add docstring skip in hybrid script (#1668)

* add docstring skip in hybrid script

* fix lint

python/tvm/hybrid/parser.py

@@ -3,7 +3,7 @@
 import ast
 import operator
 import sys
-from .util import make_nop, halide_imm_types
+from .util import make_nop, halide_imm_types, is_docstring
 from .intrin import LOOP_INTRIN, MATH_INTRIN
 from .var_decl import determine_variable_usage
 from ..api import thread_axis
@@ -15,7 +15,7 @@ from .. import ir_pass as _ir_pass
 
 def list_to_block(visit, lst):
     """Convert a list of Python IR nodes to HalideIR Block"""
-    lst = list(map(visit, lst))
+    lst = [visit(stmt) for stmt in lst if not is_docstring(stmt)]
     lst = [stmt for stmt in lst if not _ir_pass.Equal(stmt, make_nop())]
     if not lst:
         return make_nop()

python/tvm/hybrid/util.py

 """Internal utilities for parsing Python subset to HalideIR"""
 
+import ast
 import inspect
 import numpy
 from .intrin import HYBRID_GLOBALS
@@ -22,6 +23,11 @@ def make_nop():
     return _make.Evaluate(_api.const(0, dtype='int32'))
 
 
+def is_docstring(node):
+    """Checks if a Python AST node is a docstring"""
+    return isinstance(node, ast.Expr) and isinstance(node.value, ast.Str)
+
+
 def _pruned_source(func):
     """Prune source code's extra leading spaces"""
     lines = inspect.getsource(func).split('\n')

tests/python/unittest/test_hybrid_script.py

@@ -43,6 +43,7 @@ def run_and_check(func, args, outs, var_dict={}, target='llvm'):
 
 @script
 def outer_product(n, m, a, b, c):
+    """This is a simple outer product"""
     for i in range(n):
         for j in range(m):
             c[i, j] = a[i] * b[j]