[llvm] [AArch64] Fix #94909: Optimize vector fmul(sitofp(x), 0.5) -> scvtf(x, 2) (PR #141480)

[David Green via llvm-commits]

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@@ -3952,6 +3960,156 @@ static bool checkCVTFixedPointOperandWithFBits(SelectionDAG *CurDAG, SDValue N,
   return true;
 }
 
+static bool checkCVTFixedPointOperandWithFBitsForVectors(SelectionDAG *CurDAG,
+                                                         SDValue N,
+                                                         SDValue &FixedPos,
+                                                         unsigned RegWidth,
+                                                         bool isReciprocal) {
+
+  // Fast Path
+  if (N.getOpcode() == ISD::BUILD_VECTOR) {
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davemgreen wrote:

I think this can use isConstantSplatVector to check for BUILD_VECTOR or SPLAT, and then some extra logic to check for DUP of a constant or MOVIshift.

https://github.com/llvm/llvm-project/pull/141480