#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Pass.h"
-#include "llvm/Support/InstVisitor.h"
+#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/CallSite.h"
+#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
-#include "llvm/ADT/hash_map"
+#include "llvm/Support/InstVisitor.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
-#include <set>
using namespace llvm;
-// LatticeVal class - This class represents the different lattice values that an
-// instruction may occupy. It is a simple class with value semantics.
-//
-namespace {
+STATISTIC(NumInstRemoved, "Number of instructions removed");
+STATISTIC(NumDeadBlocks , "Number of basic blocks unreachable");
+
+STATISTIC(IPNumInstRemoved, "Number ofinstructions removed by IPSCCP");
+STATISTIC(IPNumDeadBlocks , "Number of basic blocks unreachable by IPSCCP");
+STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP");
+STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP");
-class LatticeVal {
+namespace {
+/// LatticeVal class - This class represents the different lattice values that
+/// an LLVM value may occupy. It is a simple class with value semantics.
+///
+class VISIBILITY_HIDDEN LatticeVal {
enum {
- undefined, // This instruction has no known value
- constant, // This instruction has a constant value
- overdefined // This instruction has an unknown value
- } LatticeValue; // The current lattice position
+ /// undefined - This LLVM Value has no known value yet.
+ undefined,
+
+ /// constant - This LLVM Value has a specific constant value.
+ constant,
+
+ /// forcedconstant - This LLVM Value was thought to be undef until
+ /// ResolvedUndefsIn. This is treated just like 'constant', but if merged
+ /// with another (different) constant, it goes to overdefined, instead of
+ /// asserting.
+ forcedconstant,
+
+ /// overdefined - This instruction is not known to be constant, and we know
+ /// it has a value.
+ overdefined
+ } LatticeValue; // The current lattice position
+
Constant *ConstantVal; // If Constant value, the current value
public:
inline LatticeVal() : LatticeValue(undefined), ConstantVal(0) {}
-
+
// markOverdefined - Return true if this is a new status to be in...
inline bool markOverdefined() {
if (LatticeValue != overdefined) {
return false;
}
- // markConstant - Return true if this is a new status for us...
+ // markConstant - Return true if this is a new status for us.
inline bool markConstant(Constant *V) {
if (LatticeValue != constant) {
- LatticeValue = constant;
- ConstantVal = V;
+ if (LatticeValue == undefined) {
+ LatticeValue = constant;
+ assert(V && "Marking constant with NULL");
+ ConstantVal = V;
+ } else {
+ assert(LatticeValue == forcedconstant &&
+ "Cannot move from overdefined to constant!");
+ // Stay at forcedconstant if the constant is the same.
+ if (V == ConstantVal) return false;
+
+ // Otherwise, we go to overdefined. Assumptions made based on the
+ // forced value are possibly wrong. Assuming this is another constant
+ // could expose a contradiction.
+ LatticeValue = overdefined;
+ }
return true;
} else {
assert(ConstantVal == V && "Marking constant with different value");
return false;
}
- inline bool isUndefined() const { return LatticeValue == undefined; }
- inline bool isConstant() const { return LatticeValue == constant; }
+ inline void markForcedConstant(Constant *V) {
+ assert(LatticeValue == undefined && "Can't force a defined value!");
+ LatticeValue = forcedconstant;
+ ConstantVal = V;
+ }
+
+ inline bool isUndefined() const { return LatticeValue == undefined; }
+ inline bool isConstant() const {
+ return LatticeValue == constant || LatticeValue == forcedconstant;
+ }
inline bool isOverdefined() const { return LatticeValue == overdefined; }
inline Constant *getConstant() const {
}
};
-} // end anonymous namespace
-
-
//===----------------------------------------------------------------------===//
//
/// SCCPSolver - This class is a general purpose solver for Sparse Conditional
/// Constant Propagation.
///
class SCCPSolver : public InstVisitor<SCCPSolver> {
- std::set<BasicBlock*> BBExecutable;// The basic blocks that are executable
- hash_map<Value*, LatticeVal> ValueState; // The state each value is in...
+ SmallSet<BasicBlock*, 16> BBExecutable;// The basic blocks that are executable
+ std::map<Value*, LatticeVal> ValueState; // The state each value is in.
/// GlobalValue - If we are tracking any values for the contents of a global
/// variable, we keep a mapping from the constant accessor to the element of
/// the global, to the currently known value. If the value becomes
/// overdefined, it's entry is simply removed from this map.
- hash_map<GlobalVariable*, LatticeVal> TrackedGlobals;
+ DenseMap<GlobalVariable*, LatticeVal> TrackedGlobals;
/// TrackedFunctionRetVals - If we are tracking arguments into and the return
/// value out of a function, it will have an entry in this map, indicating
/// what the known return value for the function is.
- hash_map<Function*, LatticeVal> TrackedFunctionRetVals;
+ DenseMap<Function*, LatticeVal> TrackedFunctionRetVals;
// The reason for two worklists is that overdefined is the lowest state
// on the lattice, and moving things to overdefined as fast as possible
/// MarkBlockExecutable - This method can be used by clients to mark all of
/// the blocks that are known to be intrinsically live in the processed unit.
void MarkBlockExecutable(BasicBlock *BB) {
- DEBUG(std::cerr << "Marking Block Executable: " << BB->getName() << "\n");
+ DOUT << "Marking Block Executable: " << BB->getName() << "\n";
BBExecutable.insert(BB); // Basic block is executable!
BBWorkList.push_back(BB); // Add the block to the work list!
}
///
void Solve();
- /// ResolveBranchesIn - While solving the dataflow for a function, we assume
+ /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
/// that branches on undef values cannot reach any of their successors.
/// However, this is not a safe assumption. After we solve dataflow, this
/// method should be use to handle this. If this returns true, the solver
/// should be rerun.
