// * Assumes values are constant unless proven otherwise
// * Assumes BasicBlocks are dead unless proven otherwise
// * Proves values to be constant, and replaces them with constants
-// . Proves conditional branches constant, and unconditionalizes them
+// * Proves conditional branches constant, and unconditionalizes them
// * Folds multiple identical constants in the constant pool together
//
// Notice that:
//
//===----------------------------------------------------------------------===//
-#include "llvm/Optimizations/ConstantProp.h"
-#include "llvm/Optimizations/ConstantHandling.h"
-#include "llvm/Method.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/ConstantHandling.h"
+#include "llvm/Function.h"
#include "llvm/BasicBlock.h"
-#include "llvm/ConstPoolVals.h"
-#include "llvm/InstrTypes.h"
-#include "llvm/iOther.h"
+#include "llvm/iPHINode.h"
#include "llvm/iMemory.h"
#include "llvm/iTerminators.h"
-#include "llvm/Support/STLExtras.h"
-#include "llvm/Assembly/Writer.h"
+#include "llvm/iOther.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/InstVisitor.h"
+#include "Support/STLExtras.h"
#include <algorithm>
-#include <map>
#include <set>
+#include <iostream>
+using std::cerr;
+
+#if 0 // Enable this to get SCCP debug output
+#define DEBUG_SCCP(X) X
+#else
+#define DEBUG_SCCP(X)
+#endif
// InstVal class - This class represents the different lattice values that an
-// instruction may occupy. It is a simple class with value semantics. The
-// potential constant value that is pointed to is owned by the constant pool
-// for the method being optimized.
+// instruction may occupy. It is a simple class with value semantics.
//
+namespace {
class InstVal {
enum {
- Undefined, // This instruction has no known value
- Constant, // This instruction has a constant value
+ undefined, // This instruction has no known value
+ constant, // This instruction has a constant value
// Range, // This instruction is known to fall within a range
- Overdefined // This instruction has an unknown value
- } LatticeValue; // The current lattice position
- ConstPoolVal *ConstantVal; // If Constant value, the current value
+ overdefined // This instruction has an unknown value
+ } LatticeValue; // The current lattice position
+ Constant *ConstantVal; // If Constant value, the current value
public:
- inline InstVal() : LatticeValue(Undefined), ConstantVal(0) {}
+ inline InstVal() : LatticeValue(undefined), ConstantVal(0) {}
// markOverdefined - Return true if this is a new status to be in...
inline bool markOverdefined() {
- if (LatticeValue != Overdefined) {
- LatticeValue = Overdefined;
+ if (LatticeValue != overdefined) {
+ LatticeValue = overdefined;
return true;
}
return false;
}
// markConstant - Return true if this is a new status for us...
- inline bool markConstant(ConstPoolVal *V) {
- if (LatticeValue != Constant) {
- LatticeValue = Constant;
+ inline bool markConstant(Constant *V) {
+ if (LatticeValue != constant) {
+ LatticeValue = constant;
ConstantVal = V;
return true;
} else {
return false;
}
- inline bool isUndefined() const { return LatticeValue == Undefined; }
- inline bool isConstant() const { return LatticeValue == Constant; }
- inline bool isOverdefined() const { return LatticeValue == Overdefined; }
+ inline bool isUndefined() const { return LatticeValue == undefined; }
+ inline bool isConstant() const { return LatticeValue == constant; }
+ inline bool isOverdefined() const { return LatticeValue == overdefined; }
- inline ConstPoolVal *getConstant() const { return ConstantVal; }
+ inline Constant *getConstant() const { return ConstantVal; }
};
+} // end anonymous namespace
//===----------------------------------------------------------------------===//
// SCCP Class
//
// This class does all of the work of Sparse Conditional Constant Propogation.
-// It's public interface consists of a constructor and a doSCCP() method.
//
-class SCCP {
- Method *M; // The method that we are working on...
