// * Proves values to be constant, and replaces them with constants
// * Proves conditional branches to be unconditional
//
-// Notice that:
-// * This pass has a habit of making definitions be dead. It is a good idea
-// to to run a DCE pass sometime after running this pass.
-//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "sccp"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
-#include "llvm/LLVMContext.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/ConstantFolding.h"
-#include "llvm/Analysis/MemoryBuiltins.h"
-#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
-#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/STLExtras.h"
#include <algorithm>
-#include <map>
using namespace llvm;
STATISTIC(NumInstRemoved, "Number of instructions removed");
STATISTIC(NumDeadBlocks , "Number of basic blocks unreachable");
STATISTIC(IPNumInstRemoved, "Number of instructions 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");
/// an LLVM value may occupy. It is a simple class with value semantics.
///
class LatticeVal {
- enum {
+ enum LatticeValueTy {
/// undefined - This LLVM Value has no known value yet.
undefined,
-
+
/// constant - This LLVM Value has a specific constant value.
constant,
/// 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
+ };
+
+ /// Val: This stores the current lattice value along with the Constant* for
+ /// the constant if this is a 'constant' or 'forcedconstant' value.
+ PointerIntPair<Constant *, 2, LatticeValueTy> Val;
+
+ LatticeValueTy getLatticeValue() const {
+ return Val.getInt();
+ }
+
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) {
- LatticeValue = overdefined;
- return true;
- }
- return false;
+ LatticeVal() : Val(0, undefined) {}
+
+ bool isUndefined() const { return getLatticeValue() == undefined; }
+ bool isConstant() const {
+ return getLatticeValue() == constant || getLatticeValue() == forcedconstant;
}
+ bool isOverdefined() const { return getLatticeValue() == overdefined; }
- // markConstant - Return true if this is a new status for us.
- inline bool markConstant(Constant *V) {
- if (LatticeValue != constant) {
- 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;
+ Constant *getConstant() const {
+ assert(isConstant() && "Cannot get the constant of a non-constant!");
+ return Val.getPointer();
+ }
+
+ /// markOverdefined - Return true if this is a change in status.
+ bool markOverdefined() {
+ if (isOverdefined())
+ return false;
+
+ Val.setInt(overdefined);
+ return true;
+ }
+
+ /// markConstant - Return true if this is a change in status.
+ bool markConstant(Constant *V) {
+ if (getLatticeValue() == constant) { // Constant but not forcedconstant.
+ assert(getConstant() == V && "Marking constant with different value");
+ return false;
+ }
+
+ if (isUndefined()) {
+ Val.setInt(constant);
+ assert(V && "Marking constant with NULL");
+ Val.setPointer(V);
} else {
- assert(ConstantVal == V && "Marking constant with different value");
+ assert(getLatticeValue() == forcedconstant &&
+ "Cannot move from overdefined to constant!");
+ // Stay at forcedconstant if the constant is the same.
+ if (V == getConstant()) 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.
+ Val.setInt(overdefined);
}
- return false;
+ return true;
}
- 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;
+ /// getConstantInt - If this is a constant with a ConstantInt value, return it
+ /// otherwise return null.
+ ConstantInt *getConstantInt() const {
+ if (isConstant())
+ return dyn_cast<ConstantInt>(getConstant());
+ return 0;
}
- inline bool isOverdefined() const { return LatticeValue == overdefined; }
- inline Constant *getConstant() const {
- assert(isConstant() && "Cannot get the constant of a non-constant!");
- return ConstantVal;
+ void markForcedConstant(Constant *V) {
+ assert(isUndefined() && "Can't force a defined value!");
+ Val.setInt(forcedconstant);
+ Val.setPointer(V);
}
};
+} // end anonymous namespace.
+
+
+namespace {
//===----------------------------------------------------------------------===//
//
/// Constant Propagation.
///
class SCCPSolver : public InstVisitor<SCCPSolver> {
- LLVMContext *Context;
- DenseSet<BasicBlock*> BBExecutable;// The basic blocks that are executable
- std::map<Value*, LatticeVal> ValueState; // The state each value is in.
+ const TargetData *TD;
+ const TargetLibraryInfo *TLI;
+ SmallPtrSet<BasicBlock*, 8> BBExecutable; // The BBs that are executable.
+ DenseMap<Value*, LatticeVal> ValueState; // The state each value is in.
+
+ /// StructValueState - This maintains ValueState for values that have
+ /// StructType, for example for formal arguments, calls, insertelement, etc.
+ ///
+ DenseMap<std::pair<Value*, unsigned>, LatticeVal> StructValueState;
/// 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
/// that return multiple values.
DenseMap<std::pair<Function*, unsigned>, LatticeVal> TrackedMultipleRetVals;
- // The reason for two worklists is that overdefined is the lowest state
- // on the lattice, and moving things to overdefined as fast as possible
- // makes SCCP converge much faster.
- // By having a separate worklist, we accomplish this because everything
- // possibly overdefined will become overdefined at the soonest possible
- // point.
+ /// MRVFunctionsTracked - Each function in TrackedMultipleRetVals is
+ /// represented here for efficient lookup.
+ SmallPtrSet<Function*, 16> MRVFunctionsTracked;
+
+ /// TrackingIncomingArguments - This is the set of functions for whose
+ /// arguments we make optimistic assumptions about and try to prove as
+ /// constants.
+ SmallPtrSet<Function*, 16> TrackingIncomingArguments;
+
+ /// The reason for two worklists is that overdefined is the lowest state
+ /// on the lattice, and moving things to overdefined as fast as possible
+ /// makes SCCP converge much faster.
+ ///
+ /// By having a separate worklist, we accomplish this because everything
+ /// possibly overdefined will become overdefined at the soonest possible
+ /// point.
SmallVector<Value*, 64> OverdefinedInstWorkList;
SmallVector<Value*, 64> InstWorkList;
SmallVector<BasicBlock*, 64> BBWorkList; // The BasicBlock work list
- /// UsersOfOverdefinedPHIs - Keep track of any users of PHI nodes that are not
- /// overdefined, despite the fact that the PHI node is overdefined.
- std::multimap<PHINode*, Instruction*> UsersOfOverdefinedPHIs;
-
/// KnownFeasibleEdges - Entries in this set are edges which have already had
/// PHI nodes retriggered.
typedef std::pair<BasicBlock*, BasicBlock*> Edge;
DenseSet<Edge> KnownFeasibleEdges;
public:
- void setContext(LLVMContext *C) { Context = C; }
+ SCCPSolver(const TargetData *td, const TargetLibraryInfo *tli)
+ : TD(td), TLI(tli) {}
/// 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(errs() << "Marking Block Executable: " << BB->getName() << "\n");
- BBExecutable.insert(BB); // Basic block is executable!
+ ///
+ /// This returns true if the block was not considered live before.
+ bool MarkBlockExecutable(BasicBlock *BB) {
+ if (!BBExecutable.insert(BB)) return false;
+ DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << "\n");
BBWorkList.push_back(BB); // Add the block to the work list!
+ return true;
}
/// TrackValueOfGlobalVariable - Clients can use this method to
/// specified global variable if it can. This is only legal to call if
/// performing Interprocedural SCCP.
void TrackValueOfGlobalVariable(GlobalVariable *GV) {
- const Type *ElTy = GV->getType()->getElementType();
- if (ElTy->isFirstClassType()) {
+ // We only track the contents of scalar globals.
+ if (GV->getType()->getElementType()->isSingleValueType()) {
LatticeVal &IV = TrackedGlobals[GV];
if (!isa<UndefValue>(GV->getInitializer()))
IV.markConstant(GV->getInitializer());
/// and out of the specified function (which cannot have its address taken),
/// this method must be called.
void AddTrackedFunction(Function *F) {
- assert(F->hasLocalLinkage() && "Can only track internal functions!");
// Add an entry, F -> undef.
- if (const StructType *STy = dyn_cast<StructType>(F->getReturnType())) {
+ if (StructType *STy = dyn_cast<StructType>(F->getReturnType())) {
+ MRVFunctionsTracked.insert(F);
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
TrackedMultipleRetVals.insert(std::make_pair(std::make_pair(F, i),
LatticeVal()));
TrackedRetVals.insert(std::make_pair(F, LatticeVal()));
}
+ void AddArgumentTrackedFunction(Function *F) {
+ TrackingIncomingArguments.insert(F);
+ }
+
/// Solve - Solve for constants and executable blocks.
///
void Solve();
return BBExecutable.count(BB);
}
- /// getValueMapping - Once we have solved for constants, return the mapping of
- /// LLVM values to LatticeVals.
- std::map<Value*, LatticeVal> &getValueMapping() {
- return ValueState;
+ LatticeVal getLatticeValueFor(Value *V) const {
+ DenseMap<Value*, LatticeVal>::const_iterator I = ValueState.find(V);
+ assert(I != ValueState.end() && "V is not in valuemap!");
+ return I->second;
}
+ /*LatticeVal getStructLatticeValueFor(Value *V, unsigned i) const {
+ DenseMap<std::pair<Value*, unsigned>, LatticeVal>::const_iterator I =
+ StructValueState.find(std::make_pair(V, i));
+ assert(I != StructValueState.end() && "V is not in valuemap!");
+ return I->second;
+ }*/
+
/// getTrackedRetVals - Get the inferred return value map.
///
const DenseMap<Function*, LatticeVal> &getTrackedRetVals() {
return TrackedGlobals;
}
- inline void markOverdefined(Value *V) {
+ void markOverdefined(Value *V) {
+ assert(!V->getType()->isStructTy() && "Should use other method");
markOverdefined(ValueState[V], V);
}
+ /// markAnythingOverdefined - Mark the specified value overdefined. This
+ /// works with both scalars and structs.
+ void markAnythingOverdefined(Value *V) {
+ if (StructType *STy = dyn_cast<StructType>(V->getType()))
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
+ markOverdefined(getStructValueState(V, i), V);
+ else
+ markOverdefined(V);
+ }
+
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
// the users of the instruction are updated later.
