#define DEBUG_TYPE "sccp"
#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/IPO.h"
#include "llvm/Constants.h"
-#include "llvm/Function.h"
-#include "llvm/GlobalVariable.h"
+#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Pass.h"
-#include "llvm/Type.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Support/CallSite.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/hash_map"
#include "llvm/ADT/Statistic.h"
// instruction may occupy. It is a simple class with value semantics.
//
namespace {
- Statistic<> NumInstRemoved("sccp", "Number of instructions removed");
class LatticeVal {
enum {
std::set<BasicBlock*> BBExecutable;// The basic blocks that are executable
hash_map<Value*, LatticeVal> ValueState; // The state each value is in...
+ /// GlobalValue - If we are tracking any values for the contents of a global
+ /// variable, we keep a mapping from the constant accessor to the element of
+ /// the global, to the currently known value. If the value becomes
+ /// overdefined, it's entry is simply removed from this map.
+ hash_map<GlobalVariable*, LatticeVal> TrackedGlobals;
+
+ /// TrackedFunctionRetVals - If we are tracking arguments into and the return
+ /// value out of a function, it will have an entry in this map, indicating
+ /// what the known return value for the function is.
+ hash_map<Function*, LatticeVal> TrackedFunctionRetVals;
+
// 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.
- std::vector<Instruction*> OverdefinedInstWorkList;// The overdefined
- // instruction work list
- std::vector<Instruction*> InstWorkList;// The instruction work list
+ std::vector<Value*> OverdefinedInstWorkList;
+ std::vector<Value*> InstWorkList;
std::vector<BasicBlock*> BBWorkList; // The BasicBlock work list
BBWorkList.push_back(BB); // Add the block to the work list!
}
+ /// TrackValueOfGlobalVariable - Clients can use this method to
+ /// inform the SCCPSolver that it should track loads and stores to the
+ /// 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()) {
+ LatticeVal &IV = TrackedGlobals[GV];
+ if (!isa<UndefValue>(GV->getInitializer()))
+ IV.markConstant(GV->getInitializer());
+ }
+ }
+
+ /// AddTrackedFunction - If the SCCP solver is supposed to track calls into
+ /// and out of the specified function (which cannot have its address taken),
+ /// this method must be called.
+ void AddTrackedFunction(Function *F) {
+ assert(F->hasInternalLinkage() && "Can only track internal functions!");
+ // Add an entry, F -> undef.
+ TrackedFunctionRetVals[F];
+ }
+
/// Solve - Solve for constants and executable blocks.
///
void Solve();
+ /// ResolveBranchesIn - While solving the dataflow for a function, we assume
+ /// that branches on undef values cannot reach any of their successors.
+ /// However, this is not a safe assumption. After we solve dataflow, this
+ /// method should be use to handle this. If this returns true, the solver
+ /// should be rerun.
+ bool ResolveBranchesIn(Function &F);
+
/// getExecutableBlocks - Once we have solved for constants, return the set of
/// blocks that is known to be executable.
std::set<BasicBlock*> &getExecutableBlocks() {
return ValueState;
}
+ /// getTrackedFunctionRetVals - Get the inferred return value map.
+ ///
+ const hash_map<Function*, LatticeVal> &getTrackedFunctionRetVals() {
+ return TrackedFunctionRetVals;
+ }
+
+ /// getTrackedGlobals - Get and return the set of inferred initializers for
+ /// global variables.