+namespace {
+class SCCP : public FunctionPass, public InstVisitor<SCCP> {
+ std::set<BasicBlock*> BBExecutable;// The basic blocks that are executable
+ std::map<Value*, InstVal> ValueState; // The state each value is in...
- set<BasicBlock*> BBExecutable; // The basic blocks that are executable
- map<Value*, InstVal> ValueState; // The state each value is in...
+ std::vector<Instruction*> InstWorkList;// The instruction work list
+ std::vector<BasicBlock*> BBWorkList; // The BasicBlock work list
+public:
- vector<Instruction*> InstWorkList; // The instruction work list
- vector<BasicBlock*> BBWorkList; // The BasicBlock work list
+ const char *getPassName() const {
+ return "Sparse Conditional Constant Propogation";
+ }
- //===--------------------------------------------------------------------===//
- // The public interface for this class
+ // runOnFunction - Run the Sparse Conditional Constant Propogation algorithm,
+ // and return true if the function was modified.
//
-public:
+ bool runOnFunction(Function *F);
- // SCCP Ctor - Save the method to operate on...
- inline SCCP(Method *m) : M(m) {}
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.preservesCFG();
+ }
- // doSCCP() - Run the Sparse Conditional Constant Propogation algorithm, and
- // return true if the method was modified.
- bool doSCCP();
//===--------------------------------------------------------------------===//
// The implementation of this class
//
private:
+ friend class InstVisitor<SCCP>; // Allow callbacks from visitor
// markValueOverdefined - 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 bool markConstant(Instruction *I, ConstPoolVal *V) {
- //cerr << "markConstant: " << V << " = " << I;
+ inline bool markConstant(Instruction *I, Constant *V) {
+ DEBUG_SCCP(cerr << "markConstant: " << V << " = " << I);
+
if (ValueState[I].markConstant(V)) {
InstWorkList.push_back(I);
return true;
inline bool markOverdefined(Value *V) {
if (ValueState[V].markOverdefined()) {
if (Instruction *I = dyn_cast<Instruction>(V)) {
- //cerr << "markOverdefined: " << V;
+ DEBUG_SCCP(cerr << "markOverdefined: " << V);
InstWorkList.push_back(I); // Only instructions go on the work list
}
return true;
// getValueState - Return the InstVal object that corresponds to the value.
// This function is neccesary because not all values should start out in the
- // underdefined state... MethodArgument's should be overdefined, and constants
- // should be marked as constants. If a value is not known to be an
+ // 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 InstVal &getValueState(Value *V) {
- map<Value*, InstVal>::iterator I = ValueState.find(V);
+ std::map<Value*, InstVal>::iterator I = ValueState.find(V);
if (I != ValueState.end()) return I->second; // Common case, in the map
- if (ConstPoolVal *CPV = dyn_cast<ConstPoolVal>(V)) {//Constants are constant
+ if (Constant *CPV = dyn_cast<Constant>(V)) { // Constants are constant
ValueState[CPV].markConstant(CPV);
- } else if (isa<MethodArgument>(V)) { // MethodArgs are overdefined
+ } else if (isa<Argument>(V)) { // Arguments are overdefined
ValueState[V].markOverdefined();
}
// All others are underdefined by default...
//
void markExecutable(BasicBlock *BB) {
if (BBExecutable.count(BB)) return;
- //cerr << "Marking BB Executable: " << BB;
+ DEBUG_SCCP(cerr << "Marking BB Executable: " << BB);
BBExecutable.insert(BB); // Basic block is executable!
BBWorkList.push_back(BB); // Add the block to the work list!
}
- // UpdateInstruction - 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 UpdateInstruction(Instruction *I);
+ void visitPHINode(PHINode *I);
+
+ // Terminators
+ void visitReturnInst(ReturnInst *I) { /*does not have an effect*/ }
+ void visitTerminatorInst(TerminatorInst *TI);
+
+ void visitUnaryOperator(Instruction *I);
+ void visitCastInst(CastInst *I) { visitUnaryOperator(I); }
+ void visitBinaryOperator(Instruction *I);
+ void visitShiftInst(ShiftInst *I) { visitBinaryOperator(I); }
+
+ // Instructions that cannot be folded away...