//
- inline void markConstant(LatticeVal &IV, Value *V, Constant *C) {
- if (IV.markConstant(C)) {
- DEBUG(errs() << "markConstant: " << *C << ": " << *V << '\n');
+ void markConstant(LatticeVal &IV, Value *V, Constant *C) {
+ if (!IV.markConstant(C)) return;
+ DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n');
+ if (IV.isOverdefined())
+ OverdefinedInstWorkList.push_back(V);
+ else
InstWorkList.push_back(V);
- }
- }
-
- inline void markForcedConstant(LatticeVal &IV, Value *V, Constant *C) {
- IV.markForcedConstant(C);
- DEBUG(errs() << "markForcedConstant: " << *C << ": " << *V << '\n');
- InstWorkList.push_back(V);
}
-
- inline void markConstant(Value *V, Constant *C) {
+
+ void markConstant(Value *V, Constant *C) {
+ assert(!V->getType()->isStructTy() && "Should use other method");
markConstant(ValueState[V], V, C);
}
+ void markForcedConstant(Value *V, Constant *C) {
+ assert(!V->getType()->isStructTy() && "Should use other method");
+ LatticeVal &IV = ValueState[V];
+ IV.markForcedConstant(C);
+ DEBUG(dbgs() << "markForcedConstant: " << *C << ": " << *V << '\n');
+ if (IV.isOverdefined())
+ OverdefinedInstWorkList.push_back(V);
+ else
+ InstWorkList.push_back(V);
+ }
+
+
// markOverdefined - Make a value be marked as "overdefined". If the
// 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(errs() << "markOverdefined: ";
- if (Function *F = dyn_cast<Function>(V))
- errs() << "Function '" << F->getName() << "'\n";
- else
- errs() << *V << '\n');
- // Only instructions go on the work list
- OverdefinedInstWorkList.push_back(V);
- }
+ void markOverdefined(LatticeVal &IV, Value *V) {
+ if (!IV.markOverdefined()) return;
+
+ DEBUG(dbgs() << "markOverdefined: ";
+ if (Function *F = dyn_cast<Function>(V))
+ dbgs() << "Function '" << F->getName() << "'\n";
+ else
+ dbgs() << *V << '\n');
+ // Only instructions go on the work list
+ OverdefinedInstWorkList.push_back(V);
}
- inline void mergeInValue(LatticeVal &IV, Value *V, LatticeVal &MergeWithV) {
+ void mergeInValue(LatticeVal &IV, Value *V, LatticeVal MergeWithV) {
if (IV.isOverdefined() || MergeWithV.isUndefined())
return; // Noop.
if (MergeWithV.isOverdefined())
else if (IV.getConstant() != MergeWithV.getConstant())
markOverdefined(IV, V);
}
-
- inline void mergeInValue(Value *V, LatticeVal &MergeWithV) {
- return mergeInValue(ValueState[V], V, MergeWithV);
+
+ void mergeInValue(Value *V, LatticeVal MergeWithV) {
+ assert(!V->getType()->isStructTy() && "Should use other method");
+ 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
- // underdefined state... Argument's should be overdefined, and
- // constants should be marked as constants. If a value is not known to be an
- // Instruction object, then use this accessor to get its value from the map.
- //
- inline LatticeVal &getValueState(Value *V) {
- std::map<Value*, LatticeVal>::iterator I = ValueState.find(V);
- if (I != ValueState.end()) return I->second; // Common case, in the map
+ /// getValueState - Return the LatticeVal object that corresponds to the
+ /// value. This function handles the case when the value hasn't been seen yet
+ /// by properly seeding constants etc.
+ LatticeVal &getValueState(Value *V) {
+ assert(!V->getType()->isStructTy() && "Should use getStructValueState");
+
+ std::pair<DenseMap<Value*, LatticeVal>::iterator, bool> I =
+ ValueState.insert(std::make_pair(V, LatticeVal()));
+ LatticeVal &LV = I.first->second;
+
+ if (!I.second)
+ return LV; // Common case, already in the map.
if (Constant *C = dyn_cast<Constant>(V)) {
- if (isa<UndefValue>(V)) {
- // Nothing to do, remain undefined.
- } else {
- LatticeVal &LV = ValueState[C];
+ // Undef values remain undefined.
+ if (!isa<UndefValue>(V))
LV.markConstant(C); // Constants are constant
- return LV;
- }
}
- // All others are underdefined by default...
- return ValueState[V];
+
+ // All others are underdefined by default.
+ return LV;
}
- // markEdgeExecutable - Mark a basic block as executable, adding it to the BB
- // work list if it is not already executable...
- //
+ /// getStructValueState - Return the LatticeVal object that corresponds to the
+ /// value/field pair. This function handles the case when the value hasn't
+ /// been seen yet by properly seeding constants etc.
+ LatticeVal &getStructValueState(Value *V, unsigned i) {
+ assert(V->getType()->isStructTy() && "Should use getValueState");
+ assert(i < cast<StructType>(V->getType())->getNumElements() &&
+ "Invalid element #");
+
+ std::pair<DenseMap<std::pair<Value*, unsigned>, LatticeVal>::iterator,
+ bool> I = StructValueState.insert(
+ std::make_pair(std::make_pair(V, i), LatticeVal()));
+ LatticeVal &LV = I.first->second;
+
+ if (!I.second)
+ return LV; // Common case, already in the map.
+
+ if (Constant *C = dyn_cast<Constant>(V)) {
+ Constant *Elt = C->getAggregateElement(i);
+
+ if (Elt == 0)
+ LV.markOverdefined(); // Unknown sort of constant.
+ else if (isa<UndefValue>(Elt))
+ ; // Undef values remain undefined.
+ else
+ LV.markConstant(Elt); // Constants are constant.
+ }
+
+ // All others are underdefined by default.
+ return LV;
+ }
+
+
+ /// 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!
- if (BBExecutable.count(Dest)) {
- DEBUG(errs() << "Marking Edge Executable: " << Source->getName()
- << " -> " << Dest->getName() << "\n");
-
- // The destination is already executable, but we just made an edge
+ if (!MarkBlockExecutable(Dest)) {
+ // If the destination is already executable, we just made an *edge*
// feasible that wasn't before. Revisit the PHI nodes in the block
// because they have potentially new operands.
- for (BasicBlock::iterator I = Dest->begin(); isa<PHINode>(I); ++I)
- visitPHINode(*cast<PHINode>(I));
+ DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName()
+ << " -> " << Dest->getName() << "\n");
- } else {
- MarkBlockExecutable(Dest);
+ PHINode *PN;
+ for (BasicBlock::iterator I = Dest->begin();
+ (PN = dyn_cast<PHINode>(I)); ++I)
+ visitPHINode(*PN);
}
}
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...
+ // block to the 'To' basic block is currently feasible.
//
bool isEdgeFeasible(BasicBlock *From, BasicBlock *To);
// OperandChangedState - This method is invoked on all of the users of an
- // instruction that was just changed state somehow.... Based on this
+ // instruction that was just changed state somehow. Based on this
// information, we need to update the specified user of this instruction.
//
- void OperandChangedState(User *U) {
- // Only instructions use other variable values!
- Instruction &I = cast<Instruction>(*U);
- if (BBExecutable.count(I.getParent())) // Inst is executable?
- visit(I);
+ void OperandChangedState(Instruction *I) {
+ if (BBExecutable.count(I->getParent())) // Inst is executable?
+ visit(*I);
}
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.
- //
void visitPHINode(PHINode &I);
// Terminators
void visitShuffleVectorInst(ShuffleVectorInst &I);
void visitExtractValueInst(ExtractValueInst &EVI);
void visitInsertValueInst(InsertValueInst &IVI);
+ void visitLandingPadInst(LandingPadInst &I) { markAnythingOverdefined(&I); }
- // Instructions that cannot be folded away...
- void visitStoreInst (Instruction &I);
+ // Instructions that cannot be folded away.
+ void visitStoreInst (StoreInst &I);
void visitLoadInst (LoadInst &I);
void visitGetElementPtrInst(GetElementPtrInst &I);
void visitCallInst (CallInst &I) {
- if (isFreeCall(&I))
- return;
- visitCallSite(CallSite::get(&I));
+ visitCallSite(&I);
}
void visitInvokeInst (InvokeInst &II) {
- visitCallSite(CallSite::get(&II));
+ visitCallSite(&II);
visitTerminatorInst(II);
}
void visitCallSite (CallSite CS);
+ void visitResumeInst (TerminatorInst &I) { /*returns void*/ }
void visitUnwindInst (TerminatorInst &I) { /*returns void*/ }
void visitUnreachableInst(TerminatorInst &I) { /*returns void*/ }
+ void visitFenceInst (FenceInst &I) { /*returns void*/ }
+ void visitAtomicCmpXchgInst (AtomicCmpXchgInst &I) { markOverdefined(&I); }
+ void visitAtomicRMWInst (AtomicRMWInst &I) { markOverdefined(&I); }
void visitAllocaInst (Instruction &I) { markOverdefined(&I); }
- void visitVANextInst (Instruction &I) { markOverdefined(&I); }
- void visitVAArgInst (Instruction &I) { markOverdefined(&I); }
+ void visitVAArgInst (Instruction &I) { markAnythingOverdefined(&I); }
void visitInstruction(Instruction &I) {
- // If a new instruction is added to LLVM that we don't handle...
- errs() << "SCCP: Don't know how to handle: " << I;
- markOverdefined(&I); // Just in case
+ // If a new instruction is added to LLVM that we don't handle.
+ dbgs() << "SCCP: Don't know how to handle: " << I;
+ markAnythingOverdefined(&I); // Just in case
}
};
if (BranchInst *BI = dyn_cast<BranchInst>(&TI)) {
if (BI->isUnconditional()) {
Succs[0] = true;
- } else {
- LatticeVal &BCValue = getValueState(BI->getCondition());
- if (BCValue.isOverdefined() ||
- (BCValue.isConstant() && !isa<ConstantInt>(BCValue.getConstant()))) {
- // Overdefined condition variables, and branches on unfoldable constant
- // conditions, mean the branch could go either way.
+ return;
+ }
+
+ LatticeVal BCValue = getValueState(BI->getCondition());
+ ConstantInt *CI = BCValue.getConstantInt();
+ if (CI == 0) {
+ // Overdefined condition variables, and branches on unfoldable constant
+ // conditions, mean the branch could go either way.
+ if (!BCValue.isUndefined())
Succs[0] = Succs[1] = true;
- } else if (BCValue.isConstant()) {
- // Constant condition variables mean the branch can only go a single way
- Succs[BCValue.getConstant() == ConstantInt::getFalse(*Context)] = true;
- }
+ return;
}
- } else if (isa<InvokeInst>(&TI)) {
+
+ // Constant condition variables mean the branch can only go a single way.
