[mlir] Fix generating checks for multiple funcs in generate-test-checks

[benmxwl-arm]

Summary

This regressed in D154458 due to the added tracking of used variable
names that now also has to be cleared alongside the counter.

[benmxwl-arm]

Rebase

[c-rhodes]

LGTM cheers

[awarzynski]

This makes sense to me, but it would make even more sense if I saw an example of what triggers the issue and how it manifests itself ;-) That's only a nice-to-have.

LGTM, ta!

[benmxwl-arm]

The issue is a simple one :)
Pass some MLIR with multiple functions to generate-test-checks.py and it'll (incorrectly) throw "VAL_0: duplicate variable name".

func.func @func_a(...) {
 // SSA values in here.
 // The script names them VAL_0, 1, 2, 3 etc..
} 
// End of function: clear counter, but forget to clear used_attribute_names.

func.func @func_b(...) {
 // More SSA values in here.
 // Since counter is at zero VAL_0 is used again, but VAL_0 is still in used_attribute_names.
 // Erroneously throw "duplicate variable name"
}

mlir/utils/generate-test-checks.py

def __init__(self, variable_names):
 
         # Number of variable names to still generate in parent scope
         self.generate_in_parent_scope_left = 0
 
         # Parse variable names
         self.variable_names = [name.upper() for name in variable_names.split(',')]
         self.used_variable_names = set()
 
-    # Generate the following 'n' variable names in the parent scope. 
+    # Generate the following 'n' variable names in the parent scope.
     def generate_in_parent_scope(self, n):
         self.generate_in_parent_scope_left = n
 
     # Generate a substitution name for the given ssa value name.
     def generate_name(self, source_variable_name):
 
         # Compute variable name
         variable_name = self.variable_names.pop(0) if len(self.variable_names) > 0 else ''
class VariableNamer:
     # Pop the last variable name scope.
     def pop_name_scope(self):
         self.scopes.pop()
 
     # Return the level of nesting (number of pushed scopes).
     def num_scopes(self):
         return len(self.scopes)
 
-    # Reset the counter.
-    def clear_counter(self):
+    # Reset the counter and used variable names.
+    def clear_names(self):
         self.name_counter = 0
+        self.used_variable_names = set()
 
 class AttributeNamer:
 
     def __init__(self, attribute_names):
         self.name_counter = 0
         self.attribute_names = [name.upper() for name in attribute_names.split(',')]
         self.map = {}
         self.used_attribute_names = set()
-    
     # Generate a substitution name for the given attribute name.
     def generate_name(self, source_attribute_name):
 
         # Compute FileCheck name
         attribute_name = self.attribute_names.pop(0) if len(self.attribute_names) > 0 else ''
         if attribute_name == '':
             attribute_name = "ATTR_" + str(self.name_counter)
             self.name_counter += 1
for input_line in input_lines:
             variable_namer.pop_name_scope()
             cur_level = variable_namer.num_scopes()
 
         # If the line ends with a '{', push a new name scope.
         if input_line[-1] == "{":
             variable_namer.push_name_scope()
             if cur_level == args.starts_from_scope:
                 output_segments.append([])
-           
             # Result SSA values must still be pushed to parent scope
             num_ssa_results = get_num_ssa_results(input_line)
             variable_namer.generate_in_parent_scope(num_ssa_results)
 
         # Omit lines at the near top level e.g. "module {".
         if cur_level < args.starts_from_scope:
             continue
 
         if len(output_segments[-1]) == 0:
-            variable_namer.clear_counter()
+            variable_namer.clear_names()
 
         # Preprocess the input to remove any sequences that may be problematic with
         # FileCheck.
         input_line = preprocess_line(input_line)
 
         # Process uses of attributes in this line
         input_line = process_attribute_references(input_line, attribute_namer)