//===- SCCP.cpp - Sparse Conditional Constant Propagation -----------------===//
-//
+//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
+//
//===----------------------------------------------------------------------===//
//
// This file implements sparse conditional constant propagation and merging:
namespace {
class LatticeVal {
- enum {
+ enum {
undefined, // This instruction has no known value
constant, // This instruction has a constant value
overdefined // This instruction has an unknown value
private:
// markConstant - Make a value be marked as "constant". If the value
- // is not already a constant, add it to the instruction work list so that
+ // is not already a constant, add it to the instruction work list so that
// the users of the instruction are updated later.
//
inline void markConstant(LatticeVal &IV, Value *V, Constant *C) {
}
// markOverdefined - Make a value be marked as "overdefined". If the
- // value is not already overdefined, add it to the overdefined instruction
+ // value is not already overdefined, add it to the overdefined instruction
// work list so that the users of the instruction are updated later.
-
+
inline void markOverdefined(LatticeVal &IV, Value *V) {
if (IV.markOverdefined()) {
- DEBUG(std::cerr << "markOverdefined: " << *V);
+ DEBUG(std::cerr << "markOverdefined: ";
+ if (Function *F = dyn_cast<Function>(V))
+ std::cerr << "Function '" << F->getName() << "'\n";
+ else
+ std::cerr << *V);
// Only instructions go on the work list
OverdefinedInstWorkList.push_back(V);
}
return ValueState[V];
}
- // markEdgeExecutable - Mark a basic block as executable, adding it to the BB
+ // markEdgeExecutable - Mark a basic block as executable, adding it to the BB
// work list if it is not already executable...
- //
+ //
void markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) {
if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second)
return; // This edge is already known to be executable!
private:
friend class InstVisitor<SCCPSolver>;
- // visit implementations - Something changed in this instruction... Either an
+ // visit implementations - Something changed in this instruction... Either an
// operand made a transition, or the instruction is newly executable. Change
// the value type of I to reflect these changes if appropriate.
//
// Make sure the source basic block is executable!!
if (!BBExecutable.count(From)) return false;
-
+
// Check to make sure this edge itself is actually feasible now...
TerminatorInst *TI = From->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (!isa<ConstantBool>(BCValue.getConstant())) return true;
// Constant condition variables mean the branch can only go a single way
- return BI->getSuccessor(BCValue.getConstant() ==
+ return BI->getSuccessor(BCValue.getConstant() ==
ConstantBool::False) == To;
}
return false;
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
LatticeVal &IV = getValueState(PN.getIncomingValue(i));
if (IV.isUndefined()) continue; // Doesn't influence PHI node.
-
+
if (isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent())) {
if (IV.isOverdefined()) { // PHI node becomes overdefined!
markOverdefined(PNIV, &PN);
// There is already a reachable operand. If we conflict with it,
// then the PHI node becomes overdefined. If we agree with it, we
// can continue on.
-
+
// Check to see if there are two different constants merging...
if (IV.getConstant() != OperandVal) {
// Yes there is. This means the PHI node is not constant.
LatticeVal &V2State = getValueState(I.getOperand(1));
if (V1State.isOverdefined() || V2State.isOverdefined()) {
+ // If this is an AND or OR with 0 or -1, it doesn't matter that the other
+ // operand is overdefined.
+ if (I.getOpcode() == Instruction::And || I.getOpcode() == Instruction::Or) {
+ LatticeVal *NonOverdefVal = 0;
+ if (!V1State.isOverdefined()) {
+ NonOverdefVal = &V1State;
+ } else if (!V2State.isOverdefined()) {
+ NonOverdefVal = &V2State;
+ }
+
+ if (NonOverdefVal) {
+ if (NonOverdefVal->isUndefined()) {
+ // Could annihilate value.
+ if (I.getOpcode() == Instruction::And)
+ markConstant(IV, &I, Constant::getNullValue(I.getType()));
+ else
+ markConstant(IV, &I, ConstantInt::getAllOnesValue(I.getType()));
+ return;
+ } else {
+ if (I.getOpcode() == Instruction::And) {
+ if (NonOverdefVal->getConstant()->isNullValue()) {
+ markConstant(IV, &I, NonOverdefVal->getConstant());
+ return; // X or 0 = -1
+ }
+ } else {
+ if (ConstantIntegral *CI =
+ dyn_cast<ConstantIntegral>(NonOverdefVal->getConstant()))
+ if (CI->isAllOnesValue()) {
+ markConstant(IV, &I, NonOverdefVal->getConstant());
+ return; // X or -1 = -1
+ }
+ }
+ }
+ }
+ }
+
+
// If both operands are PHI nodes, it is possible that this instruction has
// a constant value, despite the fact that the PHI node doesn't. Check for
// this condition now.
