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[RegAllocGreedy]: Allow recoloring of done register if it's non-tied

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Summary:
If we have a non-allocated register, we allow us to try recoloring of an
already allocated and "Done" register, even if they are of the same
register class, if the non-allocated register has at least one tied def
and the allocated one has none.

It should be easier to recolor the non-tied register than the tied one, so
it might be an improvement even if they use the same regclasses.

Reviewers: qcolombet

Reviewed By: qcolombet

Subscribers: llvm-commits, MatzeB

Differential Revision: https://reviews.llvm.org/D38309

llvm-svn: 314388
This commit is contained in:
Mikael Holmen 2017-09-28 08:22:35 +00:00
parent a788a011f7
commit 5ffc451050
1 changed files with 14 additions and 2 deletions
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16
lib/CodeGen/RegAllocGreedy.cpp
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@ -2054,6 +2054,15 @@ unsigned RAGreedy::trySplit(LiveInterval &VirtReg, AllocationOrder &Order,
// Last Chance Recoloring
//===----------------------------------------------------------------------===//
/// Return true if \p reg has any tied def operand.
static bool hasTiedDef(MachineRegisterInfo *MRI, unsigned reg) {
for (const MachineOperand &MO : MRI->def_operands(reg))
if (MO.isTied())
return true;
return false;
}
/// mayRecolorAllInterferences - Check if the virtual registers that
/// interfere with \p VirtReg on \p PhysReg (or one of its aliases) may be
/// recolored to free \p PhysReg.
@ -2082,8 +2091,11 @@ RAGreedy::mayRecolorAllInterferences(unsigned PhysReg, LiveInterval &VirtReg,
LiveInterval *Intf = Q.interferingVRegs()[i - 1];
// If Intf is done and sit on the same register class as VirtReg,
// it would not be recolorable as it is in the same state as VirtReg.
if ((getStage(*Intf) == RS_Done &&
MRI->getRegClass(Intf->reg) == CurRC) ||
// However, if VirtReg has tied defs and Intf doesn't, then
// there is still a point in examining if it can be recolorable.
if (((getStage(*Intf) == RS_Done &&
MRI->getRegClass(Intf->reg) == CurRC) &&
!(hasTiedDef(MRI, VirtReg.reg) && !hasTiedDef(MRI, Intf->reg))) ||
FixedRegisters.count(Intf->reg)) {
DEBUG(dbgs() << "Early abort: the interference is not recolorable.\n");
return false;