- bool ResolveBranchesIn(Function &F);
+ bool ResolvedUndefsIn(Function &F);
/// getExecutableBlocks - Once we have solved for constants, return the set of
/// blocks that is known to be executable.
- std::set<BasicBlock*> &getExecutableBlocks() {
+ SmallSet<BasicBlock*, 16> &getExecutableBlocks() {
return BBExecutable;
}
/// getValueMapping - Once we have solved for constants, return the mapping of
/// LLVM values to LatticeVals.
- hash_map<Value*, LatticeVal> &getValueMapping() {
+ std::map<Value*, LatticeVal> &getValueMapping() {
return ValueState;
}
/// getTrackedFunctionRetVals - Get the inferred return value map.
///
- const hash_map<Function*, LatticeVal> &getTrackedFunctionRetVals() {
+ const DenseMap<Function*, LatticeVal> &getTrackedFunctionRetVals() {
return TrackedFunctionRetVals;
}
/// getTrackedGlobals - Get and return the set of inferred initializers for
/// global variables.
- const hash_map<GlobalVariable*, LatticeVal> &getTrackedGlobals() {
+ const DenseMap<GlobalVariable*, LatticeVal> &getTrackedGlobals() {
return TrackedGlobals;
}
+ inline void markOverdefined(Value *V) {
+ markOverdefined(ValueState[V], V);
+ }
private:
// markConstant - Make a value be marked as "constant". If the value
//
inline void markConstant(LatticeVal &IV, Value *V, Constant *C) {
if (IV.markConstant(C)) {
- DEBUG(std::cerr << "markConstant: " << *C << ": " << *V);
+ DOUT << "markConstant: " << *C << ": " << *V;
InstWorkList.push_back(V);
}
}
+
+ inline void markForcedConstant(LatticeVal &IV, Value *V, Constant *C) {
+ IV.markForcedConstant(C);
+ DOUT << "markForcedConstant: " << *C << ": " << *V;
+ InstWorkList.push_back(V);
+ }
+
inline void markConstant(Value *V, Constant *C) {
markConstant(ValueState[V], V, C);
}
inline void markOverdefined(LatticeVal &IV, Value *V) {
if (IV.markOverdefined()) {
- DEBUG(std::cerr << "markOverdefined: ";
+ DEBUG(DOUT << "markOverdefined: ";
if (Function *F = dyn_cast<Function>(V))
- std::cerr << "Function '" << F->getName() << "'\n";
+ DOUT << "Function '" << F->getName() << "'\n";
else
- std::cerr << *V);
+ DOUT << *V);
// Only instructions go on the work list
OverdefinedInstWorkList.push_back(V);
}
}
- inline void markOverdefined(Value *V) {
- markOverdefined(ValueState[V], V);
- }
inline void mergeInValue(LatticeVal &IV, Value *V, LatticeVal &MergeWithV) {
if (IV.isOverdefined() || MergeWithV.isUndefined())
else if (IV.getConstant() != MergeWithV.getConstant())
markOverdefined(IV, V);
}
+
+ inline void mergeInValue(Value *V, LatticeVal &MergeWithV) {
+ return mergeInValue(ValueState[V], V, MergeWithV);
+ }
+
// getValueState - Return the LatticeVal object that corresponds to the value.
// This function is necessary because not all values should start out in the
// Instruction object, then use this accessor to get its value from the map.
//
inline LatticeVal &getValueState(Value *V) {
- hash_map<Value*, LatticeVal>::iterator I = ValueState.find(V);
+ std::map<Value*, LatticeVal>::iterator I = ValueState.find(V);
if (I != ValueState.end()) return I->second; // Common case, in the map
- if (Constant *CPV = dyn_cast<Constant>(V)) {
+ if (Constant *C = dyn_cast<Constant>(V)) {
if (isa<UndefValue>(V)) {
// Nothing to do, remain undefined.
} else {
- ValueState[CPV].markConstant(CPV); // Constants are constant
+ LatticeVal &LV = ValueState[C];
+ LV.markConstant(C); // Constants are constant
+ return LV;
}
}
// All others are underdefined by default...
return; // This edge is already known to be executable!
if (BBExecutable.count(Dest)) {
- DEBUG(std::cerr << "Marking Edge Executable: " << Source->getName()
- << " -> " << Dest->getName() << "\n");
+ DOUT << "Marking Edge Executable: " << Source->getName()
+ << " -> " << Dest->getName() << "\n";
// The destination is already executable, but we just made an edge
// feasible that wasn't before. Revisit the PHI nodes in the block
// getFeasibleSuccessors - Return a vector of booleans to indicate which
// successors are reachable from a given terminator instruction.
//
- void getFeasibleSuccessors(TerminatorInst &TI, std::vector<bool> &Succs);
+ void getFeasibleSuccessors(TerminatorInst &TI, SmallVector<bool, 16> &Succs);
// isEdgeFeasible - Return true if the control flow edge from the 'From' basic
// block to the 'To' basic block is currently feasible...
void visitCastInst(CastInst &I);
void visitSelectInst(SelectInst &I);
void visitBinaryOperator(Instruction &I);
- void visitShiftInst(ShiftInst &I) { visitBinaryOperator(I); }
+ void visitCmpInst(CmpInst &I);
+ void visitExtractElementInst(ExtractElementInst &I);
+ void visitInsertElementInst(InsertElementInst &I);
+ void visitShuffleVectorInst(ShuffleVectorInst &I);
// Instructions that cannot be folded away...
void visitStoreInst (Instruction &I);
void visitInstruction(Instruction &I) {
// If a new instruction is added to LLVM that we don't handle...
- std::cerr << "SCCP: Don't know how to handle: " << I;
+ cerr << "SCCP: Don't know how to handle: " << I;
markOverdefined(&I); // Just in case
}
};
+} // end anonymous namespace
+
+
// getFeasibleSuccessors - Return a vector of booleans to indicate which
// successors are reachable from a given terminator instruction.
