| //===- PreSelection.cpp - Specialize LLVM code for target machine ---------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines the PreSelection pass which specializes LLVM code for a |
| // target machine, while remaining in legal portable LLVM form and |
| // preserving type information and type safety. This is meant to enable |
| // dataflow optimizations on target-specific operations such as accesses to |
| // constants, globals, and array indexing. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "SparcInternals.h" |
| #include "llvm/Constants.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/iMemory.h" |
| #include "llvm/iPHINode.h" |
| #include "llvm/iOther.h" |
| #include "llvm/Module.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/InstVisitor.h" |
| #include "llvm/Target/TargetInstrInfo.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/Transforms/Scalar.h" |
| #include <algorithm> |
| |
| namespace llvm { |
| |
| namespace { |
| |
| //===--------------------------------------------------------------------===// |
| // PreSelection Pass - Specialize LLVM code for the current target machine. |
| // |
| class PreSelection : public FunctionPass, public InstVisitor<PreSelection> { |
| const TargetInstrInfo &instrInfo; |
| |
| public: |
| PreSelection(const TargetMachine &T) |
| : instrInfo(T.getInstrInfo()) {} |
| |
| // runOnFunction - apply this pass to each Function |
| bool runOnFunction(Function &F) { |
| visit(F); |
| return true; |
| } |
| |
| // These methods do the actual work of specializing code |
| void visitInstruction(Instruction &I); // common work for every instr. |
| void visitGetElementPtrInst(GetElementPtrInst &I); |
| void visitCallInst(CallInst &I); |
| void visitPHINode(PHINode &PN); |
| |
| // Helper functions for visiting operands of every instruction |
| // |
| // visitOperands() works on every operand in [firstOp, lastOp-1]. |
| // If lastOp==0, lastOp defaults to #operands or #incoming Phi values. |
| // |
| // visitOneOperand() does all the work for one operand. |
| // |
| void visitOperands(Instruction &I, int firstOp=0); |
| void visitOneOperand(Instruction &I, Value* Op, unsigned opNum, |
| Instruction& insertBefore); |
| }; |
| |
| #if 0 |
| // Register the pass... |
| RegisterPass<PreSelection> X("preselect", |
| "Specialize LLVM code for a target machine" |
| createPreselectionPass); |
| #endif |
| |
| } // end anonymous namespace |
| |
| |
| //------------------------------------------------------------------------------ |
| // Helper functions used by methods of class PreSelection |
| //------------------------------------------------------------------------------ |
| |
| |
| // getGlobalAddr(): Put address of a global into a v. register. |
| static GetElementPtrInst* getGlobalAddr(Value* ptr, Instruction& insertBefore) { |
| if (isa<ConstantPointerRef>(ptr)) |
| ptr = cast<ConstantPointerRef>(ptr)->getValue(); |
| |
| return (isa<GlobalVariable>(ptr)) |
| ? new GetElementPtrInst(ptr, |
| std::vector<Value*>(1, ConstantSInt::get(Type::LongTy, 0U)), |
| "addrOfGlobal", &insertBefore) |
| : NULL; |
| } |
| |
| |
| // Wrapper on Constant::classof to use in find_if :-( |
| inline static bool nonConstant(const Use& U) { |
| return ! isa<Constant>(U); |
| } |
| |
| |
| static Instruction* DecomposeConstantExpr(ConstantExpr* CE, |
| Instruction& insertBefore) |
| { |
| Value *getArg1, *getArg2; |
| |
| switch(CE->getOpcode()) |
| { |
| case Instruction::Cast: |
| getArg1 = CE->getOperand(0); |
| if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1)) |
| getArg1 = DecomposeConstantExpr(CEarg, insertBefore); |
| return new CastInst(getArg1, CE->getType(), "constantCast",&insertBefore); |
| |
| case Instruction::GetElementPtr: |
| assert(find_if(CE->op_begin()+1, CE->op_end(),nonConstant) == CE->op_end() |
| && "All indices in ConstantExpr getelementptr must be constant!"); |
| getArg1 = CE->getOperand(0); |
| if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1)) |
| getArg1 = DecomposeConstantExpr(CEarg, insertBefore); |
| else if (GetElementPtrInst* gep = getGlobalAddr(getArg1, insertBefore)) |
| getArg1 = gep; |
| return new GetElementPtrInst(getArg1, |
| std::vector<Value*>(CE->op_begin()+1, CE->op_end()), |
| "constantGEP", &insertBefore); |
| |
| default: // must be a binary operator |
| assert(CE->getOpcode() >= Instruction::BinaryOpsBegin && |
| CE->getOpcode() < Instruction::BinaryOpsEnd && |
| "Unrecognized opcode in ConstantExpr"); |
| getArg1 = CE->getOperand(0); |
| if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1)) |
| getArg1 = DecomposeConstantExpr(CEarg, insertBefore); |
| getArg2 = CE->getOperand(1); |
