#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/MallocHelper.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include <cstdio>
/// as an efficient mechanism to determine the expression-wise equivalence of
/// two values.
namespace {
- struct VISIBILITY_HIDDEN Expression {
+ 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,
+ 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,
+ FPTOSI, UITOFP, SITOFP, FPTRUNC, FPEXT,
PTRTOINT, INTTOPTR, BITCAST, GEP, CALL, CONSTANT,
EMPTY, TOMBSTONE };
uint32_t thirdVN;
SmallVector<uint32_t, 4> varargs;
Value* function;
-
+
Expression() { }
Expression(ExpressionOpcode o) : opcode(o) { }
-
+
bool operator==(const Expression &other) const {
if (opcode != other.opcode)
return false;
else {
if (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 VISIBILITY_HIDDEN ValueTable {
+
+ class ValueTable {
private:
DenseMap<Value*, uint32_t> valueNumbering;
DenseMap<Expression, uint32_t> expressionNumbering;
AliasAnalysis* AA;
MemoryDependenceAnalysis* MD;
DominatorTree* DT;
-
+
uint32_t nextValueNumber;
-
+
Expression::ExpressionOpcode getOpcode(BinaryOperator* BO);
Expression::ExpressionOpcode getOpcode(CmpInst* C);
Expression::ExpressionOpcode getOpcode(CastInst* C);
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 = e.firstVN + hash * 37;
hash = e.secondVN + hash * 37;
hash = e.thirdVN + hash * 37;
-
+
hash = ((unsigned)((uintptr_t)e.type >> 4) ^
(unsigned)((uintptr_t)e.type >> 9)) +
hash * 37;
-
+
for (SmallVector<uint32_t, 4>::const_iterator I = e.varargs.begin(),
E = e.varargs.end(); I != E; ++I)
hash = *I + hash * 37;
-
+
hash = ((unsigned)((uintptr_t)e.function >> 4) ^
(unsigned)((uintptr_t)e.function >> 9)) +
hash * 37;
-
+
return hash;
}
static bool isEqual(const Expression &LHS, const Expression &RHS) {
Expression ValueTable::create_expression(CallInst* C) {
Expression e;
-
+
e.type = C->getType();
e.firstVN = 0;
e.secondVN = 0;
e.thirdVN = 0;
e.function = C->getCalledFunction();
e.opcode = Expression::CALL;
-
+
for (CallInst::op_iterator I = C->op_begin()+1, E = C->op_end();
I != E; ++I)
e.varargs.push_back(lookup_or_add(*I));
-
+
return e;
}
Expression ValueTable::create_expression(BinaryOperator* BO) {
Expression e;
-
+
e.firstVN = lookup_or_add(BO->getOperand(0));
e.secondVN = lookup_or_add(BO->getOperand(1));
e.thirdVN = 0;
e.function = 0;
e.type = BO->getType();
e.opcode = getOpcode(BO);
-
+
return e;
}
Expression ValueTable::create_expression(CmpInst* C) {
Expression e;
-
+
e.firstVN = lookup_or_add(C->getOperand(0));
e.secondVN = lookup_or_add(C->getOperand(1));
e.thirdVN = 0;
e.function = 0;
e.type = C->getType();
e.opcode = getOpcode(C);
-
+
return e;
}
Expression ValueTable::create_expression(CastInst* C) {
Expression e;
-
+
e.firstVN = lookup_or_add(C->getOperand(0));
e.secondVN = 0;
e.thirdVN = 0;
e.function = 0;
e.type = C->getType();
e.opcode = getOpcode(C);
-
+
return e;
}
Expression ValueTable::create_expression(ShuffleVectorInst* S) {
Expression e;
-
+
e.firstVN = lookup_or_add(S->getOperand(0));
e.secondVN = lookup_or_add(S->getOperand(1));
e.thirdVN = lookup_or_add(S->getOperand(2));
e.function = 0;
e.type = S->getType();
e.opcode = Expression::SHUFFLE;
-
+
return e;
}
Expression ValueTable::create_expression(ExtractElementInst* E) {
Expression e;
-
+
e.firstVN = lookup_or_add(E->getOperand(0));
e.secondVN = lookup_or_add(E->getOperand(1));
e.thirdVN = 0;
e.function = 0;
e.type = E->getType();
e.opcode = Expression::EXTRACT;
-
+
return e;
}
Expression ValueTable::create_expression(InsertElementInst* I) {
Expression e;
-
+
e.firstVN = lookup_or_add(I->getOperand(0));
e.secondVN = lookup_or_add(I->getOperand(1));
e.thirdVN = lookup_or_add(I->getOperand(2));
e.function = 0;
e.type = I->getType();
e.opcode = Expression::INSERT;
-
+
return e;
}
Expression ValueTable::create_expression(SelectInst* I) {
Expression e;
-
+
e.firstVN = lookup_or_add(I->getCondition());
e.secondVN = lookup_or_add(I->getTrueValue());
e.thirdVN = lookup_or_add(I->getFalseValue());
e.function = 0;
e.type = I->getType();
e.opcode = Expression::SELECT;
-
+
return e;
}
Expression ValueTable::create_expression(GetElementPtrInst* G) {
Expression e;
-
+
e.firstVN = lookup_or_add(G->getPointerOperand());
e.secondVN = 0;
e.thirdVN = 0;
e.function = 0;
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_or_add(*I));
-
+
return e;
}
DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
if (VI != valueNumbering.end())
return VI->second;
-
+
if (CallInst* C = dyn_cast<CallInst>(V)) {
if (AA->doesNotAccessMemory(C)) {
Expression e = create_expression(C);
-
+
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
if (EI != expressionNumbering.end()) {
valueNumbering.insert(std::make_pair(V, EI->second));
} else {
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
