mirror of
https://github.com/c64scene-ar/llvm-6502.git
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e88280a422
is a move between two registers, at least one of the registers is virtual and the two live intervals do not overlap. This results in about 40% reduction in intervals, 30% decrease in the register allocators running time and a 20% increase in peephole optimizations (mainly move eliminations). The option can be enabled by passing -join-liveintervals where appropriate. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10965 91177308-0d34-0410-b5e6-96231b3b80d8
551 lines
19 KiB
C++
551 lines
19 KiB
C++
//===-- LiveIntervals.cpp - Live Interval Analysis ------------------------===//
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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 implements the LiveInterval analysis pass which is used
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// by the Linear Scan Register allocator. This pass linearizes the
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// basic blocks of the function in DFS order and uses the
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// LiveVariables pass to conservatively compute live intervals for
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// each virtual and physical register.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "liveintervals"
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#include "llvm/CodeGen/LiveIntervals.h"
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#include "llvm/Function.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/CodeGen/LiveVariables.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/SSARegMap.h"
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#include "llvm/Target/MRegisterInfo.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/Target/TargetRegInfo.h"
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#include "llvm/Support/CFG.h"
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#include "Support/CommandLine.h"
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#include "Support/Debug.h"
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#include "Support/DepthFirstIterator.h"
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#include "Support/Statistic.h"
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#include <cmath>
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#include <iostream>
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#include <limits>
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using namespace llvm;
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namespace {
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RegisterAnalysis<LiveIntervals> X("liveintervals",
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"Live Interval Analysis");
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Statistic<> numIntervals("liveintervals", "Number of intervals");
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cl::opt<bool>
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join("join-liveintervals",
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cl::desc("Join compatible live intervals"),
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cl::init(false));
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};
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void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const
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{
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AU.addPreserved<LiveVariables>();
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AU.addRequired<LiveVariables>();
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AU.addPreservedID(PHIEliminationID);
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AU.addRequiredID(PHIEliminationID);
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AU.addRequiredID(TwoAddressInstructionPassID);
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AU.addRequired<LoopInfo>();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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/// runOnMachineFunction - Register allocate the whole function
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///
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bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
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DEBUG(std::cerr << "Machine Function\n");
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mf_ = &fn;
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tm_ = &fn.getTarget();
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mri_ = tm_->getRegisterInfo();
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lv_ = &getAnalysis<LiveVariables>();
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mbbi2mbbMap_.clear();
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mi2iMap_.clear();
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r2iMap_.clear();
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r2iMap_.clear();
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r2rMap_.clear();
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intervals_.clear();
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// number MachineInstrs
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unsigned miIndex = 0;
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for (MachineFunction::iterator mbb = mf_->begin(), mbbEnd = mf_->end();
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mbb != mbbEnd; ++mbb) {
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const std::pair<MachineBasicBlock*, unsigned>& entry =
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lv_->getMachineBasicBlockInfo(&*mbb);
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bool inserted = mbbi2mbbMap_.insert(std::make_pair(entry.second,
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entry.first)).second;
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assert(inserted && "multiple index -> MachineBasicBlock");
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for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
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mi != miEnd; ++mi) {
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inserted = mi2iMap_.insert(std::make_pair(*mi, miIndex)).second;
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assert(inserted && "multiple MachineInstr -> index mappings");
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++miIndex;
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}
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}
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computeIntervals();
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// compute spill weights
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const LoopInfo& loopInfo = getAnalysis<LoopInfo>();
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const TargetInstrInfo& tii = tm_->getInstrInfo();
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for (MachineFunction::const_iterator mbbi = mf_->begin(),
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mbbe = mf_->end(); mbbi != mbbe; ++mbbi) {
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const MachineBasicBlock* mbb = mbbi;
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unsigned loopDepth = loopInfo.getLoopDepth(mbb->getBasicBlock());
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for (MachineBasicBlock::const_iterator mii = mbb->begin(),
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mie = mbb->end(); mii != mie; ++mii) {
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MachineInstr* mi = *mii;
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for (int i = mi->getNumOperands() - 1; i >= 0; --i) {
