[FRONTEND] Fix arg name conflict bug (triton-lang#3383)

There is a bug introduced in latest triton code where AttributeError is
getting thrown if kernel function args has same name as global variable.

Co-authored-by: Keren Zhou <kerenzhou@openai.com>

python/triton/runtime/jit.py

@@ -36,6 +36,9 @@ def ret(self):
         return self.hasher.hexdigest()
 
     def visit_Name(self, node):
+        if node.id in self.local_names:
+            # The global name is hidden by the local name.
+            return None
         return self.globals.get(node.id, None)
 
     def visit_Attribute(self, node):
@@ -77,6 +80,21 @@ def is_triton_builtin(func):
             key = func_cache_key + noinline
             self.hasher.update(key.encode("utf-8"))
 
+    def visit_FunctionDef(self, node):
+        # Save the local name which may hide the global name.
+        self.local_names = [arg.arg for arg in node.args.args]
+        self.generic_visit(node)
+
+    def visit_Assign(self, node):
+        _names = []
+        for target in node.targets:
+            _names += [self.visit(target)]
+        if len(_names) == 1:
+            self.local_names += _names
+        else:
+            raise TypeError("Simultaneous multiple assignment is not supported.")
+        self.generic_visit(node)
+
 
 # -----------------------------------------------------------------------------
 # JITFunction