valueNumbering.insert(std::make_pair(V, nextValueNumber));
-
+
return nextValueNumber++;
}
} else if (AA->onlyReadsMemory(C)) {
Expression e = create_expression(C);
-
+
if (expressionNumbering.find(e) == expressionNumbering.end()) {
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
valueNumbering.insert(std::make_pair(V, nextValueNumber));
return nextValueNumber++;
}
-
+
MemDepResult local_dep = MD->getDependency(C);
-
+
if (!local_dep.isDef() && !local_dep.isNonLocal()) {
valueNumbering.insert(std::make_pair(V, nextValueNumber));
return nextValueNumber++;
if (local_dep.isDef()) {
CallInst* local_cdep = cast<CallInst>(local_dep.getInst());
-
+
if (local_cdep->getNumOperands() != C->getNumOperands()) {
valueNumbering.insert(std::make_pair(V, nextValueNumber));
return nextValueNumber++;
}
-
+
for (unsigned i = 1; i < C->getNumOperands(); ++i) {
uint32_t c_vn = lookup_or_add(C->getOperand(i));
uint32_t cd_vn = lookup_or_add(local_cdep->getOperand(i));
return nextValueNumber++;
}
}
-
+
uint32_t v = lookup_or_add(local_cdep);
valueNumbering.insert(std::make_pair(V, v));
return v;
}
// Non-local case.
- const MemoryDependenceAnalysis::NonLocalDepInfo &deps =
+ const MemoryDependenceAnalysis::NonLocalDepInfo &deps =
MD->getNonLocalCallDependency(CallSite(C));
// FIXME: call/call dependencies for readonly calls should return def, not
// clobber! Move the checking logic to MemDep!
CallInst* cdep = 0;
-
+
// Check to see if we have a single dominating call instruction that is
// identical to C.
for (unsigned i = 0, e = deps.size(); i != e; ++i) {
cdep = 0;
break;
}
-
+
CallInst *NonLocalDepCall = dyn_cast<CallInst>(I->second.getInst());
// FIXME: All duplicated with non-local case.
if (NonLocalDepCall && DT->properlyDominates(I->first, C->getParent())){
cdep = NonLocalDepCall;
continue;
}
-
+
cdep = 0;
break;
}
-
+
if (!cdep) {
valueNumbering.insert(std::make_pair(V, nextValueNumber));
return nextValueNumber++;
}
-
+
if (cdep->getNumOperands() != C->getNumOperands()) {
valueNumbering.insert(std::make_pair(V, nextValueNumber));
return nextValueNumber++;
return nextValueNumber++;
}
}
-
+
uint32_t v = lookup_or_add(cdep);
valueNumbering.insert(std::make_pair(V, v));
return v;
-
+
} else {
valueNumbering.insert(std::make_pair(V, nextValueNumber));
return nextValueNumber++;
}
} else if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) {
Expression e = create_expression(BO);
-
+
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
if (EI != expressionNumbering.end()) {
valueNumbering.insert(std::make_pair(V, EI->second));
} else {
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
valueNumbering.insert(std::make_pair(V, nextValueNumber));
-
+
return nextValueNumber++;
}
} else if (CmpInst* C = dyn_cast<CmpInst>(V)) {
Expression e = create_expression(C);
-
+
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
if (EI != expressionNumbering.end()) {
valueNumbering.insert(std::make_pair(V, EI->second));
} else {
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
valueNumbering.insert(std::make_pair(V, nextValueNumber));
-
+
return nextValueNumber++;
}
} else if (ShuffleVectorInst* U = dyn_cast<ShuffleVectorInst>(V)) {
Expression e = create_expression(U);
-
+
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
if (EI != expressionNumbering.end()) {
valueNumbering.insert(std::make_pair(V, EI->second));
} 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));
} 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));
} 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));
} 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));
} 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));
} else {
expressionNumbering.insert(std::make_pair(e, nextValueNumber));
valueNumbering.insert(std::make_pair(V, nextValueNumber));
-
+
return nextValueNumber++;
}
} else {
//===----------------------------------------------------------------------===//
namespace {
- struct VISIBILITY_HIDDEN ValueNumberScope {
+ struct ValueNumberScope {
ValueNumberScope* parent;
DenseMap<uint32_t, Value*> table;
-
+
ValueNumberScope(ValueNumberScope* p) : parent(p) { }
};
}
namespace {
- class VISIBILITY_HIDDEN GVN : public FunctionPass {
+ class GVN : public FunctionPass {
bool runOnFunction(Function &F);
public:
static char ID; // Pass identification, replacement for typeid
ValueTable VN;
DenseMap<BasicBlock*, ValueNumberScope*> localAvail;
-
+
typedef DenseMap<Value*, SmallPtrSet<Instruction*, 4> > PhiMapType;
PhiMapType phiMap;
-
-
+
+
// This transformation requires dominator postdominator info
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DominatorTree>();
AU.addRequired<MemoryDependenceAnalysis>();
AU.addRequired<AliasAnalysis>();
-
+
AU.addPreserved<DominatorTree>();
AU.addPreserved<AliasAnalysis>();