//
void SCCPSolver::getFeasibleSuccessors(TerminatorInst &TI,
- std::vector<bool> &Succs) {
+ SmallVector<bool, 16> &Succs) {
Succs.resize(TI.getNumSuccessors());
if (BranchInst *BI = dyn_cast<BranchInst>(&TI)) {
if (BI->isUnconditional()) {
} else {
LatticeVal &BCValue = getValueState(BI->getCondition());
if (BCValue.isOverdefined() ||
- (BCValue.isConstant() && !isa<ConstantBool>(BCValue.getConstant()))) {
+ (BCValue.isConstant() && !isa<ConstantInt>(BCValue.getConstant()))) {
// Overdefined condition variables, and branches on unfoldable constant
// conditions, mean the branch could go either way.
Succs[0] = Succs[1] = true;
} else if (BCValue.isConstant()) {
// Constant condition variables mean the branch can only go a single way
- Succs[BCValue.getConstant() == ConstantBool::False] = true;
+ Succs[BCValue.getConstant() == ConstantInt::getFalse()] = true;
}
}
- } else if (InvokeInst *II = dyn_cast<InvokeInst>(&TI)) {
+ } else if (isa<InvokeInst>(&TI)) {
// Invoke instructions successors are always executable.
Succs[0] = Succs[1] = true;
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(&TI)) {
Succs[0] = true;
}
} else {
- std::cerr << "SCCP: Don't know how to handle: " << TI;
- Succs.assign(TI.getNumSuccessors(), true);
+ assert(0 && "SCCP: Don't know how to handle this terminator!");
}
}
return true;
} else if (BCValue.isConstant()) {
// Not branching on an evaluatable constant?
- if (!isa<ConstantBool>(BCValue.getConstant())) return true;
+ if (!isa<ConstantInt>(BCValue.getConstant())) return true;
// Constant condition variables mean the branch can only go a single way
return BI->getSuccessor(BCValue.getConstant() ==
- ConstantBool::False) == To;
+ ConstantInt::getFalse()) == To;
}
return false;
}
- } else if (InvokeInst *II = dyn_cast<InvokeInst>(TI)) {
+ } else if (isa<InvokeInst>(TI)) {
// Invoke instructions successors are always executable.
return true;
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
}
return false;
} else {
- std::cerr << "Unknown terminator instruction: " << *TI;
+ cerr << "Unknown terminator instruction: " << *TI;
abort();
}
}
std::multimap<PHINode*, Instruction*>::iterator I, E;
tie(I, E) = UsersOfOverdefinedPHIs.equal_range(&PN);
if (I != E) {
- std::vector<Instruction*> Users;
- Users.reserve(std::distance(I, E));
+ SmallVector<Instruction*, 16> Users;
for (; I != E; ++I) Users.push_back(I->second);
while (!Users.empty()) {
visit(Users.back());
// If we are tracking the return value of this function, merge it in.
Function *F = I.getParent()->getParent();
if (F->hasInternalLinkage() && !TrackedFunctionRetVals.empty()) {
- hash_map<Function*, LatticeVal>::iterator TFRVI =
+ DenseMap<Function*, LatticeVal>::iterator TFRVI =
TrackedFunctionRetVals.find(F);
if (TFRVI != TrackedFunctionRetVals.end() &&
!TFRVI->second.isOverdefined()) {
void SCCPSolver::visitTerminatorInst(TerminatorInst &TI) {
- std::vector<bool> SuccFeasible;
+ SmallVector<bool, 16> SuccFeasible;
getFeasibleSuccessors(TI, SuccFeasible);
BasicBlock *BB = TI.getParent();
if (VState.isOverdefined()) // Inherit overdefinedness of operand
markOverdefined(&I);
else if (VState.isConstant()) // Propagate constant value
- markConstant(&I, ConstantExpr::getCast(VState.getConstant(), I.getType()));
+ markConstant(&I, ConstantExpr::getCast(I.getOpcode(),
+ VState.getConstant(), I.getType()));
}
void SCCPSolver::visitSelectInst(SelectInst &I) {
LatticeVal &CondValue = getValueState(I.getCondition());
- if (CondValue.isOverdefined())
+ if (CondValue.isUndefined())
+ return;
+ if (CondValue.isConstant()) {
+ if (ConstantInt *CondCB = dyn_cast<ConstantInt>(CondValue.getConstant())){
+ mergeInValue(&I, getValueState(CondCB->getZExtValue() ? I.getTrueValue()
+ : I.getFalseValue()));
+ return;
+ }
+ }
+
+ // Otherwise, the condition is overdefined or a constant we can't evaluate.
+ // See if we can produce something better than overdefined based on the T/F
+ // value.
+ LatticeVal &TVal = getValueState(I.getTrueValue());
+ LatticeVal &FVal = getValueState(I.getFalseValue());
+
+ // select ?, C, C -> C.
+ if (TVal.isConstant() && FVal.isConstant() &&
+ TVal.getConstant() == FVal.getConstant()) {
+ markConstant(&I, FVal.getConstant());
+ return;
+ }
+
+ if (TVal.isUndefined()) { // select ?, undef, X -> X.
+ mergeInValue(&I, FVal);
+ } else if (FVal.isUndefined()) { // select ?, X, undef -> X.
