[llvm] [LV] Support EVL for partial reduction and VPExpressionRecipe. (PR #205741)

[Luke Lau via llvm-commits]

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@@ -3655,10 +3657,13 @@ class VPExpressionRecipe : public VPSingleDefRecipe {
     return getOperand(getNumOperands() - OpIdx);
   }
 
-  /// Insert the recipes of the expression back into the VPlan, directly before
-  /// the current recipe. Leaves the expression recipe empty, which must be
-  /// removed before codegen.
-  void decompose();
+  /// Return and insert the recipes of the expression back into the VPlan,
+  /// directly before the current recipe. Leaves the expression recipe empty,
+  /// which must be removed before codegen.
+  ArrayRef<VPSingleDefRecipe *> decompose();
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lukel97 wrote:

You could also add `[[maybe_unused]]` if you want to avoid the `(void)` in convertToConcreteRecipes, but I'm not strongly opinionated

https://github.com/llvm/llvm-project/pull/205741