JIT: Skip tailcall IR validation for struct calls (#96719)

When structs are involved the correct return patterns can be very
complex if they involve decomposed field stores produced by physical
promotion. Skip the validation for these cases.

src/coreclr/jit/morph.cpp

@@ -6340,10 +6340,19 @@ GenTree* Compiler::fgMorphPotentialTailCall(GenTreeCall* call)
 // Notes:
 //   This function needs to handle somewhat complex IR that appears after
 //   tailcall candidates due to inlining.
+//   Does not support checking struct returns since physical promotion can
+//   create very hard to validate IR patterns.
 //
 void Compiler::fgValidateIRForTailCall(GenTreeCall* call)
 {
 #ifdef DEBUG
+    if (call->TypeIs(TYP_STRUCT))
+    {
+        // Due to struct fields it can be very hard to track valid return
+        // patterns; just give up on validating those.
+        return;
+    }
+
     class TailCallIRValidatorVisitor final : public GenTreeVisitor<TailCallIRValidatorVisitor>
     {
         GenTreeCall* m_tailcall;