llvm-6502/lib/CodeGen/LiveIntervalAnalysis.cpp
Alkis Evlogimenos 79b0c3f0b9 Fix failing test cases with joined live intervals. It turns out that
when joining we need to check if we overlap with the second interval
or any of its aliases.

Also make joining intervals the default.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10973 91177308-0d34-0410-b5e6-96231b3b80d8
2004-01-23 13:37:51 +00:00

572 lines
20 KiB
C++

//===-- LiveIntervals.cpp - Live Interval Analysis ------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the LiveInterval analysis pass which is used
// by the Linear Scan Register allocator. This pass linearizes the
// basic blocks of the function in DFS order and uses the
// LiveVariables pass to conservatively compute live intervals for
// each virtual and physical register.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "liveintervals"
#include "llvm/CodeGen/LiveIntervals.h"
#include "llvm/Function.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/SSARegMap.h"
#include "llvm/Target/MRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegInfo.h"
#include "llvm/Support/CFG.h"
#include "Support/CommandLine.h"
#include "Support/Debug.h"
#include "Support/DepthFirstIterator.h"
#include "Support/Statistic.h"
#include <cmath>
#include <iostream>
#include <limits>
using namespace llvm;
namespace {
RegisterAnalysis<LiveIntervals> X("liveintervals",
"Live Interval Analysis");
Statistic<> numIntervals("liveintervals", "Number of intervals");
cl::opt<bool>
join("join-liveintervals",
cl::desc("Join compatible live intervals"),
cl::init(true));
};
void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const
{
AU.addPreserved<LiveVariables>();
AU.addRequired<LiveVariables>();
AU.addPreservedID(PHIEliminationID);
AU.addRequiredID(PHIEliminationID);
AU.addRequiredID(TwoAddressInstructionPassID);
AU.addRequired<LoopInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
/// runOnMachineFunction - Register allocate the whole function
///
bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
DEBUG(std::cerr << "Machine Function\n");
mf_ = &fn;
tm_ = &fn.getTarget();
mri_ = tm_->getRegisterInfo();
lv_ = &getAnalysis<LiveVariables>();
mbbi2mbbMap_.clear();
mi2iMap_.clear();
r2iMap_.clear();
r2iMap_.clear();
r2rMap_.clear();
intervals_.clear();
// number MachineInstrs
unsigned miIndex = 0;
for (MachineFunction::iterator mbb = mf_->begin(), mbbEnd = mf_->end();
mbb != mbbEnd; ++mbb) {
const std::pair<MachineBasicBlock*, unsigned>& entry =
lv_->getMachineBasicBlockInfo(&*mbb);
bool inserted = mbbi2mbbMap_.insert(std::make_pair(entry.second,
entry.first)).second;
assert(inserted && "multiple index -> MachineBasicBlock");
for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
mi != miEnd; ++mi) {
inserted = mi2iMap_.insert(std::make_pair(*mi, miIndex)).second;
assert(inserted && "multiple MachineInstr -> index mappings");
++miIndex;
}
}
computeIntervals();
// compute spill weights
const LoopInfo& loopInfo = getAnalysis<LoopInfo>();
const TargetInstrInfo& tii = tm_->getInstrInfo();
for (MachineFunction::const_iterator mbbi = mf_->begin(),
mbbe = mf_->end(); mbbi != mbbe; ++mbbi) {
const MachineBasicBlock* mbb = mbbi;
unsigned loopDepth = loopInfo.getLoopDepth(mbb->getBasicBlock());
for (MachineBasicBlock::const_iterator mii = mbb->begin(),
mie = mbb->end(); mii != mie; ++mii) {
MachineInstr* mi = *mii;
for (int i = mi->getNumOperands() - 1; i >= 0; --i) {
MachineOperand& mop = mi->getOperand(i);
if (!mop.isVirtualRegister())