}
-
+
// Helper fuctions
// FIXME: eliminate or document these better
bool processLoad(LoadInst* L,
void dump(DenseMap<uint32_t, Value*>& d);
bool iterateOnFunction(Function &F);
Value* CollapsePhi(PHINode* p);
- bool isSafeReplacement(PHINode* p, Instruction* inst);
bool performPRE(Function& F);
Value* lookupNumber(BasicBlock* BB, uint32_t num);
- bool mergeBlockIntoPredecessor(BasicBlock* BB);
Value* AttemptRedundancyElimination(Instruction* orig, unsigned valno);
void cleanupGlobalSets();
void verifyRemoved(const Instruction *I) const;
};
-
+
char GVN::ID = 0;
}
printf("}\n");
}
+static bool isSafeReplacement(PHINode* p, Instruction* inst) {
+ if (!isa<PHINode>(inst))
+ return true;
+
+ for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end();
+ UI != E; ++UI)
+ if (PHINode* use_phi = dyn_cast<PHINode>(UI))
+ if (use_phi->getParent() == inst->getParent())
+ return false;
+
+ return true;
+}
+
Value* GVN::CollapsePhi(PHINode* p) {
- Value* constVal = p->hasConstantValue();
+ Value* constVal = p->hasConstantValue(DT);
if (!constVal) return 0;
-
+
Instruction* inst = dyn_cast<Instruction>(constVal);
if (!inst)
return constVal;
-
+
if (DT->dominates(inst, p))
if (isSafeReplacement(p, inst))
return inst;
return 0;
}
-bool GVN::isSafeReplacement(PHINode* p, Instruction* inst) {
- if (!isa<PHINode>(inst))
- return true;
-
- for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end();
- UI != E; ++UI)
- if (PHINode* use_phi = dyn_cast<PHINode>(UI))
- if (use_phi->getParent() == inst->getParent())
- return false;
-
- return true;
-}
-
/// GetValueForBlock - Get the value to use within the specified basic block.
/// available values are in Phis.
Value *GVN::GetValueForBlock(BasicBlock *BB, Instruction* orig,
DenseMap<BasicBlock*, Value*> &Phis,
- bool top_level) {
-
+ bool top_level) {
+
// If we have already computed this value, return the previously computed val.
DenseMap<BasicBlock*, Value*>::iterator V = Phis.find(BB);
if (V != Phis.end() && !top_level) return V->second;
-
+
// If the block is unreachable, just return undef, since this path
// can't actually occur at runtime.
if (!DT->isReachableFromEntry(BB))
return Phis[BB] = UndefValue::get(orig->getType());
-
+
if (BasicBlock *Pred = BB->getSinglePredecessor()) {
Value *ret = GetValueForBlock(Pred, orig, Phis);
Phis[BB] = ret;
NumPreds = ExistingPN->getNumIncomingValues();
else
NumPreds = std::distance(pred_begin(BB), pred_end(BB));
-
+
// Otherwise, the idom is the loop, so we need to insert a PHI node. Do so
// now, then get values to fill in the incoming values for the PHI.
PHINode *PN = PHINode::Create(orig->getType(), orig->getName()+".rle",
BB->begin());
PN->reserveOperandSpace(NumPreds);
-
+
Phis.insert(std::make_pair(BB, PN));
-
+
// Fill in the incoming values for the block.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
Value* val = GetValueForBlock(*PI, orig, Phis);
PN->addIncoming(val, *PI);
}
-
+
VN.getAliasAnalysis()->copyValue(orig, PN);
-
+
// Attempt to collapse PHI nodes that are trivially redundant
Value* v = CollapsePhi(PN);
if (!v) {
phiMap[L->getPointerOperand()].insert(PN);
else
phiMap[orig].insert(PN);
-
+
return PN;
}
-
+
PN->replaceAllUsesWith(v);
if (isa<PointerType>(v->getType()))
MD->invalidateCachedPointerInfo(v);
/// currently speculating that it will be.
/// 3) we are speculating for this block and have used that to speculate for
/// other blocks.
-static bool IsValueFullyAvailableInBlock(BasicBlock *BB,
+static bool IsValueFullyAvailableInBlock(BasicBlock *BB,
DenseMap<BasicBlock*, char> &FullyAvailableBlocks) {
// Optimistically assume that the block is fully available and check to see
// if we already know about this block in one lookup.
- std::pair<DenseMap<BasicBlock*, char>::iterator, char> IV =
+ std::pair<DenseMap<BasicBlock*, char>::iterator, char> IV =
FullyAvailableBlocks.insert(std::make_pair(BB, 2));
// If the entry already existed for this block, return the precomputed value.
IV.first->second = 3;
return IV.first->second != 0;
}
-
+
// Otherwise, see if it is fully available in all predecessors.
pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
-
+
// If this block has no predecessors, it isn't live-in here.
if (PI == PE)
goto SpeculationFailure;
-
+
for (; PI != PE; ++PI)
// If the value isn't fully available in one of our predecessors, then it
// isn't fully available in this block either. Undo our previous
// optimistic assumption and bail out.
if (!IsValueFullyAvailableInBlock(*PI, FullyAvailableBlocks))
goto SpeculationFailure;
-
+
return true;
-
+
// SpeculationFailure - If we get here, we found out that this is not, after
// all, a fully-available block. We have a problem if we speculated on this and
// used the speculation to mark other blocks as available.