+ mergeInValue(&I, TVal);
+ } else {
markOverdefined(&I);
- else if (CondValue.isConstant()) {
- if (CondValue.getConstant() == ConstantBool::True) {
- LatticeVal &Val = getValueState(I.getTrueValue());
- if (Val.isOverdefined())
- markOverdefined(&I);
- else if (Val.isConstant())
- markConstant(&I, Val.getConstant());
- } else if (CondValue.getConstant() == ConstantBool::False) {
- LatticeVal &Val = getValueState(I.getFalseValue());
- if (Val.isOverdefined())
- markOverdefined(&I);
- else if (Val.isConstant())
- markConstant(&I, Val.getConstant());
- } else
- markOverdefined(&I);
}
}
// Could annihilate value.
if (I.getOpcode() == Instruction::And)
markConstant(IV, &I, Constant::getNullValue(I.getType()));
+ else if (const VectorType *PT = dyn_cast<VectorType>(I.getType()))
+ markConstant(IV, &I, ConstantVector::getAllOnesValue(PT));
else
markConstant(IV, &I, ConstantInt::getAllOnesValue(I.getType()));
return;
if (I.getOpcode() == Instruction::And) {
if (NonOverdefVal->getConstant()->isNullValue()) {
markConstant(IV, &I, NonOverdefVal->getConstant());
- return; // X or 0 = -1
+ return; // X and 0 = 0
}
} else {
- if (ConstantIntegral *CI =
- dyn_cast<ConstantIntegral>(NonOverdefVal->getConstant()))
+ if (ConstantInt *CI =
+ dyn_cast<ConstantInt>(NonOverdefVal->getConstant()))
if (CI->isAllOnesValue()) {
markConstant(IV, &I, NonOverdefVal->getConstant());
return; // X or -1 = -1
}
}
+// Handle ICmpInst instruction...
+void SCCPSolver::visitCmpInst(CmpInst &I) {
+ LatticeVal &IV = ValueState[&I];
+ if (IV.isOverdefined()) return;
+
+ LatticeVal &V1State = getValueState(I.getOperand(0));
+ LatticeVal &V2State = getValueState(I.getOperand(1));
+
+ if (V1State.isOverdefined() || V2State.isOverdefined()) {
+ // 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.
+ if (PHINode *PN1 = dyn_cast<PHINode>(I.getOperand(0)))
+ if (PHINode *PN2 = dyn_cast<PHINode>(I.getOperand(1)))
+ if (PN1->getParent() == PN2->getParent()) {
+ // Since the two PHI nodes are in the same basic block, they must have
+ // entries for the same predecessors. Walk the predecessor list, and
+ // if all of the incoming values are constants, and the result of
+ // evaluating this expression with all incoming value pairs is the
+ // same, then this expression is a constant even though the PHI node
+ // is not a constant!
+ LatticeVal Result;
+ for (unsigned i = 0, e = PN1->getNumIncomingValues(); i != e; ++i) {
+ LatticeVal &In1 = getValueState(PN1->getIncomingValue(i));
+ BasicBlock *InBlock = PN1->getIncomingBlock(i);
+ LatticeVal &In2 =
+ getValueState(PN2->getIncomingValueForBlock(InBlock));
+
+ if (In1.isOverdefined() || In2.isOverdefined()) {
+ Result.markOverdefined();
+ break; // Cannot fold this operation over the PHI nodes!
+ } else if (In1.isConstant() && In2.isConstant()) {
+ Constant *V = ConstantExpr::getCompare(I.getPredicate(),
+ In1.getConstant(),
+ In2.getConstant());
+ if (Result.isUndefined())
+ Result.markConstant(V);
+ else if (Result.isConstant() && Result.getConstant() != V) {
+ Result.markOverdefined();
+ break;
+ }
+ }
+ }
+
+ // If we found a constant value here, then we know the instruction is
+ // constant despite the fact that the PHI nodes are overdefined.
+ if (Result.isConstant()) {
+ markConstant(IV, &I, Result.getConstant());
+ // Remember that this instruction is virtually using the PHI node
+ // operands.
+ UsersOfOverdefinedPHIs.insert(std::make_pair(PN1, &I));
+ UsersOfOverdefinedPHIs.insert(std::make_pair(PN2, &I));
+ return;
+ } else if (Result.isUndefined()) {
+ return;
+ }
+
+ // Okay, this really is overdefined now. Since we might have
+ // speculatively thought that this was not overdefined before, and
+ // added ourselves to the UsersOfOverdefinedPHIs list for the PHIs,
+ // make sure to clean out any entries that we put there, for
+ // efficiency.
+ std::multimap<PHINode*, Instruction*>::iterator It, E;
+ tie(It, E) = UsersOfOverdefinedPHIs.equal_range(PN1);
+ while (It != E) {
+ if (It->second == &I) {
+ UsersOfOverdefinedPHIs.erase(It++);
+ } else
+ ++It;
+ }
+ tie(It, E) = UsersOfOverdefinedPHIs.equal_range(PN2);
+ while (It != E) {
+ if (It->second == &I) {
+ UsersOfOverdefinedPHIs.erase(It++);
+ } else
+ ++It;
+ }
+ }
+
+ markOverdefined(IV, &I);
+ } else if (V1State.isConstant() && V2State.isConstant()) {
+ markConstant(IV, &I, ConstantExpr::getCompare(I.getPredicate(),
+ V1State.getConstant(),
+ V2State.getConstant()));
+ }
+}
+
+void SCCPSolver::visitExtractElementInst(ExtractElementInst &I) {
+ // FIXME : SCCP does not handle vectors properly.
+ markOverdefined(&I);
+ return;
+
+#if 0
+ LatticeVal &ValState = getValueState(I.getOperand(0));
+ LatticeVal &IdxState = getValueState(I.getOperand(1));
+
+ if (ValState.isOverdefined() || IdxState.isOverdefined())
+ markOverdefined(&I);
+ else if(ValState.isConstant() && IdxState.isConstant())
+ markConstant(&I, ConstantExpr::getExtractElement(ValState.getConstant(),
+ IdxState.getConstant()));
+#endif
+}
+
+void SCCPSolver::visitInsertElementInst(InsertElementInst &I) {
+ // FIXME : SCCP does not handle vectors properly.
