[PATCH] D60459: SILoadStoreOptimizer pass mischedules s_add,s_addc with interfering s_lshl

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec added inline comments.


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Comment at: lib/Target/AMDGPU/SILoadStoreOptimizer.cpp:276
+      return &*I;
+  assert(0 && "Failed to find carry instr");
+  return nullptr;
----------------
ronlieb wrote:
> rampitec wrote:
> > It can be defined in another block. It can be also undef.
> Splitting a pair of instructions across basic block boundaries in this situation seems really crazy. These instruction pairs are implementing a 64 bit add or 64 bit subtract. I understand that generally speaking we could see both situations (split or under).  If this were to occur in this pass, i would want to assert (which is what this patch will do) so we can go look into it, rather than having broken code generated. To split them would mean that $SCC is live in to the block.
Why not? What if half of that pair was hoisted out of the block into parent?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D60459/new/

https://reviews.llvm.org/D60459