SpeculationFailure:
char &BBVal = FullyAvailableBlocks[BB];
-
+
// If we didn't speculate on this, just return with it set to false.
if (BBVal == 2) {
BBVal = 0;
// 0 if set to one.
SmallVector<BasicBlock*, 32> BBWorklist;
BBWorklist.push_back(BB);
-
+
while (!BBWorklist.empty()) {
BasicBlock *Entry = BBWorklist.pop_back_val();
// Note that this sets blocks to 0 (unavailable) if they happen to not
// Mark as unavailable.
EntryVal = 0;
-
+
for (succ_iterator I = succ_begin(Entry), E = succ_end(Entry); I != E; ++I)
BBWorklist.push_back(*I);
}
-
+
return false;
}
bool GVN::processNonLocalLoad(LoadInst *LI,
SmallVectorImpl<Instruction*> &toErase) {
// Find the non-local dependencies of the load.
- SmallVector<MemoryDependenceAnalysis::NonLocalDepEntry, 64> Deps;
+ SmallVector<MemoryDependenceAnalysis::NonLocalDepEntry, 64> Deps;
MD->getNonLocalPointerDependency(LI->getOperand(0), true, LI->getParent(),
Deps);
//DEBUG(errs() << "INVESTIGATING NONLOCAL LOAD: "
// << Deps.size() << *LI << '\n');
-
+
// If we had to process more than one hundred blocks to find the
// dependencies, this load isn't worth worrying about. Optimizing
// it will be too expensive.
);
return false;
}
-
+
// Filter out useless results (non-locals, etc). Keep track of the blocks
// where we have a value available in repl, also keep track of whether we see
// dependencies that produce an unknown value for the load (such as a call
// that could potentially clobber the load).
SmallVector<std::pair<BasicBlock*, Value*>, 16> ValuesPerBlock;
SmallVector<BasicBlock*, 16> UnavailableBlocks;
-
+
for (unsigned i = 0, e = Deps.size(); i != e; ++i) {
BasicBlock *DepBB = Deps[i].first;
MemDepResult DepInfo = Deps[i].second;
-
+
if (DepInfo.isClobber()) {
UnavailableBlocks.push_back(DepBB);
continue;
}
-
+
Instruction *DepInst = DepInfo.getInst();
-
+
// Loading the allocation -> undef.
- if (isa<AllocationInst>(DepInst)) {
- ValuesPerBlock.push_back(std::make_pair(DepBB,
+ if (isa<AllocationInst>(DepInst) || isMalloc(DepInst)) {
+ ValuesPerBlock.push_back(std::make_pair(DepBB,
UndefValue::get(LI->getType())));
continue;
}
-
+
if (StoreInst* S = dyn_cast<StoreInst>(DepInst)) {
- // Reject loads and stores that are to the same address but are of
+ // Reject loads and stores that are to the same address but are of
// different types.
// NOTE: 403.gcc does have this case (e.g. in readonly_fields_p) because
// of bitfield access, it would be interesting to optimize for it at some
UnavailableBlocks.push_back(DepBB);
continue;
}
-
+
ValuesPerBlock.push_back(std::make_pair(DepBB, S->getOperand(0)));
-
+
} else if (LoadInst* LD = dyn_cast<LoadInst>(DepInst)) {
if (LD->getType() != LI->getType()) {
UnavailableBlocks.push_back(DepBB);
continue;
}
}
-
+
// If we have no predecessors that produce a known value for this load, exit
// early.
if (ValuesPerBlock.empty()) return false;
-
+
// If all of the instructions we depend on produce a known value for this
// load, then it is fully redundant and we can use PHI insertion to compute
// its value. Insert PHIs and remove the fully redundant value now.
NumGVNLoad++;
return true;
}
-
+
ValuesPerBlock.push_back(std::make_pair((*I)->getParent(), *I));
}
-
+
DEBUG(errs() << "GVN REMOVING NONLOCAL LOAD: " << *LI << '\n');
-
+
DenseMap<BasicBlock*, Value*> BlockReplValues;
BlockReplValues.insert(ValuesPerBlock.begin(), ValuesPerBlock.end());
// Perform PHI construction.
Value* v = GetValueForBlock(LI->getParent(), LI, BlockReplValues, true);
LI->replaceAllUsesWith(v);
-
+
if (isa<PHINode>(v))
v->takeName(LI);
if (isa<PointerType>(v->getType()))
NumGVNLoad++;
return true;
}
-
+
if (!EnablePRE || !EnableLoadPRE)
return false;
// prefer to not increase code size. As such, we only do this when we know
// that we only have to insert *one* load (which means we're basically moving
// the load, not inserting a new one).
-
+
SmallPtrSet<BasicBlock *, 4> Blockers;
for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
Blockers.insert(UnavailableBlocks[i]);
if (TmpBB->getTerminator()->getNumSuccessors() != 1)
allSingleSucc = false;
}
-
+
assert(TmpBB);
LoadBB = TmpBB;
-
+
// If we have a repl set with LI itself in it, this means we have a loop where
// at least one of the values is LI. Since this means that we won't be able
// to eliminate LI even if we insert uses in the other predecessors, we will
for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i)
if (ValuesPerBlock[i].second == LI)
return false;
-
+
if (isSinglePred) {
bool isHot = false;
for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i)
if (Instruction *I = dyn_cast<Instruction>(ValuesPerBlock[i].second))
- // "Hot" Instruction is in some loop (because it dominates its dep.