continue;
unsigned reg = mop.getAllocatedRegNum();
Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
assert(r2iit != r2iMap_.end());
r2iit->second->weight += pow(10.0F, loopDepth);
}
}
}
// join intervals if requested
if (join) joinIntervals();
numIntervals += intervals_.size();
return true;
}
void LiveIntervals::printRegName(unsigned reg) const
{
if (reg < MRegisterInfo::FirstVirtualRegister)
std::cerr << mri_->getName(reg);
else
std::cerr << '%' << reg;
}
void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
MachineBasicBlock::iterator mi,
unsigned reg)
{
DEBUG(std::cerr << "\t\tregister: ";printRegName(reg); std::cerr << '\n');
unsigned instrIndex = getInstructionIndex(*mi);
LiveVariables::VarInfo& vi = lv_->getVarInfo(reg);
Interval* interval = 0;
Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
if (r2iit == r2iMap_.end()) {
// add new interval
intervals_.push_back(Interval(reg));
// update interval index for this register
bool inserted =
r2iMap_.insert(std::make_pair(reg, --intervals_.end())).second;
assert(inserted);
interval = &intervals_.back();
}
else {
interval = &*r2iit->second;
}
for (MbbIndex2MbbMap::iterator
it = mbbi2mbbMap_.begin(), itEnd = mbbi2mbbMap_.end();
it != itEnd; ++it) {
unsigned liveBlockIndex = it->first;
MachineBasicBlock* liveBlock = it->second;
if (liveBlockIndex < vi.AliveBlocks.size() &&
vi.AliveBlocks[liveBlockIndex] &&
!liveBlock->empty()) {
unsigned start = getInstructionIndex(liveBlock->front());
unsigned end = getInstructionIndex(liveBlock->back()) + 1;
interval->addRange(start, end);
}
}
bool killedInDefiningBasicBlock = false;
for (int i = 0, e = vi.Kills.size(); i != e; ++i) {
MachineBasicBlock* killerBlock = vi.Kills[i].first;
MachineInstr* killerInstr = vi.Kills[i].second;
unsigned start = (mbb == killerBlock ?
instrIndex :
getInstructionIndex(killerBlock->front()));
unsigned end = getInstructionIndex(killerInstr) + 1;
if (start < end) {
killedInDefiningBasicBlock |= mbb == killerBlock;
interval->addRange(start, end);
}
}
if (!killedInDefiningBasicBlock) {
unsigned end = getInstructionIndex(mbb->back()) + 1;
interval->addRange(instrIndex, end);
}
}
void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock* mbb,
MachineBasicBlock::iterator mi,
unsigned reg)
{
DEBUG(std::cerr << "\t\tregister: "; printRegName(reg));
unsigned start = getInstructionIndex(*mi);
unsigned end = start;
// register can be dead by the instruction defining it but it can
// only be killed by subsequent instructions
for (LiveVariables::killed_iterator
ki = lv_->dead_begin(*mi),
ke = lv_->dead_end(*mi);
ki != ke; ++ki) {
if (reg == ki->second) {
end = getInstructionIndex(ki->first) + 1;
DEBUG(std::cerr << " dead\n");
goto exit;
}
}
++mi;
for (MachineBasicBlock::iterator e = mbb->end(); mi != e; ++mi) {
for (LiveVariables::killed_iterator
ki = lv_->dead_begin(*mi),
ke = lv_->dead_end(*mi);
ki != ke; ++ki) {
if (reg == ki->second) {
end = getInstructionIndex(ki->first) + 1;
DEBUG(std::cerr << " dead\n");
goto exit;
}
}
for (LiveVariables::killed_iterator
ki = lv_->killed_begin(*mi),
ke = lv_->killed_end(*mi);
ki != ke; ++ki) {
if (reg == ki->second) {
end = getInstructionIndex(ki->first) + 1;
DEBUG(std::cerr << " killed\n");
goto exit;
}
}
}
exit:
assert(start < end && "did not find end of interval?");
Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
if (r2iit != r2iMap_.end()) {
Interval& interval = *r2iit->second;
interval.addRange(start, end);
}
else {
intervals_.push_back(Interval(reg));