+ markOverdefined(&I);
+ return;
+#if 0
+ LatticeVal &ValState = getValueState(I.getOperand(0));
+ LatticeVal &EltState = getValueState(I.getOperand(1));
+ LatticeVal &IdxState = getValueState(I.getOperand(2));
+
+ if (ValState.isOverdefined() || EltState.isOverdefined() ||
+ IdxState.isOverdefined())
+ markOverdefined(&I);
+ else if(ValState.isConstant() && EltState.isConstant() &&
+ IdxState.isConstant())
+ markConstant(&I, ConstantExpr::getInsertElement(ValState.getConstant(),
+ EltState.getConstant(),
+ IdxState.getConstant()));
+ else if (ValState.isUndefined() && EltState.isConstant() &&
+ IdxState.isConstant())
+ markConstant(&I,ConstantExpr::getInsertElement(UndefValue::get(I.getType()),
+ EltState.getConstant(),
+ IdxState.getConstant()));
+#endif
+}
+
+void SCCPSolver::visitShuffleVectorInst(ShuffleVectorInst &I) {
+ // FIXME : SCCP does not handle vectors properly.
+ markOverdefined(&I);
+ return;
+#if 0
+ LatticeVal &V1State = getValueState(I.getOperand(0));
+ LatticeVal &V2State = getValueState(I.getOperand(1));
+ LatticeVal &MaskState = getValueState(I.getOperand(2));
+
+ if (MaskState.isUndefined() ||
+ (V1State.isUndefined() && V2State.isUndefined()))
+ return; // Undefined output if mask or both inputs undefined.
+
+ if (V1State.isOverdefined() || V2State.isOverdefined() ||
+ MaskState.isOverdefined()) {
+ markOverdefined(&I);
+ } else {
+ // A mix of constant/undef inputs.
+ Constant *V1 = V1State.isConstant() ?
+ V1State.getConstant() : UndefValue::get(I.getType());
+ Constant *V2 = V2State.isConstant() ?
+ V2State.getConstant() : UndefValue::get(I.getType());
+ Constant *Mask = MaskState.isConstant() ?
+ MaskState.getConstant() : UndefValue::get(I.getOperand(2)->getType());
+ markConstant(&I, ConstantExpr::getShuffleVector(V1, V2, Mask));
+ }
+#endif
+}
+
// Handle getelementptr instructions... if all operands are constants then we
// can turn this into a getelementptr ConstantExpr.
//
LatticeVal &IV = ValueState[&I];
if (IV.isOverdefined()) return;
- std::vector<Constant*> Operands;
+ SmallVector<Constant*, 8> Operands;
Operands.reserve(I.getNumOperands());
for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
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[0],
+ Operands.size()));
}
void SCCPSolver::visitStoreInst(Instruction &SI) {
if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
return;
GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1));
- hash_map<GlobalVariable*, LatticeVal>::iterator I = TrackedGlobals.find(GV);
+ DenseMap<GlobalVariable*, LatticeVal>::iterator I = TrackedGlobals.find(GV);
if (I == TrackedGlobals.end() || I->second.isOverdefined()) return;
// Get the value we are storing into the global.
if (PtrVal.isUndefined()) return; // The pointer is not resolved yet!
if (PtrVal.isConstant() && !I.isVolatile()) {
Value *Ptr = PtrVal.getConstant();
- if (isa<ConstantPointerNull>(Ptr)) {
+ // TODO: Consider a target hook for valid address spaces for this xform.
+ if (isa<ConstantPointerNull>(Ptr) &&
+ cast<PointerType>(Ptr->getType())->getAddressSpace() == 0) {
// load null -> null
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()) {
- if (!GV->isExternal()) {
+ if (!GV->isDeclaration()) {
markConstant(IV, &I, GV->getInitializer());
return;
}
} else if (!TrackedGlobals.empty()) {
// If we are tracking this global, merge in the known value for it.
- hash_map<GlobalVariable*, LatticeVal>::iterator It =
+ DenseMap<GlobalVariable*, LatticeVal>::iterator It =
TrackedGlobals.find(GV);
if (It != TrackedGlobals.end()) {
mergeInValue(IV, &I, It->second);
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 (GV->isConstant() && !GV->isDeclaration())
if (Constant *V =
ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE)) {
markConstant(IV, &I, V);
// If we are tracking this function, we must make sure to bind arguments as
// appropriate.
- hash_map<Function*, LatticeVal>::iterator TFRVI =TrackedFunctionRetVals.end();
+ DenseMap<Function*, LatticeVal>::iterator TFRVI =TrackedFunctionRetVals.end();
if (F && F->hasInternalLinkage())
TFRVI = TrackedFunctionRetVals.find(F);
return;
}
- if (F == 0 || !F->isExternal() || !canConstantFoldCallTo(F)) {
+ if (F == 0 || !F->isDeclaration() || !canConstantFoldCallTo(F)) {
markOverdefined(IV, I);
return;
}
- std::vector<Constant*> Operands;
+ SmallVector<Constant*, 8> Operands;
Operands.reserve(I->getNumOperands()-1);
for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
Operands.push_back(State.getConstant());
}
- if (Constant *C = ConstantFoldCall(F, Operands))
+ if (Constant *C = ConstantFoldCall(F, &Operands[0], Operands.size()))
markConstant(IV, I, C);
else
markOverdefined(IV, I);
Value *I = OverdefinedInstWorkList.back();
OverdefinedInstWorkList.pop_back();
- DEBUG(std::cerr << "\nPopped off OI-WL: " << *I);
+ DOUT << "\nPopped off OI-WL: " << *I;
// "I" got into the work list because it either made the transition from
// bottom to constant
Value *I = InstWorkList.back();
InstWorkList.pop_back();
- DEBUG(std::cerr << "\nPopped off I-WL: " << *I);
+ DOUT << "\nPopped off I-WL: " << *I;
// "I" got into the work list because it either made the transition from
// bottom to constant
BasicBlock *BB = BBWorkList.back();
BBWorkList.pop_back();
- DEBUG(std::cerr << "\nPopped off BBWL: " << *BB);
+ DOUT << "\nPopped off BBWL: " << *BB;
// Notify all instructions in this basic block that they are newly
// executable.