- // instruction).
- if (DT->dominates(LI, I)) {
- isHot = true;
- break;
- }
+ // "Hot" Instruction is in some loop (because it dominates its dep.
+ // instruction).
+ if (DT->dominates(LI, I)) {
+ isHot = true;
+ break;
+ }
// We are interested only in "hot" instructions. We don't want to do any
// mis-optimizations here.
PI != E; ++PI) {
if (IsValueFullyAvailableInBlock(*PI, FullyAvailableBlocks))
continue;
-
+
// If this load is not available in multiple predecessors, reject it.
if (UnavailablePred && UnavailablePred != *PI)
return false;
UnavailablePred = *PI;
}
-
+
assert(UnavailablePred != 0 &&
"Fully available value should be eliminated above!");
-
+
// If the loaded pointer is PHI node defined in this block, do PHI translation
// to get its value in the predecessor.
Value *LoadPtr = LI->getOperand(0)->DoPHITranslation(LoadBB, UnavailablePred);
-
+
// Make sure the value is live in the predecessor. If it was defined by a
// non-PHI instruction in this block, we don't know how to recompute it above.
if (Instruction *LPInst = dyn_cast<Instruction>(LoadPtr))
<< *LPInst << '\n' << *LI << "\n");
return false;
}
-
+
// We don't currently handle critical edges :(
if (UnavailablePred->getTerminator()->getNumSuccessors() != 1) {
DEBUG(errs() << "COULD NOT PRE LOAD BECAUSE OF CRITICAL EDGE '"
// and using PHI construction to get the value in the other predecessors, do
// it.
DEBUG(errs() << "GVN REMOVING PRE LOAD: " << *LI << '\n');
-
+
Value *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre", false,
LI->getAlignment(),
UnavailablePred->getTerminator());
-
+
SmallPtrSet<Instruction*, 4> &p = phiMap[LI->getPointerOperand()];
for (SmallPtrSet<Instruction*, 4>::iterator I = p.begin(), E = p.end();
I != E; ++I)
ValuesPerBlock.push_back(std::make_pair((*I)->getParent(), *I));
-
+
DenseMap<BasicBlock*, Value*> BlockReplValues;
BlockReplValues.insert(ValuesPerBlock.begin(), ValuesPerBlock.end());
BlockReplValues[UnavailablePred] = NewLoad;
-
+
// Perform PHI construction.
Value* v = GetValueForBlock(LI->getParent(), LI, BlockReplValues, true);
LI->replaceAllUsesWith(v);
return true;
}
+/// CoerceAvailableValueToLoadType - If we saw a store of a value to memory, and
+/// then a load from a must-aliased pointer of a different type, try to coerce
+/// the stored value. LoadedTy is the type of the load we want to replace and
+/// InsertPt is the place to insert new instructions.
+///
+/// If we can't do it, return null.
+static Value *CoerceAvailableValueToLoadType(Value *StoredVal,
+ const Type *LoadedTy,
+ Instruction *InsertPt,
+ const TargetData &TD) {
+ const Type *StoredValTy = StoredVal->getType();
+
+ uint64_t StoreSize = TD.getTypeSizeInBits(StoredValTy);
+ uint64_t LoadSize = TD.getTypeSizeInBits(LoadedTy);
+
+ // If the store and reload are the same size, we can always reuse it.
+ if (StoreSize == LoadSize) {
+ if (isa<PointerType>(StoredValTy) && isa<PointerType>(LoadedTy)) {
+ // Pointer to Pointer -> use bitcast.
+ return new BitCastInst(StoredVal, LoadedTy, "", InsertPt);
+ }
+
+ // Convert source pointers to integers, which can be bitcast.
+ if (isa<PointerType>(StoredValTy)) {
+ StoredValTy = TD.getIntPtrType(StoredValTy->getContext());
+ StoredVal = new PtrToIntInst(StoredVal, StoredValTy, "", InsertPt);
+ }
+
+ const Type *TypeToCastTo = LoadedTy;
+ if (isa<PointerType>(TypeToCastTo))
+ TypeToCastTo = TD.getIntPtrType(StoredValTy->getContext());
+
+ if (StoredValTy != TypeToCastTo)
+ StoredVal = new BitCastInst(StoredVal, TypeToCastTo, "", InsertPt);
+
+ // Cast to pointer if the load needs a pointer type.
+ if (isa<PointerType>(LoadedTy))
+ StoredVal = new IntToPtrInst(StoredVal, LoadedTy, "", InsertPt);
+
+ return StoredVal;
+ }
+
+ // If the loaded value is smaller than the available value, then we can
+ // extract out a piece from it. If the available value is too small, then we
+ // can't do anything.
+ if (StoreSize < LoadSize)
+ return 0;
+
+ // Convert source pointers to integers, which can be manipulated.
+ if (isa<PointerType>(StoredValTy)) {
+ StoredValTy = TD.getIntPtrType(StoredValTy->getContext());
+ StoredVal = new PtrToIntInst(StoredVal, StoredValTy, "", InsertPt);
+ }
+
+ // Convert vectors and fp to integer, which can be manipulated.
+ if (!isa<IntegerType>(StoredValTy)) {
+ StoredValTy = IntegerType::get(StoredValTy->getContext(), StoreSize);
+ StoredVal = new BitCastInst(StoredVal, StoredValTy, "", InsertPt);
+ }
+
+ // If this is a big-endian system, we need to shift the value down to the low
+ // bits so that a truncate will work.