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MachineOperand& mop = mi->getOperand(i);
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if (!mop.isVirtualRegister())
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continue;
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unsigned reg = mop.getAllocatedRegNum();
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Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
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assert(r2iit != r2iMap_.end());
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r2iit->second->weight += pow(10.0F, loopDepth);
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}
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}
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}
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// join intervals if requested
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if (join) joinIntervals();
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numIntervals += intervals_.size();
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return true;
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}
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void LiveIntervals::printRegName(unsigned reg) const
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{
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if (reg < MRegisterInfo::FirstVirtualRegister)
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std::cerr << mri_->getName(reg);
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else
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std::cerr << '%' << reg;
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}
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void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
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MachineBasicBlock::iterator mi,
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unsigned reg)
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{
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DEBUG(std::cerr << "\t\tregister: ";printRegName(reg); std::cerr << '\n');
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unsigned instrIndex = getInstructionIndex(*mi);
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LiveVariables::VarInfo& vi = lv_->getVarInfo(reg);
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Interval* interval = 0;
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Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
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if (r2iit == r2iMap_.end()) {
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// add new interval
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intervals_.push_back(Interval(reg));
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// update interval index for this register
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bool inserted =
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r2iMap_.insert(std::make_pair(reg, --intervals_.end())).second;
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assert(inserted);
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interval = &intervals_.back();
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}
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else {
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interval = &*r2iit->second;
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}
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for (MbbIndex2MbbMap::iterator
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it = mbbi2mbbMap_.begin(), itEnd = mbbi2mbbMap_.end();
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it != itEnd; ++it) {
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unsigned liveBlockIndex = it->first;
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MachineBasicBlock* liveBlock = it->second;
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if (liveBlockIndex < vi.AliveBlocks.size() &&
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vi.AliveBlocks[liveBlockIndex] &&
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!liveBlock->empty()) {
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unsigned start = getInstructionIndex(liveBlock->front());
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unsigned end = getInstructionIndex(liveBlock->back()) + 1;
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interval->addRange(start, end);
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}
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}
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bool killedInDefiningBasicBlock = false;
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for (int i = 0, e = vi.Kills.size(); i != e; ++i) {
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MachineBasicBlock* killerBlock = vi.Kills[i].first;
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MachineInstr* killerInstr = vi.Kills[i].second;
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unsigned start = (mbb == killerBlock ?
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instrIndex :
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getInstructionIndex(killerBlock->front()));
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unsigned end = getInstructionIndex(killerInstr) + 1;
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if (start < end) {
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killedInDefiningBasicBlock |= mbb == killerBlock;
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interval->addRange(start, end);
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}
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}
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if (!killedInDefiningBasicBlock) {
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unsigned end = getInstructionIndex(mbb->back()) + 1;
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interval->addRange(instrIndex, end);
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}
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}
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void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock* mbb,
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MachineBasicBlock::iterator mi,
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unsigned reg)
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{
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DEBUG(std::cerr << "\t\tregister: "; printRegName(reg));
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unsigned start = getInstructionIndex(*mi);
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unsigned end = start;
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// register can be dead by the instruction defining it but it can
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// only be killed by subsequent instructions
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for (LiveVariables::killed_iterator
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ki = lv_->dead_begin(*mi),
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ke = lv_->dead_end(*mi);
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ki != ke; ++ki) {
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if (reg == ki->second) {
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end = getInstructionIndex(ki->first) + 1;
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DEBUG(std::cerr << " dead\n");
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goto exit;
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}
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}
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++mi;
