[llvm] DAG: Implement promotion for strict_fpextend (PR #74310)

[Matt Arsenault via llvm-commits]

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@@ -2276,6 +2279,26 @@ SDValue DAGTypeLegalizer::PromoteFloatOp_FP_EXTEND(SDNode *N, unsigned OpNo) {
   return DAG.getNode(ISD::FP_EXTEND, SDLoc(N), VT, Op);
 }
 
+SDValue DAGTypeLegalizer::PromoteFloatOp_STRICT_FP_EXTEND(SDNode *N,
+                                                          unsigned OpNo) {
+  assert(OpNo == 1);
+
+  SDValue Op = GetPromotedFloat(N->getOperand(1));
+  EVT VT = N->getValueType(0);
+
+  // Desired VT is same as promoted type.  Use promoted float directly.
+  if (VT == Op->getValueType(0)) {
+    ReplaceValueWith(SDValue(N, 1), N->getOperand(0));
+    return Op;
+  }
+
+  // Else, extend the promoted float value to the desired VT.
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arsenm wrote:

I don't think it is, it would require promoting past a legal FP type to another which is probably an unusual situation 

https://github.com/llvm/llvm-project/pull/74310