionPass {
bool runOnFunction(Function &F);
public:
static char ID; // Pass identification, replacement for typeid
GVNPRE() : FunctionPass((intptr_t)&ID) { }
private:
ValueTable VN;
std::vector<Instruction*> createdExpressions;
std::map<BasicBlock*, std::set<Value*> > availableOut;
std::map<BasicBlock*, std::set<Value*> > anticipatedIn;
// This transformation requires dominator postdominator info
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<DominatorTree>();
AU.addRequired<PostDominatorTree>();
}
// Helper fuctions
// FIXME: eliminate or document these better
void dump(const std::set<Value*>& s) const;
void clean(std::set<Value*>& set);
Value* find_leader(std::set<Value*>& vals,
uint32_t v);
Value* phi_translate(Value* V, BasicBlock* pred, BasicBlock* succ);
void phi_translate_set(std::set<Value*>& anticIn, BasicBlock* pred,
BasicBlock* succ, std::set<Value*>& out);
void topo_sort(std::set<Value*>& set,
std::vector<Value*>& vec);
void cleanup();
bool elimination();
void val_insert(std::set<Value*>& s, Value* v);
void val_replace(std::set<Value*>& s, Value* v);
bool dependsOnInvoke(Value* V);
void buildsets_availout(BasicBlock::iterator I,
std::set<Value*>& currAvail,
std::set<PHINode*>& currPhis,
std::set<Value*>& currExps,
std::set<Value*>& currTemps);
void buildsets_anticout(BasicBlock* BB,
std::set<Value*>& anticOut,
std::set<BasicBlock*>& visited);
bool buildsets_anticin(BasicBlock* BB,
std::set<Value*>& anticOut,
std::set<Value*>& currExps,
std::set<Value*>& currTemps,
std::set<BasicBlock*>& visited);
unsigned buildsets(Function& F);
void insertion_pre(Value* e, BasicBlock* BB,
std::map<BasicBlock*, Value*>& avail,
std::set<Value*>& new_set);
unsigned insertion_mergepoint(std::vector<Value*>& workList,
df_iterator<DomTreeNode*> D,
std::set<Value*>& new_set);
bool insertion(Function& F);
};
char GVNPRE::ID = 0;
}
// createGVNPREPass - The public interface to this file...
FunctionPass *llvm::createGVNPREPass() { return new GVNPRE(); }
RegisterPass<GVNPRE> X("gvnpre",
"Global Value Numbering/Partial Redundancy Elimination");
STATISTIC(NumInsertedVals, "Number of values inserted");
STATISTIC(NumInsertedPhis, "Number of PHI nodes inserted");
STATISTIC(NumEliminated, "Number of redundant instructions eliminated");
/// 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* GVNPRE::find_leader(std::set<Value*>& vals, uint32_t v) {
for (std::set<Value*>::iterator I = vals.begin(), E = vals.end();
I != E; ++I)
if (v == VN.lookup(*I))
return *I;
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 GVNPRE::val_insert(std::set<Value*>& s, Value* v) {
uint32_t num = VN.lookup(v);
Value* leader = find_leader(s, num);
if (leader == 0)
s.insert(v);
}
/// val_replace - Insert a value into a set, replacing any values already in
/// the set that have the same value number
void GVNPRE::val_replace(std::set<Value*>& s, Value* v) {
uint32_t num = VN.lookup(v);
Value* leader = find_leader(s, num);