| if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg2)) |
| getArg2 = DecomposeConstantExpr(CEarg, insertBefore); |
| return BinaryOperator::create((Instruction::BinaryOps) CE->getOpcode(), |
| getArg1, getArg2, |
| "constantBinaryOp", &insertBefore); |
| } |
| } |
| |
| |
| //------------------------------------------------------------------------------ |
| // Instruction visitor methods to perform instruction-specific operations |
| //------------------------------------------------------------------------------ |
| inline void |
| PreSelection::visitOneOperand(Instruction &I, Value* Op, unsigned opNum, |
| Instruction& insertBefore) |
| { |
| assert(&insertBefore != NULL && "Must have instruction to insert before."); |
| |
| if (GetElementPtrInst* gep = getGlobalAddr(Op, insertBefore)) { |
| I.setOperand(opNum, gep); // replace global operand |
| return; // nothing more to do for this op. |
| } |
| |
| Constant* CV = dyn_cast<Constant>(Op); |
| if (CV == NULL) |
| return; |
| |
| if (ConstantExpr* CE = dyn_cast<ConstantExpr>(CV)) { |
| // load-time constant: factor it out so we optimize as best we can |
| Instruction* computeConst = DecomposeConstantExpr(CE, insertBefore); |
| I.setOperand(opNum, computeConst); // replace expr operand with result |
| } else if (instrInfo.ConstantTypeMustBeLoaded(CV)) { |
| // load address of constant into a register, then load the constant |
| // this is now done during instruction selection |
| // the constant will live in the MachineConstantPool later on |
| } else if (instrInfo.ConstantMayNotFitInImmedField(CV, &I)) { |
| // put the constant into a virtual register using a cast |
| CastInst* castI = new CastInst(CV, CV->getType(), "copyConst", |
| &insertBefore); |
| I.setOperand(opNum, castI); // replace operand with copy in v.reg. |
| } |
| } |
| |
| // visitOperands() transforms individual operands of all instructions: |
| // -- Load "large" int constants into a virtual register. What is large |
| // depends on the type of instruction and on the target architecture. |
| // -- For any constants that cannot be put in an immediate field, |
| // load address into virtual register first, and then load the constant. |
| // |
| // firstOp and lastOp can be used to skip leading and trailing operands. |
| // If lastOp is 0, it defaults to #operands or #incoming Phi values. |
| // |
| inline void PreSelection::visitOperands(Instruction &I, int firstOp) { |
| // For any instruction other than PHI, copies go just before the instr. |
| for (unsigned i = firstOp, e = I.getNumOperands(); i != e; ++i) |
| visitOneOperand(I, I.getOperand(i), i, I); |
| } |
| |
| |
| void PreSelection::visitPHINode(PHINode &PN) { |
| // For a PHI, operand copies must be before the terminator of the |
| // appropriate predecessor basic block. Remaining logic is simple |
| // so just handle PHIs and other instructions separately. |
| // |
| for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) |
| visitOneOperand(PN, PN.getIncomingValue(i), |
| PN.getOperandNumForIncomingValue(i), |
| *PN.getIncomingBlock(i)->getTerminator()); |
| // do not call visitOperands! |
| } |
| |
| |
| |
| // Common work for *all* instructions. This needs to be called explicitly |
| // by other visit<InstructionType> functions. |
| inline void PreSelection::visitInstruction(Instruction &I) { |
| visitOperands(I); // Perform operand transformations |
| } |
| |
| |
| // GetElementPtr instructions: check if pointer is a global |
| void PreSelection::visitGetElementPtrInst(GetElementPtrInst &I) { |
| Instruction* curI = &I; |
| |
| // Decompose multidimensional array references |
| if (I.getNumIndices() >= 2) { |
| // DecomposeArrayRef() replaces I and deletes it, if successful, |
| // so remember predecessor in order to find the replacement instruction. |
| // Also remember the basic block in case there is no predecessor. |
| Instruction* prevI = I.getPrev(); |
| BasicBlock* bb = I.getParent(); |
| if (DecomposeArrayRef(&I)) |
| // first instr. replacing I |
| curI = cast<GetElementPtrInst>(prevI? prevI->getNext() : &bb->front()); |
| } |
| |
| // Perform other transformations common to all instructions |
| visitInstruction(*curI); |
| } |
| |
| void PreSelection::visitCallInst(CallInst &I) { |
| // Tell visitOperands to ignore the function name if this is a direct call. |
| visitOperands(I, (/*firstOp=*/ I.getCalledFunction()? 1 : 0)); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // createPreSelectionPass - Public entrypoint for pre-selection pass |
| // and this file as a whole... |
| // |
| FunctionPass* createPreSelectionPass(const TargetMachine &TM) { |
| return new PreSelection(TM); |
| } |
| |
| } // End llvm namespace |