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Don't shrink live ranges after dead code elimination unless it is going to help. 

In particular, don't repeatedly recompute the PIC base live range after rematerialization.

llvm-svn: 129275
This commit is contained in:
Jakob Stoklund Olesen 2011-04-11 15:00:39 +00:00
parent c6f2d0a4cf
commit 96d04c8e00
1 changed files with 10 additions and 4 deletions
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14
llvm/lib/CodeGen/LiveRangeEdit.cpp
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@ -203,6 +203,7 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
SetVector<LiveInterval*,
SmallVector<LiveInterval*, 8>,
SmallPtrSet<LiveInterval*, 8> > ToShrink;
MachineRegisterInfo &MRI = VRM.getRegInfo();
for (;;) {
// Erase all dead defs.
@ -236,8 +237,13 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
continue;
LiveInterval &LI = LIS.getInterval(Reg);
// Shrink read registers.
if (MI->readsVirtualRegister(Reg))
// Shrink read registers, unless it is likely to be expensive and
// 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.killedAt(Idx)))
ToShrink.insert(&LI);
// Remove defined value.
@ -266,7 +272,7 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
// Shrink just one live interval. Then delete new dead defs.
LiveInterval *LI = ToShrink.back();
ToShrink.pop_back();
if (foldAsLoad(LI, Dead, VRM.getRegInfo(), LIS, TII))
if (foldAsLoad(LI, Dead, MRI, LIS, TII))
continue;
if (delegate_)
delegate_->LRE_WillShrinkVirtReg(LI->reg);
@ -286,7 +292,7 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
if (delegate_)
delegate_->LRE_DidCloneVirtReg(Dups.back()->reg, LI->reg);
}
ConEQ.Distribute(&Dups[0], VRM.getRegInfo());
ConEQ.Distribute(&Dups[0], MRI);
}
}