}
}
-/// ResolveBranchesIn - While solving the dataflow for a function, we assume
+/// ResolvedUndefsIn - While solving the dataflow for a function, we assume
/// that branches on undef values cannot reach any of their successors.
/// However, this is not a safe assumption. After we solve dataflow, this
/// method should be use to handle this. If this returns true, the solver
/// should be rerun.
-bool SCCPSolver::ResolveBranchesIn(Function &F) {
- bool BranchesResolved = false;
- 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(SI);
+///
+/// This method handles this by finding an unresolved branch and marking it one
+/// of the edges from the block as being feasible, even though the condition
+/// doesn't say it would otherwise be. This allows SCCP to find the rest of the
+/// CFG and only slightly pessimizes the analysis results (by marking one,
+/// potentially infeasible, edge feasible). This cannot usefully modify the
+/// constraints on the condition of the branch, as that would impact other users
+/// of the value.
+///
+/// This scan also checks for values that use undefs, whose results are actually
+/// defined. For example, 'zext i8 undef to i32' should produce all zeros
+/// conservatively, as "(zext i8 X -> i32) & 0xFF00" must always return zero,
+/// even if X isn't defined.
+bool SCCPSolver::ResolvedUndefsIn(Function &F) {
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
+ if (!BBExecutable.count(BB))
+ continue;
+
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ // Look for instructions which produce undef values.
+ if (I->getType() == Type::VoidTy) continue;
+
+ LatticeVal &LV = getValueState(I);
+ if (!LV.isUndefined()) continue;
+
+ // Get the lattice values of the first two operands for use below.
+ LatticeVal &Op0LV = getValueState(I->getOperand(0));
+ LatticeVal Op1LV;
+ if (I->getNumOperands() == 2) {
+ // If this is a two-operand instruction, and if both operands are
+ // undefs, the result stays undef.
+ Op1LV = getValueState(I->getOperand(1));
+ if (Op0LV.isUndefined() && Op1LV.isUndefined())
+ continue;
+ }
+
+ // If this is an instructions whose result is defined even if the input is
+ // not fully defined, propagate the information.
+ const Type *ITy = I->getType();
+ switch (I->getOpcode()) {
+ default: break; // Leave the instruction as an undef.
+ case Instruction::ZExt:
+ // After a zero extend, we know the top part is zero. SExt doesn't have
+ // to be handled here, because we don't know whether the top part is 1's
+ // or 0's.
+ assert(Op0LV.isUndefined());
+ markForcedConstant(LV, I, Constant::getNullValue(ITy));
+ return true;
+ case Instruction::Mul:
+ case Instruction::And:
+ // undef * X -> 0. X could be zero.
+ // undef & X -> 0. X could be zero.
+ markForcedConstant(LV, I, Constant::getNullValue(ITy));
+ return true;
+
+ case Instruction::Or:
+ // undef | X -> -1. X could be -1.
+ if (const VectorType *PTy = dyn_cast<VectorType>(ITy))
+ markForcedConstant(LV, I, ConstantVector::getAllOnesValue(PTy));
+ else
+ markForcedConstant(LV, I, ConstantInt::getAllOnesValue(ITy));
+ return true;
+
+ case Instruction::SDiv:
+ case Instruction::UDiv:
+ case Instruction::SRem:
+ case Instruction::URem:
+ // X / undef -> undef. No change.
+ // X % undef -> undef. No change.
+ if (Op1LV.isUndefined()) break;
+
+ // undef / X -> 0. X could be maxint.
+ // undef % X -> 0. X could be 1.
+ markForcedConstant(LV, I, Constant::getNullValue(ITy));
+ return true;
+
+ case Instruction::AShr:
+ // undef >>s X -> undef. No change.
+ if (Op0LV.isUndefined()) break;
+
+ // X >>s undef -> X. X could be 0, X could have the high-bit known set.
+ if (Op0LV.isConstant())
+ markForcedConstant(LV, I, Op0LV.getConstant());
+ else
+ markOverdefined(LV, I);
+ return true;
+ case Instruction::LShr:
+ case Instruction::Shl:
+ // undef >> X -> undef. No change.
+ // undef << X -> undef. No change.
+ if (Op0LV.isUndefined()) break;
+
+ // X >> undef -> 0. X could be 0.
+ // X << undef -> 0. X could be 0.
+ markForcedConstant(LV, I, Constant::getNullValue(ITy));
+ return true;
+ case Instruction::Select:
+ // undef ? X : Y -> X or Y. There could be commonality between X/Y.
+ if (Op0LV.isUndefined()) {
+ if (!Op1LV.isConstant()) // Pick the constant one if there is any.
+ Op1LV = getValueState(I->getOperand(2));
+ } else if (Op1LV.isUndefined()) {
+ // c ? undef : undef -> undef. No change.
+ Op1LV = getValueState(I->getOperand(2));
+ if (Op1LV.isUndefined())
+ break;
+ // Otherwise, c ? undef : x -> x.
+ } else {
+ // Leave Op1LV as Operand(1)'s LatticeValue.
}
+
+ if (Op1LV.isConstant())
+ markForcedConstant(LV, I, Op1LV.getConstant());
+ else
+ markOverdefined(LV, I);
+ return true;
}
}
+
+ TerminatorInst *TI = BB->getTerminator();
+ if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+ if (!BI->isConditional()) continue;
+ if (!getValueState(BI->getCondition()).isUndefined())
+ continue;
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ if (!getValueState(SI->getCondition()).isUndefined())
+ continue;
+ } else {
+ continue;
+ }
+
+ // If the edge to the first successor isn't thought to be feasible yet, mark
+ // it so now.
