[PATCH] D58419: [GISel]: Allow G_EXTRACT_VEC_ELT's result to be larger the source element type

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

I always thought this behavior in SelectionDAG was error prone. I think I broke this on every combine I ever wrote for extract_vector_elt. Should there be a separate extending opcode instead? Although that would probably make some combines more painful. In GlobalISel we already have an explicit G_BUILD_VECTOR_TRUNC instead of the old ISD::BUILD_VECTOR truncate behavior, so that would match. However I don't think G_BUILD_VECTOR_TRUNC is well developed enough to declare that was definitely a good decision yet.



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Comment at: lib/CodeGen/MachineVerifier.cpp:1276
+      report("Generic G_EXTRACT_VECTOR_ELT's dst should be scalar/pointer", MI);
+    if (DstTy.isPointer() && DstTy != SrcTy.getElementType())
+      report("Generic G_EXTRACT_VECTOR_ELT's dst and src should match when "
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Comment at: lib/CodeGen/MachineVerifier.cpp:1281
+    if (DstTy.isScalar() && SrcTy.isVector() &&
+        DstTy.getSizeInBits() < SrcTy.getElementType().getSizeInBits())
+      report("Generic G_EXTRACT_VECTOR_ELT's dst can't be smaller than src "
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Repository:
  rL LLVM

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  https://reviews.llvm.org/D58419/new/

https://reviews.llvm.org/D58419