while (leader != 0) {
s.erase(leader);
leader = find_leader(s, num);
}
s.insert(v);
}
/// phi_translate - Given a value, its parent block, and a predecessor of its
/// parent, translate the value into legal for the predecessor block. This
/// means translating its operands (and recursively, their operands) through
/// any phi nodes in the parent into values available in the predecessor
Value* GVNPRE::phi_translate(Value* V, BasicBlock* pred, BasicBlock* succ) {
if (V == 0)
return 0;
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) {
Value* newOp1 = 0;
if (isa<Instruction>(BO->getOperand(0)))
newOp1 = phi_translate(find_leader(anticipatedIn[succ],
VN.lookup(BO->getOperand(0))),
pred, succ);
else
newOp1 = BO->getOperand(0);
if (newOp1 == 0)
return 0;
Value* newOp2 = 0;
if (isa<Instruction>(BO->getOperand(1)))
newOp2 = phi_translate(find_leader(anticipatedIn[succ],
VN.lookup(BO->getOperand(1))),
pred, succ);
else
newOp2 = BO->getOperand(1);
if (newOp2 == 0)
return 0;
if (newOp1 != BO->getOperand(0) || newOp2 != BO->getOperand(1)) {
Instruction* newVal = BinaryOperator::create(BO->getOpcode(),
newOp1, newOp2,
BO->getName()+".expr");
uint32_t v = VN.lookup_or_add(newVal);
Value* leader = find_leader(availableOut[pred], v);
if (leader == 0) {
createdExpressions.push_back(newVal);
return newVal;
} else {
VN.erase(newVal);
delete newVal;
return leader;
}
}
} else if (PHINode* P = dyn_cast<PHINode>(V)) {
if (P->getParent() == succ)
return P->getIncomingValueForBlock(pred);
} else if (CmpInst* C = dyn_cast<CmpInst>(V)) {
Value* newOp1 = 0;
if (isa<Instruction>(C->getOperand(0)))
newOp1 = phi_translate(find_leader(anticipatedIn[succ],
VN.lookup(C->getOperand(0))),
pred, succ);
else
newOp1 = C->getOperand(0);
if (newOp1 == 0)
return 0;
Value* newOp2 = 0;
if (isa<Instruction>(C->getOperand(1)))
newOp2 = phi_translate(find_leader(anticipatedIn[succ],
VN.lookup(C->getOperand(1))),
pred, succ);
else
newOp2 = C->getOperand(1);
if (newOp2 == 0)
return 0;
if (newOp1 != C->getOperand(0) || newOp2 != C->getOperand(1)) {
Instruction* newVal = CmpInst::create(C->getOpcode(),
C->getPredicate(),
newOp1, newOp2,
C->getName()+".expr");
uint32_t v = VN.lookup_or_add(newVal);
Value* leader = find_leader(availableOut[pred], v);
if (leader == 0) {
createdExpressions.push_back(newVal);
return newVal;
} else {
VN.erase(newVal);
delete newVal;
return leader;
}
}
}
return V;
}
/// phi_translate_set - Perform phi translation on every element of a set
void GVNPRE::phi_translate_set(std::set<Value*>& anticIn,
BasicBlock* pred, BasicBlock* succ,
std::set<Value*>& out) {
for (std::set<Value*>::iterator I = anticIn.begin(),
E = anticIn.end(); I != E; ++I) {
Value* V = phi_translate(*I, pred, succ);
if (V != 0)
out.insert(V);
}
}
/// dependsOnInvoke - Test if a value has an phi node as an operand, any of
/// whose inputs is an invoke instruction. If this is true, we cannot safely
/// PRE the instruction or anything that depends on it.
