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c0b9dc5be7
ilist of MachineInstr objects. This allows constant time removal and insertion of MachineInstr instances from anywhere in each MachineBasicBlock. It also allows for constant time splicing of MachineInstrs into or out of MachineBasicBlocks. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11340 91177308-0d34-0410-b5e6-96231b3b80d8
415 lines
15 KiB
C++
415 lines
15 KiB
C++
//===- InstrSelection.cpp - Machine Independent Inst Selection Driver -----===//
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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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// Machine-independent driver file for instruction selection. This file
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// constructs a forest of BURG instruction trees and then uses the
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// BURG-generated tree grammar (BURM) to find the optimal instruction sequences
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// for a given machine.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/InstrSelection.h"
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#include "llvm/Function.h"
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#include "llvm/IntrinsicLowering.h"
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#include "llvm/iPHINode.h"
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#include "llvm/iOther.h"
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#include "llvm/Pass.h"
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#include "llvm/CodeGen/InstrForest.h"
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#include "llvm/CodeGen/InstrSelectionSupport.h"
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#include "llvm/CodeGen/MachineCodeForInstruction.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetRegInfo.h"
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#include "Support/CommandLine.h"
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#include "Support/LeakDetector.h"
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namespace llvm {
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std::vector<MachineInstr*>
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FixConstantOperandsForInstr(Instruction *I, MachineInstr *MI,
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TargetMachine &TM);
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}
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namespace {
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//===--------------------------------------------------------------------===//
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// SelectDebugLevel - Allow command line control over debugging.
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//
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enum SelectDebugLevel_t {
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Select_NoDebugInfo,
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Select_PrintMachineCode,
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Select_DebugInstTrees,
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Select_DebugBurgTrees,
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};
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// Enable Debug Options to be specified on the command line
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cl::opt<SelectDebugLevel_t>
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SelectDebugLevel("dselect", cl::Hidden,
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cl::desc("enable instruction selection debug information"),
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cl::values(
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clEnumValN(Select_NoDebugInfo, "n", "disable debug output"),
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clEnumValN(Select_PrintMachineCode, "y", "print generated machine code"),
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clEnumValN(Select_DebugInstTrees, "i",
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"print debugging info for instruction selection"),
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clEnumValN(Select_DebugBurgTrees, "b", "print burg trees"),
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0));
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//===--------------------------------------------------------------------===//
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// InstructionSelection Pass
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//
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// This is the actual pass object that drives the instruction selection
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// process.
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//
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class InstructionSelection : public FunctionPass {
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TargetMachine &Target;
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void InsertCodeForPhis(Function &F);
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void InsertPhiElimInstructions(BasicBlock *BB,
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const std::vector<MachineInstr*>& CpVec);
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void SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt);
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void PostprocessMachineCodeForTree(InstructionNode* instrNode,
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int ruleForNode, short* nts);
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public:
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InstructionSelection(TargetMachine &TM) : Target(TM) {}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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}
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bool runOnFunction(Function &F);
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virtual const char *getPassName() const { return "Instruction Selection"; }
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};
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}
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TmpInstruction::TmpInstruction(MachineCodeForInstruction& mcfi,
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Value *s1, Value *s2, const std::string &name)
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: Instruction(s1->getType(), Instruction::UserOp1, name)
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{
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mcfi.addTemp(this);
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Operands.push_back(Use(s1, this)); // s1 must be non-null
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if (s2)
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Operands.push_back(Use(s2, this));
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// TmpInstructions should not be garbage checked.
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LeakDetector::removeGarbageObject(this);
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}
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// Constructor that requires the type of the temporary to be specified.
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// Both S1 and S2 may be NULL.(
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TmpInstruction::TmpInstruction(MachineCodeForInstruction& mcfi,
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const Type *Ty, Value *s1, Value* s2,
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const std::string &name)
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: Instruction(Ty, Instruction::UserOp1, name)
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{
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mcfi.addTemp(this);
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if (s1)
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Operands.push_back(Use(s1, this));
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if (s2)
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Operands.push_back(Use(s2, this));
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// TmpInstructions should not be garbage checked.
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LeakDetector::removeGarbageObject(this);
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}
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bool InstructionSelection::runOnFunction(Function &F) {
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// First pass - Walk the function, lowering any calls to intrinsic functions
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// which the instruction selector cannot handle.
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for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; )
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if (CallInst *CI = dyn_cast<CallInst>(I++))
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if (Function *F = CI->getCalledFunction())
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switch (F->getIntrinsicID()) {
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#undef va_start
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#undef va_copy
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#undef va_end
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case Intrinsic::not_intrinsic:
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case Intrinsic::va_start:
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case Intrinsic::va_copy:
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case Intrinsic::va_end:
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// We directly implement these intrinsics. Note that this knowledge
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// is incestuously entangled with the code in
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// SparcInstrSelection.cpp and must be updated when it is updated.
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// Since ALL of the code in this library is incestuously intertwined
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// with it already and sparc specific, we will live with this.
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break;
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default:
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// All other intrinsic calls we must lower.
