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Disable local spill hoisting for non-killing copies. 

If the source register is live after the copy being spilled, there is no
point to hoisting it.  Hoisting inside a basic block only serves to
resolve interferences by shortening the live range of the source.

llvm-svn: 139882
This commit is contained in:
Jakob Stoklund Olesen 2011-09-16 00:03:33 +00:00
parent 5798cfddd7
commit e8339b2e63
1 changed files with 15 additions and 5 deletions
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20
llvm/lib/CodeGen/InlineSpiller.cpp
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@ -90,6 +90,9 @@ public:
// True when value is defined by an original PHI not from splitting.
bool DefByOrigPHI;
// True when the COPY defining this value killed its source.
bool KillsSource;
// The preferred register to spill.
unsigned SpillReg;
@ -112,7 +115,7 @@ public:
TinyPtrVector<VNInfo*> Deps;
SibValueInfo(unsigned Reg, VNInfo *VNI)
: AllDefsAreReloads(true), DefByOrigPHI(false),
: AllDefsAreReloads(true), DefByOrigPHI(false), KillsSource(false),
SpillReg(Reg), SpillVNI(VNI), SpillMBB(0), DefMI(0) {}
// Returns true when a def has been found.
@ -319,6 +322,8 @@ static raw_ostream &operator<<(raw_ostream &OS,
OS << " all-reloads";
if (SVI.DefByOrigPHI)
OS << " orig-phi";
if (SVI.KillsSource)
OS << " kill";
OS << " deps[";
for (unsigned i = 0, e = SVI.Deps.size(); i != e; ++i)
OS << ' ' << SVI.Deps[i]->id << '@' << SVI.Deps[i]->def;
@ -402,7 +407,7 @@ void InlineSpiller::propagateSiblingValue(SibValueMap::iterator SVI,
if (PropSpill && SV.SpillVNI != DepSV.SpillVNI) {
if (SV.SpillMBB == DepSV.SpillMBB) {
// DepSV is in the same block. Hoist when dominated.
if (SV.SpillVNI->def < DepSV.SpillVNI->def) {
if (DepSV.KillsSource && SV.SpillVNI->def < DepSV.SpillVNI->def) {
// This is an alternative def earlier in the same MBB.
// Hoist the spill as far as possible in SpillMBB. This can ease
// register pressure:
@ -418,6 +423,7 @@ void InlineSpiller::propagateSiblingValue(SibValueMap::iterator SVI,
// spill x
// y = use x<kill>
//
// This hoist only helps when the DepSV copy kills its source.
Changed = true;
DepSV.SpillReg = SV.SpillReg;
DepSV.SpillVNI = SV.SpillVNI;
@ -572,10 +578,14 @@ MachineInstr *InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI,
if (unsigned SrcReg = isFullCopyOf(MI, Reg)) {
if (isSibling(SrcReg)) {
LiveInterval &SrcLI = LIS.getInterval(SrcReg);
VNInfo *SrcVNI = SrcLI.getVNInfoAt(VNI->def.getUseIndex());
assert(SrcVNI && "Copy from non-existing value");
LiveRange *SrcLR = SrcLI.getLiveRangeContaining(VNI->def.getUseIndex());
assert(SrcLR && "Copy from non-existing value");
// Check if this COPY kills its source.
SVI->second.KillsSource = (SrcLR->end == VNI->def);
VNInfo *SrcVNI = SrcLR->valno;
DEBUG(dbgs() << "copy of " << PrintReg(SrcReg) << ':'
<< SrcVNI->id << '@' << SrcVNI->def << '\n');
<< SrcVNI->id << '@' << SrcVNI->def
<< " kill=" << unsigned(SVI->second.KillsSource) << '\n');
// Known sibling source value? Try an insertion.
tie(SVI, Inserted) = SibValues.insert(std::make_pair(SrcVNI,
SibValueInfo(SrcReg, SrcVNI)));