bool GVNPRE::dependsOnInvoke(Value* V) {
if (PHINode* p = dyn_cast<PHINode>(V)) {
for (PHINode::op_iterator I = p->op_begin(), E = p->op_end(); I != E; ++I)
if (isa<InvokeInst>(*I))
return true;
return false;
} else {
return false;
}
}
/// clean - Remove all non-opaque values from the set whose operands are not
/// themselves in the set, as well as all values that depend on invokes (see
/// above)
void GVNPRE::clean(std::set<Value*>& set) {
std::vector<Value*> worklist;
topo_sort(set, worklist);
for (unsigned i = 0; i < worklist.size(); ++i) {
Value* v = worklist[i];
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(v)) {
bool lhsValid = !isa<Instruction>(BO->getOperand(0));
if (!lhsValid)
for (std::set<Value*>::iterator I = set.begin(), E = set.end();
I != E; ++I)
if (VN.lookup(*I) == VN.lookup(BO->getOperand(0))) {
lhsValid = true;
break;
}
if (lhsValid)
lhsValid = !dependsOnInvoke(BO->getOperand(0));
bool rhsValid = !isa<Instruction>(BO->getOperand(1));
if (!rhsValid)
for (std::set<Value*>::iterator I = set.begin(), E = set.end();
I != E; ++I)
if (VN.lookup(*I) == VN.lookup(BO->getOperand(1))) {
rhsValid = true;
break;
}
if (rhsValid)
rhsValid = !dependsOnInvoke(BO->getOperand(1));
if (!lhsValid || !rhsValid)
set.erase(BO);
} else if (CmpInst* C = dyn_cast<CmpInst>(v)) {
bool lhsValid = !isa<Instruction>(C->getOperand(0));
if (!lhsValid)
for (std::set<Value*>::iterator I = set.begin(), E = set.end();
I != E; ++I)
if (VN.lookup(*I) == VN.lookup(C->getOperand(0))) {
lhsValid = true;
break;
}
if (lhsValid)
lhsValid = !dependsOnInvoke(C->getOperand(0));
bool rhsValid = !isa<Instruction>(C->getOperand(1));
if (!rhsValid)
for (std::set<Value*>::iterator I = set.begin(), E = set.end();
I != E; ++I)
if (VN.lookup(*I) == VN.lookup(C->getOperand(1))) {
rhsValid = true;
break;
}
if (rhsValid)
rhsValid = !dependsOnInvoke(C->getOperand(1));
if (!lhsValid || !rhsValid)
set.erase(C);
}
}
}
/// topo_sort - Given a set of values, sort them by topological
/// order into the provided vector.
void GVNPRE::topo_sort(std::set<Value*>& set, std::vector<Value*>& vec) {
std::set<Value*> toErase;
for (std::set<Value*>::iterator I = set.begin(), E = set.end();
I != E; ++I) {
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(*I))
for (std::set<Value*>::iterator SI = set.begin(); SI != E; ++SI) {
if (VN.lookup(BO->getOperand(0)) == VN.lookup(*SI) ||
VN.lookup(BO->getOperand(1)) == VN.lookup(*SI)) {
toErase.insert(*SI);
}
}
else if (CmpInst* C = dyn_cast<CmpInst>(*I))
for (std::set<Value*>::iterator SI = set.begin(); SI != E; ++SI) {
if (VN.lookup(C->getOperand(0)) == VN.lookup(*SI) ||
VN.lookup(C->getOperand(1)) == VN.lookup(*SI)) {
toErase.insert(*SI);
}
}
}
std::vector<Value*> Q;
for (std::set<Value*>::iterator I = set.begin(), E = set.end();
I != E; ++I) {
if (toErase.find(*I) == toErase.end())
Q.push_back(*I);
}
std::set<Value*> visited;
while (!Q.empty()) {
Value* e = Q.back();
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(e)) {
Value* l = find_leader(set, VN.lookup(BO->getOperand(0)));
Value* r = find_leader(set, VN.lookup(BO->getOperand(1)));
if (l != 0 && isa<Instruction>(l) &&
visited.find(l) == visited.end())
Q.push_back(l);
else if (r != 0 && isa<Instruction>(r) &&
visited.find(r) == visited.end())
Q.push_back(r);
else {
vec.push_back(e);
visited.insert(e);
Q.pop_back();
}
} else if (CmpInst* C = dyn_cast<CmpInst>(e)) {
Value* l = find_leader(set, VN.lookup(C->getOperand(0)));
Value* r = find_leader(set, VN.lookup(C->getOperand(1)));
if (l != 0 && isa<Instruction>(l) &&
visited.find(l) == visited.end())
Q.push_back(l);
else if (r != 0 && isa<Instruction>(r) &&
visited.find(r) == visited.end())
Q.push_back(r);
else {
vec.push_back(e);
visited.insert(e);
Q.pop_back();
}
} else {
visited.insert(e);
vec.push_back(e);
Q.pop_back();
}
}
}
/// dump - Dump a set of values to standard error
void GVNPRE::dump(const std::set<Value*>& s) const {
DOUT << "{ ";
for (std::set<Value*>::iterator I = s.begin(), E = s.end();
I != E; ++I) {
DEBUG((*I)->dump());
}
DOUT << "}\n\n";
}
/// elimination - Phase 3 of the main algorithm. Perform full redundancy
/// elimination by walking the dominator tree and removing any instruction that
/// is dominated by another instruction with the same value number.
