refactor depth tracking of binary expressions

m2cgen/ast.py

@@ -120,7 +120,7 @@ class CompOpType(Enum):
     NOT_EQ = '!='
 
 
-class CompExpr(BoolExpr, BinExpr):
+class CompExpr(BoolExpr):
     def __init__(self, left, right, op):
         assert left.output_size == 1, "Only scalars are supported"
         assert right.output_size == 1, "Only scalars are supported"

m2cgen/interpreters/interpreter.py

@@ -7,27 +7,32 @@
 class BaseAstInterpreter:
 
     # disabled by default
-    depth_threshold = sys.maxsize
+    bin_depth_threshold = sys.maxsize
 
     def interpret(self, expr):
         return self._do_interpret(expr)
 
     # Private methods implementing visitor pattern
 
-    def _do_interpret(self, expr, depth=1, **kwargs):
+    def _do_interpret(self, expr, bin_depth=None, **kwargs):
 
-        # We track depth of the expression and if it exceeds specified limit,
-        # we will call hook.
-        if depth > self.depth_threshold and isinstance(expr, ast.BinExpr):
-            return self.depth_threshold_hook(expr, **kwargs)
+        # We track depth of the binary expressions and call a hook if it
+        # exceeds specified limit.
+        if isinstance(expr, ast.BinExpr):
+            bin_depth = bin_depth+1 if bin_depth is not None else 1
+
+            if bin_depth > self.bin_depth_threshold:
+                return self.bin_depth_threshold_hook(expr, **kwargs)
+        else:
+            bin_depth = 0
 
         try:
             handler = self._select_handler(expr)
         except NotImplementedError:
             if isinstance(expr, ast.TransparentExpr):
-                return self._do_interpret(expr.expr, depth=depth+1, **kwargs)
+                return self._do_interpret(expr.expr, bin_depth=bin_depth, **kwargs)
             raise
-        return handler(expr, depth=depth+1, **kwargs)
+        return handler(expr, bin_depth=bin_depth, **kwargs)
 
     def _select_handler(self, expr):
         handler_name = self._handler_name(type(expr))
@@ -45,7 +50,7 @@ def _handler_name(expr_tpe):
     def _normalize_expr_name(name):
         return re.sub("(?!^)([A-Z]+)", r"_\1", name).lower()
 
-    def depth_threshold_hook(self, expr, **kwargs):
+    def bin_depth_threshold_hook(self, expr, **kwargs):
         raise NotImplementedError
 
 
@@ -105,7 +110,7 @@ def interpret_vector_val(self, expr, **kwargs):
         return self._cg.vector_init(nested)
 
     # Default implementation. Simply adds new variable.
-    def depth_threshold_hook(self, expr, **kwargs):
+    def bin_depth_threshold_hook(self, expr, **kwargs):
         var_name = self._cg.add_var_declaration(expr.output_size)
         result = self._do_interpret(expr, **kwargs)
         self._cg.add_var_assignment(var_name, result, expr.output_size)

m2cgen/interpreters/python/interpreter.py

@@ -6,7 +6,7 @@ class PythonInterpreter(interpreters.AstToCodeInterpreter):
 
     # 93 may raise MemoryError, so use something close enough to it not to
     # create unnecessary overhead.
-    depth_threshold = 80
+    bin_depth_threshold = 80
 
     def __init__(self, indent=4, *args, **kwargs):
         cg = PythonCodeGenerator(indent=indent)

tests/interpreters/test_python.py

@@ -172,7 +172,7 @@ def  score(input):
 
 
 class CustomPythonInterpreter(interpreters.PythonInterpreter):
-    depth_threshold = 2
+    bin_depth_threshold = 2
 
 
 def test_depth_threshold_with_bin_expr():
@@ -205,16 +205,13 @@ def  score(input):
     if (1) == (1):
         var0 = 1
     else:
-        var1 = (1) == (1)
-        if var1:
+        if (1) == (1):
             var0 = 1
         else:
-            var2 = (1) == (1)
-            if var2:
+            if (1) == (1):
                 var0 = 1
             else:
-                var3 = (1) == (1)
-                if var3:
+                if (1) == (1):
                     var0 = 1
                 else:
                     var0 = 1