Fix AssignAndPushReferenceValue ignoring var value coercion

OpenDreamProject · Jan 28, 2025 · a89c4aa · a89c4aa
1 parent d12f5ef
commit a89c4aa
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/DMCompiler/Optimizer/PeepholeOptimizations.cs b/DMCompiler/Optimizer/PeepholeOptimizations.cs
@@ -638,6 +638,11 @@ public bool CheckPreconditions(List<IAnnotatedBytecode> input, int index) {
         AnnotatedBytecodeReference assignTarget = firstInstruction.GetArg<AnnotatedBytecodeReference>(0);
         AnnotatedBytecodeReference pushTarget = secondInstruction.GetArg<AnnotatedBytecodeReference>(0);
 
+        // Assigning certain values to certain vars (e.g. setting a SrcField like "dir" to null)
+        // actually causes the value to be coerced to something different than the value on the stack.
+        // We don't have a good way to identify those vars at this point, so just restrict the opt to locals and args since those shouldn't have side effects
+        if (pushTarget.RefType != DMReference.Type.Local && pushTarget.RefType != DMReference.Type.Argument) return false;
+
         return assignTarget.Equals(pushTarget);
     }