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Instruction *Before = CI->getPrev();
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Target.getIntrinsicLowering().LowerIntrinsicCall(CI);
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if (Before) { // Move iterator to instruction after call
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I = Before; ++I;
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} else {
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I = BB->begin();
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}
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}
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//
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// Build the instruction trees to be given as inputs to BURG.
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//
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InstrForest instrForest(&F);
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if (SelectDebugLevel >= Select_DebugInstTrees) {
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std::cerr << "\n\n*** Input to instruction selection for function "
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<< F.getName() << "\n\n" << F
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<< "\n\n*** Instruction trees for function "
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<< F.getName() << "\n\n";
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instrForest.dump();
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}
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//
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// Invoke BURG instruction selection for each tree
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//
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for (InstrForest::const_root_iterator RI = instrForest.roots_begin();
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RI != instrForest.roots_end(); ++RI) {
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InstructionNode* basicNode = *RI;
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assert(basicNode->parent() == NULL && "A `root' node has a parent?");
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// Invoke BURM to label each tree node with a state
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burm_label(basicNode);
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if (SelectDebugLevel >= Select_DebugBurgTrees) {
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printcover(basicNode, 1, 0);
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std::cerr << "\nCover cost == " << treecost(basicNode, 1, 0) <<"\n\n";
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printMatches(basicNode);
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}
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// Then recursively walk the tree to select instructions
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SelectInstructionsForTree(basicNode, /*goalnt*/1);
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}
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//
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// Create the MachineBasicBlock records and add all of the MachineInstrs
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// defined in the MachineCodeForInstruction objects to also live in the
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// MachineBasicBlock objects.
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//
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MachineFunction &MF = MachineFunction::get(&F);
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for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
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MachineBasicBlock *MCBB = new MachineBasicBlock(BI);
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MF.getBasicBlockList().push_back(MCBB);
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for (BasicBlock::iterator II = BI->begin(); II != BI->end(); ++II) {
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MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(II);
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MCBB->insert(MCBB->end(), mvec.begin(), mvec.end());
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}
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}
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// Insert phi elimination code
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InsertCodeForPhis(F);
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if (SelectDebugLevel >= Select_PrintMachineCode) {
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std::cerr << "\n*** Machine instructions after INSTRUCTION SELECTION\n";
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MachineFunction::get(&F).dump();
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}
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return true;
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}
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//-------------------------------------------------------------------------
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// This method inserts phi elimination code for all BBs in a method
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//-------------------------------------------------------------------------
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void
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InstructionSelection::InsertCodeForPhis(Function &F) {
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// for all basic blocks in function
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//
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MachineFunction &MF = MachineFunction::get(&F);
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for (MachineFunction::iterator BB = MF.begin(); BB != MF.end(); ++BB) {
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for (BasicBlock::const_iterator IIt = BB->getBasicBlock()->begin();
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const PHINode *PN = dyn_cast<PHINode>(IIt); ++IIt) {
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// FIXME: This is probably wrong...
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Value *PhiCpRes = new PHINode(PN->getType(), "PhiCp:");
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// The leak detector shouldn't track these nodes. They are not garbage,
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// even though their parent field is never filled in.
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//
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LeakDetector::removeGarbageObject(PhiCpRes);
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// for each incoming value of the phi, insert phi elimination
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//
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for (unsigned i = 0; i < PN->getNumIncomingValues(); ++i) {
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// insert the copy instruction to the predecessor BB
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std::vector<MachineInstr*> mvec, CpVec;
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Target.getRegInfo().cpValue2Value(PN->getIncomingValue(i), PhiCpRes,
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mvec);
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for (std::vector<MachineInstr*>::iterator MI=mvec.begin();
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MI != mvec.end(); ++MI) {
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std::vector<MachineInstr*> CpVec2 =
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FixConstantOperandsForInstr(const_cast<PHINode*>(PN), *MI, Target);
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CpVec2.push_back(*MI);
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CpVec.insert(CpVec.end(), CpVec2.begin(), CpVec2.end());
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}
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InsertPhiElimInstructions(PN->getIncomingBlock(i), CpVec);
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}
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std::vector<MachineInstr*> mvec;
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Target.getRegInfo().cpValue2Value(PhiCpRes, const_cast<PHINode*>(PN),
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mvec);
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BB->insert(BB->begin(), mvec.begin(), mvec.end());
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} // for each Phi Instr in BB
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} // for all BBs in function
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}
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//-------------------------------------------------------------------------
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// Thid method inserts a copy instruction to a predecessor BB as a result
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// of phi elimination.
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//-------------------------------------------------------------------------
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void
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InstructionSelection::InsertPhiElimInstructions(BasicBlock *BB,
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const std::vector<MachineInstr*>& CpVec)
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{
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Instruction *TermInst = (Instruction*)BB->getTerminator();
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MachineCodeForInstruction &MC4Term = MachineCodeForInstruction::get(TermInst);
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MachineInstr *FirstMIOfTerm = MC4Term.front();
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assert (FirstMIOfTerm && "No Machine Instrs for terminator");
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MachineFunction &MF = MachineFunction::get(BB->getParent());
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// FIXME: if PHI instructions existed in the machine code, this would be
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// unnecessary.
