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[RegAllocGreedy] Fix the list of NewVRegs for last chance recoloring.

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When trying to recolor a register we may split live-ranges in the
process. When we create new live-ranges we will have to process them,
but when we move a register from Assign to Split, the allocation is not
changed until the whole recoloring session is successful.
Therefore, only push the live-ranges that changed from Assign to
Split when the recoloring is successful.

Same as the previous commit, I was not able to produce a test case that
reproduce the problem with in-tree targets.

Note: The bug has been here since the recoloring scheme has been added
back in r200883 (Feb 2014).

llvm-svn: 281783
This commit is contained in:
Quentin Colombet 2016-09-16 22:00:50 +00:00
parent 9b569523e7
commit 617500b648
1 changed files with 22 additions and 2 deletions
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24
lib/CodeGen/RegAllocGreedy.cpp
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@ -2108,6 +2108,10 @@ unsigned RAGreedy::tryLastChanceRecoloring(LiveInterval &VirtReg,
// Mark VirtReg as fixed, i.e., it will not be recolored pass this point in
// this recoloring "session".
FixedRegisters.insert(VirtReg.reg);
// Remember the ID of the last vreg in case the recoloring fails.
unsigned LastVReg =
TargetRegisterInfo::index2VirtReg(MRI->getNumVirtRegs() - 1);
SmallVector<unsigned, 4> CurrentNewVRegs;
Order.rewind();
while (unsigned PhysReg = Order.next()) {
@ -2115,6 +2119,7 @@ unsigned RAGreedy::tryLastChanceRecoloring(LiveInterval &VirtReg,
<< PrintReg(PhysReg, TRI) << '\n');
RecoloringCandidates.clear();
VirtRegToPhysReg.clear();
CurrentNewVRegs.clear();
// It is only possible to recolor virtual register interference.
if (Matrix->checkInterference(VirtReg, PhysReg) >
@ -2159,8 +2164,11 @@ unsigned RAGreedy::tryLastChanceRecoloring(LiveInterval &VirtReg,
// If we cannot recolor all the interferences, we will have to start again
// at this point for the next physical register.
SmallVirtRegSet SaveFixedRegisters(FixedRegisters);
if (tryRecoloringCandidates(RecoloringQueue, NewVRegs, FixedRegisters,
Depth)) {
if (tryRecoloringCandidates(RecoloringQueue, CurrentNewVRegs,
FixedRegisters, Depth)) {
// Push the queued vregs into the main queue.
for (unsigned NewVReg : CurrentNewVRegs)
NewVRegs.push_back(NewVReg);
// Do not mess up with the global assignment process.
// I.e., VirtReg must be unassigned.
Matrix->unassign(VirtReg);
@ -2174,6 +2182,18 @@ unsigned RAGreedy::tryLastChanceRecoloring(LiveInterval &VirtReg,
FixedRegisters = SaveFixedRegisters;
Matrix->unassign(VirtReg);
// When we move a register from RS_Assign to RS_Split, we do not
// actually do anything with it. I.e., it should not end up in NewVRegs.
// For the other cases, since we created new live-ranges, we need to
// process them.
for (SmallVectorImpl<unsigned>::iterator Next = CurrentNewVRegs.begin(),
End = CurrentNewVRegs.end();
Next != End; ++Next) {
if (*Next <= LastVReg && getStage(LIS->getInterval(*Next)) == RS_Split)
continue;
NewVRegs.push_back(*Next);
}
for (SmallLISet::iterator It = RecoloringCandidates.begin(),
EndIt = RecoloringCandidates.end();
It != EndIt; ++It) {