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LiveRangeEdit: Fix liveranges not shrinking on subrange kill.

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If a dead instruction we may not only have a last-use in the main live
range but also in a subregister range if subregisters are tracked. We
need to partially rebuild live ranges in both cases.

The testcase only broke when subregister liveness was enabled. I
commited it in the current form because there is currently no flag to
enable/disable subregister liveness.

This fixes PR23720.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238785 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthias Braun
2015-06-01 21:26:26 +00:00
parent a3698105eb
commit fa2b7e5cb4
3 changed files with 77 additions and 3 deletions
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21
lib/CodeGen/LiveRangeEdit.cpp
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@@ -218,6 +218,22 @@ bool LiveRangeEdit::foldAsLoad(LiveInterval *LI,
return true;
}
bool LiveRangeEdit::useIsKill(const LiveInterval &LI,
const MachineOperand &MO) const {
const MachineInstr *MI = MO.getParent();
SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot();
if (LI.Query(Idx).isKill())
return true;
const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
unsigned SubReg = MO.getSubReg();
unsigned LaneMask = TRI.getSubRegIndexLaneMask(SubReg);
for (const LiveInterval::SubRange &S : LI.subranges()) {
if ((S.LaneMask & LaneMask) != 0 && S.Query(Idx).isKill())
return true;
}
return false;
}
/// Find all live intervals that need to shrink, then remove the instruction.
void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink) {
assert(MI->allDefsAreDead() && "Def isn't really dead");
@@ -266,9 +282,8 @@ void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink) {
// unlikely to change anything. We typically don't want to shrink the
// PIC base register that has lots of uses everywhere.
// Always shrink COPY uses that probably come from live range splitting.
if (MI->readsVirtualRegister(Reg) &&
(MI->isCopy() || MOI->isDef() || MRI.hasOneNonDBGUse(Reg) ||
LI.Query(Idx).isKill()))
if ((MI->readsVirtualRegister(Reg) && (MI->isCopy() || MOI->isDef())) ||
(MOI->readsReg() && (MRI.hasOneNonDBGUse(Reg) || useIsKill(LI, *MOI))))
ToShrink.insert(&LI);
// Remove defined value.