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MachineBasicBlock *MBB = 0;
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for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
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if (I->getBasicBlock() == BB) {
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MBB = I;
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break;
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}
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MachineBasicBlock::iterator MCIt = FirstMIOfTerm;
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assert(MCIt != MBB->end() && "Start inst of terminator not found");
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// insert the copy instructions just before the first machine instruction
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// generated for the terminator
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MBB->insert(MCIt, CpVec.begin(), CpVec.end());
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}
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//---------------------------------------------------------------------------
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// Function SelectInstructionsForTree
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//
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// Recursively walk the tree to select instructions.
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// Do this top-down so that child instructions can exploit decisions
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// made at the child instructions.
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//
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// E.g., if br(setle(reg,const)) decides the constant is 0 and uses
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// a branch-on-integer-register instruction, then the setle node
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// can use that information to avoid generating the SUBcc instruction.
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//
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// Note that this cannot be done bottom-up because setle must do this
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// only if it is a child of the branch (otherwise, the result of setle
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// may be used by multiple instructions).
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//---------------------------------------------------------------------------
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void
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InstructionSelection::SelectInstructionsForTree(InstrTreeNode* treeRoot,
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int goalnt)
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{
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// Get the rule that matches this node.
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//
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int ruleForNode = burm_rule(treeRoot->state, goalnt);
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if (ruleForNode == 0) {
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std::cerr << "Could not match instruction tree for instr selection\n";
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abort();
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}
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// Get this rule's non-terminals and the corresponding child nodes (if any)
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//
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short *nts = burm_nts[ruleForNode];
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// First, select instructions for the current node and rule.
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// (If this is a list node, not an instruction, then skip this step).
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// This function is specific to the target architecture.
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//
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if (treeRoot->opLabel != VRegListOp) {
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std::vector<MachineInstr*> minstrVec;
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InstructionNode* instrNode = (InstructionNode*)treeRoot;
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assert(instrNode->getNodeType() == InstrTreeNode::NTInstructionNode);
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GetInstructionsByRule(instrNode, ruleForNode, nts, Target, minstrVec);
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MachineCodeForInstruction &mvec =
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MachineCodeForInstruction::get(instrNode->getInstruction());
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mvec.insert(mvec.end(), minstrVec.begin(), minstrVec.end());
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}
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// Then, recursively compile the child nodes, if any.
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//
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if (nts[0]) {
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// i.e., there is at least one kid
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InstrTreeNode* kids[2];
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int currentRule = ruleForNode;
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burm_kids(treeRoot, currentRule, kids);
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// First skip over any chain rules so that we don't visit
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// the current node again.
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//
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while (ThisIsAChainRule(currentRule)) {
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currentRule = burm_rule(treeRoot->state, nts[0]);
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nts = burm_nts[currentRule];
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burm_kids(treeRoot, currentRule, kids);
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}
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// Now we have the first non-chain rule so we have found
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// the actual child nodes. Recursively compile them.
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//
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for (unsigned i = 0; nts[i]; i++) {
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assert(i < 2);
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InstrTreeNode::InstrTreeNodeType nodeType = kids[i]->getNodeType();
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if (nodeType == InstrTreeNode::NTVRegListNode ||
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nodeType == InstrTreeNode::NTInstructionNode)
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SelectInstructionsForTree(kids[i], nts[i]);
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}
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}
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// Finally, do any post-processing on this node after its children
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// have been translated
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//
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if (treeRoot->opLabel != VRegListOp)
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PostprocessMachineCodeForTree((InstructionNode*)treeRoot, ruleForNode, nts);
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}
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//---------------------------------------------------------------------------
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// Function PostprocessMachineCodeForTree
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//
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// Apply any final cleanups to machine code for the root of a subtree
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// after selection for all its children has been completed.
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//
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void
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InstructionSelection::PostprocessMachineCodeForTree(InstructionNode* instrNode,
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int ruleForNode,
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short* nts)
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{
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// Fix up any constant operands in the machine instructions to either
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// use an immediate field or to load the constant into a register
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// Walk backwards and use direct indexes to allow insertion before current
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//
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Instruction* vmInstr = instrNode->getInstruction();
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MachineCodeForInstruction &mvec = MachineCodeForInstruction::get(vmInstr);
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for (unsigned i = mvec.size(); i != 0; --i) {
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std::vector<MachineInstr*> loadConstVec =
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FixConstantOperandsForInstr(vmInstr, mvec[i-1], Target);
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mvec.insert(mvec.begin()+i-1, loadConstVec.begin(), loadConstVec.end());
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}
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}
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//===----------------------------------------------------------------------===//
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// createInstructionSelectionPass - Public entrypoint for instruction selection
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// and this file as a whole...
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//
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FunctionPass *llvm::createInstructionSelectionPass(TargetMachine &TM) {
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return new InstructionSelection(TM);
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}
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