[llvm] [InstCombine] Transform high latency, dependent FSQRT/FDIV into FMUL (PR #87474)

[Sushant Gokhale via llvm-commits]

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@@ -1864,6 +1949,64 @@ static Instruction *foldFDivSqrtDivisor(BinaryOperator &I,
   return BinaryOperator::CreateFMulFMF(Op0, NewSqrt, &I);
 }
 
+// Change
+// X = 1/sqrt(a)
+// R1 = X * X
+// R2 = a * X
+//
+// TO
+//
+// FDiv = 1/a
+// FSqrt = sqrt(a)
+// FMul = FDiv * FSqrt
+// Replace Uses Of R1 With FDiv
+// Replace Uses Of R2 With FSqrt
+// Replace Uses Of X With FMul
+static Value *convertFSqrtDivIntoFMul(CallInst *CI, Instruction *X,
+                                      SmallPtrSetImpl<Instruction *> &R1,
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sushgokh wrote:

done

https://github.com/llvm/llvm-project/pull/87474