+ const hash_map<GlobalVariable*, LatticeVal> &getTrackedGlobals() {
+ return TrackedGlobals;
+ }
+
+
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, Instruction *I, Constant *C) {
+ inline void markConstant(LatticeVal &IV, Value *V, Constant *C) {
if (IV.markConstant(C)) {
- DEBUG(std::cerr << "markConstant: " << *C << ": " << *I);
- InstWorkList.push_back(I);
+ DEBUG(std::cerr << "markConstant: " << *C << ": " << *V);
+ InstWorkList.push_back(V);
}
}
- inline void markConstant(Instruction *I, Constant *C) {
- markConstant(ValueState[I], I, C);
+ inline void markConstant(Value *V, Constant *C) {
+ markConstant(ValueState[V], V, C);
}
// 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, Instruction *I) {
+ inline void markOverdefined(LatticeVal &IV, Value *V) {
if (IV.markOverdefined()) {
- DEBUG(std::cerr << "markOverdefined: " << *I);
+ DEBUG(std::cerr << "markOverdefined: ";
+ if (Function *F = dyn_cast<Function>(V))
+ std::cerr << "Function '" << F->getName() << "'\n";
+ else
+ std::cerr << *V);
// Only instructions go on the work list
- OverdefinedInstWorkList.push_back(I);
+ OverdefinedInstWorkList.push_back(V);
}
}
- inline void markOverdefined(Instruction *I) {
- markOverdefined(ValueState[I], I);
+ inline void markOverdefined(Value *V) {
+ markOverdefined(ValueState[V], V);
+ }
+
+ inline void mergeInValue(LatticeVal &IV, Value *V, LatticeVal &MergeWithV) {
+ if (IV.isOverdefined() || MergeWithV.isUndefined())
+ return; // Noop.
+ if (MergeWithV.isOverdefined())
+ markOverdefined(IV, V);
+ else if (IV.isUndefined())
+ markConstant(IV, V, MergeWithV.getConstant());
+ else if (IV.getConstant() != MergeWithV.getConstant())
+ markOverdefined(IV, V);
}
// getValueState - Return the LatticeVal object that corresponds to the value.
// The destination is already executable, but 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) {
- PHINode *PN = cast<PHINode>(I);
- visitPHINode(*PN);
- }
+ for (BasicBlock::iterator I = Dest->begin(); isa<PHINode>(I); ++I)
+ visitPHINode(*cast<PHINode>(I));
} else {
MarkBlockExecutable(Dest);
void visitPHINode(PHINode &I);
// Terminators
- void visitReturnInst(ReturnInst &I) { /*does not have an effect*/ }
+ void visitReturnInst(ReturnInst &I);
void visitTerminatorInst(TerminatorInst &TI);
void visitCastInst(CastInst &I);
void visitShiftInst(ShiftInst &I) { visitBinaryOperator(I); }
// Instructions that cannot be folded away...
- void visitStoreInst (Instruction &I) { /*returns void*/ }
+ void visitStoreInst (Instruction &I);
void visitLoadInst (LoadInst &I);
void visitGetElementPtrInst(GetElementPtrInst &I);
- void visitCallInst (CallInst &I);
- void visitInvokeInst (TerminatorInst &I) {
- if (I.getType() != Type::VoidTy) markOverdefined(&I);
- visitTerminatorInst(I);
+ void visitCallInst (CallInst &I) { visitCallSite(CallSite::get(&I)); }
+ void visitInvokeInst (InvokeInst &II) {
+ visitCallSite(CallSite::get(&II));
+ visitTerminatorInst(II);
}
+ void visitCallSite (CallSite CS);
void visitUnwindInst (TerminatorInst &I) { /*returns void*/ }
void visitUnreachableInst(TerminatorInst &I) { /*returns void*/ }
void visitAllocationInst(Instruction &I) { markOverdefined(&I); }
markConstant(PNIV, &PN, OperandVal); // Acquire operand value
}
+void SCCPSolver::visitReturnInst(ReturnInst &I) {
+ if (I.getNumOperands() == 0) return; // Ret void
+
+ // If we are tracking the return value of this function, merge it in.
