LiveIntervalAnalysis: fix a crash in repairOldRegInRange
Summary:
See the new test case for one that was (non-deterministically) crashing
on trunk and deterministically hit the assertion that I added in D23302.
Basically, the machine function contains a sequence
DS_WRITE_B32 %vreg4, %vreg14:sub0, ...
DS_WRITE_B32 %vreg4, %vreg14:sub0, ...
%vreg14:sub1<def> = COPY %vreg14:sub0
and SILoadStoreOptimizer::mergeWrite2Pair merges the two DS_WRITE_B32
instructions into one before calling repairIntervalsInRange.
Now repairIntervalsInRange wants to repair %vreg14, in particular, and
ends up trying to repair %vreg14:sub1 as well, but that only becomes
active _after_ the range that is to be repaired, hence the crash due
to LR.find(...) == LR.begin() at the start of repairOldRegInRange.
I believe that just skipping those subrange is fine, but again, not too
familiar with that code.
Reviewers: MatzeB, kparzysz, tstellarAMD
Subscribers: llvm-commits, MatzeB
Differential Revision: https://reviews.llvm.org/D23303
llvm-svn: 278268
diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index 8fd0585..26b5cba 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1396,6 +1396,11 @@
LaneBitmask LaneMask) {
LiveInterval::iterator LII = LR.find(endIdx);
SlotIndex lastUseIdx;
+ if (LII == LR.begin()) {
+ // This happens when the function is called for a subregister that only
+ // occurs _after_ the range that is to be repaired.
+ return;
+ }
if (LII != LR.end() && LII->start < endIdx)
lastUseIdx = LII->end;
else