+ void visitStoreInst (Instruction *I) { /*returns void*/ }
+ void visitMemAccessInst (Instruction *I) { markOverdefined(I); }
+ void visitCallInst (Instruction *I) { markOverdefined(I); }
+ void visitInvokeInst (Instruction *I) { markOverdefined(I); }
+ void visitAllocationInst(Instruction *I) { markOverdefined(I); }
+ void visitFreeInst (Instruction *I) { /*returns void*/ }
+
+ void visitInstruction(Instruction *I) {
+ // If a new instruction is added to LLVM that we don't handle...
+ cerr << "SCCP: Don't know how to handle: " << I;
+ markOverdefined(I); // Just in case
+ }
+
+ // getFeasibleSuccessors - Return a vector of booleans to indicate which
+ // successors are reachable from a given terminator instruction.
+ //
+ void getFeasibleSuccessors(TerminatorInst *I, std::vector<bool> &Succs);
+
+ // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
+ // 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
// information, we need to update the specified user of this instruction.
//
- void OperandChangedState(User *U);
+ void OperandChangedState(User *U) {
+ // Only instructions use other variable values!
+ Instruction *I = cast<Instruction>(U);
+ if (!BBExecutable.count(I->getParent())) return;// Inst not executable yet!
+ visit(I);
+ }
};
+} // end anonymous namespace
+
+
+// createSCCPPass - This is the public interface to this file...
+//
+Pass *createSCCPPass() {
+ return new SCCP();
+}
+
//===----------------------------------------------------------------------===//
// SCCP Class Implementation
-// doSCCP() - Run the Sparse Conditional Constant Propogation algorithm, and
-// return true if the method was modified.
+// runOnFunction() - Run the Sparse Conditional Constant Propogation algorithm,
+// and return true if the function was modified.
//
-bool SCCP::doSCCP() {
- // Mark the first block of the method as being executable...
- markExecutable(M->front());
+bool SCCP::runOnFunction(Function *F) {
+ // Mark the first block of the function as being executable...
+ markExecutable(F->front());
// Process the work lists until their are empty!
while (!BBWorkList.empty() || !InstWorkList.empty()) {
Instruction *I = InstWorkList.back();
InstWorkList.pop_back();
- //cerr << "\nPopped off I-WL: " << I;
+ DEBUG_SCCP(cerr << "\nPopped off I-WL: " << I);
// "I" got into the work list because it either made the transition from
BasicBlock *BB = BBWorkList.back();
BBWorkList.pop_back();
- //cerr << "\nPopped off BBWL: " << BB;
+ DEBUG_SCCP(cerr << "\nPopped off BBWL: " << BB);
// If this block only has a single successor, mark it as executable as
// well... if not, terminate the do loop.
//
if (BB->getTerminator()->getNumSuccessors() == 1)
- markExecutable(BB->getTerminator()->getSuccessor(0));
+ markExecutable(BB->getTerminator()->getSuccessor(0));
- // Loop over all of the instructions and notify them that they are newly
- // executable...
- for_each(BB->begin(), BB->end(),
- bind_obj(this, &SCCP::UpdateInstruction));
+ // Notify all instructions in this basic block that they are newly
+ // executable.
+ visit(BB);
}
}
#if 0
- for (Method::iterator BBI = M->begin(), BBEnd = M->end(); BBI != BBEnd; ++BBI)
+ for (Function::iterator BBI = F->begin(), BBEnd = F->end();
+ BBI != BBEnd; ++BBI)
if (!BBExecutable.count(*BBI))
cerr << "BasicBlock Dead:" << *BBI;
#endif
- // Iterate over all of the instructions in a method, replacing them with
+ // Iterate over all of the instructions in a function, replacing them with
// constants if we have found them to be of constant values.
