[llvm] [AArch64] Fix SVE cost model for various math intrinsics (PR #184358)

[David Green via llvm-commits]

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@@ -696,6 +696,13 @@ AArch64TTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
     break;
   }
   case Intrinsic::abs: {
+    if (isa<ScalableVectorType>(RetTy) && ST->isSVEorStreamingSVEAvailable()) {
+      auto LT = getTypeLegalizationCost(RetTy);
+      return LT.first;
+    }
+
+    // TODO: Why can't we just always return
+    // getTypeLegalizationCost(RetTy).first for all types?
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davemgreen wrote:

It is best not to add TODO comments like this, especially if they are not necessarily correct.

https://github.com/llvm/llvm-project/pull/184358