Disable nvfusertest_serde_check if DEBUG_SERDE=disable (#3304)

This is another attempt to fix the codediff CI job

Fixes #3265. Fixes #3283.

tests/python/utils.py

@@ -274,6 +274,7 @@ def check_cpp_translation(reference_outputs, fd, inputs, device=None):
 
 # This DEBUG_SERDE environment flag is used to debug serialization failures.
 #
+# If DEBUG_SERDE=debug
 # 1) It disables automatically saving FusionCache upon program exit. Therefore,
 # it has to be a global flag not per-test.
 #
@@ -283,8 +284,14 @@ def check_cpp_translation(reference_outputs, fd, inputs, device=None):
 #
 # 3) It keeps the temporary files that are created during serde_check.
 # Normally, these files are deleted after each test.
-env_var_debug_serde = os.getenv("DEBUG_SERDE")
-debug_serde: bool = env_var_debug_serde in ("true", "1")
+#
+# DEBUG_SERDE=disable
+# 1) It disables the @nvfusertest_serde_check decorator. This disables checking
+# that serde round-trips preserve the definition during testing.
+env_var_debug_serde = os.getenv("DEBUG_SERDE", "").lower()
+debug_serde: bool = env_var_debug_serde == "debug"
+disable_serde: bool = env_var_debug_serde == "disable"
+del env_var_debug_serde
 
 
 # The pytest framework and test_python_frontend.py use different arguments for
@@ -314,7 +321,7 @@ def basic_serde_check():
                 )
             else:
                 raise RuntimeError(
-                    "***** Use DEBUG_SERDE=true to debug serialization failure."
+                    "***** Use DEBUG_SERDE=debug to debug serialization failure."
                 )
 
 
@@ -323,6 +330,11 @@ def basic_serde_check():
 # binary. Call FusionCache.reset() to clear the cache after running an error
 # test in `test_python_frontend.py'.
 def atexit_serde_check():
+    if disable_serde:
+        # Ignore FusionCache and automatic serialization if serde check is
+        # disabled
+        return
+
     from nvfuser import FusionCache
 
     if not debug_serde:
@@ -343,6 +355,8 @@ def nvfusertest_serde_check(test_fn: Callable):
     function. Currently, it uses serialization to rebuild the FusionCache
     structure.
     """
+    if disable_serde:
+        return test_fn
 
     def inner_fn(*args, **kwargs):
         self, fusion_func, inputs = args

tools/codediff/compare_codegen.sh

@@ -189,7 +189,7 @@ collect_kernels() {
     # Make tests reproducible
     export NVFUSER_TEST_RANDOM_SEED=0
     export NVFUSER_DISABLE=parallel_compile
-    export DEBUG_SERDE=true
+    export DEBUG_SERDE=disable
     # run tests and benchmarks with cuda_to_file and dump output to files
 
     mkdir -p "$outdir/$commit"