//
bool MadeChanges = false;
- for (Method::inst_iterator II = M->inst_begin(); II != M->inst_end(); ) {
- Instruction *Inst = *II;
- InstVal &IV = ValueState[Inst];
- if (IV.isConstant()) {
- ConstPoolVal *Const = IV.getConstant();
- // cerr << "Constant: " << Inst << " is: " << Const;
-
- // Replaces all of the uses of a variable with uses of the constant.
- Inst->replaceAllUsesWith(Const);
-
- // Remove the operator from the list of definitions...
- Inst->getParent()->getInstList().remove(II.getInstructionIterator());
-
- // The new constant inherits the old name of the operator...
- if (Inst->hasName() && !Const->hasName())
- Const->setName(Inst->getName(), M->getSymbolTableSure());
-
- // Delete the operator now...
- delete Inst;
-
- // Incrementing the iterator in an unchecked manner could mess up the
- // internals of 'II'. To make sure everything is happy, tell it we might
- // have broken it.
- II.resyncInstructionIterator();
-
- // Hey, we just changed something!
- MadeChanges = true;
- continue; // Skip the ++II at the end of the loop here...
- } else if (Inst->isTerminator()) {
- MadeChanges |= opt::ConstantFoldTerminator(cast<TerminatorInst>(Inst));
+ for (Function::iterator FI = F->begin(), FE = F->end(); FI != FE; ++FI) {
+ BasicBlock *BB = *FI;
+ for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
+ Instruction *Inst = *BI;
+ InstVal &IV = ValueState[Inst];
+ if (IV.isConstant()) {
+ Constant *Const = IV.getConstant();
+ DEBUG_SCCP(cerr << "Constant: " << Inst << " is: " << Const);
+
+ // Replaces all of the uses of a variable with uses of the constant.
+ Inst->replaceAllUsesWith(Const);
+
+ // Remove the operator from the list of definitions... and delete it.
+ delete BB->getInstList().remove(BI);
+
+ // Hey, we just changed something!
+ MadeChanges = true;
+ } else {
+ ++BI;
+ }
}
-
- ++II;
}
- // Merge identical constants last: this is important because we may have just
- // introduced constants that already exist, and we don't want to pollute later
- // stages with extraneous constants.
- //
+ // Reset state so that the next invocation will have empty data structures
+ BBExecutable.clear();
+ ValueState.clear();
+
return MadeChanges;
}
-// UpdateInstruction - Something changed in this instruction... Either an
+// getFeasibleSuccessors - Return a vector of booleans to indicate which
+// successors are reachable from a given terminator instruction.
+//
+void SCCP::getFeasibleSuccessors(TerminatorInst *TI, std::vector<bool> &Succs) {
+ assert(Succs.size() == TI->getNumSuccessors() && "Succs vector wrong size!");
+ if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+ if (BI->isUnconditional()) {
+ Succs[0] = true;
+ } else {
+ InstVal &BCValue = getValueState(BI->getCondition());
+ if (BCValue.isOverdefined()) {
+ // Overdefined condition variables mean the branch could go either way.
+ Succs[0] = Succs[1] = true;
+ } else if (BCValue.isConstant()) {
+ // Constant condition variables mean the branch can only go a single way
+ Succs[BCValue.getConstant() == ConstantBool::False] = true;
+ }
+ }
+ } else if (InvokeInst *II = dyn_cast<InvokeInst>(TI)) {
+ // Invoke instructions successors are always executable.
+ Succs[0] = Succs[1] = true;
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ InstVal &SCValue = getValueState(SI->getCondition());
+ if (SCValue.isOverdefined()) { // Overdefined condition?
+ // All destinations are executable!
+ Succs.assign(TI->getNumSuccessors(), true);
+ } else if (SCValue.isConstant()) {
+ Constant *CPV = SCValue.getConstant();
+ // 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 right branch...