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for (MachineBasicBlock::iterator e = mbb->end(); mi != e; ++mi) {
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for (LiveVariables::killed_iterator
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ki = lv_->dead_begin(*mi),
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ke = lv_->dead_end(*mi);
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ki != ke; ++ki) {
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if (reg == ki->second) {
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end = getInstructionIndex(ki->first) + 1;
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DEBUG(std::cerr << " dead\n");
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goto exit;
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}
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}
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for (LiveVariables::killed_iterator
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ki = lv_->killed_begin(*mi),
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ke = lv_->killed_end(*mi);
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ki != ke; ++ki) {
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if (reg == ki->second) {
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end = getInstructionIndex(ki->first) + 1;
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DEBUG(std::cerr << " killed\n");
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goto exit;
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}
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}
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}
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exit:
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assert(start < end && "did not find end of interval?");
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Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
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if (r2iit != r2iMap_.end()) {
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Interval& interval = *r2iit->second;
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interval.addRange(start, end);
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}
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else {
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intervals_.push_back(Interval(reg));
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Interval& interval = intervals_.back();
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// update interval index for this register
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bool inserted =
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r2iMap_.insert(std::make_pair(reg, --intervals_.end())).second;
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assert(inserted);
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interval.addRange(start, end);
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}
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}
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void LiveIntervals::handleRegisterDef(MachineBasicBlock* mbb,
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MachineBasicBlock::iterator mi,
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unsigned reg)
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{
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if (reg < MRegisterInfo::FirstVirtualRegister) {
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if (lv_->getAllocatablePhysicalRegisters()[reg]) {
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handlePhysicalRegisterDef(mbb, mi, reg);
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for (const unsigned* as = mri_->getAliasSet(reg); *as; ++as)
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handlePhysicalRegisterDef(mbb, mi, *as);
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}
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}
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else {
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handleVirtualRegisterDef(mbb, mi, reg);
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}
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}
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unsigned LiveIntervals::getInstructionIndex(MachineInstr* instr) const
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{
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assert(mi2iMap_.find(instr) != mi2iMap_.end() &&
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"instruction not assigned a number");
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return mi2iMap_.find(instr)->second;
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}
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/// computeIntervals - computes the live intervals for virtual
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/// registers. for some ordering of the machine instructions [1,N] a
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/// live interval is an interval [i, j] where 1 <= i <= j <= N for
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/// which a variable is live
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void LiveIntervals::computeIntervals()
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{
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DEBUG(std::cerr << "computing live intervals:\n");
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for (MbbIndex2MbbMap::iterator
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it = mbbi2mbbMap_.begin(), itEnd = mbbi2mbbMap_.end();
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it != itEnd; ++it) {
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MachineBasicBlock* mbb = it->second;
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DEBUG(std::cerr << "machine basic block: "
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<< mbb->getBasicBlock()->getName() << "\n");
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for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
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mi != miEnd; ++mi) {
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MachineInstr* instr = *mi;
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const TargetInstrDescriptor& tid =
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tm_->getInstrInfo().get(instr->getOpcode());
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DEBUG(std::cerr << "\t[" << getInstructionIndex(instr) << "] ";
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instr->print(std::cerr, *tm_););
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// handle implicit defs
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for (const unsigned* id = tid.ImplicitDefs; *id; ++id)
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handleRegisterDef(mbb, mi, *id);
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// handle explicit defs
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for (int i = instr->getNumOperands() - 1; i >= 0; --i) {
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MachineOperand& mop = instr->getOperand(i);
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if (!mop.isRegister())
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continue;
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// handle defs - build intervals
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if (mop.isDef())
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handleRegisterDef(mbb, mi, mop.getAllocatedRegNum());
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}
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}
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}
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intervals_.sort(StartPointComp());