+ Function *F = I.getParent()->getParent();
+ if (F->hasInternalLinkage() && !TrackedFunctionRetVals.empty()) {
+ hash_map<Function*, LatticeVal>::iterator TFRVI =
+ TrackedFunctionRetVals.find(F);
+ if (TFRVI != TrackedFunctionRetVals.end() &&
+ !TFRVI->second.isOverdefined()) {
+ LatticeVal &IV = getValueState(I.getOperand(0));
+ mergeInValue(TFRVI->second, F, IV);
+ }
+ }
+}
+
+
void SCCPSolver::visitTerminatorInst(TerminatorInst &TI) {
std::vector<bool> SuccFeasible;
getFeasibleSuccessors(TI, SuccFeasible);
LatticeVal &V2State = getValueState(I.getOperand(1));
if (V1State.isOverdefined() || V2State.isOverdefined()) {
+ // If this is an AND or OR with 0 or -1, it doesn't matter that the other
+ // operand is overdefined.
+ if (I.getOpcode() == Instruction::And || I.getOpcode() == Instruction::Or) {
+ LatticeVal *NonOverdefVal = 0;
+ if (!V1State.isOverdefined()) {
+ NonOverdefVal = &V1State;
+ } else if (!V2State.isOverdefined()) {
+ NonOverdefVal = &V2State;
+ }
+
+ if (NonOverdefVal) {
+ if (NonOverdefVal->isUndefined()) {
+ // Could annihilate value.
+ if (I.getOpcode() == Instruction::And)
+ markConstant(IV, &I, Constant::getNullValue(I.getType()));
+ else
+ markConstant(IV, &I, ConstantInt::getAllOnesValue(I.getType()));
+ return;
+ } else {
+ if (I.getOpcode() == Instruction::And) {
+ if (NonOverdefVal->getConstant()->isNullValue()) {
+ markConstant(IV, &I, NonOverdefVal->getConstant());
+ return; // X or 0 = -1
+ }
+ } else {
+ if (ConstantIntegral *CI =
+ dyn_cast<ConstantIntegral>(NonOverdefVal->getConstant()))
+ if (CI->isAllOnesValue()) {
+ markConstant(IV, &I, NonOverdefVal->getConstant());
+ return; // X or -1 = -1
+ }
+ }
+ }
+ }
+ }
+
+
// If both operands are PHI nodes, it is possible that this instruction has
// a constant value, despite the fact that the PHI node doesn't. Check for
// this condition now.
ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
if (CS == 0) return 0;
if (CU->getValue() >= CS->getNumOperands()) return 0;
- C = CS->getOperand(CU->getValue());
+ C = CS->getOperand((unsigned)CU->getValue());
} else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
ConstantArray *CA = dyn_cast<ConstantArray>(C);
if (CA == 0) return 0;
if ((uint64_t)CS->getValue() >= CA->getNumOperands()) return 0;
- C = CA->getOperand(CS->getValue());
+ C = CA->getOperand((unsigned)CS->getValue());
} else
return 0;
return C;
}
+void SCCPSolver::visitStoreInst(Instruction &SI) {
+ if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
+ return;
+ GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1));
+ hash_map<GlobalVariable*, LatticeVal>::iterator I = TrackedGlobals.find(GV);
+ 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);
+ 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) {
}
// Transform load (constant global) into the value loaded.
- if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr))
- if (GV->isConstant() && !GV->isExternal()) {
- markConstant(IV, &I, GV->getInitializer());
- return;
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
+ if (GV->isConstant()) {
+ if (!GV->isExternal()) {
+ markConstant(IV, &I, GV->getInitializer());
+ return;
+ }
+ } else if (!TrackedGlobals.empty()) {
+ // If we are tracking this global, merge in the known value for it.
+ hash_map<GlobalVariable*, LatticeVal>::iterator It =
+ 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))
markOverdefined(IV, &I);
}
-void SCCPSolver::visitCallInst(CallInst &I) {
- LatticeVal &IV = ValueState[&I];
+void SCCPSolver::visitCallSite(CallSite CS) {
+ Function *F = CS.getCalledFunction();
+
+ // If we are tracking this function, we must make sure to bind arguments as
+ // appropriate.
