[PATCH] D57478: GlobalISel: Implement fewerElementsVector for shifts

[Amara Emerson via Phabricator via llvm-commits]

aemerson added inline comments.


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Comment at: include/llvm/CodeGen/GlobalISel/LegalizerHelper.h:162
+  /// Legalize a instruction with a vector type where each operand may have a
+  /// different element type type. All operands must have the same number of
+  /// elements.
----------------
type type


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Comment at: lib/CodeGen/GlobalISel/LegalizerHelper.cpp:1816
 
+LegalizerHelper::LegalizeResult LegalizerHelper::fewerElementsVectorMultiType(
+    MachineInstr &MI, unsigned TypeIdx, LLT NarrowTyArg) {
----------------
I'm finding it difficult to tell exactly what this function is trying to do. Can we have some comments throughout to explain what each phase is trying to achieve, with a small example if it's not clear enough from prose.


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Comment at: lib/CodeGen/GlobalISel/LegalizerHelper.cpp:1850
+                      LeftoverRegs))
+      llvm_unreachable("should have been able to extractParts");
+
----------------
We can return 0 here to fall back instead of dying.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D57478/new/

https://reviews.llvm.org/D57478