From d3185c0aa73cce511cee66fb0c7d0bceef348976 Mon Sep 17 00:00:00 2001
From: Katelyn Gadd <kg@luminance.org>
Date: Thu, 22 May 2025 09:00:33 -0700
Subject: [PATCH] Implement CEE_LDOBJ and CEE_STOBJ in the interpreter via
 ldind/stind

---
 src/coreclr/interpreter/compiler.cpp     | 19 ++++++++++++++++
 src/tests/JIT/interpreter/Interpreter.cs | 29 ++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/src/coreclr/interpreter/compiler.cpp b/src/coreclr/interpreter/compiler.cpp
index 9b3a3a809a26f8..d0d5b90e2090ab 100644
--- a/src/coreclr/interpreter/compiler.cpp
+++ b/src/coreclr/interpreter/compiler.cpp
@@ -2427,6 +2427,25 @@ int InterpCompiler::GenerateCode(CORINFO_METHOD_INFO* methodInfo)
                 m_ip++;
                 break;
 
+            case CEE_LDOBJ:
+            case CEE_STOBJ:
+            {
+                CHECK_STACK(*m_ip == CEE_LDOBJ ? 1 : 2);
+                CORINFO_RESOLVED_TOKEN resolvedToken;
+                ResolveToken(getU4LittleEndian(m_ip + 1), CORINFO_TOKENKIND_Class, &resolvedToken);
+                InterpType interpType = GetInterpType(m_compHnd->asCorInfoType(resolvedToken.hClass));
+                if (*m_ip == CEE_LDOBJ)
+                {
+                    EmitLdind(interpType, resolvedToken.hClass, 0);
+                }
+                else
+                {
+                    EmitStind(interpType, resolvedToken.hClass, 0, false);
+                }
+                m_ip += 5;
+                break;
+            }
+
             case CEE_RET:
             {
                 CORINFO_SIG_INFO sig = methodInfo->args;
diff --git a/src/tests/JIT/interpreter/Interpreter.cs b/src/tests/JIT/interpreter/Interpreter.cs
index a78df5ef49b14e..b0b059a422e62c 100644
--- a/src/tests/JIT/interpreter/Interpreter.cs
+++ b/src/tests/JIT/interpreter/Interpreter.cs
@@ -416,6 +416,9 @@ public static void RunInterpreterTests()
         if (!TestArray())
             Environment.FailFast(null);
 
+        if (!TestXxObj())
+            Environment.FailFast(null);
+
         if (!TestSizeof())
             Environment.FailFast(null);
 
@@ -956,6 +959,32 @@ public static bool ArrayDouble(int length, double value)
         return true;
     }
 
+    public static unsafe bool TestXxObj()
+    {
+        // FIXME: There is no way to generate cpobj opcodes with roslyn at present.
+        // The only source of cpobj I've found other than hand-written IL tests is ilmarshalers.h, so once pinvoke marshaling is
+        //  supported, we can use that to verify that cpobj works. Until then, this method only tests ldobj/stobj.
+        TestStruct4fi a = new TestStruct4fi
+        {
+            a = 1,
+            b = 2,
+            c = 3,
+            d = 4,
+        }, b = default;
+        ref TestStruct4fi c = ref a,
+            d = ref b;
+
+        if (b.a == a.a)
+            return false;
+
+        c = d;
+
+        if (b.a != a.a)
+            return false;
+
+        return true;
+    }
+
     public static unsafe bool TestSizeof()
     {
         if (sizeof(int) != 4)