+ if (TD.isBigEndian()) {
+ Constant *Val = ConstantInt::get(StoredVal->getType(), StoreSize-LoadSize);
+ StoredVal = BinaryOperator::CreateLShr(StoredVal, Val, "tmp", InsertPt);
+ }
+
+ // Truncate the integer to the right size now.
+ const Type *NewIntTy = IntegerType::get(StoredValTy->getContext(), LoadSize);
+ StoredVal = new TruncInst(StoredVal, NewIntTy, "trunc", InsertPt);
+
+ if (LoadedTy == NewIntTy)
+ return StoredVal;
+
+ // If the result is a pointer, inttoptr.
+ if (isa<PointerType>(LoadedTy))
+ return new IntToPtrInst(StoredVal, LoadedTy, "inttoptr", InsertPt);
+
+ // Otherwise, bitcast.
+ return new BitCastInst(StoredVal, LoadedTy, "bitcast", InsertPt);
+}
+
+
/// processLoad - Attempt to eliminate a load, first by eliminating it
/// locally, and then attempting non-local elimination if that fails.
bool GVN::processLoad(LoadInst *L, SmallVectorImpl<Instruction*> &toErase) {
if (L->isVolatile())
return false;
-
- Value* pointer = L->getPointerOperand();
// ... to a pointer that has been loaded from before...
MemDepResult dep = MD->getDependency(L);
-
+
// If the value isn't available, don't do anything!
if (dep.isClobber()) {
+ // FIXME: In the future, we should handle things like:
+ // store i32 123, i32* %P
+ // %A = bitcast i32* %P to i8*
+ // %B = gep i8* %A, i32 1
+ // %C = load i8* %B
+ //
+ // We could do that by recognizing if the clobber instructions are obviously
+ // a common base + constant offset, and if the previous store (or memset)
+ // completely covers this load. This sort of thing can happen in bitfield
+ // access code.
DEBUG(
// fast print dep, using operator<< on instruction would be too slow
errs() << "GVN: load ";
Instruction *DepInst = dep.getInst();
if (StoreInst *DepSI = dyn_cast<StoreInst>(DepInst)) {
- // Only forward substitute stores to loads of the same type.
- // FIXME: Could do better!
- if (DepSI->getPointerOperand()->getType() != pointer->getType())
- return false;
+ Value *StoredVal = DepSI->getOperand(0);
+ // The store and load are to a must-aliased pointer, but they may not
+ // actually have the same type. See if we know how to reuse the stored
+ // value (depending on its type).
+ const TargetData *TD = 0;
+ if (StoredVal->getType() != L->getType() &&
+ (TD = getAnalysisIfAvailable<TargetData>())) {
+ StoredVal = CoerceAvailableValueToLoadType(StoredVal, L->getType(), L, *TD);
+ if (StoredVal == 0)
+ return false;
+
+ DEBUG(errs() << "GVN COERCED STORE:\n" << *DepSI << '\n' << *StoredVal
+ << '\n' << *L << "\n\n\n");
+ }
+
// Remove it!
- L->replaceAllUsesWith(DepSI->getOperand(0));
- if (isa<PointerType>(DepSI->getOperand(0)->getType()))
- MD->invalidateCachedPointerInfo(DepSI->getOperand(0));
+ L->replaceAllUsesWith(StoredVal);
+ if (isa<PointerType>(StoredVal->getType()))
+ MD->invalidateCachedPointerInfo(StoredVal);
toErase.push_back(L);
NumGVNLoad++;
return true;
}
if (LoadInst *DepLI = dyn_cast<LoadInst>(DepInst)) {
- // Only forward substitute stores to loads of the same type.
- // FIXME: Could do better! load i32 -> load i8 -> truncate on little endian.
- if (DepLI->getType() != L->getType())
- return false;
+ Value *AvailableVal = DepLI;
+
+ // The loads are of a must-aliased pointer, but they may not actually have
+ // the same type. See if we know how to reuse the previously loaded value
+ // (depending on its type).
+ const TargetData *TD = 0;
+ if (DepLI->getType() != L->getType() &&
+ (TD = getAnalysisIfAvailable<TargetData>())) {
+ AvailableVal = CoerceAvailableValueToLoadType(DepLI, L->getType(), L, *TD);
+ if (AvailableVal == 0)
+ return false;
+
+ DEBUG(errs() << "GVN COERCED LOAD:\n" << *DepLI << "\n" << *AvailableVal
+ << "\n" << *L << "\n\n\n");
+ }
// Remove it!
- L->replaceAllUsesWith(DepLI);
+ L->replaceAllUsesWith(AvailableVal);
if (isa<PointerType>(DepLI->getType()))
MD->invalidateCachedPointerInfo(DepLI);
toErase.push_back(L);
NumGVNLoad++;
return true;
}
+
+ // FIXME: We should handle memset/memcpy/memmove as dependent instructions to
+ // forward the value if available.
+ //if (isa<MemIntrinsic>(DepInst))
+ // errs() << "LOAD DEPENDS ON MEM: " << *L << "\n" << *DepInst << "\n\n";
+
// If this load really doesn't depend on anything, then we must be loading an
// undef value. This can happen when loading for a fresh allocation with no
// intervening stores, for example.