+ Succs[i] = true;
+ return;
+ }
+ }
+
+ // Constant value not equal to any of the branches... must execute
+ // default branch then...
+ Succs[0] = true;
+ }
+ } else {
+ cerr << "SCCP: Don't know how to handle: " << TI;
+ Succs.assign(TI->getNumSuccessors(), true);
+ }
+}
+
+
+// isEdgeFeasible - Return true if the control flow edge from the 'From' basic
+// block to the 'To' basic block is currently feasible...
+//
+bool SCCP::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...
+ TerminatorInst *FT = From->getTerminator();
+ std::vector<bool> SuccFeasible(FT->getNumSuccessors());
+ getFeasibleSuccessors(FT, SuccFeasible);
+
+ // Check all edges from From to To. If any are feasible, return true.
+ for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
+ if (FT->getSuccessor(i) == To && SuccFeasible[i])
+ return true;
+
+ // Otherwise, none of the edges are actually feasible at this time...
+ return false;
+}
+
+// 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:
// 7. If a conditional branch has a value that is overdefined, make all
// successors executable.
//
-void SCCP::UpdateInstruction(Instruction *I) {
- InstVal &IValue = ValueState[I];
- if (IValue.isOverdefined())
- return; // If already overdefined, we aren't going to effect anything
-
- switch (I->getOpcode()) {
- //===-----------------------------------------------------------------===//
- // Handle PHI nodes...
- //
- case Instruction::PHINode: {
- PHINode *PN = cast<PHINode>(I);
- unsigned NumValues = PN->getNumIncomingValues(), i;
- InstVal *OperandIV = 0;
-
- // 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, and they agree with each other, the PHI becomes the identical
- // constant. If they are constant and don't agree, the PHI is overdefined.
- // If there are no executable operands, the PHI remains undefined.
- //
- for (i = 0; i < NumValues; ++i) {
- if (BBExecutable.count(PN->getIncomingBlock(i))) {
- InstVal &IV = getValueState(PN->getIncomingValue(i));
- if (IV.isUndefined()) continue; // Doesn't influence PHI node.
- if (IV.isOverdefined()) { // PHI node becomes overdefined!
- markOverdefined(PN);
- return;
- }
-
- if (OperandIV == 0) { // Grab the first value...
- OperandIV = &IV;
- } 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() != OperandIV->getConstant()) {
- // Yes there is. This means the PHI node is not constant.
- // You must be overdefined poor PHI.
- //
- markOverdefined(I); // The PHI node now becomes overdefined
- return; // I'm done analyzing you
- }
- }
- }
- }
- // If we exited the loop, this means that the PHI node only has constant
- // arguments that agree with each other(and OperandIV is a pointer to one
- // of their InstVal's) or OperandIV is null because there are no defined
- // incoming arguments. If this is the case, the PHI remains undefined.
- //
- if (OperandIV) {
- assert(OperandIV->isConstant() && "Should only be here for constants!");
- markConstant(I, OperandIV->getConstant()); // Aquire operand value
- }
- return;
- }
-
- //===-----------------------------------------------------------------===//
- // Handle instructions that unconditionally provide overdefined values...
- //
- case Instruction::Malloc:
- case Instruction::Free:
- case Instruction::Alloca:
- case Instruction::Load:
- case Instruction::Store:
- // TODO: getfield/putfield?
- case Instruction::Call:
- markOverdefined(I); // Memory and call's are all overdefined
- return;
-
- //===-----------------------------------------------------------------===//
- // Handle Terminator instructions...
- //
- case Instruction::Ret: return; // Method return doesn't affect anything
- case Instruction::Br: { // Handle conditional branches...
- BranchInst *BI = cast<BranchInst>(I);
- if (BI->isUnconditional())
- return; // Unconditional branches are already handled!