Constant *Ptr = Operands[0];
Operands.erase(Operands.begin()); // Erase the pointer from idx list...
- markConstant(IV, &I, ConstantExpr::getGetElementPtr(Ptr, Operands));
+ markConstant(IV, &I, ConstantExpr::getGetElementPtr(Ptr, Operands));
}
/// GetGEPGlobalInitializer - Given a constant and a getelementptr constantexpr,
ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
if (CS == 0) return 0;
if (CU->getValue() >= CS->getNumOperands()) return 0;
- C = CS->getOperand(CU->getValue());
+ C = CS->getOperand((unsigned)CU->getValue());
} else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
ConstantArray *CA = dyn_cast<ConstantArray>(C);
if (CA == 0) return 0;
if ((uint64_t)CS->getValue() >= CA->getNumOperands()) return 0;
- C = CA->getOperand(CS->getValue());
+ C = CA->getOperand((unsigned)CS->getValue());
} else
return 0;
return C;
markConstant(IV, &I, Constant::getNullValue(I.getType()));
return;
}
-
+
// Transform load (constant global) into the value loaded.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
if (GV->isConstant()) {
// Transform load (constantexpr_GEP global, 0, ...) into the value loaded.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
if (CE->getOpcode() == Instruction::GetElementPtr)
- if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
- if (GV->isConstant() && !GV->isExternal())
- if (Constant *V =
- GetGEPGlobalInitializer(GV->getInitializer(), CE)) {
- markConstant(IV, &I, V);
- return;
- }
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
+ if (GV->isConstant() && !GV->isExternal())
+ if (Constant *V =
+ GetGEPGlobalInitializer(GV->getInitializer(), CE)) {
+ markConstant(IV, &I, V);
+ return;
+ }
}
// Otherwise we cannot say for certain what value this load will produce.
hash_map<Function*, LatticeVal>::iterator TFRVI =TrackedFunctionRetVals.end();
if (F && F->hasInternalLinkage())
TFRVI = TrackedFunctionRetVals.find(F);
-
+
if (TFRVI != TrackedFunctionRetVals.end()) {
// If this is the first call to the function hit, mark its entry block
// executable.
MarkBlockExecutable(F->begin());
CallSite::arg_iterator CAI = CS.arg_begin();
- for (Function::aiterator AI = F->abegin(), E = F->aend();
+ for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
AI != E; ++AI, ++CAI) {
LatticeVal &IV = ValueState[AI];
if (!IV.isOverdefined())
mergeInValue(IV, I, TFRVI->second);
return;
}
-
+
if (F == 0 || !F->isExternal() || !canConstantFoldCallTo(F)) {
markOverdefined(IV, I);
return;
void SCCPSolver::Solve() {
// Process the work lists until they are empty!
- while (!BBWorkList.empty() || !InstWorkList.empty() ||
- !OverdefinedInstWorkList.empty()) {
+ while (!BBWorkList.empty() || !InstWorkList.empty() ||
+ !OverdefinedInstWorkList.empty()) {
// Process the instruction work list...
while (!OverdefinedInstWorkList.empty()) {
Value *I = OverdefinedInstWorkList.back();
OverdefinedInstWorkList.pop_back();
DEBUG(std::cerr << "\nPopped off OI-WL: " << *I);
-
+
// "I" got into the work list because it either made the transition from
// bottom to constant
//
InstWorkList.pop_back();
DEBUG(std::cerr << "\nPopped off I-WL: " << *I);
-
+
// "I" got into the work list because it either made the transition from
// bottom to constant
//
UI != E; ++UI)
OperandChangedState(*UI);
}
-
+
// Process the basic block work list...
while (!BBWorkList.empty()) {
BasicBlock *BB = BBWorkList.back();
BBWorkList.pop_back();
-
+
DEBUG(std::cerr << "\nPopped off BBWL: " << *BB);
-
+
// Notify all instructions in this basic block that they are newly
// executable.
visit(BB);
/// should be rerun.
bool SCCPSolver::ResolveBranchesIn(Function &F) {
bool BranchesResolved = false;
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
- TerminatorInst *TI = BB->getTerminator();
- if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
- if (BI->isConditional()) {
- LatticeVal &BCValue = getValueState(BI->getCondition());
- if (BCValue.isUndefined()) {
- BI->setCondition(ConstantBool::True);
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+ if (BBExecutable.count(BB)) {
+ TerminatorInst *TI = BB->getTerminator();
+ if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+ if (BI->isConditional()) {
+ LatticeVal &BCValue = getValueState(BI->getCondition());
+ if (BCValue.isUndefined()) {
+ BI->setCondition(ConstantBool::True);
+ BranchesResolved = true;
+ visit(BI);
+ }
+ }
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ LatticeVal &SCValue = getValueState(SI->getCondition());
+ if (SCValue.isUndefined()) {
+ const Type *CondTy = SI->getCondition()->getType();
+ SI->setCondition(Constant::getNullValue(CondTy));
BranchesResolved = true;
- visit(BI);
+ visit(SI);
}
}
- } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
- LatticeVal &SCValue = getValueState(SI->getCondition());
- if (SCValue.isUndefined()) {
- SI->setCondition(Constant::getNullValue(SI->getCondition()->getType()));
- BranchesResolved = true;
- visit(SI);
- }
}
- }
+
return BranchesResolved;
}
// algorithm, and return true if the function was modified.
