[llvm] [VPlan] Return Max from computeCost without underlying instrs. (PR #109708)

[Florian Hahn via llvm-commits]

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@@ -276,14 +276,6 @@ static Instruction *getInstructionForCost(const VPRecipeBase *R) {
     return dyn_cast_or_null<Instruction>(S->getUnderlyingValue());
   if (auto *IG = dyn_cast<VPInterleaveRecipe>(R))
     return IG->getInsertPos();
-  // Currently the legacy cost model only calculates the instruction cost with
-  // underlying instruction. Removing the WidenMem here will prevent
-  // force-target-instruction-cost overwriting the cost of recipe with
-  // underlying instruction which is inconsistent with the legacy model.
-  // TODO: Remove WidenMem from this function when we don't need to compare to
-  // the legacy model.
-  if (auto *WidenMem = dyn_cast<VPWidenMemoryRecipe>(R))
-    return &WidenMem->getIngredient();
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fhahn wrote:

This has been reworked in the latest version. The function is gone and inline to `::cost()`,  which clarifies that it is only used to decide to skip and when to apply forced costs.

https://github.com/llvm/llvm-project/pull/109708