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

[via llvm-commits]

https://github.com/abhishek-kaushik22 updated https://github.com/llvm/llvm-project/pull/121809

>From 9f62f4105035091b57c6912a22f3e0d7f72bdf2b Mon Sep 17 00:00:00 2001
From: abhishek-kaushik22 <abhishek.kaushik at intel.com>
Date: Tue, 7 Jan 2025 03:19:13 +0530
Subject: [PATCH] Update LegalizeVectorOps.cpp

---
 .../SelectionDAG/LegalizeVectorOps.cpp        | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
index 154c8aea6bcd17..2be9239202b021 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
@@ -1776,6 +1776,27 @@ 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, Node->getValueType(0)) ==
+                        TargetLowering::Expand) ||
+      (IsStrict &&
+       TLI.getOperationAction(ISD::STRICT_FMUL, Node->getValueType(0)) ==
+           TargetLowering::Expand)) {
+    EVT FPVT = BW == 32 ? MVT::f32 : MVT::f64;
+    SDLoc DL(Node);
+    unsigned Round = IsStrict ? ISD::STRICT_FP_ROUND : ISD::FP_ROUND;
+    unsigned UIToFP = IsStrict ? ISD::STRICT_UINT_TO_FP : ISD::UINT_TO_FP;
+    SDValue Result = DAG.getNode(
+        Round, DL, Node->getValueType(0),
+        DAG.getNode(UIToFP, DL, VT.changeVectorElementType(FPVT), Src),
+        DAG.getTargetConstant(
+            0, DL,
+            DAG.getTargetLoweringInfo().getPointerTy(DAG.getDataLayout())));
+    Results.push_back(Result);
+    return;
+  }
+
   SDValue HalfWord = DAG.getConstant(BW / 2, DL, VT);
 
   // Constants to clear the upper part of the word.