+ Succs[CI->isZero()] = true;
+ return;
+ }
+
+ if (isa<InvokeInst>(TI)) {
// Invoke instructions successors are always executable.
Succs[0] = Succs[1] = true;
- } else if (SwitchInst *SI = dyn_cast<SwitchInst>(&TI)) {
- LatticeVal &SCValue = getValueState(SI->getCondition());
- if (SCValue.isOverdefined() || // Overdefined condition?
- (SCValue.isConstant() && !isa<ConstantInt>(SCValue.getConstant()))) {
+ return;
+ }
+
+ if (SwitchInst *SI = dyn_cast<SwitchInst>(&TI)) {
+ if (!SI->getNumCases()) {
+ Succs[0] = true;
+ return;
+ }
+ LatticeVal SCValue = getValueState(SI->getCondition());
+ ConstantInt *CI = SCValue.getConstantInt();
+
+ if (CI == 0) { // Overdefined or undefined condition?
// All destinations are executable!
- Succs.assign(TI.getNumSuccessors(), true);
- } else if (SCValue.isConstant())
- Succs[SI->findCaseValue(cast<ConstantInt>(SCValue.getConstant()))] = true;
- } else {
- llvm_unreachable("SCCP: Don't know how to handle this terminator!");
+ if (!SCValue.isUndefined())
+ Succs.assign(TI.getNumSuccessors(), true);
+ return;
+ }
+
+ Succs[SI->findCaseValue(CI).getSuccessorIndex()] = true;
+ return;
}
+
+ // TODO: This could be improved if the operand is a [cast of a] BlockAddress.
+ if (isa<IndirectBrInst>(&TI)) {
+ // Just mark all destinations executable!
+ Succs.assign(TI.getNumSuccessors(), true);
+ return;
+ }
+
+#ifndef NDEBUG
+ dbgs() << "Unknown terminator instruction: " << TI << '\n';
+#endif
+ llvm_unreachable("SCCP: Don't know how to handle this terminator!");
}
// isEdgeFeasible - Return true if the control flow edge from the 'From' basic
-// block to the 'To' basic block is currently feasible...
+// block to the 'To' basic block is currently feasible.
//
bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
assert(BBExecutable.count(To) && "Dest should always be alive!");
// 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...
+ // Check to make sure this edge itself is actually feasible now.
TerminatorInst *TI = From->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isUnconditional())
return true;
- else {
- LatticeVal &BCValue = getValueState(BI->getCondition());
- if (BCValue.isOverdefined()) {
- // Overdefined condition variables mean the branch could go either way.
- return true;
- } else if (BCValue.isConstant()) {
- // Not branching on an evaluatable constant?
- if (!isa<ConstantInt>(BCValue.getConstant())) return true;
- // Constant condition variables mean the branch can only go a single way
- return BI->getSuccessor(BCValue.getConstant() ==
- ConstantInt::getFalse(*Context)) == To;
- }
- return false;
- }
- } else if (isa<InvokeInst>(TI)) {
- // Invoke instructions successors are always executable.
+ LatticeVal BCValue = getValueState(BI->getCondition());
+
+ // Overdefined condition variables mean the branch could go either way,
+ // undef conditions mean that neither edge is feasible yet.
+ ConstantInt *CI = BCValue.getConstantInt();
+ if (CI == 0)
+ return !BCValue.isUndefined();
+
+ // Constant condition variables mean the branch can only go a single way.
+ return BI->getSuccessor(CI->isZero()) == To;
+ }
+
+ // Invoke instructions successors are always executable.
+ if (isa<InvokeInst>(TI))
return true;
- } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
- LatticeVal &SCValue = getValueState(SI->getCondition());
- if (SCValue.isOverdefined()) { // Overdefined condition?
- // All destinations are executable!
+
+ if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ if (SI->getNumCases() < 1)
return true;
- } else if (SCValue.isConstant()) {
- Constant *CPV = SCValue.getConstant();
- if (!isa<ConstantInt>(CPV))
- return true; // not a foldable constant?
-
- // Make sure to skip the "default value" which isn't a value
- for (unsigned i = 1, E = SI->getNumSuccessors(); i != E; ++i)
- if (SI->getSuccessorValue(i) == CPV) // Found the taken branch...
- return SI->getSuccessor(i) == To;
-
- // Constant value not equal to any of the branches... must execute
- // default branch then...
- return SI->getDefaultDest() == To;
- }
- return false;
- } else {
+
+ LatticeVal SCValue = getValueState(SI->getCondition());
+ ConstantInt *CI = SCValue.getConstantInt();
+
+ if (CI == 0)
+ return !SCValue.isUndefined();
+
+ return SI->findCaseValue(CI).getCaseSuccessor() == To;
+ }
+
+ // Just mark all destinations executable!
+ // TODO: This could be improved if the operand is a [cast of a] BlockAddress.
+ if (isa<IndirectBrInst>(TI))
+ return true;
+
#ifndef NDEBUG
- errs() << "Unknown terminator instruction: " << *TI << '\n';
+ dbgs() << "Unknown terminator instruction: " << *TI << '\n';
#endif
- llvm_unreachable(0);
- }
+ llvm_unreachable(0);
}
-// 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. This method
// makes sure to do the following actions:
// successors executable.
//
void SCCPSolver::visitPHINode(PHINode &PN) {
- LatticeVal &PNIV = getValueState(&PN);
- if (PNIV.isOverdefined()) {
- // There may be instructions using this PHI node that are not overdefined
- // themselves. If so, make sure that they know that the PHI node operand
- // changed.
- std::multimap<PHINode*, Instruction*>::iterator I, E;
- tie(I, E) = UsersOfOverdefinedPHIs.equal_range(&PN);
- if (I != E) {
- SmallVector<Instruction*, 16> Users;
- for (; I != E; ++I) Users.push_back(I->second);
- while (!Users.empty()) {
- visit(Users.back());
- Users.pop_back();
- }
- }
+ // If this PN returns a struct, just mark the result overdefined.
+ // TODO: We could do a lot better than this if code actually uses this.
+ if (PN.getType()->isStructTy())
+ return markAnythingOverdefined(&PN);
+
+ if (getValueState(&PN).isOverdefined())
return; // Quick exit
- }
// Super-extra-high-degree PHI nodes are unlikely to ever be marked constant,
// and slow us down a lot. Just mark them overdefined.
- if (PN.getNumIncomingValues() > 64) {
- markOverdefined(PNIV, &PN);
- return;
- }
+ if (PN.getNumIncomingValues() > 64)
+ return markOverdefined(&PN);
// Look at all of the executable operands of the PHI node. If any of them
// are overdefined, the PHI becomes overdefined as well. If they are all
//
Constant *OperandVal = 0;
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
- LatticeVal &IV = getValueState(PN.getIncomingValue(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(&PN);
- return;
- }
+ if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent()))
+ continue;
- if (OperandVal == 0) { // Grab the first value...
- OperandVal = IV.getConstant();
- } else { // Another value is being merged in!
- // 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.
- // You must be overdefined poor PHI.
- //
- markOverdefined(&PN); // The PHI node now becomes overdefined
- return; // I'm done analyzing you
- }
- }
+ if (IV.isOverdefined()) // PHI node becomes overdefined!
+ return markOverdefined(&PN);
+
+ if (OperandVal == 0) { // Grab the first value.
+ OperandVal = IV.getConstant();
+ continue;
}
+
+ // 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 so, the PHI
+ // node is overdefined.
+ if (IV.getConstant() != OperandVal)
+ return markOverdefined(&PN);
}
// If we exited the loop, this means that the PHI node only has constant
markConstant(&PN, OperandVal); // Acquire operand value
}
+
+
+
void SCCPSolver::visitReturnInst(ReturnInst &I) {
- if (I.getNumOperands() == 0) return; // Ret void
+ if (I.getNumOperands() == 0) return; // ret void
Function *F = I.getParent()->getParent();
- // If we are tracking the return value of this function, merge it in.
- if (!F->hasLocalLinkage())
- return;
+ Value *ResultOp = I.getOperand(0);
- if (!TrackedRetVals.empty() && I.getNumOperands() == 1) {
+ // If we are tracking the return value of this function, merge it in.
+ if (!TrackedRetVals.empty() && !ResultOp->getType()->isStructTy()) {
DenseMap<Function*, LatticeVal>::iterator TFRVI =
TrackedRetVals.find(F);
- if (TFRVI != TrackedRetVals.end() &&
- !TFRVI->second.isOverdefined()) {
- LatticeVal &IV = getValueState(I.getOperand(0));
- mergeInValue(TFRVI->second, F, IV);
+ if (TFRVI != TrackedRetVals.end()) {
+ mergeInValue(TFRVI->second, F, getValueState(ResultOp));
return;
}
}
-
+
// Handle functions that return multiple values.
- if (!TrackedMultipleRetVals.empty() && I.getNumOperands() > 1) {
- for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
- DenseMap<std::pair<Function*, unsigned>, LatticeVal>::iterator
- It = TrackedMultipleRetVals.find(std::make_pair(F, i));
- if (It == TrackedMultipleRetVals.end()) break;
- mergeInValue(It->second, F, getValueState(I.getOperand(i)));
- }
- } else if (!TrackedMultipleRetVals.empty() &&
- I.getNumOperands() == 1 &&
- isa<StructType>(I.getOperand(0)->getType())) {
- for (unsigned i = 0, e = I.getOperand(0)->getType()->getNumContainedTypes();
- i != e; ++i) {
- DenseMap<std::pair<Function*, unsigned>, LatticeVal>::iterator
- It = TrackedMultipleRetVals.find(std::make_pair(F, i));
- if (It == TrackedMultipleRetVals.end()) break;
- if (Value *Val = FindInsertedValue(I.getOperand(0), i, I.getContext()))
- mergeInValue(It->second, F, getValueState(Val));
- }
+ if (!TrackedMultipleRetVals.empty()) {
+ if (StructType *STy = dyn_cast<StructType>(ResultOp->getType()))
+ if (MRVFunctionsTracked.count(F))
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
+ mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F,
+ getStructValueState(ResultOp, i));
+
}
}
BasicBlock *BB = TI.getParent();
- // Mark all feasible successors executable...