bool GVNPRE::elimination() {
DOUT << "\n\nPhase 3: Elimination\n\n";
bool changed_function = false;
std::vector<std::pair<Instruction*, Value*> > replace;
std::vector<Instruction*> erase;
DominatorTree& DT = getAnalysis<DominatorTree>();
for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
E = df_end(DT.getRootNode()); DI != E; ++DI) {
BasicBlock* BB = DI->getBlock();
DOUT << "Block: " << BB->getName() << "\n";
dump(availableOut[BB]);
DOUT << "\n\n";
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
BI != BE; ++BI) {
if (isa<BinaryOperator>(BI) || isa<CmpInst>(BI)) {
Value *leader = find_leader(availableOut[BB], VN.lookup(BI));
if (leader != 0)
if (Instruction* Instr = dyn_cast<Instruction>(leader))
if (Instr->getParent() != 0 && Instr != BI) {
replace.push_back(std::make_pair(BI, leader));
erase.push_back(BI);
++NumEliminated;
}
}
}
}
while (!replace.empty()) {
std::pair<Instruction*, Value*> rep = replace.back();
replace.pop_back();
rep.first->replaceAllUsesWith(rep.second);
changed_function = true;
}
for (std::vector<Instruction*>::iterator I = erase.begin(), E = erase.end();
I != E; ++I)
(*I)->eraseFromParent();
return changed_function;
}
/// cleanup - Delete any extraneous values that were created to represent
/// expressions without leaders.
void GVNPRE::cleanup() {
while (!createdExpressions.empty()) {
Instruction* I = createdExpressions.back();
createdExpressions.pop_back();
delete I;
}
}
/// buildsets_availout - When calculating availability, handle an instruction
/// by inserting it into the appropriate sets
void GVNPRE::buildsets_availout(BasicBlock::iterator I,
std::set<Value*>& currAvail,
std::set<PHINode*>& currPhis,
std::set<Value*>& currExps,
std::set<Value*>& currTemps) {
// Handle PHI nodes...
if (PHINode* p = dyn_cast<PHINode>(I)) {
VN.lookup_or_add(p);
currPhis.insert(p);
// Handle binary ops...
} else if (BinaryOperator* BO = dyn_cast<BinaryOperator>(I)) {
Value* leftValue = BO->getOperand(0);
Value* rightValue = BO->getOperand(1);
VN.lookup_or_add(BO);
if (isa<Instruction>(leftValue))
val_insert(currExps, leftValue);
if (isa<Instruction>(rightValue))
val_insert(currExps, rightValue);
val_insert(currExps, BO);
// Handle cmp ops...