+ hash_map<Function*, LatticeVal>::iterator TFRVI =TrackedFunctionRetVals.end();
+ if (F && F->hasInternalLinkage())
+ TFRVI = TrackedFunctionRetVals.find(F);
+
+ if (TFRVI != TrackedFunctionRetVals.end()) {
+ // If this is the first call to the function hit, mark its entry block
+ // executable.
+ if (!BBExecutable.count(F->begin()))
+ MarkBlockExecutable(F->begin());
+
+ CallSite::arg_iterator CAI = CS.arg_begin();
+ for (Function::aiterator AI = F->abegin(), E = F->aend();
+ AI != E; ++AI, ++CAI) {
+ LatticeVal &IV = ValueState[AI];
+ if (!IV.isOverdefined())
+ mergeInValue(IV, AI, getValueState(*CAI));
+ }
+ }
+ Instruction *I = CS.getInstruction();
+ if (I->getType() == Type::VoidTy) return;
+
+ LatticeVal &IV = ValueState[I];
if (IV.isOverdefined()) return;
- Function *F = I.getCalledFunction();
- if (F == 0 || !canConstantFoldCallTo(F)) {
- markOverdefined(IV, &I);
+ // Propagate the return value of the function to the value of the instruction.
+ if (TFRVI != TrackedFunctionRetVals.end()) {
+ mergeInValue(IV, I, TFRVI->second);
+ return;
+ }
+
+ if (F == 0 || !F->isExternal() || !canConstantFoldCallTo(F)) {
+ markOverdefined(IV, I);
return;
}
std::vector<Constant*> Operands;
- Operands.reserve(I.getNumOperands()-1);
+ Operands.reserve(I->getNumOperands()-1);
- for (unsigned i = 1, e = I.getNumOperands(); i != e; ++i) {
- LatticeVal &State = getValueState(I.getOperand(i));
+ for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
+ AI != E; ++AI) {
+ LatticeVal &State = getValueState(*AI);
if (State.isUndefined())
return; // Operands are not resolved yet...
else if (State.isOverdefined()) {
- markOverdefined(IV, &I);
+ markOverdefined(IV, I);
return;
}
assert(State.isConstant() && "Unknown state!");
}
if (Constant *C = ConstantFoldCall(F, Operands))
- markConstant(IV, &I, C);
+ markConstant(IV, I, C);
else
- markOverdefined(IV, &I);
+ markOverdefined(IV, I);
}
!OverdefinedInstWorkList.empty()) {
// Process the instruction work list...
while (!OverdefinedInstWorkList.empty()) {
- Instruction *I = OverdefinedInstWorkList.back();
+ Value *I = OverdefinedInstWorkList.back();
OverdefinedInstWorkList.pop_back();
- DEBUG(std::cerr << "\nPopped off OI-WL: " << I);
+ DEBUG(std::cerr << "\nPopped off OI-WL: " << *I);
// "I" got into the work list because it either made the transition from
// bottom to constant
}
// Process the instruction work list...
while (!InstWorkList.empty()) {
- Instruction *I = InstWorkList.back();
+ Value *I = InstWorkList.back();
InstWorkList.pop_back();
DEBUG(std::cerr << "\nPopped off I-WL: " << *I);
}
}
+/// ResolveBranchesIn - While solving the dataflow for a function, we assume
+/// that branches on undef values cannot reach any of their successors.
+/// However, this is not a safe assumption. After we solve dataflow, this
+/// method should be use to handle this. If this returns true, the solver
+/// should be rerun.