+ // Mark all feasible successors executable.
for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
if (SuccFeasible[i])
markEdgeExecutable(BB, TI.getSuccessor(i));
}
void SCCPSolver::visitCastInst(CastInst &I) {
- Value *V = I.getOperand(0);
- LatticeVal &VState = getValueState(V);
- if (VState.isOverdefined()) // Inherit overdefinedness of operand
+ LatticeVal OpSt = getValueState(I.getOperand(0));
+ if (OpSt.isOverdefined()) // Inherit overdefinedness of operand
markOverdefined(&I);
- else if (VState.isConstant()) // Propagate constant value
- markConstant(&I, ConstantExpr::getCast(I.getOpcode(),
- VState.getConstant(), I.getType()));
+ else if (OpSt.isConstant()) // Propagate constant value
+ markConstant(&I, ConstantExpr::getCast(I.getOpcode(),
+ OpSt.getConstant(), I.getType()));
}
-void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) {
- Value *Aggr = EVI.getAggregateOperand();
- // If the operand to the extractvalue is an undef, the result is undef.
- if (isa<UndefValue>(Aggr))
- return;
-
- // Currently only handle single-index extractvalues.
- if (EVI.getNumIndices() != 1) {
- markOverdefined(&EVI);
- return;
- }
-
- Function *F = 0;
- if (CallInst *CI = dyn_cast<CallInst>(Aggr))
- F = CI->getCalledFunction();
- else if (InvokeInst *II = dyn_cast<InvokeInst>(Aggr))
- F = II->getCalledFunction();
-
- // TODO: If IPSCCP resolves the callee of this function, we could propagate a
- // result back!
- if (F == 0 || TrackedMultipleRetVals.empty()) {
- markOverdefined(&EVI);
- return;
- }
-
- // See if we are tracking the result of the callee. If not tracking this
- // function (for example, it is a declaration) just move to overdefined.
- if (!TrackedMultipleRetVals.count(std::make_pair(F, *EVI.idx_begin()))) {
- markOverdefined(&EVI);
- return;
+void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) {
+ // If this returns a struct, mark all elements over defined, we don't track
+ // structs in structs.
+ if (EVI.getType()->isStructTy())
+ return markAnythingOverdefined(&EVI);
+
+ // If this is extracting from more than one level of struct, we don't know.
+ if (EVI.getNumIndices() != 1)
+ return markOverdefined(&EVI);
+
+ Value *AggVal = EVI.getAggregateOperand();
+ if (AggVal->getType()->isStructTy()) {
+ unsigned i = *EVI.idx_begin();
+ LatticeVal EltVal = getStructValueState(AggVal, i);
+ mergeInValue(getValueState(&EVI), &EVI, EltVal);
+ } else {
+ // Otherwise, must be extracting from an array.
+ return markOverdefined(&EVI);
}
-
- // Otherwise, the value will be merged in here as a result of CallSite
- // handling.
}
void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) {
- Value *Aggr = IVI.getAggregateOperand();
- Value *Val = IVI.getInsertedValueOperand();
+ StructType *STy = dyn_cast<StructType>(IVI.getType());
+ if (STy == 0)
+ return markOverdefined(&IVI);
- // If the operands to the insertvalue are undef, the result is undef.
- if (isa<UndefValue>(Aggr) && isa<UndefValue>(Val))
- return;
-
- // Currently only handle single-index insertvalues.
- if (IVI.getNumIndices() != 1) {
- markOverdefined(&IVI);
- return;
- }
+ // If this has more than one index, we can't handle it, drive all results to
+ // undef.
+ if (IVI.getNumIndices() != 1)
+ return markAnythingOverdefined(&IVI);
- // Currently only handle insertvalue instructions that are in a single-use
- // chain that builds up a return value.
- for (const InsertValueInst *TmpIVI = &IVI; ; ) {
- if (!TmpIVI->hasOneUse()) {
- markOverdefined(&IVI);
- return;
+ Value *Aggr = IVI.getAggregateOperand();
+ unsigned Idx = *IVI.idx_begin();
+
+ // Compute the result based on what we're inserting.
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+ // This passes through all values that aren't the inserted element.
+ if (i != Idx) {
+ LatticeVal EltVal = getStructValueState(Aggr, i);
+ mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal);
+ continue;
}
- const Value *V = *TmpIVI->use_begin();
- if (isa<ReturnInst>(V))
- break;
- TmpIVI = dyn_cast<InsertValueInst>(V);
- if (!TmpIVI) {
- markOverdefined(&IVI);
- return;
+
+ Value *Val = IVI.getInsertedValueOperand();
+ if (Val->getType()->isStructTy())
+ // We don't track structs in structs.
+ markOverdefined(getStructValueState(&IVI, i), &IVI);
+ else {
+ LatticeVal InVal = getValueState(Val);
+ mergeInValue(getStructValueState(&IVI, i), &IVI, InVal);
}
}
-
- // See if we are tracking the result of the callee.
- Function *F = IVI.getParent()->getParent();
- DenseMap<std::pair<Function*, unsigned>, LatticeVal>::iterator
- It = TrackedMultipleRetVals.find(std::make_pair(F, *IVI.idx_begin()));
-
- // Merge in the inserted member value.
- if (It != TrackedMultipleRetVals.end())
- mergeInValue(It->second, F, getValueState(Val));
-
- // Mark the aggregate result of the IVI overdefined; any tracking that we do
- // will be done on the individual member values.
- markOverdefined(&IVI);
}
void SCCPSolver::visitSelectInst(SelectInst &I) {
- LatticeVal &CondValue = getValueState(I.getCondition());
+ // If this select returns a struct, just mark the result overdefined.
+ // TODO: We could do a lot better than this if code actually uses this.
+ if (I.getType()->isStructTy())
+ return markAnythingOverdefined(&I);
+
+ LatticeVal CondValue = getValueState(I.getCondition());
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;
- }
+
+ if (ConstantInt *CondCB = CondValue.getConstantInt()) {
+ Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue();
+ mergeInValue(&I, getValueState(OpVal));
+ 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;
- }
+ LatticeVal TVal = getValueState(I.getTrueValue());
+ LatticeVal FVal = getValueState(I.getFalseValue());
- if (TVal.isUndefined()) { // select ?, undef, X -> X.
- mergeInValue(&I, FVal);
- } else if (FVal.isUndefined()) { // select ?, X, undef -> X.
- mergeInValue(&I, TVal);
- } else {
- markOverdefined(&I);
- }
+ // select ?, C, C -> C.
+ if (TVal.isConstant() && FVal.isConstant() &&
+ TVal.getConstant() == FVal.getConstant())
+ return markConstant(&I, FVal.getConstant());
+
+ if (TVal.isUndefined()) // select ?, undef, X -> X.
+ return mergeInValue(&I, FVal);
+ if (FVal.isUndefined()) // select ?, X, undef -> X.
+ return mergeInValue(&I, TVal);
+ markOverdefined(&I);
}
-// Handle BinaryOperators and Shift Instructions...
+// Handle Binary Operators.
void SCCPSolver::visitBinaryOperator(Instruction &I) {
+ LatticeVal V1State = getValueState(I.getOperand(0));
+ LatticeVal V2State = getValueState(I.getOperand(1));
+
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 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 (V1State.isConstant() && V2State.isConstant())
+ return markConstant(IV, &I,
+ ConstantExpr::get(I.getOpcode(), V1State.getConstant(),
+ V2State.getConstant()));
+
+ // If something is undef, wait for it to resolve.
+ if (!V1State.isOverdefined() && !V2State.isOverdefined())
+ return;
+
+ // Otherwise, one of our operands is overdefined. Try to produce something
+ // better than overdefined with some tricks.
+
+ // 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 if (VectorType *PT = dyn_cast<VectorType>(I.getType()))
+ markConstant(IV, &I, Constant::getAllOnesValue(PT));
+ else
+ markConstant(IV, &I,
+ Constant::getAllOnesValue(I.getType()));
+ return;
}
- if (NonOverdefVal) {
- if (NonOverdefVal->isUndefined()) {
- // 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, Constant::getAllOnesValue(PT));
- else
- markConstant(IV, &I,
- Constant::getAllOnesValue(I.getType()));
- return;
- } else {
- if (I.getOpcode() == Instruction::And) {
- if (NonOverdefVal->getConstant()->isNullValue()) {
- markConstant(IV, &I, NonOverdefVal->getConstant());
- return; // X and 0 = 0
- }
- } else {
- if (ConstantInt *CI =
- dyn_cast<ConstantInt>(NonOverdefVal->getConstant()))
- if (CI->isAllOnesValue()) {
- markConstant(IV, &I, NonOverdefVal->getConstant());
- return; // X or -1 = -1
- }
- }
- }
+ if (I.getOpcode() == Instruction::And) {
+ // X and 0 = 0
+ if (NonOverdefVal->getConstant()->isNullValue())
+ return markConstant(IV, &I, NonOverdefVal->getConstant());
+ } else {
+ if (ConstantInt *CI = NonOverdefVal->getConstantInt())
+ if (CI->isAllOnesValue()) // X or -1 = -1
+ return markConstant(IV, &I, NonOverdefVal->getConstant());
}
}
+ }
- // 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::get(I.getOpcode(), 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::get(I.getOpcode(), V1State.getConstant(),
- V2State.getConstant()));
- }
+ markOverdefined(&I);
}
-// Handle ICmpInst instruction...
+// Handle ICmpInst instruction.
void SCCPSolver::visitCmpInst(CmpInst &I) {
+ LatticeVal V1State = getValueState(I.getOperand(0));
+ LatticeVal V2State = getValueState(I.getOperand(1));
+
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;
- }
+ if (V1State.isConstant() && V2State.isConstant())
+ return markConstant(IV, &I, ConstantExpr::getCompare(I.getPredicate(),
+ V1State.getConstant(),
+ V2State.getConstant()));
- // 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;
- }
- }
+ // If operands are still undefined, wait for it to resolve.
+ if (!V1State.isOverdefined() && !V2State.isOverdefined())
+ return;
- markOverdefined(IV, &I);
- } else if (V1State.isConstant() && V2State.isConstant()) {
- markConstant(IV, &I, ConstantExpr::getCompare(I.getPredicate(),
- V1State.getConstant(),
- V2State.getConstant()));
- }
+ markOverdefined(&I);
}
void SCCPSolver::visitExtractElementInst(ExtractElementInst &I) {
- // FIXME : SCCP does not handle vectors properly.
- markOverdefined(&I);
- return;
+ // TODO : SCCP does not handle vectors properly.
+ return markOverdefined(&I);
#if 0
LatticeVal &ValState = getValueState(I.getOperand(0));
}
void SCCPSolver::visitInsertElementInst(InsertElementInst &I) {
- // FIXME : SCCP does not handle vectors properly.