} else if (CmpInst* C = dyn_cast<CmpInst>(I)) {
Value* leftValue = C->getOperand(0);
Value* rightValue = C->getOperand(1);
VN.lookup_or_add(C);
if (isa<Instruction>(leftValue))
val_insert(currExps, leftValue);
if (isa<Instruction>(rightValue))
val_insert(currExps, rightValue);
val_insert(currExps, C);
// Handle unsupported ops
} else if (!I->isTerminator()){
VN.lookup_or_add(I);
currTemps.insert(I);
}
if (!I->isTerminator())
val_insert(currAvail, I);
}
/// buildsets_anticout - When walking the postdom tree, calculate the ANTIC_OUT
/// set as a function of the ANTIC_IN set of the block's predecessors
void GVNPRE::buildsets_anticout(BasicBlock* BB,
std::set<Value*>& anticOut,
std::set<BasicBlock*>& visited) {
if (BB->getTerminator()->getNumSuccessors() == 1) {
if (visited.find(BB->getTerminator()->getSuccessor(0)) == visited.end())
phi_translate_set(VN.getMaximalValues(), BB,
BB->getTerminator()->getSuccessor(0), anticOut);
else
phi_translate_set(anticipatedIn[BB->getTerminator()->getSuccessor(0)],
BB, BB->getTerminator()->getSuccessor(0), anticOut);
} else if (BB->getTerminator()->getNumSuccessors() > 1) {
BasicBlock* first = BB->getTerminator()->getSuccessor(0);
anticOut.insert(anticipatedIn[first].begin(), anticipatedIn[first].end());
for (unsigned i = 1; i < BB->getTerminator()->getNumSuccessors(); ++i) {
BasicBlock* currSucc = BB->getTerminator()->getSuccessor(i);
std::set<Value*>& succAnticIn = anticipatedIn[currSucc];
std::set<Value*> temp;
std::insert_iterator<std::set<Value*> > temp_ins(temp, temp.begin());
std::set_intersection(anticOut.begin(), anticOut.end(),
succAnticIn.begin(), succAnticIn.end(), temp_ins);
anticOut.clear();
anticOut.insert(temp.begin(), temp.end());
}
}
}
/// buildsets_anticin - Walk the postdom tree, calculating ANTIC_OUT for
/// each block. ANTIC_IN is then a function of ANTIC_OUT and the GEN
/// sets populated in buildsets_availout
bool GVNPRE::buildsets_anticin(BasicBlock* BB,
std::set<Value*>& anticOut,
std::set<Value*>& currExps,
std::set<Value*>& currTemps,
std::set<BasicBlock*>& visited) {
std::set<Value*>& anticIn = anticipatedIn[BB];
std::set<Value*> old (anticIn.begin(), anticIn.end());
buildsets_anticout(BB, anticOut, visited);
std::set<Value*> S;
std::insert_iterator<std::set<Value*> > s_ins(S, S.begin());
std::set_difference(anticOut.begin(), anticOut.end(),
currTemps.begin(), currTemps.end(), s_ins);
anticIn.clear();
std::insert_iterator<std::set<Value*> > ai_ins(anticIn, anticIn.begin());
std::set_difference(currExps.begin(), currExps.end(),
currTemps.begin(), currTemps.end(), ai_ins);
for (std::set<Value*>::iterator I = S.begin(), E = S.end();
I != E; ++I) {
// For non-opaque values, we should already have a value numbering.
// However, for opaques, such as constants within PHI nodes, it is
// possible that they have not yet received a number. Make sure they do
// so now.
if (!isa<BinaryOperator>(*I) && !isa<CmpInst>(*I))
VN.lookup_or_add(*I);
val_insert(anticIn, *I);
}
clean(anticIn);
anticOut.clear();
if (old.size() != anticIn.size())
return true;
else
return false;
}
/// buildsets - Phase 1 of the main algorithm. Construct the AVAIL_OUT
/// and the ANTIC_IN sets.