//
bool runOnFunction(Function &F);
-
+
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
}
// Mark all arguments to the function as being overdefined.
hash_map<Value*, LatticeVal> &Values = Solver.getValueMapping();
- for (Function::aiterator AI = F.abegin(), E = F.aend(); AI != E; ++AI)
+ for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E; ++AI)
Values[AI].markOverdefined();
// Solve for constants.
bool ResolvedBranches = true;
while (ResolvedBranches) {
Solver.Solve();
+ DEBUG(std::cerr << "RESOLVING UNDEF BRANCHES\n");
ResolvedBranches = Solver.ResolveBranchesIn(F);
}
Constant *Const = IV.isConstant()
? IV.getConstant() : UndefValue::get(Inst->getType());
DEBUG(std::cerr << " Constant: " << *Const << " = " << *Inst);
-
+
// Replaces all of the uses of a variable with uses of the constant.
Inst->replaceAllUsesWith(Const);
-
+
// Delete the instruction.
BB->getInstList().erase(Inst);
-
+
// Hey, we just changed something!
MadeChanges = true;
++NumInstRemoved;
static bool AddressIsTaken(GlobalValue *GV) {
+ // Delete any dead constantexpr klingons.
+ GV->removeDeadConstantUsers();
+
for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
UI != E; ++UI)
if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
if (!F->hasInternalLinkage() || AddressIsTaken(F)) {
if (!F->isExternal())
Solver.MarkBlockExecutable(F->begin());
- for (Function::aiterator AI = F->abegin(), E = F->aend(); AI != E; ++AI)
+ for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
+ AI != E; ++AI)
Values[AI].markOverdefined();
} else {
Solver.AddTrackedFunction(F);
// Loop over global variables. We inform the solver about any internal global
// variables that do not have their 'addresses taken'. If they don't have
// their addresses taken, we can propagate constants through them.
- for (Module::giterator G = M.gbegin(), E = M.gend(); G != E; ++G)
+ for (Module::global_iterator G = M.global_begin(), E = M.global_end();
+ G != E; ++G)
if (!G->isConstant() && G->hasInternalLinkage() && !AddressIsTaken(G))
Solver.TrackValueOfGlobalVariable(G);
while (ResolvedBranches) {
Solver.Solve();
+ DEBUG(std::cerr << "RESOLVING UNDEF BRANCHES\n");
ResolvedBranches = false;
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
ResolvedBranches |= Solver.ResolveBranchesIn(*F);
//
std::set<BasicBlock*> &ExecutableBBs = Solver.getExecutableBlocks();
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
- for (Function::aiterator AI = F->abegin(), E = F->aend(); AI != E; ++AI)
+ for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
+ AI != E; ++AI)
if (!AI->use_empty()) {
LatticeVal &IV = Values[AI];
if (IV.isConstant() || IV.isUndefined()) {
Constant *CST = IV.isConstant() ?
IV.getConstant() : UndefValue::get(AI->getType());
DEBUG(std::cerr << "*** Arg " << *AI << " = " << *CST <<"\n");
-
+
// Replaces all of the uses of a variable with uses of the
// constant.
AI->replaceAllUsesWith(CST);
MadeChanges = true;
++IPNumInstRemoved;
}
-
+
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
BasicBlock *Succ = TI->getSuccessor(i);
if (Succ->begin() != Succ->end() && isa<PHINode>(Succ->begin()))
Constant *Const = IV.isConstant()
? IV.getConstant() : UndefValue::get(Inst->getType());
DEBUG(std::cerr << " Constant: " << *Const << " = " << *Inst);
-
+
// Replaces all of the uses of a variable with uses of the
// constant.
Inst->replaceAllUsesWith(Const);
-
+
// Delete the instruction.
if (!isa<TerminatorInst>(Inst) && !isa<CallInst>(Inst))
BB->getInstList().erase(Inst);
bool Folded = ConstantFoldTerminator(I->getParent());
assert(Folded && "Didn't fold away reference to block!");
}
-
+
// Finally, delete the basic block.
F->getBasicBlockList().erase(DeadBB);
}
SI->eraseFromParent();
}
M.getGlobalList().erase(GV);
+ ++IPNumGlobalConst;
}
-
+
return MadeChanges;
}
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