- markOverdefined(&I);
- return;
+ // TODO : SCCP does not handle vectors properly.
+ return markOverdefined(&I);
#if 0
LatticeVal &ValState = getValueState(I.getOperand(0));
LatticeVal &EltState = getValueState(I.getOperand(1));
EltState.getConstant(),
IdxState.getConstant()));
else if (ValState.isUndefined() && EltState.isConstant() &&
- IdxState.isConstant())
+ IdxState.isConstant())
markConstant(&I,ConstantExpr::getInsertElement(UndefValue::get(I.getType()),
EltState.getConstant(),
IdxState.getConstant()));
}
void SCCPSolver::visitShuffleVectorInst(ShuffleVectorInst &I) {
- // FIXME : SCCP does not handle vectors properly.
- markOverdefined(&I);
- return;
+ // TODO : SCCP does not handle vectors properly.
+ return markOverdefined(&I);
#if 0
LatticeVal &V1State = getValueState(I.getOperand(0));
LatticeVal &V2State = getValueState(I.getOperand(1));
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() ?
+ Constant *V1 = V1State.isConstant() ?
V1State.getConstant() : UndefValue::get(I.getType());
- Constant *V2 = V2State.isConstant() ?
+ Constant *V2 = V2State.isConstant() ?
V2State.getConstant() : UndefValue::get(I.getType());
- Constant *Mask = MaskState.isConstant() ?
+ 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
+// Handle getelementptr instructions. If all operands are constants then we
// can turn this into a getelementptr ConstantExpr.
//
void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) {
- LatticeVal &IV = ValueState[&I];
- if (IV.isOverdefined()) return;
+ if (ValueState[&I].isOverdefined()) return;
SmallVector<Constant*, 8> Operands;
Operands.reserve(I.getNumOperands());
for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
- LatticeVal &State = getValueState(I.getOperand(i));
+ LatticeVal State = getValueState(I.getOperand(i));
if (State.isUndefined())
- return; // Operands are not resolved yet...
- else if (State.isOverdefined()) {
- markOverdefined(IV, &I);
- return;
- }
+ return; // Operands are not resolved yet.
+
+ if (State.isOverdefined())
+ return markOverdefined(&I);
+
assert(State.isConstant() && "Unknown state!");
Operands.push_back(State.getConstant());
}
Constant *Ptr = Operands[0];
- Operands.erase(Operands.begin()); // Erase the pointer from idx list...
-
- markConstant(IV, &I, ConstantExpr::getGetElementPtr(Ptr, &Operands[0],
- Operands.size()));
+ ArrayRef<Constant *> Indices(Operands.begin() + 1, Operands.end());
+ markConstant(&I, ConstantExpr::getGetElementPtr(Ptr, Indices));
}
-void SCCPSolver::visitStoreInst(Instruction &SI) {
+void SCCPSolver::visitStoreInst(StoreInst &SI) {
+ // If this store is of a struct, ignore it.
+ if (SI.getOperand(0)->getType()->isStructTy())
+ return;
+
if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
return;
+
GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1));
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.
- LatticeVal &PtrVal = getValueState(SI.getOperand(0));
-
- mergeInValue(I->second, GV, PtrVal);
+ // Get the value we are storing into the global, then merge it.
+ mergeInValue(I->second, GV, getValueState(SI.getOperand(0)));
if (I->second.isOverdefined())
TrackedGlobals.erase(I); // No need to keep tracking this!
}
// Handle load instructions. If the operand is a constant pointer to a constant
// global, we can replace the load with the loaded constant value!
void SCCPSolver::visitLoadInst(LoadInst &I) {
+ // If this load is of a struct, just mark the result overdefined.
+ if (I.getType()->isStructTy())
+ return markAnythingOverdefined(&I);
+
+ LatticeVal PtrVal = getValueState(I.getOperand(0));
+ if (PtrVal.isUndefined()) return; // The pointer is not resolved yet!
+
LatticeVal &IV = ValueState[&I];
if (IV.isOverdefined()) return;
- LatticeVal &PtrVal = getValueState(I.getOperand(0));
- if (PtrVal.isUndefined()) return; // The pointer is not resolved yet!
- if (PtrVal.isConstant() && !I.isVolatile()) {
- Value *Ptr = PtrVal.getConstant();
- // TODO: Consider a target hook for valid address spaces for this xform.
- if (isa<ConstantPointerNull>(Ptr) && I.getPointerAddressSpace() == 0) {
- // load null -> null
- markConstant(IV, &I, Constant::getNullValue(I.getType()));
- return;
- }
+ if (!PtrVal.isConstant() || I.isVolatile())
+ return markOverdefined(IV, &I);
- // Transform load (constant global) into the value loaded.
- if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
- if (GV->isConstant()) {
- if (GV->hasDefinitiveInitializer()) {
- markConstant(IV, &I, GV->getInitializer());
- return;
- }
- } else if (!TrackedGlobals.empty()) {
- // If we are tracking this global, merge in the known value for it.
- DenseMap<GlobalVariable*, LatticeVal>::iterator It =
- TrackedGlobals.find(GV);
- if (It != TrackedGlobals.end()) {
- mergeInValue(IV, &I, It->second);
- return;
- }
+ Constant *Ptr = PtrVal.getConstant();
+
+ // load null -> null
+ if (isa<ConstantPointerNull>(Ptr) && I.getPointerAddressSpace() == 0)
+ return markConstant(IV, &I, Constant::getNullValue(I.getType()));
+
+ // Transform load (constant global) into the value loaded.
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
+ if (!TrackedGlobals.empty()) {
+ // If we are tracking this global, merge in the known value for it.
+ DenseMap<GlobalVariable*, LatticeVal>::iterator It =
+ TrackedGlobals.find(GV);
+ if (It != TrackedGlobals.end()) {
+ mergeInValue(IV, &I, It->second);
+ return;
}
}
-
- // 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->hasDefinitiveInitializer())
- if (Constant *V =
- ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE)) {
- markConstant(IV, &I, V);
- return;
- }
}
+ // Transform load from a constant into a constant if possible.
+ if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, TD))
+ return markConstant(IV, &I, C);
+
// Otherwise we cannot say for certain what value this load will produce.
// Bail out.
markOverdefined(IV, &I);
void SCCPSolver::visitCallSite(CallSite CS) {
Function *F = CS.getCalledFunction();
Instruction *I = CS.getInstruction();
-
+
// The common case is that we aren't tracking the callee, either because we
// are not doing interprocedural analysis or the callee is indirect, or is
// external. Handle these cases first.
- if (F == 0 || !F->hasLocalLinkage()) {
+ if (F == 0 || F->isDeclaration()) {
CallOverdefined:
// Void return and not tracking callee, just bail.
if (I->getType()->isVoidTy()) return;
-
+
// Otherwise, if we have a single return value case, and if the function is
// a declaration, maybe we can constant fold it.
- if (!isa<StructType>(I->getType()) && F && F->isDeclaration() &&
+ if (F && F->isDeclaration() && !I->getType()->isStructTy() &&
canConstantFoldCallTo(F)) {
-
+
SmallVector<Constant*, 8> Operands;
for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
AI != E; ++AI) {
- LatticeVal &State = getValueState(*AI);
+ LatticeVal State = getValueState(*AI);
+
if (State.isUndefined())
return; // Operands are not resolved yet.
- else if (State.isOverdefined()) {
- markOverdefined(I);
- return;
- }
+ if (State.isOverdefined())
+ return markOverdefined(I);
assert(State.isConstant() && "Unknown state!");
Operands.push_back(State.getConstant());
}
-
+
// If we can constant fold this, mark the result of the call as a
// constant.
- if (Constant *C = ConstantFoldCall(F, Operands.data(), Operands.size())) {
- markConstant(I, C);
- return;
- }
+ if (Constant *C = ConstantFoldCall(F, Operands, TLI))
+ return markConstant(I, C);
}
// Otherwise, we don't know anything about this call, mark it overdefined.
- markOverdefined(I);
- return;
+ return markAnythingOverdefined(I);
}
- // If this is a single/zero retval case, see if we're tracking the function.
- DenseMap<Function*, LatticeVal>::iterator TFRVI = TrackedRetVals.find(F);
- if (TFRVI != TrackedRetVals.end()) {
- // If so, propagate the return value of the callee into this call result.
- mergeInValue(I, TFRVI->second);
- } else if (isa<StructType>(I->getType())) {
- // Check to see if we're tracking this callee, if not, handle it in the
- // common path above.
- DenseMap<std::pair<Function*, unsigned>, LatticeVal>::iterator
- TMRVI = TrackedMultipleRetVals.find(std::make_pair(F, 0));
- if (TMRVI == TrackedMultipleRetVals.end())
- goto CallOverdefined;
-
- // Need to mark as overdefined, otherwise it stays undefined which
- // creates extractvalue undef, <idx>
- markOverdefined(I);
- // If we are tracking this callee, propagate the return values of the call
- // into this call site. We do this by walking all the uses. Single-index
- // ExtractValueInst uses can be tracked; anything more complicated is
- // currently handled conservatively.
- for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
- UI != E; ++UI) {
- if (ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(*UI)) {
- if (EVI->getNumIndices() == 1) {
- mergeInValue(EVI,
- TrackedMultipleRetVals[std::make_pair(F, *EVI->idx_begin())]);
- continue;
+ // If this is a local function that doesn't have its address taken, mark its
+ // entry block executable and merge in the actual arguments to the call into
+ // the formal arguments of the function.
+ if (!TrackingIncomingArguments.empty() && TrackingIncomingArguments.count(F)){
+ MarkBlockExecutable(F->begin());
+
+ // Propagate information from this call site into the callee.
+ CallSite::arg_iterator CAI = CS.arg_begin();
+ for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
+ AI != E; ++AI, ++CAI) {
+ // If this argument is byval, and if the function is not readonly, there
+ // will be an implicit copy formed of the input aggregate.
+ if (AI->hasByValAttr() && !F->onlyReadsMemory()) {
+ markOverdefined(AI);
+ continue;
+ }
+
+ if (StructType *STy = dyn_cast<StructType>(AI->getType())) {
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+ LatticeVal CallArg = getStructValueState(*CAI, i);
+ mergeInValue(getStructValueState(AI, i), AI, CallArg);
}
+ } else {
+ mergeInValue(AI, getValueState(*CAI));
}
- // The aggregate value is used in a way not handled here. Assume nothing.