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DEBUG(std::copy(intervals_.begin(), intervals_.end(),
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std::ostream_iterator<Interval>(std::cerr, "\n")));
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}
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unsigned LiveIntervals::rep(unsigned reg)
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{
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Reg2RegMap::iterator it = r2rMap_.find(reg);
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if (it != r2rMap_.end())
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return it->second = rep(it->second);
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return reg;
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}
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void LiveIntervals::joinIntervals()
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{
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DEBUG(std::cerr << "joining compatible intervals:\n");
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const TargetInstrInfo& tii = tm_->getInstrInfo();
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for (MachineFunction::const_iterator mbbi = mf_->begin(),
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mbbe = mf_->end(); mbbi != mbbe; ++mbbi) {
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const MachineBasicBlock* mbb = mbbi;
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DEBUG(std::cerr << "machine basic block: "
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<< mbb->getBasicBlock()->getName() << "\n");
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for (MachineBasicBlock::const_iterator mii = mbb->begin(),
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mie = mbb->end(); mii != mie; ++mii) {
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MachineInstr* mi = *mii;
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const TargetInstrDescriptor& tid =
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tm_->getInstrInfo().get(mi->getOpcode());
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DEBUG(std::cerr << "\t\tinstruction["
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<< getInstructionIndex(mi) << "]: ";
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mi->print(std::cerr, *tm_););
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unsigned srcReg, dstReg;
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if (tii.isMoveInstr(*mi, srcReg, dstReg) &&
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(srcReg >= MRegisterInfo::FirstVirtualRegister ||
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lv_->getAllocatablePhysicalRegisters()[srcReg]) &&
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(dstReg >= MRegisterInfo::FirstVirtualRegister ||
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lv_->getAllocatablePhysicalRegisters()[dstReg])) {
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// get representative registers
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srcReg = rep(srcReg);
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dstReg = rep(dstReg);
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// if they are already joined we continue
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if (srcReg == dstReg)
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continue;
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Reg2IntervalMap::iterator r2iSrc = r2iMap_.find(srcReg);
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assert(r2iSrc != r2iMap_.end());
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Reg2IntervalMap::iterator r2iDst = r2iMap_.find(dstReg);
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assert(r2iDst != r2iMap_.end());
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Intervals::iterator srcInt = r2iSrc->second;
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Intervals::iterator dstInt = r2iDst->second;
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if (srcInt->reg < MRegisterInfo::FirstVirtualRegister) {
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if (dstInt->reg == srcInt->reg ||
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(dstInt->reg >= MRegisterInfo::FirstVirtualRegister &&
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!dstInt->overlaps(*srcInt))) {
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srcInt->join(*dstInt);
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r2iDst->second = r2iSrc->second;
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r2rMap_.insert(std::make_pair(dstInt->reg, srcInt->reg));
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intervals_.erase(dstInt);
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}
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}
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else if (dstInt->reg < MRegisterInfo::FirstVirtualRegister) {
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if (srcInt->reg == dstInt->reg ||
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(srcInt->reg >= MRegisterInfo::FirstVirtualRegister &&
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!srcInt->overlaps(*dstInt))) {
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dstInt->join(*srcInt);
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r2iSrc->second = r2iDst->second;
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r2rMap_.insert(std::make_pair(srcInt->reg, dstInt->reg));
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intervals_.erase(srcInt);
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}
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}
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else {
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const TargetRegisterClass *srcRc, *dstRc;
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srcRc = mf_->getSSARegMap()->getRegClass(srcInt->reg);
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dstRc = mf_->getSSARegMap()->getRegClass(dstInt->reg);
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if (srcRc == dstRc && !dstInt->overlaps(*srcInt)) {
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srcInt->join(*dstInt);
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r2iDst->second = r2iSrc->second;
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r2rMap_.insert(std::make_pair(dstInt->reg, srcInt->reg));
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intervals_.erase(dstInt);
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}
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}
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}
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}
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}
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intervals_.sort(StartPointComp());
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DEBUG(std::copy(intervals_.begin(), intervals_.end(),
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std::ostream_iterator<Interval>(std::cerr, "\n")));
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DEBUG(for (Reg2RegMap::const_iterator i = r2rMap_.begin(),
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e = r2rMap_.end(); i != e; ++i)
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std::cerr << i->first << " -> " << i->second << '\n';);
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}
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LiveIntervals::Interval::Interval(unsigned r)
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: reg(r),
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weight((r < MRegisterInfo::FirstVirtualRegister ?