- if (isa<AllocationInst>(DepInst)) {
+ if (isa<AllocationInst>(DepInst) || isMalloc(DepInst)) {
L->replaceAllUsesWith(UndefValue::get(L->getType()));
toErase.push_back(L);
NumGVNLoad++;
DenseMap<BasicBlock*, ValueNumberScope*>::iterator I = localAvail.find(BB);
if (I == localAvail.end())
return 0;
-
+
ValueNumberScope* locals = I->second;
-
+
while (locals) {
DenseMap<uint32_t, Value*>::iterator I = locals->table.find(num);
if (I != locals->table.end())
else
locals = locals->parent;
}
-
+
return 0;
}
/// AttemptRedundancyElimination - If the "fast path" of redundancy elimination
-/// by inheritance from the dominator fails, see if we can perform phi
+/// by inheritance from the dominator fails, see if we can perform phi
/// construction to eliminate the redundancy.
Value* GVN::AttemptRedundancyElimination(Instruction* orig, unsigned valno) {
BasicBlock* BaseBlock = orig->getParent();
-
+
SmallPtrSet<BasicBlock*, 4> Visited;
SmallVector<BasicBlock*, 8> Stack;
Stack.push_back(BaseBlock);
-
+
DenseMap<BasicBlock*, Value*> Results;
-
+
// Walk backwards through our predecessors, looking for instances of the
// value number we're looking for. Instances are recorded in the Results
// map, which is then used to perform phi construction.
while (!Stack.empty()) {
BasicBlock* Current = Stack.back();
Stack.pop_back();
-
+
// If we've walked all the way to a proper dominator, then give up. Cases
// where the instance is in the dominator will have been caught by the fast
// path, and any cases that require phi construction further than this are
// probably not worth it anyways. Note that this is a SIGNIFICANT compile
// time improvement.
if (DT->properlyDominates(Current, orig->getParent())) return 0;
-
+
DenseMap<BasicBlock*, ValueNumberScope*>::iterator LA =
localAvail.find(Current);
if (LA == localAvail.end()) return 0;
DenseMap<uint32_t, Value*>::iterator V = LA->second->table.find(valno);
-
+
if (V != LA->second->table.end()) {
// Found an instance, record it.
Results.insert(std::make_pair(Current, V->second));
continue;
}
-
+
// If we reach the beginning of the function, then give up.
if (pred_begin(Current) == pred_end(Current))
return 0;
-
+
for (pred_iterator PI = pred_begin(Current), PE = pred_end(Current);
PI != PE; ++PI)
if (Visited.insert(*PI))
Stack.push_back(*PI);
}
-
+
// If we didn't find instances, give up. Otherwise, perform phi construction.
if (Results.size() == 0)
return 0;
SmallVectorImpl<Instruction*> &toErase) {
if (LoadInst* L = dyn_cast<LoadInst>(I)) {
bool changed = processLoad(L, toErase);
-
+
if (!changed) {
unsigned num = VN.lookup_or_add(L);
localAvail[I->getParent()]->table.insert(std::make_pair(num, L));
}
-
+
return changed;
}
-
+
uint32_t nextNum = VN.getNextUnusedValueNumber();
unsigned num = VN.lookup_or_add(I);
-
+
if (BranchInst* BI = dyn_cast<BranchInst>(I)) {
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
-
+
if (!BI->isConditional() || isa<Constant>(BI->getCondition()))
return false;
-
+
Value* branchCond = BI->getCondition();
uint32_t condVN = VN.lookup_or_add(branchCond);
-
+
BasicBlock* trueSucc = BI->getSuccessor(0);
BasicBlock* falseSucc = BI->getSuccessor(1);
-
+
if (trueSucc->getSinglePredecessor())
- localAvail[trueSucc]->table[condVN] =
+ localAvail[trueSucc]->table[condVN] =
ConstantInt::getTrue(trueSucc->getContext());
if (falseSucc->getSinglePredecessor())
localAvail[falseSucc]->table[condVN] =
ConstantInt::getFalse(trueSucc->getContext());
return false;
-
+
// Allocations are always uniquely numbered, so we can save time and memory
- // by fast failing them.
- } else if (isa<AllocationInst>(I) || isa<TerminatorInst>(I)) {
+ // by fast failing them.
+ } else if (isa<AllocationInst>(I) || isMalloc(I) || isa<TerminatorInst>(I)) {
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
return false;
}
-
+
// Collapse PHI nodes
if (PHINode* p = dyn_cast<PHINode>(I)) {
Value* constVal = CollapsePhi(p);
-
+
if (constVal) {
for (PhiMapType::iterator PI = phiMap.begin(), PE = phiMap.end();
PI != PE; ++PI)
PI->second.erase(p);
-
+
p->replaceAllUsesWith(constVal);
if (isa<PointerType>(constVal->getType()))
MD->invalidateCachedPointerInfo(constVal);
VN.erase(p);
-
+
toErase.push_back(p);
} else {
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
}
-
+
// If the number we were assigned was a brand new VN, then we don't
// need to do a lookup to see if the number already exists
// somewhere in the domtree: it can't!
} else if (num == nextNum) {
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
-
+
// Perform fast-path value-number based elimination of values inherited from
// dominators.
} else if (Value* repl = lookupNumber(I->getParent(), num)) {
} else {
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
}
-
+
return false;
}
VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>());
VN.setMemDep(MD);
VN.setDomTree(DT);
-
+
bool changed = false;
bool shouldContinue = true;
-
+
// Merge unconditional branches, allowing PRE to catch more
// optimization opportunities.