Interval& interval = intervals_.back();
// update interval index for this register
bool inserted =
r2iMap_.insert(std::make_pair(reg, --intervals_.end())).second;
assert(inserted);
interval.addRange(start, end);
}
}
void LiveIntervals::handleRegisterDef(MachineBasicBlock* mbb,
MachineBasicBlock::iterator mi,
unsigned reg)
{
if (reg < MRegisterInfo::FirstVirtualRegister) {
if (lv_->getAllocatablePhysicalRegisters()[reg]) {
handlePhysicalRegisterDef(mbb, mi, reg);
for (const unsigned* as = mri_->getAliasSet(reg); *as; ++as)
handlePhysicalRegisterDef(mbb, mi, *as);
}
}
else {
handleVirtualRegisterDef(mbb, mi, reg);
}
}
unsigned LiveIntervals::getInstructionIndex(MachineInstr* instr) const
{
assert(mi2iMap_.find(instr) != mi2iMap_.end() &&
"instruction not assigned a number");
return mi2iMap_.find(instr)->second;
}
/// computeIntervals - computes the live intervals for virtual
/// registers. for some ordering of the machine instructions [1,N] a
/// live interval is an interval [i, j] where 1 <= i <= j <= N for
/// which a variable is live
void LiveIntervals::computeIntervals()
{
DEBUG(std::cerr << "computing live intervals:\n");
for (MbbIndex2MbbMap::iterator
it = mbbi2mbbMap_.begin(), itEnd = mbbi2mbbMap_.end();
it != itEnd; ++it) {
MachineBasicBlock* mbb = it->second;
DEBUG(std::cerr << "machine basic block: "
<< mbb->getBasicBlock()->getName() << "\n");
for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
mi != miEnd; ++mi) {
MachineInstr* instr = *mi;
const TargetInstrDescriptor& tid =
tm_->getInstrInfo().get(instr->getOpcode());
DEBUG(std::cerr << "\t[" << getInstructionIndex(instr) << "] ";
instr->print(std::cerr, *tm_););
// handle implicit defs
for (const unsigned* id = tid.ImplicitDefs; *id; ++id)
handleRegisterDef(mbb, mi, *id);
// handle explicit defs
for (int i = instr->getNumOperands() - 1; i >= 0; --i) {
MachineOperand& mop = instr->getOperand(i);
if (!mop.isRegister())
continue;
// handle defs - build intervals
if (mop.isDef())
handleRegisterDef(mbb, mi, mop.getAllocatedRegNum());
}
}
}
intervals_.sort(StartPointComp());
DEBUG(std::copy(intervals_.begin(), intervals_.end(),
std::ostream_iterator<Interval>(std::cerr, "\n")));
}
unsigned LiveIntervals::rep(unsigned reg)
{
Reg2RegMap::iterator it = r2rMap_.find(reg);
if (it != r2rMap_.end())
return it->second = rep(it->second);
return reg;
}
void LiveIntervals::joinIntervals()
{
DEBUG(std::cerr << "joining compatible intervals:\n");
const TargetInstrInfo& tii = tm_->getInstrInfo();
for (MachineFunction::const_iterator mbbi = mf_->begin(),
mbbe = mf_->end(); mbbi != mbbe; ++mbbi) {
const MachineBasicBlock* mbb = mbbi;
DEBUG(std::cerr << "machine basic block: "
<< mbb->getBasicBlock()->getName() << "\n");
for (MachineBasicBlock::const_iterator mii = mbb->begin(),
mie = mbb->end(); mii != mie; ++mii) {
MachineInstr* mi = *mii;
const TargetInstrDescriptor& tid =
tm_->getInstrInfo().get(mi->getOpcode());
DEBUG(std::cerr << "\t\tinstruction["
<< getInstructionIndex(mi) << "]: ";
mi->print(std::cerr, *tm_););
unsigned srcReg, dstReg;
if (tii.isMoveInstr(*mi, srcReg, dstReg) &&
(srcReg >= MRegisterInfo::FirstVirtualRegister ||
lv_->getAllocatablePhysicalRegisters()[srcReg]) &&
(dstReg >= MRegisterInfo::FirstVirtualRegister ||
lv_->getAllocatablePhysicalRegisters()[dstReg])) {
// get representative registers
srcReg = rep(srcReg);
dstReg = rep(dstReg);
// if they are already joined we continue
if (srcReg == dstReg)
continue;
Reg2IntervalMap::iterator r2iSrc = r2iMap_.find(srcReg);
