[llvm] [GlobalISel] Import llvm.stepvector (PR #115721)

[Matt Arsenault via llvm-commits]

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@@ -2597,6 +2597,10 @@ bool IRTranslator::translateKnownIntrinsic(const CallInst &CI, Intrinsic::ID ID,
     return translateExtractVector(CI, MIRBuilder);
   case Intrinsic::vector_insert:
     return translateInsertVector(CI, MIRBuilder);
+  case Intrinsic::stepvector: {
+    MIRBuilder.buildStepVector(getOrCreateVReg(CI), 1);
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arsenm wrote:

Not sure why this has an operand the intrinsic doesn't but it's already that way. I'm confused by the DAG API, it's one level removed but doing the same thing 

https://github.com/llvm/llvm-project/pull/115721