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Nicolai Haehnle 592ddac7f2 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
2016-08-10 18:51:14 +00:00
..
2016-08-08 14:46:15 +00:00