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std::numeric_limits<float>::max() : 0.0F))
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{
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}
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bool LiveIntervals::Interval::liveAt(unsigned index) const
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{
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Ranges::const_iterator r = ranges.begin();
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while (r != ranges.end() && index < (r->second - 1)) {
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if (index >= r->first)
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return true;
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++r;
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}
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return false;
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}
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bool LiveIntervals::Interval::overlaps(const Interval& other) const
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{
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Ranges::const_iterator i = ranges.begin();
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Ranges::const_iterator j = other.ranges.begin();
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while (i != ranges.end() && j != other.ranges.end()) {
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if (i->first < j->first) {
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if ((i->second - 1) > j->first) {
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return true;
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}
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else {
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++i;
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}
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}
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else if (j->first < i->first) {
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if ((j->second - 1) > i->first) {
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return true;
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}
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else {
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++j;
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}
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}
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else {
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return true;
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}
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}
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return false;
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}
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void LiveIntervals::Interval::addRange(unsigned start, unsigned end)
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{
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DEBUG(std::cerr << "\t\t\tadding range: [" << start <<','<< end << ") -> ");
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//assert(start < end && "invalid range?");
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Range range = std::make_pair(start, end);
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Ranges::iterator it =
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ranges.insert(std::upper_bound(ranges.begin(), ranges.end(), range),
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range);
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it = mergeRangesForward(it);
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it = mergeRangesBackward(it);
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DEBUG(std::cerr << "\t\t\t\tafter merging: " << *this << '\n');
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}
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void LiveIntervals::Interval::join(const LiveIntervals::Interval& other)
|
|
{
|
|
DEBUG(std::cerr << "\t\t\t\tjoining intervals: "
|
|
<< other << " and " << *this << '\n');
|
|
Ranges::iterator cur = ranges.begin();
|
|
|
|
for (Ranges::const_iterator i = other.ranges.begin(),
|
|
e = other.ranges.end(); i != e; ++i) {
|
|
cur = ranges.insert(std::upper_bound(cur, ranges.end(), *i), *i);
|
|
cur = mergeRangesForward(cur);
|
|
cur = mergeRangesBackward(cur);
|
|
}
|
|
if (reg >= MRegisterInfo::FirstVirtualRegister)
|
|
weight += other.weight;
|
|
|
|
DEBUG(std::cerr << "\t\t\t\tafter merging: " << *this << '\n');
|
|
}
|
|
|
|
LiveIntervals::Interval::Ranges::iterator
|
|
LiveIntervals::Interval::mergeRangesForward(Ranges::iterator it)
|
|
{
|
|
for (Ranges::iterator next = it + 1;
|
|
next != ranges.end() && it->second >= next->first; ) {
|
|
it->second = std::max(it->second, next->second);
|
|
next = ranges.erase(next);
|
|
}
|
|
return it;
|
|
}
|
|
|
|
LiveIntervals::Interval::Ranges::iterator
|
|
LiveIntervals::Interval::mergeRangesBackward(Ranges::iterator it)
|
|
{
|
|
for (Ranges::iterator prev = it - 1;
|
|
it != ranges.begin() && it->first <= prev->second; ) {
|
|
it->first = std::min(it->first, prev->first);
|
|
it->second = std::max(it->second, prev->second);
|
|
it = ranges.erase(prev);
|
|
prev = it - 1;
|
|
}
|
|
|
|
return it;
|
|
}
|
|
|
|
std::ostream& llvm::operator<<(std::ostream& os,
|
|
const LiveIntervals::Interval& li)
|
|
{
|
|
os << "%reg" << li.reg << ',' << li.weight << " = ";
|
|
for (LiveIntervals::Interval::Ranges::const_iterator
|
|
i = li.ranges.begin(), e = li.ranges.end(); i != e; ++i) {
|
|
os << "[" << i->first << "," << i->second << ")";
|
|
}
|
|
return os;
|
|
}
|