unsigned GVNPRE::buildsets(Function& F) {
std::map<BasicBlock*, std::set<Value*> > generatedExpressions;
std::map<BasicBlock*, std::set<PHINode*> > generatedPhis;
std::map<BasicBlock*, std::set<Value*> > generatedTemporaries;
DominatorTree &DT = getAnalysis<DominatorTree>();
// Phase 1, Part 1: calculate AVAIL_OUT
// 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 sets to update for this block
std::set<Value*>& currExps = generatedExpressions[DI->getBlock()];
std::set<PHINode*>& currPhis = generatedPhis[DI->getBlock()];
std::set<Value*>& currTemps = generatedTemporaries[DI->getBlock()];
std::set<Value*>& currAvail = availableOut[DI->getBlock()];
BasicBlock* BB = DI->getBlock();
// A block inherits AVAIL_OUT from its dominator
if (DI->getIDom() != 0)
currAvail.insert(availableOut[DI->getIDom()->getBlock()].begin(),
availableOut[DI->getIDom()->getBlock()].end());
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
BI != BE; ++BI)
buildsets_availout(BI, currAvail, currPhis, currExps, currTemps);
}
// If function has no exit blocks, only perform GVN
PostDominatorTree &PDT = getAnalysis<PostDominatorTree>();
if (PDT[&F.getEntryBlock()] == 0) {
bool changed_function = elimination();
cleanup();
if (changed_function)
return 2; // Bailed early, made changes
else
return 1; // Bailed early, no changes
}
// Phase 1, Part 2: calculate ANTIC_IN
std::set<BasicBlock*> visited;
bool changed = true;
unsigned iterations = 0;
while (changed) {
changed = false;
std::set<Value*> anticOut;
// Top-down walk of the postdominator tree
for (df_iterator<DomTreeNode*> PDI =
df_begin(PDT.getRootNode()), E = df_end(PDT.getRootNode());
PDI != E; ++PDI) {
BasicBlock* BB = PDI->getBlock();
if (BB == 0)
continue;
visited.insert(BB);
changed |= buildsets_anticin(BB, anticOut, generatedTemporaries[BB],
generatedExpressions[BB], visited);
}
iterations++;
}
return 0; // No bail, no changes
}
/// insertion_pre - When a partial redundancy has been identified, eliminate it
/// by inserting appropriate values into the predecessors and a phi node in
/// the main block
void GVNPRE::insertion_pre(Value* e, BasicBlock* BB,
std::map<BasicBlock*, Value*>& avail,
std::set<Value*>& new_set) {
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
Value* e2 = avail[*PI];
if (!find_leader(availableOut[*PI], VN.lookup(e2))) {
User* U = cast<User>(e2);
Value* s1 = 0;
if (isa<BinaryOperator>(U->getOperand(0)) ||
isa<CmpInst>(U->getOperand(0)))
s1 = find_leader(availableOut[*PI], VN.lookup(U->getOperand(0)));
else
s1 = U->getOperand(0);
Value* s2 = 0;
if (isa<BinaryOperator>(U->getOperand(1)) ||
isa<CmpInst>(U->getOperand(1)))
s2 = find_leader(availableOut[*PI], VN.lookup(U->getOperand(1)));
else
s2 = U->getOperand(1);
Value* newVal = 0;
if (BinaryOperator* BO = dyn_cast<BinaryOperator>(U))
newVal = BinaryOperator::create(BO->getOpcode(), s1, s2,
BO->getName()+".gvnpre",
(*PI)->getTerminator());
else if (CmpInst* C = dyn_cast<CmpInst>(U))
newVal = CmpInst::create(C->getOpcode(), C->getPredicate(), s1, s2,
C->getName()+".gvnpre",
(*PI)->getTerminator());
VN.add(newVal, VN.lookup(U));
std::set<Value*>& predAvail = availableOut[*PI];
val_replace(predAvail, newVal);
std::map<BasicBlock*, Value*>::iterator av = avail.find(*PI);
if (av != avail.end())
avail.erase(av);
avail.insert(std::make_pair(*PI, newVal));
++NumInsertedVals;
}
}
PHINode* p = 0;
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
if (p == 0)
p = new PHINode(avail[*PI]->getType(), "gvnpre-join", BB->begin());
p->addIncoming(avail[*PI], *PI);
}
VN.add(p, VN.lookup(e));
val_replace(availableOut[BB], p);
new_set.insert(p);
++NumInsertedPhis;
}
/// insertion_mergepoint - When walking the dom tree, check at each merge
/// block for the possibility of a partial redundancy. If present, eliminate it