+bool SCCPSolver::ResolveBranchesIn(Function &F) {
+ bool BranchesResolved = false;
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+ if (BBExecutable.count(BB)) {
+ TerminatorInst *TI = BB->getTerminator();
+ if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+ if (BI->isConditional()) {
+ LatticeVal &BCValue = getValueState(BI->getCondition());
+ if (BCValue.isUndefined()) {
+ BI->setCondition(ConstantBool::True);
+ BranchesResolved = true;
+ visit(BI);
+ }
+ }
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ LatticeVal &SCValue = getValueState(SI->getCondition());
+ if (SCValue.isUndefined()) {
+ const Type *CondTy = SI->getCondition()->getType();
+ SI->setCondition(Constant::getNullValue(CondTy));
+ BranchesResolved = true;
+ visit(SI);
+ }
+ }
+ }
+
+ return BranchesResolved;
+}
+
namespace {
-//===----------------------------------------------------------------------===//
-//
-/// SCCP Class - This class does all of the work of Sparse Conditional Constant
-/// Propagation.
-///
-class SCCP : public FunctionPass, public InstVisitor<SCCP> {
-public:
+ Statistic<> NumInstRemoved("sccp", "Number of instructions removed");
+ Statistic<> NumDeadBlocks ("sccp", "Number of basic blocks unreachable");
- // 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();
- }
-};
+ /// SCCP Class - This class uses the SCCPSolver to implement a per-function
+ /// Sparse Conditional COnstant Propagator.
+ ///
+ struct SCCP : public FunctionPass {
+ // 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();
+ }
+ };
RegisterOpt<SCCP> X("sccp", "Sparse Conditional Constant Propagation");
} // end anonymous namespace
}
-//===----------------------------------------------------------------------===//
-// SCCP Class Implementation
-
-
// runOnFunction() - Run the Sparse Conditional Constant Propagation algorithm,
// and return true if the function was modified.
//
Values[AI].markOverdefined();
// Solve for constants.
- Solver.Solve();
+ bool ResolvedBranches = true;
+ while (ResolvedBranches) {
+ Solver.Solve();
+ DEBUG(std::cerr << "RESOLVING UNDEF BRANCHES\n");
+ ResolvedBranches = Solver.ResolveBranchesIn(F);
+ }
bool MadeChanges = false;
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (!ExecutableBBs.count(BB)) {
DEBUG(std::cerr << " BasicBlock Dead:" << *BB);
+ ++NumDeadBlocks;
+
// Delete the instructions backwards, as it has a reduced likelihood of
// having to update as many def-use and use-def chains.
std::vector<Instruction*> Insts;
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() != Type::VoidTy) {
+ LatticeVal &IV = Values[Inst];
+ if (IV.isConstant() || IV.isUndefined() &&
+ !isa<TerminatorInst>(Inst)) {
+ Constant *Const = IV.isConstant()
+ ? IV.getConstant() : UndefValue::get(Inst->getType());
+ DEBUG(std::cerr << " Constant: " << *Const << " = " << *Inst);
+
+ // Replaces all of the uses of a variable with uses of the constant.
+ Inst->replaceAllUsesWith(Const);
+
+ // Delete the instruction.
+ BB->getInstList().erase(Inst);
+
+ // Hey, we just changed something!
+ MadeChanges = true;
+ ++NumInstRemoved;
+ }
+ }
+ }
+ }
+
+ return MadeChanges;
+}
+
+namespace {
+ Statistic<> IPNumInstRemoved("ipsccp", "Number of instructions removed");
+ Statistic<> IPNumDeadBlocks ("ipsccp", "Number of basic blocks unreachable");
+ Statistic<> IPNumArgsElimed ("ipsccp",
+ "Number of arguments constant propagated");
+ Statistic<> IPNumGlobalConst("ipsccp",
+ "Number of globals found to be constant");
+
+ //===--------------------------------------------------------------------===//
+ //
+ /// IPSCCP Class - This class implements interprocedural Sparse Conditional
+ /// Constant Propagation.
+ ///
+ struct IPSCCP : public ModulePass {
+ bool runOnModule(Module &M);
+ };
+
+ RegisterOpt<IPSCCP>
+ Y("ipsccp", "Interprocedural Sparse Conditional Constant Propagation");
+} // end anonymous namespace
+
+// createIPSCCPPass - This is the public interface to this file...