-
- InstVal &BCValue = getValueState(BI->getCondition());
- if (BCValue.isOverdefined()) {
- // Overdefined condition variables mean the branch could go either way.
- markExecutable(BI->getSuccessor(0));
- markExecutable(BI->getSuccessor(1));
- } else if (BCValue.isConstant()) {
- // Constant condition variables mean the branch can only go a single way.
- ConstPoolBool *CPB = cast<ConstPoolBool>(BCValue.getConstant());
- if (CPB->getValue()) // If the branch condition is TRUE...
- markExecutable(BI->getSuccessor(0));
- else // Else if the br cond is FALSE...
- markExecutable(BI->getSuccessor(1));
- }
- return;
- }
+void SCCP::visitPHINode(PHINode *PN) {
+ unsigned NumValues = PN->getNumIncomingValues(), i;
+ InstVal *OperandIV = 0;
- case Instruction::Switch: {
- SwitchInst *SI = cast<SwitchInst>(I);
- InstVal &SCValue = getValueState(SI->getCondition());
- if (SCValue.isOverdefined()) { // Overdefined condition? All dests are exe
- for(unsigned i = 0; BasicBlock *Succ = SI->getSuccessor(i); ++i)
- markExecutable(Succ);
- } else if (SCValue.isConstant()) {
- ConstPoolVal *CPV = SCValue.getConstant();
- // 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 right branch...
- markExecutable(SI->getSuccessor(i));
- return;
- }
+ // 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, and they agree with each other, the PHI becomes the identical
+ // constant. If they are constant and don't agree, the PHI is overdefined.
+ // If there are no executable operands, the PHI remains undefined.
+ //
+ for (i = 0; i < NumValues; ++i) {
+ if (isEdgeFeasible(PN->getIncomingBlock(i), PN->getParent())) {
+ InstVal &IV = getValueState(PN->getIncomingValue(i));
+ if (IV.isUndefined()) continue; // Doesn't influence PHI node.
+ if (IV.isOverdefined()) { // PHI node becomes overdefined!
+ markOverdefined(PN);
+ return;
}
-
- // Constant value not equal to any of the branches... must execute
- // default branch then...
- markExecutable(SI->getDefaultDest());
- }
- return;
- }
- default: break; // Handle math operators as groups.
- } // end switch(I->getOpcode())
-
-
- //===-------------------------------------------------------------------===//
- // Handle Unary instructions...
- // Also treated as unary here, are cast instructions and getelementptr
- // instructions on struct* operands.
- //
- if (isa<UnaryOperator>(I) || isa<CastInst>(I) ||
- (isa<GetElementPtrInst>(I) &&
- cast<GetElementPtrInst>(I)->isStructSelector())) {
-
- Value *V = I->getOperand(0);
- InstVal &VState = getValueState(V);
- if (VState.isOverdefined()) { // Inherit overdefinedness of operand
- markOverdefined(I);
- } else if (VState.isConstant()) { // Propogate constant value
- ConstPoolVal *Result =
- opt::ConstantFoldUnaryInstruction(I->getOpcode(),
- VState.getConstant());
-
- if (Result) {
- // This instruction constant folds!
- markConstant(I, Result);
- } else {
- markOverdefined(I); // Don't know how to fold this instruction. :(
+ if (OperandIV == 0) { // Grab the first value...
+ OperandIV = &IV;
+ } 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() != OperandIV->getConstant()) {
+ // 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
+ }
}
}
- return;
}
- //===-----------------------------------------------------------------===//
- // Handle Binary instructions...
+ // If we exited the loop, this means that the PHI node only has constant
+ // arguments that agree with each other(and OperandIV is a pointer to one
+ // of their InstVal's) or OperandIV is null because there are no defined
+ // incoming arguments. If this is the case, the PHI remains undefined.
