[llvm] [Analysis] Use BaseT::getArithmeticInstrCost() as the base cost for RecipThroughput (PR #176515)

[Simon Pilgrim via llvm-commits]

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@@ -1058,9 +1058,13 @@ class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
     std::pair<InstructionCost, MVT> LT = getTypeLegalizationCost(Ty);
 
     bool IsFloat = Ty->isFPOrFPVectorTy();
-    // Assume that floating point arithmetic operations cost twice as much as
-    // integer operations.
-    InstructionCost OpCost = (IsFloat ? 2 : 1);
+    InstructionCost OpCost;
+    if (IsFloat)
+      // Should update to Expensive? For now just want to modify integer costing
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RKSimon wrote:

@bababuck What x86 changes do you mean? These things have grown as the middle-end have become more cost driven - LV/SLP/VectorCombine especially - we now accumulate costs a lot more so "Free/Basic/Expensive" just doesn't work.

https://github.com/llvm/llvm-project/pull/176515