- markOverdefined(*UI);
}
- } else {
- // Otherwise we're not tracking this callee, so handle it in the
- // common path above.
- goto CallOverdefined;
}
-
- // Finally, if this is the first call to the function hit, mark its entry
- // block executable.
- if (!BBExecutable.count(F->begin()))
- MarkBlockExecutable(F->begin());
-
- // Propagate information from this call site into the callee.
- CallSite::arg_iterator CAI = CS.arg_begin();
- for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
- AI != E; ++AI, ++CAI) {
- LatticeVal &IV = ValueState[AI];
- if (AI->hasByValAttr() && !F->onlyReadsMemory()) {
- IV.markOverdefined();
- continue;
- }
- if (!IV.isOverdefined())
- mergeInValue(IV, AI, getValueState(*CAI));
+
+ // If this is a single/zero retval case, see if we're tracking the function.
+ if (StructType *STy = dyn_cast<StructType>(F->getReturnType())) {
+ if (!MRVFunctionsTracked.count(F))
+ goto CallOverdefined; // Not tracking this callee.
+
+ // If we are tracking this callee, propagate the result of the function
+ // into this call site.
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
+ mergeInValue(getStructValueState(I, i), I,
+ TrackedMultipleRetVals[std::make_pair(F, i)]);
+ } else {
+ DenseMap<Function*, LatticeVal>::iterator TFRVI = TrackedRetVals.find(F);
+ if (TFRVI == TrackedRetVals.end())
+ goto CallOverdefined; // Not tracking this callee.
+
+ // If so, propagate the return value of the callee into this call result.
+ mergeInValue(I, TFRVI->second);
}
}
// Process the work lists until they are empty!
while (!BBWorkList.empty() || !InstWorkList.empty() ||
!OverdefinedInstWorkList.empty()) {
- // Process the instruction work list...
+ // Process the overdefined instruction's work list first, which drives other
+ // things to overdefined more quickly.
while (!OverdefinedInstWorkList.empty()) {
- Value *I = OverdefinedInstWorkList.back();
- OverdefinedInstWorkList.pop_back();
+ Value *I = OverdefinedInstWorkList.pop_back_val();
- DEBUG(errs() << "\nPopped off OI-WL: " << *I << '\n');
+ DEBUG(dbgs() << "\nPopped off OI-WL: " << *I << '\n');
// "I" got into the work list because it either made the transition from
// bottom to constant
//
// Anything on this worklist that is overdefined need not be visited
// since all of its users will have already been marked as overdefined
- // Update all of the users of this instruction's value...
+ // Update all of the users of this instruction's value.
//
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI)
- OperandChangedState(*UI);
+ if (Instruction *I = dyn_cast<Instruction>(*UI))
+ OperandChangedState(I);
}
- // Process the instruction work list...
+
+ // Process the instruction work list.
while (!InstWorkList.empty()) {
- Value *I = InstWorkList.back();
- InstWorkList.pop_back();
+ Value *I = InstWorkList.pop_back_val();
- DEBUG(errs() << "\nPopped off I-WL: " << *I << '\n');
+ DEBUG(dbgs() << "\nPopped off I-WL: " << *I << '\n');
- // "I" got into the work list because it either made the transition from
- // bottom to constant
+ // "I" got into the work list because it made the transition from undef to
+ // constant.
//
// Anything on this worklist that is overdefined need not be visited
// since all of its users will have already been marked as overdefined.
- // Update all of the users of this instruction's value...
+ // Update all of the users of this instruction's value.
//
- if (!getValueState(I).isOverdefined())
+ if (I->getType()->isStructTy() || !getValueState(I).isOverdefined())
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI)
- OperandChangedState(*UI);
+ if (Instruction *I = dyn_cast<Instruction>(*UI))
+ OperandChangedState(I);
}
- // Process the basic block work list...
+ // Process the basic block work list.
while (!BBWorkList.empty()) {
BasicBlock *BB = BBWorkList.back();
BBWorkList.pop_back();
- DEBUG(errs() << "\nPopped off BBWL: " << *BB << '\n');
+ DEBUG(dbgs() << "\nPopped off BBWL: " << *BB << '\n');
// Notify all instructions in this basic block that they are newly
// executable.
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()->isVoidTy()) continue;
-
+
+ if (StructType *STy = dyn_cast<StructType>(I->getType())) {
+ // Only a few things that can be structs matter for undef.
+
+ // Tracked calls must never be marked overdefined in ResolvedUndefsIn.
+ if (CallSite CS = CallSite(I))
+ if (Function *F = CS.getCalledFunction())
+ if (MRVFunctionsTracked.count(F))
+ continue;
+
+ // extractvalue and insertvalue don't need to be marked; they are
+ // tracked as precisely as their operands.
+ if (isa<ExtractValueInst>(I) || isa<InsertValueInst>(I))
+ continue;
+
+ // Send the results of everything else to overdefined. We could be
+ // more precise than this but it isn't worth bothering.
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+ LatticeVal &LV = getStructValueState(I, i);
+ if (LV.isUndefined())
+ markOverdefined(LV, I);
+ }
+ 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));
+ // extractvalue is safe; check here because the argument is a struct.
+ if (isa<ExtractValueInst>(I))
+ continue;
+
+ // Compute the operand LatticeVals, for convenience below.
+ // Anything taking a struct is conservatively assumed to require
+ // overdefined markings.
+ if (I->getOperand(0)->getType()->isStructTy()) {
+ markOverdefined(I);
+ return true;
+ }
+ 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.
+ if (I->getOperand(1)->getType()->isStructTy()) {
+ markOverdefined(I);
+ return true;
+ }
+
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();
+ Type *ITy = I->getType();
switch (I->getOpcode()) {
- default: break; // Leave the instruction as an undef.
+ case Instruction::Add:
+ case Instruction::Sub:
+ case Instruction::Trunc:
+ case Instruction::FPTrunc:
+ case Instruction::BitCast:
+ break; // Any undef -> undef
+ case Instruction::FSub:
+ case Instruction::FAdd:
+ case Instruction::FMul:
+ case Instruction::FDiv:
+ case Instruction::FRem:
+ // Floating-point binary operation: be conservative.
+ if (Op0LV.isUndefined() && Op1LV.isUndefined())
+ markForcedConstant(I, Constant::getNullValue(ITy));
+ else
+ markOverdefined(I);
+ return true;
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));
+ case Instruction::SExt:
+ case Instruction::FPToUI:
+ case Instruction::FPToSI:
+ case Instruction::FPExt:
+ case Instruction::PtrToInt:
+ case Instruction::IntToPtr:
+ case Instruction::SIToFP:
+ case Instruction::UIToFP:
+ // undef -> 0; some outputs are impossible
+ markForcedConstant(I, Constant::getNullValue(ITy));
return true;
case Instruction::Mul:
case Instruction::And:
+ // Both operands undef -> undef
+ if (Op0LV.isUndefined() && Op1LV.isUndefined())
+ break;
// undef * X -> 0. X could be zero.
// undef & X -> 0. X could be zero.
- markForcedConstant(LV, I, Constant::getNullValue(ITy));
+ markForcedConstant(I, Constant::getNullValue(ITy));
return true;
case Instruction::Or:
+ // Both operands undef -> undef
+ if (Op0LV.isUndefined() && Op1LV.isUndefined())
+ break;
// undef | X -> -1. X could be -1.
- if (const VectorType *PTy = dyn_cast<VectorType>(ITy))
- markForcedConstant(LV, I,
- Constant::getAllOnesValue(PTy));
- else
- markForcedConstant(LV, I, Constant::getAllOnesValue(ITy));
+ markForcedConstant(I, Constant::getAllOnesValue(ITy));
return true;
+ case Instruction::Xor:
+ // undef ^ undef -> 0; strictly speaking, this is not strictly
+ // necessary, but we try to be nice to people who expect this
+ // behavior in simple cases
+ if (Op0LV.isUndefined() && Op1LV.isUndefined()) {
+ markForcedConstant(I, Constant::getNullValue(ITy));
+ return true;
+ }
+ // undef ^ X -> undef
+ break;
+
case Instruction::SDiv:
case Instruction::UDiv:
case Instruction::SRem:
// 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));
+ markForcedConstant(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);
+ // X >>a undef -> undef.
+ if (Op1LV.isUndefined()) break;
+
+ // undef >>a X -> all ones
+ markForcedConstant(I, Constant::getAllOnesValue(ITy));
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));
+ // X << undef -> undef.
+ // X >> undef -> undef.
+ if (Op1LV.isUndefined()) break;
+
+ // undef << X -> 0
+ // undef >> X -> 0
+ markForcedConstant(I, Constant::getNullValue(ITy));
return true;
case Instruction::Select:
+ Op1LV = getValueState(I->getOperand(1));
// 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.
} else {
// Leave Op1LV as Operand(1)'s LatticeValue.
}
-
+
if (Op1LV.isConstant())
- markForcedConstant(LV, I, Op1LV.getConstant());
+ markForcedConstant(I, Op1LV.getConstant());
else
- markOverdefined(LV, I);
+ markOverdefined(I);
+ return true;
+ case Instruction::Load:
+ // A load here means one of two things: a load of undef from a global,
+ // a load from an unknown pointer. Either way, having it return undef
+ // is okay.
+ break;
+ case Instruction::ICmp:
+ // X == undef -> undef. Other comparisons get more complicated.
+ if (cast<ICmpInst>(I)->isEquality())
+ break;
+ markOverdefined(I);
return true;
case Instruction::Call:
- // If a call has an undef result, it is because it is constant foldable
- // but one of the inputs was undef. Just force the result to
+ case Instruction::Invoke: {
+ // There are two reasons a call can have an undef result
+ // 1. It could be tracked.
+ // 2. It could be constant-foldable.
+ // Because of the way we solve return values, tracked calls must
+ // never be marked overdefined in ResolvedUndefsIn.
+ if (Function *F = CallSite(I).getCalledFunction())
+ if (TrackedRetVals.count(F))
+ break;
+
+ // If the call is constant-foldable, we mark it overdefined because
+ // we do not know what return values are valid.
+ markOverdefined(I);
+ return true;
+ }
+ default:
+ // If we don't know what should happen here, conservatively mark it
// overdefined.
- markOverdefined(LV, I);
+ markOverdefined(I);
return true;
}
}
-
+
+ // Check to see if we have a branch or switch on an undefined value. If so
+ // we force the branch to go one way or the other to make the successor
+ // values live. It doesn't really matter which way we force it.
