When computing live intervals for earlyclobber operands,
we pushed the beginning of the interval back 1, so the
interval would overlap with inputs that die. We were
also pushing the end of the interval back 1, though,
which means the earlyclobber didn't overlap with other
output operands. Don't do this. PR 4964.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82342 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 6296e93..c690ac3 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -665,7 +665,8 @@
if (interval.empty()) {
// Get the Idx of the defining instructions.
MachineInstrIndex defIndex = getDefIndex(MIIdx);
- // Earlyclobbers move back one.
+ // Earlyclobbers move back one, so that they overlap the live range
+ // of inputs.
if (MO.isEarlyClobber())
defIndex = getUseIndex(MIIdx);
VNInfo *ValNo;
@@ -690,6 +691,11 @@
MachineInstrIndex killIdx;
if (vi.Kills[0] != mi)
killIdx = getNextSlot(getUseIndex(getInstructionIndex(vi.Kills[0])));
+ else if (MO.isEarlyClobber())
+ // Earlyclobbers that die in this instruction move up one extra, to
+ // compensate for having the starting point moved back one. This
+ // gets them to overlap the live range of other outputs.
+ killIdx = getNextSlot(getNextSlot(defIndex));
else
killIdx = getNextSlot(defIndex);
@@ -791,7 +797,9 @@
// range covering the def slot.
if (MO.isDead())
interval.addRange(
- LiveRange(RedefIndex, getNextSlot(RedefIndex), OldValNo));
+ LiveRange(RedefIndex, MO.isEarlyClobber() ?
+ getNextSlot(getNextSlot(RedefIndex)) :
+ getNextSlot(RedefIndex), OldValNo));
DEBUG({
errs() << " RESULT: ";
@@ -892,9 +900,14 @@
// If it is not used after definition, it is considered dead at
// the instruction defining it. Hence its interval is:
// [defSlot(def), defSlot(def)+1)
+ // For earlyclobbers, the defSlot was pushed back one; the extra
+ // advance below compensates.
if (MO.isDead()) {
DEBUG(errs() << " dead");
- end = getNextSlot(start);
+ if (MO.isEarlyClobber())
+ end = getNextSlot(getNextSlot(start));
+ else
+ end = getNextSlot(start);
goto exit;
}