[llvm] [X86] Combine `uitofp <v x i32> to <v x half>` (PR #121809)

[Matt Arsenault via llvm-commits]

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@@ -1777,6 +1777,34 @@ void VectorLegalizer::ExpandUINT_TO_FLOAT(SDNode *Node,
   assert((BW == 64 || BW == 32) &&
          "Elements in vector-UINT_TO_FP must be 32 or 64 bits wide");
 
+  // If STRICT_/FMUL is not supported by the target (in case of f16) replace the
+  // UINT_TO_FP with a larger float and round to the smaller type
+  if ((!IsStrict &&
+       TLI.getOperationAction(ISD::FMUL, DstVT) == TargetLowering::Expand) ||
+      (IsStrict && TLI.getOperationAction(ISD::STRICT_FMUL, DstVT) ==
+                       TargetLowering::Expand)) {
+    EVT FPVT = BW == 32 ? MVT::f32 : MVT::f64;
+    SDValue UIToFP;
+    SDValue Result;
+    SDValue TargetZero = DAG.getIntPtrConstant(0, DL, /*isTarget=*/true);
+    if (IsStrict) {
+      UIToFP = DAG.getNode(ISD::STRICT_UINT_TO_FP, DL,
+                           {SrcVT.changeVectorElementType(FPVT), MVT::Other},
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arsenm wrote:

Share the changeVectorElementType between the paths 

https://github.com/llvm/llvm-project/pull/121809