[llvm] [VPlan] Add VPIRInstruction, use for exit block live-outs. (PR #100735)

[Florian Hahn via llvm-commits]

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@@ -1399,6 +1400,45 @@ class VPInstruction : public VPRecipeWithIRFlags {
   bool isSingleScalar() const;
 };
 
+/// A recipe to wrap on original IR instruction not to be modified during
+/// execution, execept for PHIs. For PHIs, a single VPValue operand is allowed,
+/// and it is used to add a new incoming value for the single predecessor VPBB.
+/// Expect PHIs, VPIRInstructions cannot have any operands.
+class VPIRInstruction : public VPRecipeBase {
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fhahn wrote:

It's at the moment intentionally not a VPSingleDefRecipe, as VPIRIntructions at the moment don't need their def-use chains modeled in VPlan. Making them VPSingleDefRecipe without also modeling VPIRInstruction's operands as VPValues would probably be q bit surprising as the def-use chains aren't connected.

Might be good as follow-up, however we would still need to decide how to deal with exit phis that have their original operand coming from the scalar loop, for which is not yet modeled in VPlan.

https://github.com/llvm/llvm-project/pull/100735