+ModulePass *llvm::createIPSCCPPass() {
+ return new IPSCCP();
+}
+
+
+static bool AddressIsTaken(GlobalValue *GV) {
+ for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
+ UI != E; ++UI)
+ if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
+ if (SI->getOperand(0) == GV || SI->isVolatile())
+ return true; // Storing addr of GV.
+ } else if (isa<InvokeInst>(*UI) || isa<CallInst>(*UI)) {
+ // Make sure we are calling the function, not passing the address.
+ CallSite CS = CallSite::get(cast<Instruction>(*UI));
+ for (CallSite::arg_iterator AI = CS.arg_begin(),
+ E = CS.arg_end(); AI != E; ++AI)
+ if (*AI == GV)
+ return true;
+ } else if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
+ if (LI->isVolatile())
+ return true;
+ } else {
+ return true;
}
+ return false;
+}
- // Iterate over all of the instructions in a function, replacing them with
+bool IPSCCP::runOnModule(Module &M) {
+ SCCPSolver Solver;
+
+ // Loop over all functions, marking arguments to those with their addresses
+ // taken or that are external as overdefined.
+ //
+ hash_map<Value*, LatticeVal> &Values = Solver.getValueMapping();
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
+ if (!F->hasInternalLinkage() || AddressIsTaken(F)) {
+ if (!F->isExternal())
+ Solver.MarkBlockExecutable(F->begin());
+ for (Function::aiterator AI = F->abegin(), E = F->aend(); AI != E; ++AI)
+ Values[AI].markOverdefined();
+ } else {
+ Solver.AddTrackedFunction(F);
+ }
+
+ // Loop over global variables. We inform the solver about any internal global
+ // variables that do not have their 'addresses taken'. If they don't have
+ // their addresses taken, we can propagate constants through them.
+ for (Module::giterator G = M.gbegin(), E = M.gend(); G != E; ++G)
+ if (!G->isConstant() && G->hasInternalLinkage() && !AddressIsTaken(G))
+ Solver.TrackValueOfGlobalVariable(G);
+
+ // Solve for constants.
+ bool ResolvedBranches = true;
+ while (ResolvedBranches) {
+ Solver.Solve();
+
+ DEBUG(std::cerr << "RESOLVING UNDEF BRANCHES\n");
+ ResolvedBranches = false;
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
+ ResolvedBranches |= Solver.ResolveBranchesIn(*F);
+ }
+
+ bool MadeChanges = false;
+
+ // Iterate over all of the instructions in the module, replacing them with
// constants if we have found them to be of constant values.
//
- for (Function::iterator BB = F.begin(), BBE = F.end(); BB != BBE; ++BB)
- for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
- Instruction *Inst = BI++;
- if (Inst->getType() != Type::VoidTy) {
- LatticeVal &IV = Values[Inst];
+ std::set<BasicBlock*> &ExecutableBBs = Solver.getExecutableBlocks();
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+ for (Function::aiterator AI = F->abegin(), E = F->aend(); AI != E; ++AI)
+ if (!AI->use_empty()) {
+ LatticeVal &IV = Values[AI];
if (IV.isConstant() || IV.isUndefined()) {
- Constant *Const;
- if (IV.isConstant()) {
- Const = IV.getConstant();
- DEBUG(std::cerr << " Constant: " << *Const << " = " << *Inst);
- } else {
- Const = UndefValue::get(Inst->getType());
- DEBUG(std::cerr << " Undefined: " << *Inst);
- }
-
- // Replaces all of the uses of a variable with uses of the constant.
- Inst->replaceAllUsesWith(Const);
-
- // Delete the instruction.
- BB->getInstList().erase(Inst);
+ Constant *CST = IV.isConstant() ?
+ IV.getConstant() : UndefValue::get(AI->getType());
+ DEBUG(std::cerr << "*** Arg " << *AI << " = " << *CST <<"\n");
- // Hey, we just changed something!
+ // Replaces all of the uses of a variable with uses of the
+ // constant.
