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Minimize the slot indexes spanned by register ranges created when splitting.

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When an interfering live range ends at a dead slot index between two
instructions, make sure that the inserted copy instruction gets a slot index
after the dead ones. This makes it possible to avoid the interference.

Ideally, there shouldn't be interference ending at a deleted instruction, but
physical register coalescing can sometimes do that to sub-registers.

This fixes PR9823.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130687 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2011-05-02 05:29:58 +00:00
parent 8e33095cd4
commit bb30dd40ed
3 changed files with 13 additions and 5 deletions
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lib/CodeGen/SplitKit.cpp
+7 -2
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@@ -579,15 +579,20 @@ VNInfo *SplitEditor::defFromParent(unsigned RegIdx,
SlotIndex Def;
LiveInterval *LI = Edit->get(RegIdx);
// We may be trying to avoid interference that ends at a deleted instruction,
// so always begin RegIdx 0 early and all others late.
bool Late = RegIdx != 0;
// Attempt cheap-as-a-copy rematerialization.
LiveRangeEdit::Remat RM(ParentVNI);
if (Edit->canRematerializeAt(RM, UseIdx, true, LIS)) {
Def = Edit->rematerializeAt(MBB, I, LI->reg, RM, LIS, TII, TRI);
Def = Edit->rematerializeAt(MBB, I, LI->reg, RM, LIS, TII, TRI, Late);
} else {
// Can't remat, just insert a copy from parent.
CopyMI = BuildMI(MBB, I, DebugLoc(), TII.get(TargetOpcode::COPY), LI->reg)
.addReg(Edit->getReg());
Def = LIS.InsertMachineInstrInMaps(CopyMI).getDefIndex();
Def = LIS.getSlotIndexes()->insertMachineInstrInMaps(CopyMI, Late)
.getDefIndex();
}
// Define the value in Reg.