//
- if (isa<BinaryOperator>(I) || isa<ShiftInst>(I)) {
- Value *V1 = I->getOperand(0);
- Value *V2 = I->getOperand(1);
-
- InstVal &V1State = getValueState(V1);
- InstVal &V2State = getValueState(V2);
- if (V1State.isOverdefined() || V2State.isOverdefined()) {
- markOverdefined(I);
- } else if (V1State.isConstant() && V2State.isConstant()) {
- ConstPoolVal *Result =
- opt::ConstantFoldBinaryInstruction(I->getOpcode(),
- V1State.getConstant(),
- V2State.getConstant());
- if (Result) {
- // This instruction constant folds!
- markConstant(I, Result);
- } else {
- markOverdefined(I); // Don't know how to fold this instruction. :(
- }
- }
- return;
+ if (OperandIV) {
+ assert(OperandIV->isConstant() && "Should only be here for constants!");
+ markConstant(PN, OperandIV->getConstant()); // Aquire operand value
}
-
- // Shouldn't get here... either the switch statement or one of the group
- // handlers should have kicked in...
- //
- cerr << "SCCP: Don't know how to handle: " << I;
- markOverdefined(I); // Just in case
}
+void SCCP::visitTerminatorInst(TerminatorInst *TI) {
+ std::vector<bool> SuccFeasible(TI->getNumSuccessors());
+ getFeasibleSuccessors(TI, SuccFeasible);
-
-// OperandChangedState - This method is invoked on all of the users of an
-// instruction that was just changed state somehow.... Based on this
-// information, we need to update the specified user of this instruction.
-//
-void SCCP::OperandChangedState(User *U) {
- // Only instructions use other variable values!
- Instruction *I = cast<Instruction>(U);
- if (!BBExecutable.count(I->getParent())) return; // Inst not executable yet!
-
- UpdateInstruction(I);
+ // Mark all feasible successors executable...
+ for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
+ if (SuccFeasible[i])
+ markExecutable(TI->getSuccessor(i));
}
+void SCCP::visitUnaryOperator(Instruction *I) {
+ Value *V = I->getOperand(0);
+ InstVal &VState = getValueState(V);
+ if (VState.isOverdefined()) { // Inherit overdefinedness of operand
+ markOverdefined(I);
+ } else if (VState.isConstant()) { // Propogate constant value
+ Constant *Result = isa<CastInst>(I)
+ ? ConstantFoldCastInstruction(VState.getConstant(), I->getType())
+ : ConstantFoldUnaryInstruction(I->getOpcode(), VState.getConstant());
+
+ if (Result) {
+ // This instruction constant folds!
+ markConstant(I, Result);
+ } else {
+ markOverdefined(I); // Don't know how to fold this instruction. :(
+ }
+ }
+}
-// DoSparseConditionalConstantProp - Use Sparse Conditional Constant Propogation
-// to prove whether a value is constant and whether blocks are used.
-//
-bool opt::DoSCCP(Method *M) {
- if (M->isExternal()) return false;
- SCCP S(M);
- return S.doSCCP();
+// Handle BinaryOperators and Shift Instructions...
+void SCCP::visitBinaryOperator(Instruction *I) {
+ InstVal &V1State = getValueState(I->getOperand(0));
+ InstVal &V2State = getValueState(I->getOperand(1));
+ if (V1State.isOverdefined() || V2State.isOverdefined()) {
+ markOverdefined(I);
+ } else if (V1State.isConstant() && V2State.isConstant()) {
+ Constant *Result = 0;
+ if (isa<BinaryOperator>(I))
+ Result = ConstantFoldBinaryInstruction(I->getOpcode(),
+ V1State.getConstant(),
+ V2State.getConstant());
+ else if (isa<ShiftInst>(I))
+ Result = ConstantFoldShiftInstruction(I->getOpcode(),
+ V1State.getConstant(),
+ V2State.getConstant());
+ if (Result)
+ markConstant(I, Result); // This instruction constant folds!
+ else
+ markOverdefined(I); // Don't know how to fold this instruction. :(
+ }
}
projects / oota-llvm.git / blobdiff