ci: validate untouched ECX fastcall path

.github/workflows/wp24b2-inplace-gc.yml

@@ -77,18 +77,27 @@ jobs:
           if not re.search(r"mov\s+esi,\s*ecx", collector):
               raise SystemExit("ABI validation failed: collector callback does not consume L from ECX")
 
-          # lua_close is much smaller in B2 because fragment reconstruction is gone.
-          # Zig may preserve ECX in any callee-saved register or a stack slot; do
-          # not require the B1-specific ESI allocation.
+          # B2 lua_close has no helper call before callOriginal: Zig can legally
+          # leave the incoming fastcall ECX untouched and call the trampoline
+          # directly. Accept either explicit preservation or verified no write
+          # to ECX before the first call instruction.
           close = callback_snippet("6f6ef0", 800)
-          ecx_preserved = re.search(
+          first_call = re.search(r"\bcall\b", close)
+          if not first_call:
+              raise SystemExit("ABI validation failed: lua_close trampoline call missing")
+          before_call = close[:first_call.start()]
+          ecx_saved = re.search(
               r"(?:mov\s+(?:esi|edi|ebx|ebp|eax|edx),\s*ecx|push\s+ecx|mov\s+(?:dword ptr\s*)?\[[^\]]+\],\s*ecx)",
-              close,
+              before_call,
           )
-          if not ecx_preserved:
+          ecx_written = re.search(
+              r"\b(?:mov|lea|xor|and|or|add|sub|imul|inc|dec|pop)\s+ecx\b",
+              before_call,
+          )
+          if not ecx_saved and ecx_written:
               print("lua_close callback snippet:")
               print(close)
-              raise SystemExit("ABI validation failed: lua_close callback does not preserve L from ECX")
+              raise SystemExit("ABI validation failed: lua_close clobbers incoming ECX before trampoline")
 
           # Native helper ABI observed directly in WoW 5875:
           # lua_gc_remove_objects: ECX=L, EDX=&list, stack arg all=0.