[mlir][generate-test-checks] Emit attributes with rest of CHECK lines (#143759)

Prior to this patch, generating test checks in place put the ATTR
definitions at the very top of the file, above the RUN lines and
autogenerated note. All CHECK lines should below the RUN lines and
autogenerated note.

This change ensures that the attribute definitions are emitted with the
rest of the CHECK lines.

---------

Co-authored-by: Michael Maitland <michaelmaitland@meta.com>

mlir/utils/generate-test-checks.py

@@ -220,12 +220,19 @@ def process_source_lines(source_lines, note, args):
         source_segments[-1].append(line + "\n")
     return source_segments
 
-def process_attribute_definition(line, attribute_namer, output):
+
+def process_attribute_definition(line, attribute_namer):
     m = ATTR_DEF_RE.match(line)
     if m:
         attribute_name = attribute_namer.generate_name(m.group(1))
-        line = '// CHECK: #[[' + attribute_name + ':.+]] =' + line[len(m.group(0)):] + '\n'
-        output.write(line)
+        return (
+            "// CHECK: #[["
+            + attribute_name
+            + ":.+]] ="
+            + line[len(m.group(0)) :]
+            + "\n"
+        )
+    return None
 
 def process_attribute_references(line, attribute_namer):
 
@@ -340,6 +347,9 @@ def main():
     variable_namer = VariableNamer(args.variable_names)
     attribute_namer = AttributeNamer(args.attribute_names)
 
+    # Store attribute definitions to emit at appropriate scope
+    pending_attr_defs = []
+
     # Process lines
     for input_line in input_lines:
         if not input_line:
@@ -350,8 +360,9 @@ def main():
         if input_line.startswith("// -----"):
             continue
 
-        # Check if this is an attribute definition and process it
-        process_attribute_definition(input_line, attribute_namer, output)
+        if ATTR_DEF_RE.match(input_line):
+            pending_attr_defs.append(input_line)
+            continue
 
         # Lines with blocks begin with a ^. These lines have a trailing comment
         # that needs to be stripped.
@@ -407,6 +418,13 @@ def main():
             output_line += process_line(ssa_split[1:], variable_namer)
 
         else:
+            # Emit any pending attribute definitions at the start of this scope
+            for attr in pending_attr_defs:
+                attr_line = process_attribute_definition(attr, attribute_namer)
+                if attr_line:
+                    output_segments[-1].append(attr_line)
+            pending_attr_defs.clear()
+
             # Output the first line chunk that does not contain an SSA name for the
             # label.
             output_line = "// " + args.check_prefix + "-LABEL: " + ssa_split[0] + "\n"