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Clean up spill weight computation. Also some changes to give loop induction

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variable increment / decrement slighter high priority. 

This has major impact on some micro-benchmarks. On MultiSource/Applications
and spec tests, it's a minor win. It also reduce 256.bzip instruction count
by 8%, 55 on 164.gzip on i386 / Darwin.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82485 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2009-09-21 21:12:25 +00:00
parent b2bb7db9e2
commit cf985a9545
9 changed files with 145 additions and 68 deletions
Download Patch File Download Diff File Expand all files Collapse all files

148
lib/CodeGen/SimpleRegisterCoalescing.cpp
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@ -2535,7 +2535,8 @@ void SimpleRegisterCoalescing::releaseMemory() {
ReMatDefs.clear();
}
bool SimpleRegisterCoalescing::isZeroLengthInterval(LiveInterval *li) const {
/// Returns true if the given live interval is zero length.
static bool isZeroLengthInterval(LiveInterval *li, LiveIntervals *li_) {
for (LiveInterval::Ranges::const_iterator
i = li->ranges.begin(), e = li->ranges.end(); i != e; ++i)
if (li_->getPrevIndex(i->end) > i->start)
@ -2543,6 +2544,97 @@ bool SimpleRegisterCoalescing::isZeroLengthInterval(LiveInterval *li) const {
return true;
}
void SimpleRegisterCoalescing::CalculateSpillWeights() {
SmallSet<unsigned, 4> Processed;
for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
mbbi != mbbe; ++mbbi) {
MachineBasicBlock* MBB = mbbi;
MachineInstrIndex MBBEnd = li_->getMBBEndIdx(MBB);
MachineLoop* loop = loopInfo->getLoopFor(MBB);
unsigned loopDepth = loop ? loop->getLoopDepth() : 0;
bool isExit = loop ? loop->isLoopExit(MBB) : false;
for (MachineBasicBlock::iterator mii = MBB->begin(), mie = MBB->end();
mii != mie; ++mii) {
MachineInstr *MI = mii;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &mopi = MI->getOperand(i);
if (!mopi.isReg() || mopi.getReg() == 0)
continue;
unsigned Reg = mopi.getReg();
if (!TargetRegisterInfo::isVirtualRegister(mopi.getReg()))
continue;
// Multiple uses of reg by the same instruction. It should not
// contribute to spill weight again.
if (!Processed.insert(Reg))
continue;
bool HasDef = mopi.isDef();
bool HasUse = mopi.isUse();
for (unsigned j = i+1; j != e; ++j) {
const MachineOperand &mopj = MI->getOperand(j);
if (!mopj.isReg() || mopj.getReg() != Reg)
continue;
HasDef |= mopj.isDef();
HasUse |= mopj.isUse();
}
LiveInterval &RegInt = li_->getInterval(Reg);
float Weight = li_->getSpillWeight(HasDef, HasUse, loopDepth+1);
if (HasDef && isExit) {
// Looks like this is a loop count variable update.
MachineInstrIndex DefIdx =
li_->getDefIndex(li_->getInstructionIndex(MI));
const LiveRange *DLR =
li_->getInterval(Reg).getLiveRangeContaining(DefIdx);
if (DLR->end > MBBEnd)
Weight *= 3.0F;
}
RegInt.weight += Weight;
}
Processed.clear();
}
}
for (LiveIntervals::iterator I = li_->begin(), E = li_->end(); I != E; ++I) {
LiveInterval &LI = *I->second;
if (TargetRegisterInfo::isVirtualRegister(LI.reg)) {
// If the live interval length is essentially zero, i.e. in every live
// range the use follows def immediately, it doesn't make sense to spill
// it and hope it will be easier to allocate for this li.
if (isZeroLengthInterval(&LI, li_)) {
LI.weight = HUGE_VALF;
continue;
}
bool isLoad = false;
SmallVector<LiveInterval*, 4> SpillIs;
if (li_->isReMaterializable(LI, SpillIs, isLoad)) {
// If all of the definitions of the interval are re-materializable,
// it is a preferred candidate for spilling. If non of the defs are
// loads, then it's potentially very cheap to re-materialize.
// FIXME: this gets much more complicated once we support non-trivial
// re-materialization.
if (isLoad)
LI.weight *= 0.9F;
else
LI.weight *= 0.5F;
}
// Slightly prefer live interval that has been assigned a preferred reg.
std::pair<unsigned, unsigned> Hint = mri_->getRegAllocationHint(LI.reg);
if (Hint.first || Hint.second)
LI.weight *= 1.01F;
// Divide the weight of the interval by its size. This encourages
// spilling of intervals that are large and have few uses, and
// discourages spilling of small intervals with many uses.
LI.weight /= li_->getApproximateInstructionCount(LI) * InstrSlots::NUM;
}
}
}
bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
@ -2581,8 +2673,6 @@ bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
mbbi != mbbe; ++mbbi) {
MachineBasicBlock* mbb = mbbi;
unsigned loopDepth = loopInfo->getLoopDepth(mbb);
for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
mii != mie; ) {
MachineInstr *MI = mii;
@ -2656,62 +2746,12 @@ bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
mii = mbbi->erase(mii);
++numPeep;
} else {
SmallSet<unsigned, 4> UniqueUses;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &mop = MI->getOperand(i);
if (mop.isReg() && mop.getReg() &&
TargetRegisterInfo::isVirtualRegister(mop.getReg())) {
unsigned reg = mop.getReg();
// Multiple uses of reg by the same instruction. It should not
// contribute to spill weight again.
if (UniqueUses.count(reg) != 0)
continue;
LiveInterval &RegInt = li_->getInterval(reg);
RegInt.weight +=
li_->getSpillWeight(mop.isDef(), mop.isUse(), loopDepth);
UniqueUses.insert(reg);
}
}
++mii;
}
}
}
for (LiveIntervals::iterator I = li_->begin(), E = li_->end(); I != E; ++I) {
LiveInterval &LI = *I->second;
if (TargetRegisterInfo::isVirtualRegister(LI.reg)) {
// If the live interval length is essentially zero, i.e. in every live
// range the use follows def immediately, it doesn't make sense to spill
// it and hope it will be easier to allocate for this li.
if (isZeroLengthInterval(&LI))
LI.weight = HUGE_VALF;
else {
bool isLoad = false;
SmallVector<LiveInterval*, 4> SpillIs;
if (li_->isReMaterializable(LI, SpillIs, isLoad)) {
// If all of the definitions of the interval are re-materializable,
// it is a preferred candidate for spilling. If non of the defs are
// loads, then it's potentially very cheap to re-materialize.
// FIXME: this gets much more complicated once we support non-trivial
// re-materialization.
if (isLoad)
LI.weight *= 0.9F;
else
LI.weight *= 0.5F;
}
}
// Slightly prefer live interval that has been assigned a preferred reg.
std::pair<unsigned, unsigned> Hint = mri_->getRegAllocationHint(LI.reg);
if (Hint.first || Hint.second)
LI.weight *= 1.01F;
// Divide the weight of the interval by its size. This encourages
// spilling of intervals that are large and have few uses, and
// discourages spilling of small intervals with many uses.
LI.weight /= li_->getApproximateInstructionCount(LI) * InstrSlots::NUM;
}
}
CalculateSpillWeights();
DEBUG(dump());
return true;