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ) {
++FI;
bool removedBlock = MergeBlockIntoPredecessor(BB, this);
if (removedBlock) NumGVNBlocks++;
-
+
changed |= removedBlock;
}
-
+
unsigned Iteration = 0;
-
+
while (shouldContinue) {
DEBUG(errs() << "GVN iteration: " << Iteration << "\n");
shouldContinue = iterateOnFunction(F);
changed |= shouldContinue;
++Iteration;
}
-
+
if (EnablePRE) {
bool PREChanged = true;
while (PREChanged) {
// incrementing BI before processing an instruction).
SmallVector<Instruction*, 8> toErase;
bool changed_function = false;
-
+
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
BI != BE;) {
changed_function |= processInstruction(BI, toErase);
++BI;
continue;
}
-
+
// If we need some instructions deleted, do it now.
NumGVNInstr += toErase.size();
-
+
// Avoid iterator invalidation.
bool AtStart = BI == BB->begin();
if (!AtStart)
else
++BI;
}
-
+
return changed_function;
}
for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) {
BasicBlock* CurrentBlock = *DI;
-
+
// Nothing to PRE in the entry block.
if (CurrentBlock == &F.getEntryBlock()) continue;
-
+
for (BasicBlock::iterator BI = CurrentBlock->begin(),
BE = CurrentBlock->end(); BI != BE; ) {
Instruction *CurInst = BI++;
- if (isa<AllocationInst>(CurInst) || isa<TerminatorInst>(CurInst) ||
- isa<PHINode>(CurInst) ||
+ if (isa<AllocationInst>(CurInst) || isMalloc(CurInst) ||
+ isa<TerminatorInst>(CurInst) || isa<PHINode>(CurInst) ||
(CurInst->getType() == Type::getVoidTy(F.getContext())) ||
CurInst->mayReadFromMemory() || CurInst->mayHaveSideEffects() ||
isa<DbgInfoIntrinsic>(CurInst))
continue;
uint32_t valno = VN.lookup(CurInst);
-
+
// Look for the predecessors for PRE opportunities. We're
// only trying to solve the basic diamond case, where
// a value is computed in the successor and one predecessor,
numWithout = 2;
break;
}
-
- DenseMap<uint32_t, Value*>::iterator predV =
+
+ DenseMap<uint32_t, Value*>::iterator predV =
localAvail[*PI]->table.find(valno);
if (predV == localAvail[*PI]->table.end()) {
PREPred = *PI;
numWith++;
}
}
-
+
// Don't do PRE when it might increase code size, i.e. when
// we would need to insert instructions in more than one pred.
if (numWithout != 1 || numWith == 0)
continue;
-
+
// We can't do PRE safely on a critical edge, so instead we schedule
// the edge to be split and perform the PRE the next time we iterate
// on the function.
succNum = i;
break;
}
-
+
if (isCriticalEdge(PREPred->getTerminator(), succNum)) {
toSplit.push_back(std::make_pair(PREPred->getTerminator(), succNum));
continue;
}
-
+
// Instantiate the expression the in predecessor that lacked it.
// Because we are going top-down through the block, all value numbers
// will be available in the predecessor by the time we need them. Any
Value *Op = PREInstr->getOperand(i);
if (isa<Argument>(Op) || isa<Constant>(Op) || isa<GlobalValue>(Op))
continue;
-
+
if (Value *V = lookupNumber(PREPred, VN.lookup(Op))) {
PREInstr->setOperand(i, V);
} else {
break;
}
}
-
+
// Fail out if we encounter an operand that is not available in
- // the PRE predecessor. This is typically because of loads which
+ // the PRE predecessor. This is typically because of loads which
// are not value numbered precisely.
if (!success) {
delete PREInstr;
DEBUG(verifyRemoved(PREInstr));
continue;
}
-
+
PREInstr->insertBefore(PREPred->getTerminator());
PREInstr->setName(CurInst->getName() + ".pre");
predMap[PREPred] = PREInstr;
VN.add(PREInstr, valno);
NumGVNPRE++;
-
+
// Update the availability map to include the new instruction.
localAvail[PREPred]->table.insert(std::make_pair(valno, PREInstr));
-
+
// Create a PHI to make the value available in this block.
PHINode* Phi = PHINode::Create(CurInst->getType(),
CurInst->getName() + ".pre-phi",
for (pred_iterator PI = pred_begin(CurrentBlock),
PE = pred_end(CurrentBlock); PI != PE; ++PI)
Phi->addIncoming(predMap[*PI], *PI);
-
+
VN.add(Phi, valno);
localAvail[CurrentBlock]->table[valno] = Phi;
-
+
CurInst->replaceAllUsesWith(Phi);
if (isa<PointerType>(Phi->getType()))
MD->invalidateCachedPointerInfo(Phi);
VN.erase(CurInst);
-
+
DEBUG(errs() << "GVN PRE removed: " << *CurInst << '\n');
MD->removeInstruction(CurInst);
CurInst->eraseFromParent();
Changed = true;
}
}
-
+
for (SmallVector<std::pair<TerminatorInst*, unsigned>, 4>::iterator
I = toSplit.begin(), E = toSplit.end(); I != E; ++I)
SplitCriticalEdge(I->first, I->second, this);
-
+
return Changed || toSplit.size();
}
projects / oota-llvm.git / blobdiff