forked from OSchip/llvm-project
369 lines
12 KiB
C++
369 lines
12 KiB
C++
// $Id$ -*-c++-*-
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//***************************************************************************
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// File:
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// InstrSelection.cpp
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//
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// Purpose:
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// Machine-independent driver file for instruction selection.
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// This file constructs a forest of BURG instruction trees and then
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// uses the BURG-generated tree grammar (BURM) to find the optimal
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// instruction sequences for a given machine.
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//
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// History:
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// 7/02/01 - Vikram Adve - Created
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//**************************************************************************/
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#include "llvm/CodeGen/InstrSelection.h"
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#include "llvm/CodeGen/InstrSelectionSupport.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/InstrForest.h"
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#include "llvm/CodeGen/MachineCodeForInstruction.h"
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#include "llvm/CodeGen/MachineCodeForMethod.h"
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#include "llvm/Target/MachineRegInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/Function.h"
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#include "llvm/iPHINode.h"
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#include "Support/CommandLine.h"
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#include <iostream>
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using std::cerr;
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//******************** Internal Data Declarations ************************/
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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::Enum<enum SelectDebugLevel_t> SelectDebugLevel("dselect", cl::NoFlags,
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"enable instruction selection debugging information",
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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", "print debugging info for instruction selection "),
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clEnumValN(Select_DebugBurgTrees, "b", "print burg trees"), 0);
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//******************** Forward Function Declarations ***********************/
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static bool SelectInstructionsForTree (InstrTreeNode* treeRoot,
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int goalnt,
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TargetMachine &target);
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static void PostprocessMachineCodeForTree(InstructionNode* instrNode,
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int ruleForNode,
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short* nts,
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TargetMachine &target);
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static void InsertCode4AllPhisInMeth(Function *F, TargetMachine &target);
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//******************* Externally Visible Functions *************************/
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//---------------------------------------------------------------------------
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// Entry point for instruction selection using BURG.
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// Returns true if instruction selection failed, false otherwise.
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//---------------------------------------------------------------------------
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bool
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SelectInstructionsForMethod(Function *F, TargetMachine &target)
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{
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bool failed = false;
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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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{
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cerr << "\n\n*** Input to instruction selection for function "
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<< F->getName() << "\n\n";
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F->dump();
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cerr << "\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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{
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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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{
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printcover(basicNode, 1, 0);
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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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if (SelectInstructionsForTree(basicNode, /*goalnt*/1, target))
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{
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failed = true;
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break;
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}
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}
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//
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// Record instructions in the vector for each basic block
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//
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for (Function::iterator BI = F->begin(), BE = F->end(); BI != BE; ++BI)
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{
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MachineCodeForBasicBlock& bbMvec = (*BI)->getMachineInstrVec();
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for (BasicBlock::iterator II = (*BI)->begin(); II != (*BI)->end(); ++II)
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{
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MachineCodeForInstruction &mvec =MachineCodeForInstruction::get(*II);
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for (unsigned i=0; i < mvec.size(); i++)
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bbMvec.push_back(mvec[i]);
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}
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}
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// Insert phi elimination code -- added by Ruchira
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InsertCode4AllPhisInMeth(F, target);
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if (SelectDebugLevel >= Select_PrintMachineCode)
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{
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cerr << "\n*** Machine instructions after INSTRUCTION SELECTION\n";
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MachineCodeForMethod::get(F).dump();
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}
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return false;
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}
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//*********************** Private Functions *****************************/
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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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InsertPhiElimInstructions(BasicBlock *BB, const 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.begin() );
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assert( FirstMIOfTerm && "No Machine Instrs for terminator" );
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// get an iterator to machine instructions in the BB
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MachineCodeForBasicBlock& bbMvec = BB->getMachineInstrVec();
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MachineCodeForBasicBlock::iterator MCIt = bbMvec.begin();
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// find the position of first machine instruction generated by the
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// terminator of this BB
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for( ; (MCIt != bbMvec.end()) && (*MCIt != FirstMIOfTerm) ; ++MCIt )
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;
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assert( MCIt != bbMvec.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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bbMvec.insert(MCIt, CpVec.begin(), CpVec.end());
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//cerr << "\nPhiElimination copy inst: " << *CopyInstVec[0];
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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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InsertCode4AllPhisInMeth(Function *F, TargetMachine &target)
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{
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// for all basic blocks in function
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//
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for (Function::iterator BI = F->begin(); BI != F->end(); ++BI) {
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BasicBlock *BB = *BI;
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const BasicBlock::InstListType &InstList = BB->getInstList();
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BasicBlock::InstListType::const_iterator IIt = InstList.begin();
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// for all instructions in the basic block
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//
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for( ; IIt != InstList.end(); ++IIt ) {
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if( (*IIt)->getOpcode() == Instruction::PHINode ) {
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PHINode *PN = (PHINode *) (*IIt);
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Value *PhiCpRes = new Value(PN->getType(),PN->getValueType(),"PhiCp:");
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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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MachineInstr *CpMI =
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target.getRegInfo().cpValue2Value(PN->getIncomingValue(i),
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PhiCpRes);
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vector<MachineInstr*> CpVec = FixConstantOperandsForInstr(PN, CpMI,
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target);
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CpVec.push_back(CpMI);
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InsertPhiElimInstructions(PN->getIncomingBlock(i), CpVec);
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}
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MachineInstr *CpMI2 =
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target.getRegInfo().cpValue2Value(PhiCpRes, PN);
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// get an iterator to machine instructions in the BB
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MachineCodeForBasicBlock& bbMvec = BB->getMachineInstrVec();
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bbMvec.insert( bbMvec.begin(), CpMI2);
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}
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else break; // since PHI nodes can only be at the top
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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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// 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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static void
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PostprocessMachineCodeForTree(InstructionNode* instrNode,
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int ruleForNode,
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short* nts,
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TargetMachine &target)
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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 (int i = (int) mvec.size()-1; i >= 0; i--)
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{
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std::vector<MachineInstr*> loadConstVec =
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FixConstantOperandsForInstr(vmInstr, mvec[i], target);
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if (loadConstVec.size() > 0)
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mvec.insert(mvec.begin()+i, loadConstVec.begin(), loadConstVec.end());
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}
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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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bool
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SelectInstructionsForTree(InstrTreeNode* treeRoot, int goalnt,
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TargetMachine &target)
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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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{
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cerr << "Could not match instruction tree for instr selection\n";
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assert(0);
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return true;
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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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{
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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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{
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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 (int i = 0; nts[i]; i++)
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{
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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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{
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if (SelectInstructionsForTree(kids[i], nts[i], target))
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return true; // failure
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}
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}
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}
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// Finally, do any postprocessing 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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{
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InstructionNode* instrNode = (InstructionNode*)treeRoot;
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PostprocessMachineCodeForTree(instrNode, ruleForNode, nts, target);
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}
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return false; // success
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}
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