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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@9903 91177308-0d34-0410-b5e6-96231b3b80d8
251 lines
9.6 KiB
C++
251 lines
9.6 KiB
C++
//===- PreSelection.cpp - Specialize LLVM code for target machine ---------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the PreSelection pass which specializes LLVM code for a
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// target machine, while remaining in legal portable LLVM form and
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// preserving type information and type safety. This is meant to enable
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// dataflow optimizations on target-specific operations such as accesses to
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// constants, globals, and array indexing.
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//
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//===----------------------------------------------------------------------===//
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#include "SparcInternals.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/iMemory.h"
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#include "llvm/iPHINode.h"
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#include "llvm/iOther.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/InstVisitor.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Transforms/Scalar.h"
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#include <algorithm>
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namespace llvm {
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namespace {
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//===--------------------------------------------------------------------===//
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// PreSelection Pass - Specialize LLVM code for the current target machine.
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//
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class PreSelection : public FunctionPass, public InstVisitor<PreSelection> {
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const TargetInstrInfo &instrInfo;
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public:
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PreSelection(const TargetMachine &T)
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: instrInfo(T.getInstrInfo()) {}
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// runOnFunction - apply this pass to each Function
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bool runOnFunction(Function &F) {
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visit(F);
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return true;
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}
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// These methods do the actual work of specializing code
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void visitInstruction(Instruction &I); // common work for every instr.
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void visitGetElementPtrInst(GetElementPtrInst &I);
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void visitCallInst(CallInst &I);
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void visitPHINode(PHINode &PN);
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// Helper functions for visiting operands of every instruction
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//
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// visitOperands() works on every operand in [firstOp, lastOp-1].
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// If lastOp==0, lastOp defaults to #operands or #incoming Phi values.
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//
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// visitOneOperand() does all the work for one operand.
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//
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void visitOperands(Instruction &I, int firstOp=0);
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void visitOneOperand(Instruction &I, Value* Op, unsigned opNum,
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Instruction& insertBefore);
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};
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#if 0
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// Register the pass...
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RegisterPass<PreSelection> X("preselect",
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"Specialize LLVM code for a target machine"
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createPreselectionPass);
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#endif
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} // end anonymous namespace
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//------------------------------------------------------------------------------
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// Helper functions used by methods of class PreSelection
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//------------------------------------------------------------------------------
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// getGlobalAddr(): Put address of a global into a v. register.
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static GetElementPtrInst* getGlobalAddr(Value* ptr, Instruction& insertBefore) {
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if (isa<ConstantPointerRef>(ptr))
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ptr = cast<ConstantPointerRef>(ptr)->getValue();
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return (isa<GlobalVariable>(ptr))
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? new GetElementPtrInst(ptr,
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std::vector<Value*>(1, ConstantSInt::get(Type::LongTy, 0U)),
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"addrOfGlobal", &insertBefore)
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: NULL;
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}
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// Wrapper on Constant::classof to use in find_if :-(
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inline static bool nonConstant(const Use& U) {
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return ! isa<Constant>(U);
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}
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static Instruction* DecomposeConstantExpr(ConstantExpr* CE,
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Instruction& insertBefore)
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{
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Value *getArg1, *getArg2;
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switch(CE->getOpcode())
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{
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case Instruction::Cast:
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getArg1 = CE->getOperand(0);
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if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1))
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getArg1 = DecomposeConstantExpr(CEarg, insertBefore);
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return new CastInst(getArg1, CE->getType(), "constantCast",&insertBefore);
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case Instruction::GetElementPtr:
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assert(find_if(CE->op_begin()+1, CE->op_end(),nonConstant) == CE->op_end()
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&& "All indices in ConstantExpr getelementptr must be constant!");
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getArg1 = CE->getOperand(0);
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if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1))
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getArg1 = DecomposeConstantExpr(CEarg, insertBefore);
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else if (GetElementPtrInst* gep = getGlobalAddr(getArg1, insertBefore))
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getArg1 = gep;
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return new GetElementPtrInst(getArg1,
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std::vector<Value*>(CE->op_begin()+1, CE->op_end()),
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"constantGEP", &insertBefore);
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default: // must be a binary operator
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assert(CE->getOpcode() >= Instruction::BinaryOpsBegin &&
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CE->getOpcode() < Instruction::BinaryOpsEnd &&
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"Unrecognized opcode in ConstantExpr");
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getArg1 = CE->getOperand(0);
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if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1))
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getArg1 = DecomposeConstantExpr(CEarg, insertBefore);
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getArg2 = CE->getOperand(1);
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if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg2))
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getArg2 = DecomposeConstantExpr(CEarg, insertBefore);
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return BinaryOperator::create((Instruction::BinaryOps) CE->getOpcode(),
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getArg1, getArg2,
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"constantBinaryOp", &insertBefore);
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}
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}
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//------------------------------------------------------------------------------
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// Instruction visitor methods to perform instruction-specific operations
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//------------------------------------------------------------------------------
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inline void
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PreSelection::visitOneOperand(Instruction &I, Value* Op, unsigned opNum,
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Instruction& insertBefore)
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{
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assert(&insertBefore != NULL && "Must have instruction to insert before.");
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if (GetElementPtrInst* gep = getGlobalAddr(Op, insertBefore)) {
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I.setOperand(opNum, gep); // replace global operand
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return; // nothing more to do for this op.
