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

[JP Hafer via llvm-commits]

================
@@ -3952,6 +3960,129 @@ static bool checkCVTFixedPointOperandWithFBits(SelectionDAG *CurDAG, SDValue N,
   return true;
 }
 
+static bool checkCVTFixedPointOperandWithFBitsForVectors(SelectionDAG *CurDAG,
+                                                         SDValue N,
+                                                         SDValue &FixedPos,
+                                                         unsigned FloatWidth,
+                                                         bool isReciprocal) {
+
+  // N must be a bitcast/nvcast of a vector float type.
+  if (!((N.getOpcode() == ISD::BITCAST ||
+         N.getOpcode() == AArch64ISD::NVCAST) &&
+        N.getValueType().isVector() && N.getValueType().isFloatingPoint())) {
----------------
jph-13 wrote:

updated as:
```
  SDValue ImmediateNode;
  // N must be a bitcast or nvcast
  if (N.getOpcode() == ISD::BITCAST || N.getOpcode() == AArch64ISD::NVCAST) {
    ImmediateNode = N.getOperand(0);
  } else {
    return false;
  }

  EVT NodeVT = N.getValueType();
  EVT InputVT = ImmediateNode.getValueType();
  // The input must me a vector of int but N must be a floating point
  if (!InputVT.isVector() || !InputVT.isInteger() ||
      !NodeVT.isFloatingPoint())
    return false;
    ```

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