[PATCH] D49806: [FPEnv] Widen illegal width StrictFP vector operations as needed

[Cameron McInally via Phabricator via llvm-commits]

cameron.mcinally added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp:2716
+      // Vector type, create a CONCAT_VECTORS of type NextVT
+      SDValue undefVec = DAG.getUNDEF(VT);
+      unsigned OpsToConcat = NextSize/VT.getVectorNumElements();
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craig.topper wrote:
> Is widening with undef safe for a strict instruction?
No, it's not safe to insert undef values into a strict instruction, but I don't think that's what this code is doing.

Maybe I'm misunderstanding this code, but I believe this is performing the original operation at a smaller legal width(s) and then concat'ing the result of the operation(s) with undef values to the next largest legal vector type. That should be fine since it won't introduce a trap that did not exist in the user's code.


Repository:
  rL LLVM

https://reviews.llvm.org/D49806