unsigned GVNPRE::insertion_mergepoint(std::vector<Value*>& workList,
df_iterator<DomTreeNode*> D,
std::set<Value*>& new_set) {
bool changed_function = false;
bool new_stuff = false;
BasicBlock* BB = D->getBlock();
for (unsigned i = 0; i < workList.size(); ++i) {
Value* e = workList[i];
if (isa<BinaryOperator>(e) || isa<CmpInst>(e)) {
if (find_leader(availableOut[D->getIDom()->getBlock()],
VN.lookup(e)) != 0)
continue;
std::map<BasicBlock*, Value*> avail;
bool by_some = false;
int num_avail = 0;
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;
++PI) {
Value *e2 = phi_translate(e, *PI, BB);
Value *e3 = find_leader(availableOut[*PI], VN.lookup(e2));
if (e3 == 0) {
std::map<BasicBlock*, Value*>::iterator av = avail.find(*PI);
if (av != avail.end())
avail.erase(av);
avail.insert(std::make_pair(*PI, e2));
} else {
std::map<BasicBlock*, Value*>::iterator av = avail.find(*PI);
if (av != avail.end())
avail.erase(av);
avail.insert(std::make_pair(*PI, e3));
by_some = true;
num_avail++;
}
}
if (by_some && num_avail < std::distance(pred_begin(BB), pred_end(BB))) {
insertion_pre(e, BB, avail, new_set);
changed_function = true;
new_stuff = true;
}
}
}
unsigned retval = 0;
if (changed_function)
retval += 1;
if (new_stuff)
retval += 2;
return retval;
}
/// insert - Phase 2 of the main algorithm. Walk the dominator tree looking for
/// merge points. When one is found, check for a partial redundancy. If one is
/// present, eliminate it. Repeat this walk until no changes are made.
bool GVNPRE::insertion(Function& F) {
bool changed_function = false;
DominatorTree &DT = getAnalysis<DominatorTree>();
std::map<BasicBlock*, std::set<Value*> > new_sets;
bool new_stuff = true;
while (new_stuff) {
new_stuff = false;
for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
E = df_end(DT.getRootNode()); DI != E; ++DI) {
BasicBlock* BB = DI->getBlock();
if (BB == 0)
continue;
std::set<Value*>& new_set = new_sets[BB];
std::set<Value*>& availOut = availableOut[BB];
std::set<Value*>& anticIn = anticipatedIn[BB];
new_set.clear();
// Replace leaders with leaders inherited from dominator
if (DI->getIDom() != 0) {
std::set<Value*>& dom_set = new_sets[DI->getIDom()->getBlock()];
for (std::set<Value*>::iterator I = dom_set.begin(),
E = dom_set.end(); I != E; ++I) {
new_set.insert(*I);
val_replace(availOut, *I);
}
}
// If there is more than one predecessor...
if (pred_begin(BB) != pred_end(BB) && ++pred_begin(BB) != pred_end(BB)) {
std::vector<Value*> workList;
topo_sort(anticIn, workList);
DOUT << "Merge Block: " << BB->getName() << "\n";
DOUT << "ANTIC_IN: ";
dump(anticIn);
DOUT << "\n";
unsigned result = insertion_mergepoint(workList, DI, new_set);
if (result & 1)
changed_function = true;
if (result & 2)
new_stuff = true;
}
}
}
return changed_function;
}
// GVNPRE::runOnFunction - This is the main transformation entry point for a
// function.
//
bool GVNPRE::runOnFunction(Function &F) {
// Clean out global sets from any previous functions
VN.clear();
createdExpressions.clear();
availableOut.clear();
anticipatedIn.clear();
bool changed_function = false;
// Phase 1: BuildSets
// This phase calculates the AVAIL_OUT and ANTIC_IN sets
// NOTE: If full postdom information is no available, this will bail
// early, performing GVN but not PRE
unsigned bail = buildsets(F);
//If a bail occurred, terminate early
if (bail != 0)
return (bail == 2);
// Phase 2: Insert
// This phase inserts values to make partially redundant values
// fully redundant
changed_function |= insertion(F);
// Phase 3: Eliminate
// This phase performs trivial full redundancy elimination
changed_function |= elimination();
// Phase 4: Cleanup
// This phase cleans up values that were created solely
// as leaders for expressions
cleanup();
return changed_function;
}
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