assert(r2iSrc != r2iMap_.end());
Reg2IntervalMap::iterator r2iDst = r2iMap_.find(dstReg);
assert(r2iDst != r2iMap_.end());
Intervals::iterator srcInt = r2iSrc->second;
Intervals::iterator dstInt = r2iDst->second;
// src is a physical register
if (srcInt->reg < MRegisterInfo::FirstVirtualRegister) {
if (dstInt->reg == srcInt->reg ||
(dstInt->reg >= MRegisterInfo::FirstVirtualRegister &&
!srcInt->overlaps(*dstInt) &&
!overlapsAliases(*srcInt, *dstInt))) {
srcInt->join(*dstInt);
r2iDst->second = r2iSrc->second;
r2rMap_.insert(std::make_pair(dstInt->reg, srcInt->reg));
intervals_.erase(dstInt);
}
}
// dst is a physical register
else if (dstInt->reg < MRegisterInfo::FirstVirtualRegister) {
if (srcInt->reg == dstInt->reg ||
(srcInt->reg >= MRegisterInfo::FirstVirtualRegister &&
!dstInt->overlaps(*srcInt) &&
!overlapsAliases(*dstInt, *srcInt))) {
dstInt->join(*srcInt);
r2iSrc->second = r2iDst->second;
r2rMap_.insert(std::make_pair(srcInt->reg, dstInt->reg));
intervals_.erase(srcInt);
}
}
// neither src nor dst are physical registers
else {
const TargetRegisterClass *srcRc, *dstRc;
srcRc = mf_->getSSARegMap()->getRegClass(srcInt->reg);
dstRc = mf_->getSSARegMap()->getRegClass(dstInt->reg);
if (srcRc == dstRc && !dstInt->overlaps(*srcInt)) {
srcInt->join(*dstInt);
r2iDst->second = r2iSrc->second;
r2rMap_.insert(std::make_pair(dstInt->reg, srcInt->reg));
intervals_.erase(dstInt);
}
}
}
}
}
intervals_.sort(StartPointComp());
DEBUG(std::copy(intervals_.begin(), intervals_.end(),
std::ostream_iterator<Interval>(std::cerr, "\n")));
DEBUG(for (Reg2RegMap::const_iterator i = r2rMap_.begin(),
e = r2rMap_.end(); i != e; ++i)
std::cerr << i->first << " -> " << i->second << '\n';);
}
bool LiveIntervals::overlapsAliases(const Interval& lhs,
const Interval& rhs) const
{
assert(lhs.reg < MRegisterInfo::FirstVirtualRegister &&
"first interval must describe a physical register");
for (const unsigned* as = mri_->getAliasSet(lhs.reg); *as; ++as) {
Reg2IntervalMap::const_iterator r2i = r2iMap_.find(*as);
assert(r2i != r2iMap_.end() && "alias does not have interval?");
if (rhs.overlaps(*r2i->second))
return true;
}
return false;
}
LiveIntervals::Interval::Interval(unsigned r)
: reg(r),
weight((r < MRegisterInfo::FirstVirtualRegister ?
std::numeric_limits<float>::max() : 0.0F))
{
}
bool LiveIntervals::Interval::liveAt(unsigned index) const
{
Ranges::const_iterator r = ranges.begin();
while (r != ranges.end() && index < (r->second - 1)) {
if (index >= r->first)
return true;
++r;
}
return false;
}
bool LiveIntervals::Interval::overlaps(const Interval& other) const
{
Ranges::const_iterator i = ranges.begin();
Ranges::const_iterator j = other.ranges.begin();
while (i != ranges.end() && j != other.ranges.end()) {
if (i->first < j->first) {
if ((i->second - 1) > j->first) {
return true;
}
else {
++i;
}
}
else if (j->first < i->first) {
if ((j->second - 1) > i->first) {
return true;
}
else {
++j;
}
}
else {
return true;
}
}
return false;
}
void LiveIntervals::Interval::addRange(unsigned start, unsigned end)
{
DEBUG(std::cerr << "\t\t\tadding range: [" << start <<','<< end << ") -> ");
//assert(start < end && "invalid range?");
Range range = std::make_pair(start, end);
Ranges::iterator it =
ranges.insert(std::upper_bound(ranges.begin(), ranges.end(), range),
range);
it = mergeRangesForward(it);
it = mergeRangesBackward(it);
DEBUG(std::cerr << "\t\t\t\tafter merging: " << *this << '\n');
}
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;
}