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Trace through sibling PHIs in bulk.

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When traceSiblingValue() encounters a PHI-def value created by live
range splitting, don't look at all the predecessor blocks.  That can be
very expensive in a complicated CFG.

Instead, consider that all the non-PHI defs jointly dominate all the
PHI-defs.  Tracing directly to all the non-PHI defs is much faster that
zipping around in the CFG when there are many PHIs with many
predecessors.

This significantly improves compile time for indirectbr interpreters.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139797 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2011-09-15 16:41:12 +00:00
parent b6e9a83349
commit 6b6e32d954
1 changed files with 52 additions and 25 deletions
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77
lib/CodeGen/InlineSpiller.cpp
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@ -120,11 +120,6 @@ private:
typedef DenseMap<VNInfo*, SibValueInfo> SibValueMap;
SibValueMap SibValues;
// Values live-out from basic blocks. This is the same as
// LI.getVNInfoAt(LIS.getMBBEndIdx(MBB).getPrevSlot())
typedef DenseMap<MachineBasicBlock*, VNInfo*> LiveOutMap;
LiveOutMap LiveOutValues;
// Dead defs generated during spilling.
SmallVector<MachineInstr*, 8> DeadDefs;
@ -500,6 +495,7 @@ MachineInstr *InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI,
// Trace through PHI-defs created by live range splitting.
if (VNI->isPHIDef()) {
// Stop at original PHIs. We don't know the value at the predecessors.
if (VNI->def == OrigVNI->def) {
DEBUG(dbgs() << "orig phi value\n");
SVI->second.DefByOrigPHI = true;
@ -507,28 +503,60 @@ MachineInstr *InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI,
propagateSiblingValue(SVI);
continue;
}
// Get values live-out of predecessors.
// This is a PHI inserted by live range splitting. We could trace the
// live-out value from predecessor blocks, but that search can be very
// expensive if there are many predecessors and many more PHIs as
// generated by tail-dup when it sees an indirectbr. Instead, look at
// all the non-PHI defs that have the same value as OrigVNI. They must
// jointly dominate VNI->def. This is not optimal since VNI may actually
// be jointly dominated by a smaller subset of defs, so there is a change
// we will miss a AllDefsAreReloads optimization.
// Separate all values dominated by OrigVNI into PHIs and non-PHIs.
SmallVector<VNInfo*, 8> PHIs, NonPHIs;
LiveInterval &LI = LIS.getInterval(Reg);
MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
DEBUG(dbgs() << "split phi value, check " << MBB->pred_size()
<< " preds\n");
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
// Use a cache of block live-out values. This is faster than using
// getVNInfoAt on complex intervals.
VNInfo *&PVNI = LiveOutValues[*PI];
if (!PVNI)
PVNI = LI.getVNInfoAt(LIS.getMBBEndIdx(*PI).getPrevSlot());
if (!PVNI)
LiveInterval &OrigLI = LIS.getInterval(Original);
for (LiveInterval::vni_iterator VI = LI.vni_begin(), VE = LI.vni_end();
VI != VE; ++VI) {
VNInfo *VNI2 = *VI;
if (VNI2->isUnused())
continue;
// Known predecessor value? Try an insertion.
tie(SVI, Inserted) =
SibValues.insert(std::make_pair(PVNI, SibValueInfo(Reg, PVNI)));
// This is the first time we see PVNI, add it to the worklist.
if (Inserted)
WorkList.push_back(std::make_pair(Reg, PVNI));
propagateSiblingValue(SVI, VNI);
if (!OrigLI.containsOneValue() &&
OrigLI.getVNInfoAt(VNI2->def) != OrigVNI)
continue;
if (VNI2->isPHIDef() && VNI2->def != OrigVNI->def)
PHIs.push_back(VNI2);
else
NonPHIs.push_back(VNI2);
}
DEBUG(dbgs() << "split phi value, checking " << PHIs.size()
<< " phi-defs, and " << NonPHIs.size()
<< " non-phi/orig defs\n");
// Create entries for all the PHIs. Don't add them to the worklist, we
// are processing all of them in one go here.
for (unsigned i = 0, e = PHIs.size(); i != e; ++i)
SibValues.insert(std::make_pair(PHIs[i], SibValueInfo(Reg, PHIs[i])));
// Add every PHI as a dependent of all the non-PHIs.
for (unsigned i = 0, e = NonPHIs.size(); i != e; ++i) {
VNInfo *NonPHI = NonPHIs[i];
// Known value? Try an insertion.
tie(SVI, Inserted) =
SibValues.insert(std::make_pair(NonPHI, SibValueInfo(Reg, NonPHI)));
// Add all the PHIs as dependents of NonPHI.
for (unsigned pi = 0, pe = PHIs.size(); pi != pe; ++pi)
SVI->second.Deps.push_back(PHIs[pi]);
// This is the first time we see NonPHI, add it to the worklist.
if (Inserted)
WorkList.push_back(std::make_pair(Reg, NonPHI));
else
// Propagate to all inserted PHIs, not just VNI.
propagateSiblingValue(SVI);
}
// Next work list item.
continue;
}
@ -587,7 +615,6 @@ MachineInstr *InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI,
/// Keep track of values that may be rematerializable.
void InlineSpiller::analyzeSiblingValues() {
SibValues.clear();
LiveOutValues.clear();
// No siblings at all?
if (Edit->getReg() == Original)