+ AI->replaceAllUsesWith(CST);
+ ++IPNumArgsElimed;
+ }
+ }
+
+ std::vector<BasicBlock*> BlocksToErase;
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
+ if (!ExecutableBBs.count(BB)) {
+ DEBUG(std::cerr << " BasicBlock Dead:" << *BB);
+ ++IPNumDeadBlocks;
+
+ // Delete the instructions backwards, as it has a reduced likelihood of
+ // having to update as many def-use and use-def chains.
+ std::vector<Instruction*> Insts;
+ TerminatorInst *TI = BB->getTerminator();
+ for (BasicBlock::iterator I = BB->begin(), E = TI; I != E; ++I)
+ Insts.push_back(I);
+
+ 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;
+ ++IPNumInstRemoved;
}
+
+ for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
+ BasicBlock *Succ = TI->getSuccessor(i);
+ if (Succ->begin() != Succ->end() && isa<PHINode>(Succ->begin()))
+ TI->getSuccessor(i)->removePredecessor(BB);
+ }
+ if (!TI->use_empty())
+ TI->replaceAllUsesWith(UndefValue::get(TI->getType()));
+ BB->getInstList().erase(TI);
+
+ if (&*BB != &F->front())
+ BlocksToErase.push_back(BB);
+ else
+ new UnreachableInst(BB);
+
+ } else {
+ for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
+ Instruction *Inst = BI++;
+ if (Inst->getType() != Type::VoidTy) {
+ LatticeVal &IV = Values[Inst];
+ if (IV.isConstant() || IV.isUndefined() &&
+ !isa<TerminatorInst>(Inst)) {
+ Constant *Const = IV.isConstant()
+ ? IV.getConstant() : UndefValue::get(Inst->getType());
+ DEBUG(std::cerr << " Constant: " << *Const << " = " << *Inst);
+
+ // Replaces all of the uses of a variable with uses of the
+ // constant.
+ Inst->replaceAllUsesWith(Const);
+
+ // Delete the instruction.
+ if (!isa<TerminatorInst>(Inst) && !isa<CallInst>(Inst))
+ BB->getInstList().erase(Inst);
+
+ // 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
+ // in-edges.
+ 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());
+ bool Folded = ConstantFoldTerminator(I->getParent());
+ assert(Folded && "Didn't fold away reference to block!");
}
+
+ // Finally, delete the basic block.
+ F->getBasicBlockList().erase(DeadBB);
}
+ }
+ // If we inferred constant or undef return values for a function, we replaced
+ // all call uses with the inferred value. This means we don't need to bother
+ // actually returning anything from the function. Replace all return
+ // instructions with return undef.
+ const hash_map<Function*, LatticeVal> &RV =Solver.getTrackedFunctionRetVals();
+ for (hash_map<Function*, LatticeVal>::const_iterator I = RV.begin(),
+ E = RV.end(); I != E; ++I)
+ if (!I->second.isOverdefined() &&
+ I->first->getReturnType() != Type::VoidTy) {
+ 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()));
+ }
+
+ // If we infered constant or undef values for globals variables, we can delete
+ // the global and any stores that remain to it.
+ const hash_map<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
+ for (hash_map<GlobalVariable*, LatticeVal>::const_iterator I = TG.begin(),
+ E = TG.end(); I != E; ++I) {
+ GlobalVariable *GV = I->first;
+ assert(!I->second.isOverdefined() &&
+ "Overdefined values should have been taken out of the map!");
+ DEBUG(std::cerr << "Found that GV '" << GV->getName()<< "' is constant!\n");
+ while (!GV->use_empty()) {
+ StoreInst *SI = cast<StoreInst>(GV->use_back());
+ SI->eraseFromParent();
+ }
+ M.getGlobalList().erase(GV);
+ ++IPNumGlobalConst;
+ }
+
return MadeChanges;
}
-
-
projects / oota-llvm.git / blobdiff