MLBEDSW-3858: Incorrect PAD usage bug

Fixed a bug where PAD having no consumers would result in a crash.
Now the constraint doesn't crash and thus the intended error message is shown, resulting in easier debugging.

Change-Id: I1e4403d47a6152e7adbf7bc065db86d4217d39cc
Signed-off-by: erik.andersson@arm.com <erik.andersson@arm.com>

1 files changed, 9 insertions, 11 deletions

diff --git a/ethosu/vela/supported_operators.py b/ethosu/vela/supported_operators.py
index 9d315189..1bebe9af 100644
--- a/ethosu/vela/supported_operators.py
+++ b/ethosu/vela/supported_operators.py
@@ -829,17 +829,15 @@ class SupportedOperators:
     def constraint_pad_ofm(cls, op):
         "Must be followed by one of the following operator types: {}"
         consumers = op.ofm.consumers()
-        consumers_to_pad = 0
-        for consumer in consumers:
-            if consumer.type in cls.supported_pad_consumers:
-                if consumer.attrs["padding"] == Padding.VALID:
-                    consumers_to_pad += 1
-        valid = len(consumers) > 0 and len(consumers) == consumers_to_pad
-        return (
-            valid,
-            f"Operator is followed by {consumers_to_pad} consumers with "
-            f"padding set to VALID, out of {len(consumers)} consumers",
-        )
+        unsupported_consumers = [
+            cons.type
+            for cons in consumers
+            if cons is not None
+            if cons.type not in cls.supported_pad_consumers or cons.attrs["padding"] != Padding.VALID
+        ] + [None for cons in consumers if cons is None]
+        none_string = ", ".join(["NoneType" for cons in consumers if cons is None])
+        valid = len(unsupported_consumers) == 0
+        return valid, f"PAD operator is followed by: {_optype_formatter(unsupported_consumers)+none_string}"
 
     @staticmethod
     def constraint_stridedslice_inputs_const(op):