+ if (KnownFeasibleEdges.count(Edge(BB, TI->getSuccessor(0))))
+ continue;
+
+ // Otherwise, it isn't already thought to be feasible. Mark it as such now
+ // and return. This will make other blocks reachable, which will allow new
+ // values to be discovered and existing ones to be moved in the lattice.
+ markEdgeExecutable(BB, TI->getSuccessor(0));
+ return true;
+ }
- return BranchesResolved;
+ return false;
}
namespace {
- Statistic<> NumInstRemoved("sccp", "Number of instructions removed");
- Statistic<> NumDeadBlocks ("sccp", "Number of basic blocks unreachable");
-
//===--------------------------------------------------------------------===//
//
/// SCCP Class - This class uses the SCCPSolver to implement a per-function
- /// Sparse Conditional COnstant Propagator.
+ /// Sparse Conditional Constant Propagator.
///
- struct SCCP : public FunctionPass {
+ struct VISIBILITY_HIDDEN SCCP : public FunctionPass {
+ static char ID; // Pass identification, replacement for typeid
+ SCCP() : FunctionPass((intptr_t)&ID) {}
+
// runOnFunction - Run the Sparse Conditional Constant Propagation
// algorithm, and return true if the function was modified.
//
}
};
- RegisterOpt<SCCP> X("sccp", "Sparse Conditional Constant Propagation");
+ char SCCP::ID = 0;
+ RegisterPass<SCCP> X("sccp", "Sparse Conditional Constant Propagation");
} // end anonymous namespace
// and return true if the function was modified.
//
bool SCCP::runOnFunction(Function &F) {
- DEBUG(std::cerr << "SCCP on function '" << F.getName() << "'\n");
+ DOUT << "SCCP on function '" << F.getName() << "'\n";
SCCPSolver Solver;
// Mark the first block of the function as being executable.
Solver.MarkBlockExecutable(F.begin());
// Mark all arguments to the function as being overdefined.
- hash_map<Value*, LatticeVal> &Values = Solver.getValueMapping();
- for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E; ++AI)
- Values[AI].markOverdefined();
+ for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;++AI)
+ Solver.markOverdefined(AI);
// Solve for constants.
- bool ResolvedBranches = true;
- while (ResolvedBranches) {
+ bool ResolvedUndefs = true;
+ while (ResolvedUndefs) {
Solver.Solve();
- DEBUG(std::cerr << "RESOLVING UNDEF BRANCHES\n");
- ResolvedBranches = Solver.ResolveBranchesIn(F);
+ DOUT << "RESOLVING UNDEFs\n";
+ ResolvedUndefs = Solver.ResolvedUndefsIn(F);
}
bool MadeChanges = false;
// delete their contents now. Note that we cannot actually delete the blocks,
// as we cannot modify the CFG of the function.
//
- std::set<BasicBlock*> &ExecutableBBs = Solver.getExecutableBlocks();
+ SmallSet<BasicBlock*, 16> &ExecutableBBs = Solver.getExecutableBlocks();
+ SmallVector<Instruction*, 32> Insts;
+ std::map<Value*, LatticeVal> &Values = Solver.getValueMapping();
+
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (!ExecutableBBs.count(BB)) {
- DEBUG(std::cerr << " BasicBlock Dead:" << *BB);
+ DOUT << " BasicBlock Dead:" << *BB;
++NumDeadBlocks;
// Delete the instructions backwards, as it has a reduced likelihood of
// having to update as many def-use and use-def chains.
- std::vector<Instruction*> Insts;
for (BasicBlock::iterator I = BB->begin(), E = BB->getTerminator();
I != E; ++I)
Insts.push_back(I);
Instruction *Inst = BI++;
if (Inst->getType() != Type::VoidTy) {
LatticeVal &IV = Values[Inst];
- if (IV.isConstant() || IV.isUndefined() &&
+ if ((IV.isConstant() || IV.isUndefined()) &&
!isa<TerminatorInst>(Inst)) {
Constant *Const = IV.isConstant()
? IV.getConstant() : UndefValue::get(Inst->getType());
- DEBUG(std::cerr << " Constant: " << *Const << " = " << *Inst);
+ DOUT << " Constant: " << *Const << " = " << *Inst;
// Replaces all of the uses of a variable with uses of the constant.
Inst->replaceAllUsesWith(Const);
}
namespace {
- Statistic<> IPNumInstRemoved("ipsccp", "Number of instructions removed");
- Statistic<> IPNumDeadBlocks ("ipsccp", "Number of basic blocks unreachable");
- Statistic<> IPNumArgsElimed ("ipsccp",
- "Number of arguments constant propagated");
- Statistic<> IPNumGlobalConst("ipsccp",
- "Number of globals found to be constant");
-
//===--------------------------------------------------------------------===//
//
/// IPSCCP Class - This class implements interprocedural Sparse Conditional
/// Constant Propagation.
///
- struct IPSCCP : public ModulePass {
+ struct VISIBILITY_HIDDEN IPSCCP : public ModulePass {
+ static char ID;
+ IPSCCP() : ModulePass((intptr_t)&ID) {}
bool runOnModule(Module &M);
};
- RegisterOpt<IPSCCP>
+ char IPSCCP::ID = 0;
+ RegisterPass<IPSCCP>
Y("ipsccp", "Interprocedural Sparse Conditional Constant Propagation");
} // end anonymous namespace
// Loop over all functions, marking arguments to those with their addresses
// taken or that are external as overdefined.
//
- hash_map<Value*, LatticeVal> &Values = Solver.getValueMapping();
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
if (!F->hasInternalLinkage() || AddressIsTaken(F)) {
- if (!F->isExternal())
+ if (!F->isDeclaration())
Solver.MarkBlockExecutable(F->begin());
for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
AI != E; ++AI)
- Values[AI].markOverdefined();
+ Solver.markOverdefined(AI);
} else {
Solver.AddTrackedFunction(F);
}
Solver.TrackValueOfGlobalVariable(G);
// Solve for constants.
