[llvm] [VPlan] Replace ExtractLast(Elem|LanePerPart) with ExtractLast(Lane/Part) (PR #164124)

[via llvm-commits]

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@@ -1017,12 +1017,10 @@ class LLVM_ABI_FOR_TEST VPInstruction : public VPRecipeWithIRFlags,
     ComputeAnyOfResult,
     ComputeFindIVResult,
     ComputeReductionResult,
-    // Extracts the last lane from its operand if it is a vector, or the last
-    // part if scalar. In the latter case, the recipe will be removed during
-    // unrolling.
-    ExtractLastElement,
-    // Extracts the last lane for each part from its operand.
-    ExtractLastLanePerPart,
+    // Extracts the last part of its operand.
+    ExtractLastPart,
+    // Extracts the last lane of the current part of its operand.
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ayalz wrote:

Good to mention how `ExtractLastLane` relates to `ExtractLane` below. I.e., former expects a single vector operand to extract from, relative to the latter which extracts a lane from a concatenated vector. Both operate per part.

https://github.com/llvm/llvm-project/pull/164124