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}
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Constant* CV = dyn_cast<Constant>(Op);
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if (CV == NULL)
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return;
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if (ConstantExpr* CE = dyn_cast<ConstantExpr>(CV)) {
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// load-time constant: factor it out so we optimize as best we can
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Instruction* computeConst = DecomposeConstantExpr(CE, insertBefore);
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I.setOperand(opNum, computeConst); // replace expr operand with result
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} else if (instrInfo.ConstantTypeMustBeLoaded(CV)) {
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// load address of constant into a register, then load the constant
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// this is now done during instruction selection
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// the constant will live in the MachineConstantPool later on
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} else if (instrInfo.ConstantMayNotFitInImmedField(CV, &I)) {
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// put the constant into a virtual register using a cast
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CastInst* castI = new CastInst(CV, CV->getType(), "copyConst",
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&insertBefore);
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I.setOperand(opNum, castI); // replace operand with copy in v.reg.
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}
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}
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// visitOperands() transforms individual operands of all instructions:
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// -- Load "large" int constants into a virtual register. What is large
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// depends on the type of instruction and on the target architecture.
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// -- For any constants that cannot be put in an immediate field,
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// load address into virtual register first, and then load the constant.
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//
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// firstOp and lastOp can be used to skip leading and trailing operands.
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// If lastOp is 0, it defaults to #operands or #incoming Phi values.
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//
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inline void PreSelection::visitOperands(Instruction &I, int firstOp) {
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// For any instruction other than PHI, copies go just before the instr.
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for (unsigned i = firstOp, e = I.getNumOperands(); i != e; ++i)
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visitOneOperand(I, I.getOperand(i), i, I);
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}
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void PreSelection::visitPHINode(PHINode &PN) {
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// For a PHI, operand copies must be before the terminator of the
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// appropriate predecessor basic block. Remaining logic is simple
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// so just handle PHIs and other instructions separately.
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//
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for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
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visitOneOperand(PN, PN.getIncomingValue(i),
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PN.getOperandNumForIncomingValue(i),
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*PN.getIncomingBlock(i)->getTerminator());
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// do not call visitOperands!
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}
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// Common work for *all* instructions. This needs to be called explicitly
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// by other visit<InstructionType> functions.
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inline void PreSelection::visitInstruction(Instruction &I) {
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visitOperands(I); // Perform operand transformations
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}
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// GetElementPtr instructions: check if pointer is a global
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void PreSelection::visitGetElementPtrInst(GetElementPtrInst &I) {
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Instruction* curI = &I;
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// Decompose multidimensional array references
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if (I.getNumIndices() >= 2) {
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// DecomposeArrayRef() replaces I and deletes it, if successful,
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// so remember predecessor in order to find the replacement instruction.
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// Also remember the basic block in case there is no predecessor.
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Instruction* prevI = I.getPrev();
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BasicBlock* bb = I.getParent();
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if (DecomposeArrayRef(&I))
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// first instr. replacing I
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curI = cast<GetElementPtrInst>(prevI? prevI->getNext() : &bb->front());
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}
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// Perform other transformations common to all instructions
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visitInstruction(*curI);
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}
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void PreSelection::visitCallInst(CallInst &I) {
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// Tell visitOperands to ignore the function name if this is a direct call.
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visitOperands(I, (/*firstOp=*/ I.getCalledFunction()? 1 : 0));
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}
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//===----------------------------------------------------------------------===//
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// createPreSelectionPass - Public entrypoint for pre-selection pass
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// and this file as a whole...
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//
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FunctionPass* createPreSelectionPass(const TargetMachine &TM) {
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return new PreSelection(TM);
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}
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} // End llvm namespace
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