- bool ResolvedBranches = true;
- while (ResolvedBranches) {
+ bool ResolvedUndefs = true;
+ while (ResolvedUndefs) {
Solver.Solve();
- DEBUG(std::cerr << "RESOLVING UNDEF BRANCHES\n");
- ResolvedBranches = false;
+ DOUT << "RESOLVING UNDEFS\n";
+ ResolvedUndefs = false;
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
- ResolvedBranches |= Solver.ResolveBranchesIn(*F);
+ ResolvedUndefs |= Solver.ResolvedUndefsIn(*F);
}
bool MadeChanges = false;
// Iterate over all of the instructions in the module, replacing them with
// constants if we have found them to be of constant values.
//
- std::set<BasicBlock*> &ExecutableBBs = Solver.getExecutableBlocks();
+ SmallSet<BasicBlock*, 16> &ExecutableBBs = Solver.getExecutableBlocks();
+ SmallVector<Instruction*, 32> Insts;
+ SmallVector<BasicBlock*, 32> BlocksToErase;
+ std::map<Value*, LatticeVal> &Values = Solver.getValueMapping();
+
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
AI != E; ++AI)
if (IV.isConstant() || IV.isUndefined()) {
Constant *CST = IV.isConstant() ?
IV.getConstant() : UndefValue::get(AI->getType());
- DEBUG(std::cerr << "*** Arg " << *AI << " = " << *CST <<"\n");
+ DOUT << "*** Arg " << *AI << " = " << *CST <<"\n";
// Replaces all of the uses of a variable with uses of the
// constant.
}
}
- std::vector<BasicBlock*> BlocksToErase;
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
if (!ExecutableBBs.count(BB)) {
- DEBUG(std::cerr << " BasicBlock Dead:" << *BB);
+ DOUT << " BasicBlock Dead:" << *BB;
++IPNumDeadBlocks;
// Delete the instructions backwards, as it has a reduced likelihood of
// having to update as many def-use and use-def chains.
- std::vector<Instruction*> Insts;
TerminatorInst *TI = BB->getTerminator();
for (BasicBlock::iterator I = BB->begin(), E = TI; I != E; ++I)
Insts.push_back(I);
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
BasicBlock *Succ = TI->getSuccessor(i);
- if (
Succ->begin() != Succ->end() && isa<PHINode>(Succ->begin()))
+ if (
!Succ->empty() && isa<PHINode>(Succ->begin()))
TI->getSuccessor(i)->removePredecessor(BB);
}
if (!TI->use_empty())
!isa<TerminatorInst>(Inst)) {
Constant *Const = IV.isConstant()
? IV.getConstant() : UndefValue::get(Inst->getType());
- DEBUG(std::cerr << " Constant: " << *Const << " = " << *Inst);
+ DOUT << " Constant: " << *Const << " = " << *Inst;
// Replaces all of the uses of a variable with uses of the
// constant.
while (!DeadBB->use_empty()) {
Instruction *I = cast<Instruction>(DeadBB->use_back());
bool Folded = ConstantFoldTerminator(I->getParent());
- assert(Folded && "Didn't fold away reference to block!");
+ if (!Folded) {
+ // The constant folder may not have been able to fold the terminator
+ // if this is a branch or switch on undef. Fold it manually as a
+ // branch to the first successor.
+ if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
+ assert(BI->isConditional() && isa<UndefValue>(BI->getCondition()) &&
+ "Branch should be foldable!");
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
+ assert(isa<UndefValue>(SI->getCondition()) && "Switch should fold");
+ } else {
+ assert(0 && "Didn't fold away reference to block!");
+ }
+
+ // Make this an uncond branch to the first successor.
+ TerminatorInst *TI = I->getParent()->getTerminator();
+ new BranchInst(TI->getSuccessor(0), TI);
+
+ // Remove entries in successor phi nodes to remove edges.
+ for (unsigned i = 1, e = TI->getNumSuccessors(); i != e; ++i)
+ TI->getSuccessor(i)->removePredecessor(TI->getParent());
+
+ // Remove the old terminator.
+ TI->eraseFromParent();
+ }
}
// Finally, delete the basic block.
F->getBasicBlockList().erase(DeadBB);
}
+ BlocksToErase.clear();
}
// If we inferred constant or undef return values for a function, we replaced
// all call uses with the inferred value. This means we don't need to bother
// actually returning anything from the function. Replace all return
// instructions with return undef.
- const hash_map<Function*, LatticeVal> &RV =Solver.getTrackedFunctionRetVals();
- for (hash_map<Function*, LatticeVal>::const_iterator I = RV.begin(),
+ const DenseMap<Function*, LatticeVal> &RV =Solver.getTrackedFunctionRetVals();
+ for (DenseMap<Function*, LatticeVal>::const_iterator I = RV.begin(),
E = RV.end(); I != E; ++I)
if (!I->second.isOverdefined() &&
I->first->getReturnType() != Type::VoidTy) {
// If we infered constant or undef values for globals variables, we can delete
// the global and any stores that remain to it.
- const hash_map<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
- for (hash_map<GlobalVariable*, LatticeVal>::const_iterator I = TG.begin(),
+ const DenseMap<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
+ for (DenseMap<GlobalVariable*, LatticeVal>::const_iterator I = TG.begin(),
E = TG.end(); I != E; ++I) {
GlobalVariable *GV = I->first;
assert(!I->second.isOverdefined() &&
"Overdefined values should have been taken out of the map!");
- DEBUG(std::cerr << "Found that GV '" << GV->getName()<< "' is constant!\n");
+ DOUT << "Found that GV '" << GV->getName()<< "' is constant!\n";
while (!GV->use_empty()) {
StoreInst *SI = cast<StoreInst>(GV->use_back());
SI->eraseFromParent();
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