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 (SI->getNumSuccessors()<2) // no cases
+
+ // If the input to SCCP is actually branch on undef, fix the undef to
+ // false.
+ if (isa<UndefValue>(BI->getCondition())) {
+ BI->setCondition(ConstantInt::getFalse(BI->getContext()));
+ markEdgeExecutable(BB, TI->getSuccessor(1));
+ return true;
+ }
+
+ // Otherwise, it is a branch on a symbolic value which is currently
+ // considered to be undef. Handle this by forcing the input value to the
+ // branch to false.
+ markForcedConstant(BI->getCondition(),
+ ConstantInt::getFalse(TI->getContext()));
+ return true;
+ }
+
+ if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ if (!SI->getNumCases())
continue;
if (!getValueState(SI->getCondition()).isUndefined())
continue;
- } else {
- continue;
- }
-
- // If the edge to the second successor isn't thought to be feasible yet,
- // mark it so now. We pick the second one so that this goes to some
- // enumerated value in a switch instead of going to the default destination.
- if (KnownFeasibleEdges.count(Edge(BB, TI->getSuccessor(1))))
- 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(1));
-
- // This must be a conditional branch of switch on undef. At this point,
- // force the old terminator to branch to the first successor. This is
- // required because we are now influencing the dataflow of the function with
- // the assumption that this edge is taken. If we leave the branch condition
- // as undef, then further analysis could think the undef went another way
- // leading to an inconsistent set of conclusions.
- if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
- BI->setCondition(ConstantInt::getFalse(*Context));
- } else {
- SwitchInst *SI = cast<SwitchInst>(TI);
- SI->setCondition(SI->getCaseValue(1));
+
+ // If the input to SCCP is actually switch on undef, fix the undef to
+ // the first constant.
+ if (isa<UndefValue>(SI->getCondition())) {
+ SI->setCondition(SI->caseBegin().getCaseValue());
+ markEdgeExecutable(BB, SI->caseBegin().getCaseSuccessor());
+ return true;
+ }
+
+ markForcedConstant(SI->getCondition(), SI->caseBegin().getCaseValue());
+ return true;
}
-
- return true;
}
return false;
/// Sparse Conditional Constant Propagator.
///
struct SCCP : public FunctionPass {
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<TargetLibraryInfo>();
+ }
static char ID; // Pass identification, replacement for typeid
- SCCP() : FunctionPass(&ID) {}
+ SCCP() : FunctionPass(ID) {
+ initializeSCCPPass(*PassRegistry::getPassRegistry());
+ }
// runOnFunction - Run the Sparse Conditional Constant Propagation
// algorithm, and return true if the function was modified.
//
bool runOnFunction(Function &F);
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesCFG();
- }
};
} // end anonymous namespace
char SCCP::ID = 0;
-static RegisterPass<SCCP>
-X("sccp", "Sparse Conditional Constant Propagation");
+INITIALIZE_PASS(SCCP, "sccp",
+ "Sparse Conditional Constant Propagation", false, false)
-// createSCCPPass - This is the public interface to this file...
+// createSCCPPass - This is the public interface to this file.
FunctionPass *llvm::createSCCPPass() {
return new SCCP();
}
+static void DeleteInstructionInBlock(BasicBlock *BB) {
+ DEBUG(dbgs() << " BasicBlock Dead:" << *BB);
+ ++NumDeadBlocks;
+
+ // Check to see if there are non-terminating instructions to delete.
+ if (isa<TerminatorInst>(BB->begin()))
+ return;
+
+ // Delete the instructions backwards, as it has a reduced likelihood of having
+ // to update as many def-use and use-def chains.
+ Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
+ while (EndInst != BB->begin()) {
+ // Delete the next to last instruction.
+ BasicBlock::iterator I = EndInst;
+ Instruction *Inst = --I;
+ if (!Inst->use_empty())
+ Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
+ if (isa<LandingPadInst>(Inst)) {
+ EndInst = Inst;
+ continue;
+ }
+ BB->getInstList().erase(Inst);
+ ++NumInstRemoved;
+ }
+}
// runOnFunction() - Run the Sparse Conditional Constant Propagation algorithm,
// and return true if the function was modified.
//
bool SCCP::runOnFunction(Function &F) {
- DEBUG(errs() << "SCCP on function '" << F.getName() << "'\n");
- SCCPSolver Solver;
- Solver.setContext(&F.getContext());
+ DEBUG(dbgs() << "SCCP on function '" << F.getName() << "'\n");
+ const TargetData *TD = getAnalysisIfAvailable<TargetData>();
+ const TargetLibraryInfo *TLI = &getAnalysis<TargetLibraryInfo>();
+ SCCPSolver Solver(TD, TLI);
// Mark the first block of the function as being executable.
Solver.MarkBlockExecutable(F.begin());
// Mark all arguments to the function as being overdefined.
for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;++AI)
- Solver.markOverdefined(AI);
+ Solver.markAnythingOverdefined(AI);
// Solve for constants.
bool ResolvedUndefs = true;
while (ResolvedUndefs) {
Solver.Solve();
- DEBUG(errs() << "RESOLVING UNDEFs\n");
+ DEBUG(dbgs() << "RESOLVING UNDEFs\n");
ResolvedUndefs = Solver.ResolvedUndefsIn(F);
}
// If we decided that there are basic blocks that are dead in this function,
// delete their contents now. Note that we cannot actually delete the blocks,
// as we cannot modify the CFG of the function.
- //
- SmallVector<Instruction*, 512> Insts;
- std::map<Value*, LatticeVal> &Values = Solver.getValueMapping();
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
if (!Solver.isBlockExecutable(BB)) {
- DEBUG(errs() << " 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.
- for (BasicBlock::iterator I = BB->begin(), E = BB->getTerminator();
- I != E; ++I)
- Insts.push_back(I);
- while (!Insts.empty()) {
- Instruction *I = Insts.back();
- Insts.pop_back();
- if (!I->use_empty())
- I->replaceAllUsesWith(UndefValue::get(I->getType()));
- BB->getInstList().erase(I);
- MadeChanges = true;
- ++NumInstRemoved;
- }
- } else {
- // Iterate over all of the instructions in a function, replacing them with
- // constants if we have found them to be of constant values.
- //
- for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
- Instruction *Inst = BI++;
- if (Inst->getType()->isVoidTy() || isa<TerminatorInst>(Inst))
- continue;
-
- LatticeVal &IV = Values[Inst];
- if (!IV.isConstant() && !IV.isUndefined())
- continue;
-
- Constant *Const = IV.isConstant()
- ? IV.getConstant() : UndefValue::get(Inst->getType());
- DEBUG(errs() << " Constant: " << *Const << " = " << *Inst);
+ DeleteInstructionInBlock(BB);
+ MadeChanges = true;
+ continue;
+ }
- // Replaces all of the uses of a variable with uses of the constant.
- Inst->replaceAllUsesWith(Const);
-
- // Delete the instruction.
- Inst->eraseFromParent();
-
- // Hey, we just changed something!
- MadeChanges = true;
- ++NumInstRemoved;
- }
+ // Iterate over all of the instructions in a function, replacing them with
+ // constants if we have found them to be of constant values.
+ //
+ for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
+ Instruction *Inst = BI++;
+ if (Inst->getType()->isVoidTy() || isa<TerminatorInst>(Inst))
+ continue;
+
+ // TODO: Reconstruct structs from their elements.
+ if (Inst->getType()->isStructTy())
+ continue;
+
+ LatticeVal IV = Solver.getLatticeValueFor(Inst);
+ if (IV.isOverdefined())
+ continue;
+
+ Constant *Const = IV.isConstant()
+ ? IV.getConstant() : UndefValue::get(Inst->getType());
+ DEBUG(dbgs() << " Constant: " << *Const << " = " << *Inst);
+
+ // Replaces all of the uses of a variable with uses of the constant.
+ Inst->replaceAllUsesWith(Const);
+
+ // Delete the instruction.
+ Inst->eraseFromParent();
+
+ // Hey, we just changed something!
+ MadeChanges = true;
+ ++NumInstRemoved;
}
+ }
return MadeChanges;
}
/// Constant Propagation.
///
struct IPSCCP : public ModulePass {
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<TargetLibraryInfo>();
+ }
static char ID;
- IPSCCP() : ModulePass(&ID) {}
+ IPSCCP() : ModulePass(ID) {
+ initializeIPSCCPPass(*PassRegistry::getPassRegistry());
+ }
bool runOnModule(Module &M);
};
} // end anonymous namespace
char IPSCCP::ID = 0;
-static RegisterPass<IPSCCP>
-Y("ipsccp", "Interprocedural Sparse Conditional Constant Propagation");
-
-// createIPSCCPPass - This is the public interface to this file...
+INITIALIZE_PASS_BEGIN(IPSCCP, "ipsccp",
+ "Interprocedural Sparse Conditional Constant Propagation",
+ false, false)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
+INITIALIZE_PASS_END(IPSCCP, "ipsccp",
+ "Interprocedural Sparse Conditional Constant Propagation",
+ false, false)
+
+// createIPSCCPPass - This is the public interface to this file.
ModulePass *llvm::createIPSCCPPass() {
return new IPSCCP();
}
-static bool AddressIsTaken(GlobalValue *GV) {
+static bool AddressIsTaken(const 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)) {
+ for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
+ UI != E; ++UI) {
+ const User *U = *UI;
+ if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
if (SI->getOperand(0) == GV || SI->isVolatile())
return true; // Storing addr of GV.
- } else if (isa<InvokeInst>(*UI) || isa<CallInst>(*UI)) {
+ } else if (isa<InvokeInst>(U) || isa<CallInst>(U)) {
// Make sure we are calling the function, not passing the address.
- CallSite CS = CallSite::get(cast<Instruction>(*UI));
- if (CS.hasArgument(GV))
+ ImmutableCallSite CS(cast<Instruction>(U));
+ if (!CS.isCallee(UI))
return true;
- } else if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
+ } else if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
if (LI->isVolatile())
return true;
+ } else if (isa<BlockAddress>(U)) {
+ // blockaddress doesn't take the address of the function, it takes addr
+ // of label.
