diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp index a5966e96a28..2ff10369ae2 100644 --- a/lib/Transforms/Scalar/SCCP.cpp +++ b/lib/Transforms/Scalar/SCCP.cpp @@ -30,6 +30,12 @@ #include 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. // @@ -86,7 +92,7 @@ class SCCP : public FunctionPass, public InstVisitor { std::set BBExecutable;// The basic blocks that are executable std::map ValueState; // The state each value is in... - std::vector InstWorkList;// The instruction work list + std::set InstWorkList;// The instruction work list std::vector BBWorkList; // The BasicBlock work list public: @@ -116,9 +122,10 @@ private: // the users of the instruction are updated later. // inline bool markConstant(Instruction *I, Constant *V) { - //cerr << "markConstant: " << V << " = " << I; + DEBUG_SCCP(cerr << "markConstant: " << V << " = " << I); + if (ValueState[I].markConstant(V)) { - InstWorkList.push_back(I); + InstWorkList.insert(I); return true; } return false; @@ -131,8 +138,8 @@ private: inline bool markOverdefined(Value *V) { if (ValueState[V].markOverdefined()) { if (Instruction *I = dyn_cast(V)) { - //cerr << "markOverdefined: " << V; - InstWorkList.push_back(I); // Only instructions go on the work list + DEBUG_SCCP(cerr << "markOverdefined: " << V); + InstWorkList.insert(I); // Only instructions go on the work list } return true; } @@ -163,7 +170,7 @@ private: // 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! } @@ -178,6 +185,7 @@ private: // Terminators void visitReturnInst(ReturnInst *I) { /*does not have an effect*/ } void visitBranchInst(BranchInst *I); + void visitInvokeInst(InvokeInst *I); void visitSwitchInst(SwitchInst *I); void visitUnaryOperator(Instruction *I); @@ -186,11 +194,12 @@ private: 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) { 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... @@ -198,11 +207,21 @@ private: markOverdefined(I); // Just in case } + // 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(U); + if (!BBExecutable.count(I->getParent())) return;// Inst not executable yet! + visit(I); + } }; } // end anonymous namespace @@ -230,10 +249,10 @@ bool SCCP::runOnFunction(Function *F) { while (!BBWorkList.empty() || !InstWorkList.empty()) { // Process the instruction work list... while (!InstWorkList.empty()) { - Instruction *I = InstWorkList.back(); - InstWorkList.pop_back(); + Instruction *I = *InstWorkList.begin(); + InstWorkList.erase(InstWorkList.begin()); - //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 @@ -250,7 +269,7 @@ bool SCCP::runOnFunction(Function *F) { 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. @@ -264,7 +283,7 @@ bool SCCP::runOnFunction(Function *F) { } } -#if 0 +#ifdef DEBUG_SCCP for (Function::iterator BBI = F->begin(), BBEnd = F->end(); BBI != BBEnd; ++BBI) if (!BBExecutable.count(*BBI)) @@ -283,7 +302,7 @@ bool SCCP::runOnFunction(Function *F) { InstVal &IV = ValueState[Inst]; if (IV.isConstant()) { Constant *Const = IV.getConstant(); - // cerr << "Constant: " << Inst << " is: " << Const; + DEBUG_SCCP(cerr << "Constant: " << Inst << " is: " << Const); // Replaces all of the uses of a variable with uses of the constant. Inst->replaceAllUsesWith(Const); @@ -305,17 +324,25 @@ bool SCCP::runOnFunction(Function *F) { } } - // Reset state so that the next invokation will have empty data structures + // Reset state so that the next invocation will have empty data structures BBExecutable.clear(); ValueState.clear(); - // 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. - // return MadeChanges; } +// 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; + + // This should check the terminator in From! + return true; +} // visit Implementations - Something changed in this instruction... Either an // operand made a transition, or the instruction is newly executable. Change @@ -347,7 +374,7 @@ void SCCP::visitPHINode(PHINode *PN) { // If there are no executable operands, the PHI remains undefined. // for (i = 0; i < NumValues; ++i) { - if (BBExecutable.count(PN->getIncomingBlock(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! @@ -403,6 +430,11 @@ void SCCP::visitBranchInst(BranchInst *BI) { } } +void SCCP::visitInvokeInst(InvokeInst *II) { + markExecutable(II->getNormalDest()); + markExecutable(II->getExceptionalDest()); +} + void SCCP::visitSwitchInst(SwitchInst *SI) { InstVal &SCValue = getValueState(SI->getCondition()); if (SCValue.isOverdefined()) { // Overdefined condition? All dests are exe @@ -459,15 +491,3 @@ void SCCP::visitBinaryOperator(Instruction *I) { markOverdefined(I); // Don't know how to fold this instruction. :( } } - -// 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(U); - if (!BBExecutable.count(I->getParent())) return; // Inst not executable yet! - - visit(I); -}