Update on "Make CI error on inductor fallback when decomp is available"

Fixes #99446 

Remove the warning, as that annoyed end-users who don't know what to do about it.

Instead, try to hold the line by preventing any decomp from being added without making
the corresponding change to inductor's fallbacks.

Note: we probably still need to better document how to update inductor's decomps,
for now it's pretty much "go ask the inductor team for advice"

cc soumith voznesenskym penguinwu anijain2305 EikanWang jgong5 Guobing-Chen XiaobingSuper zhuhaozhe blzheng Xia-Weiwen wenzhe-nrv jiayisunx peterbell10 desertfire

[ghstack-poisoned]

torch/_inductor/graph.py

@@ -34,7 +34,6 @@
 from .ir import Constant, FixedLayout, InputBuffer, Pointwise, Reduction, TensorBox
 from .lowering import (
     FALLBACK_ALLOW_LIST,
-    FALLBACK_DENY_LIST,
     fallback_handler,
     fallback_node_due_to_unsupported_type,
     layout_constraints,
@@ -365,7 +364,7 @@ def call_function(self, target, args, kwargs):
             base_name = target.name().split(".")[0]
             if base_name in FALLBACK_ALLOW_LIST:
                 make_fallback(target)
-            elif config.implicit_fallbacks and base_name not in FALLBACK_DENY_LIST:
+            elif config.implicit_fallbacks:
                 error = (
                     MissingOperatorWithDecomp
                     if get_decompositions([target])

torch/_inductor/lowering.py

@@ -1322,7 +1322,6 @@ def apply_constraint(arg, fx_arg):
 FALLBACK_ALLOW_LIST = {
     "torchvision::roi_align",
 }
-FALLBACK_DENY_LIST = {"aten::exponential"}  # fails accuracy on test_torch.py
 make_fallback(aten._adaptive_avg_pool2d_backward, require_dense)
 make_fallback(aten.convolution_backward, constrain_to_fx_strides)
 make_fallback(aten._cudnn_rnn, require_dense)
@@ -1496,6 +1495,9 @@ def apply_constraint(arg, fx_arg):
 make_fallback(aten._linalg_eigh)
 make_fallback(aten.zeros.names)
 
+# fails accuracy on test_torch.py, and explicit fallback required to avoid warn=True on implicit
+make_fallback(aten.exponential.default, warn=False)
+
 
 @register_lowering(aten.clone)
 def clone(x, *, memory_format=0):

torch/testing/_internal/common_utils.py

@@ -15,6 +15,7 @@
 import inspect
 import io
 import json
+import logging
 import math
 import operator
 import os
@@ -91,6 +92,7 @@
 
 from .composite_compliance import no_dispatch
 
+log = logging.getLogger(__name__)
 torch.backends.disable_global_flags()
 
 FILE_SCHEMA = "file://"
@@ -113,11 +115,10 @@
 slow_tests_dict = {}
 
 def maybe_load_json(filename):
-    if os.path.exists(filename):
+    if os.path.isfile(filename):
         with open(filename, 'r') as fp:
-            data = json.load(fp)
-            return data
-    print(f"Attempted to load {filename} but it does not exist.")
+            return json.load(fp)
+    log.warning("Attempted to load json file '%s' but it does not exist.", filename)
     return {}
 
 # set them here in case the tests are running in a subprocess that doesn't call run_tests