} else {
return true;
}
+ }
return false;
}
bool IPSCCP::runOnModule(Module &M) {
- LLVMContext *Context = &M.getContext();
-
- SCCPSolver Solver;
- Solver.setContext(Context);
+ const TargetData *TD = getAnalysisIfAvailable<TargetData>();
+ const TargetLibraryInfo *TLI = &getAnalysis<TargetLibraryInfo>();
+ SCCPSolver Solver(TD, TLI);
+
+ // AddressTakenFunctions - This set keeps track of the address-taken functions
+ // that are in the input. As IPSCCP runs through and simplifies code,
+ // functions that were address taken can end up losing their
+ // address-taken-ness. Because of this, we keep track of their addresses from
+ // the first pass so we can use them for the later simplification pass.
+ SmallPtrSet<Function*, 32> AddressTakenFunctions;
// Loop over all functions, marking arguments to those with their addresses
// taken or that are external as overdefined.
//
- for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
- if (!F->hasLocalLinkage() || AddressIsTaken(F)) {
- if (!F->isDeclaration())
- Solver.MarkBlockExecutable(F->begin());
- for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
- AI != E; ++AI)
- Solver.markOverdefined(AI);
- } else {
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+ if (F->isDeclaration())
+ continue;
+
+ // If this is a strong or ODR definition of this function, then we can
+ // propagate information about its result into callsites of it.
+ if (!F->mayBeOverridden())
Solver.AddTrackedFunction(F);
+
+ // If this function only has direct calls that we can see, we can track its
+ // arguments and return value aggressively, and can assume it is not called
+ // unless we see evidence to the contrary.
+ if (F->hasLocalLinkage()) {
+ if (AddressIsTaken(F))
+ AddressTakenFunctions.insert(F);
+ else {
+ Solver.AddArgumentTrackedFunction(F);
+ continue;
+ }
}
+ // Assume the function is called.
+ Solver.MarkBlockExecutable(F->begin());
+
+ // Assume nothing about the incoming arguments.
+ for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
+ AI != E; ++AI)
+ Solver.markAnythingOverdefined(AI);
+ }
+
// 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.
while (ResolvedUndefs) {
Solver.Solve();
- DEBUG(errs() << "RESOLVING UNDEFS\n");
+ DEBUG(dbgs() << "RESOLVING UNDEFS\n");
ResolvedUndefs = false;
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
ResolvedUndefs |= Solver.ResolvedUndefsIn(*F);
// Iterate over all of the instructions in the module, replacing them with
// constants if we have found them to be of constant values.
//
- SmallVector<Instruction*, 512> Insts;
SmallVector<BasicBlock*, 512> 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 (!AI->use_empty()) {
- LatticeVal &IV = Values[AI];
- if (IV.isConstant() || IV.isUndefined()) {
- Constant *CST = IV.isConstant() ?
- IV.getConstant() : UndefValue::get(AI->getType());
- DEBUG(errs() << "*** Arg " << *AI << " = " << *CST <<"\n");
-
- // Replaces all of the uses of a variable with uses of the
- // constant.
- AI->replaceAllUsesWith(CST);
- ++IPNumArgsElimed;
- }
+ if (Solver.isBlockExecutable(F->begin())) {
+ for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
+ AI != E; ++AI) {
+ if (AI->use_empty() || AI->getType()->isStructTy()) continue;
+
+ // TODO: Could use getStructLatticeValueFor to find out if the entire
+ // result is a constant and replace it entirely if so.
+
+ LatticeVal IV = Solver.getLatticeValueFor(AI);
+ if (IV.isOverdefined()) continue;
+
+ Constant *CST = IV.isConstant() ?
+ IV.getConstant() : UndefValue::get(AI->getType());
+ DEBUG(dbgs() << "*** Arg " << *AI << " = " << *CST <<"\n");
+
+ // Replaces all of the uses of a variable with uses of the
+ // constant.
+ AI->replaceAllUsesWith(CST);
+ ++IPNumArgsElimed;
}
+ }
- for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
if (!Solver.isBlockExecutable(BB)) {
- DEBUG(errs() << " BasicBlock Dead:" << *BB);
- ++IPNumDeadBlocks;
+ DeleteInstructionInBlock(BB);
+ MadeChanges = true;
- // Delete the instructions backwards, as it has a reduced likelihood of
- // having to update as many def-use and use-def chains.
TerminatorInst *TI = BB->getTerminator();
- for (BasicBlock::iterator I = BB->begin(), E = TI; I != E; ++I)
- Insts.push_back(I);
-
- while (!Insts.empty()) {
- Instruction *I = Insts.back();
- Insts.pop_back();
- if (!I->use_empty())
- I->replaceAllUsesWith(UndefValue::get(I->getType()));
- BB->getInstList().erase(I);
- MadeChanges = true;
- ++IPNumInstRemoved;
- }
-
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
BasicBlock *Succ = TI->getSuccessor(i);
if (!Succ->empty() && isa<PHINode>(Succ->begin()))
}
if (!TI->use_empty())
TI->replaceAllUsesWith(UndefValue::get(TI->getType()));
- BB->getInstList().erase(TI);
+ TI->eraseFromParent();
if (&*BB != &F->front())
BlocksToErase.push_back(BB);
else
new UnreachableInst(M.getContext(), BB);
+ continue;
+ }
- } else {
- for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
- Instruction *Inst = BI++;
- if (Inst->getType()->isVoidTy())
- continue;
-
- LatticeVal &IV = Values[Inst];
- if (!IV.isConstant() && !IV.isUndefined())
- continue;
-
- Constant *Const = IV.isConstant()
- ? IV.getConstant() : UndefValue::get(Inst->getType());
- DEBUG(errs() << " Constant: " << *Const << " = " << *Inst);
-
- // Replaces all of the uses of a variable with uses of the
- // constant.
- Inst->replaceAllUsesWith(Const);
-
- // Delete the instruction.
- if (!isa<CallInst>(Inst) && !isa<TerminatorInst>(Inst))
- Inst->eraseFromParent();
-
- // Hey, we just changed something!
- MadeChanges = true;
- ++IPNumInstRemoved;
- }
+ for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
+ Instruction *Inst = BI++;
+ if (Inst->getType()->isVoidTy() || Inst->getType()->isStructTy())
+ continue;
+
+ // TODO: Could use getStructLatticeValueFor to find out if the entire
+ // result is a constant and replace it entirely if so.
+
+ LatticeVal IV = Solver.getLatticeValueFor(Inst);
+ if (IV.isOverdefined())
+ continue;
+
+ Constant *Const = IV.isConstant()
+ ? IV.getConstant() : UndefValue::get(Inst->getType());
+ DEBUG(dbgs() << " Constant: " << *Const << " = " << *Inst);
+
+ // Replaces all of the uses of a variable with uses of the
+ // constant.
+ Inst->replaceAllUsesWith(Const);
+
+ // Delete the instruction.
+ if (!isa<CallInst>(Inst) && !isa<TerminatorInst>(Inst))
+ Inst->eraseFromParent();
+
+ // Hey, we just changed something!
+ MadeChanges = true;
+ ++IPNumInstRemoved;
}
+ }
// Now that all instructions in the function are constant folded, erase dead
// blocks, because we can now use ConstantFoldTerminator to get rid of
for (unsigned i = 0, e = BlocksToErase.size(); i != e; ++i) {
// If there are any PHI nodes in this successor, drop entries for BB now.
BasicBlock *DeadBB = BlocksToErase[i];
- while (!DeadBB->use_empty()) {
- Instruction *I = cast<Instruction>(DeadBB->use_back());
+ for (Value::use_iterator UI = DeadBB->use_begin(), UE = DeadBB->use_end();
+ UI != UE; ) {
+ // Grab the user and then increment the iterator early, as the user
+ // will be deleted. Step past all adjacent uses from the same user.
+ Instruction *I = dyn_cast<Instruction>(*UI);
+ do { ++UI; } while (UI != UE && *UI == I);
+
+ // Ignore blockaddress users; BasicBlock's dtor will handle them.
+ if (!I) continue;
+
bool Folded = ConstantFoldTerminator(I->getParent());
if (!Folded) {
// The constant folder may not have been able to fold the terminator
llvm_unreachable("Didn't fold away reference to block!");
}
#endif
-
+
// Make this an uncond branch to the first successor.
TerminatorInst *TI = I->getParent()->getTerminator();
BranchInst::Create(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();
}
// 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.
+ //
+ // Do this in two stages: first identify the functions we should process, then
+ // actually zap their returns. This is important because we can only do this
+ // if the address of the function isn't taken. In cases where a return is the
+ // last use of a function, the order of processing functions would affect
+ // whether other functions are optimizable.
+ SmallVector<ReturnInst*, 8> ReturnsToZap;
+
// TODO: Process multiple value ret instructions also.
const DenseMap<Function*, LatticeVal> &RV = Solver.getTrackedRetVals();
for (DenseMap<Function*, LatticeVal>::const_iterator I = RV.begin(),
- E = RV.end(); I != E; ++I)
- if (!I->second.isOverdefined() &&
- !I->first->getReturnType()->isVoidTy()) {
- Function *F = I->first;
- for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
- if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
- if (!isa<UndefValue>(RI->getOperand(0)))
- RI->setOperand(0, UndefValue::get(F->getReturnType()));
- }
+ E = RV.end(); I != E; ++I) {
+ Function *F = I->first;
+ if (I->second.isOverdefined() || F->getReturnType()->isVoidTy())
+ continue;
+
+ // We can only do this if we know that nothing else can call the function.
+ if (!F->hasLocalLinkage() || AddressTakenFunctions.count(F))
+ continue;
+
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
+ if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
+ if (!isa<UndefValue>(RI->getOperand(0)))
+ ReturnsToZap.push_back(RI);
+ }
+
+ // Zap all returns which we've identified as zap to change.
+ for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
+ Function *F = ReturnsToZap[i]->getParent()->getParent();
+ ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
+ }
- // If we infered constant or undef values for globals variables, we can delete
+ // If we inferred constant or undef values for globals variables, we can delete
// the global and any stores that remain to it.
const DenseMap<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
for (DenseMap<GlobalVariable*, LatticeVal>::const_iterator I = TG.begin(),
GlobalVariable *GV = I->first;
assert(!I->second.isOverdefined() &&
"Overdefined values should have been taken out of the map!");
- DEBUG(errs() << "Found that GV '" << GV->getName() << "' is constant!\n");
+ DEBUG(dbgs() << "Found that GV '" << GV->getName() << "' is constant!\n");
while (!GV->use_empty()) {
StoreInst *SI = cast<StoreInst>(GV->use_back());
SI->eraseFromParent();
projects / oota-llvm.git / blobdiff