check whether intbv call argument is constant

myhdl/conversion/_misc.py

@@ -23,6 +23,7 @@
 
 
 import inspect
+import compiler
 from compiler import ast as astNode
 
 import myhdl
@@ -163,3 +164,23 @@ class _UniqueSuffixGenerator(object):
         return "_%s" % self.i
 
 _genUniqueSuffix = _UniqueSuffixGenerator()
+
+
+# check if expression is constant
+def _isConstant(ast, symdict):
+    v = _namesVisitor()
+    compiler.walk(ast, v)
+    for name in v.names:
+        if name not in symdict:
+            return False
+        if not isinstance(symdict[name], int):
+            return False
+    return True
+
+class _namesVisitor(object):
+    
+    def __init__(self):
+        self.names = []
+
+    def visitName(self, node):
+        self.names.append(node.name)

myhdl/conversion/_toVHDL.py

@@ -47,7 +47,7 @@ from myhdl._always_comb import _AlwaysComb
 from myhdl._always import _Always
 from myhdl._instance import _Instantiator
 from myhdl.conversion._misc import (_error, _access, _kind,_context,
-                                    _ConversionMixin, _Label, _genUniqueSuffix)
+                                    _ConversionMixin, _Label, _genUniqueSuffix, _isConstant)
 from myhdl.conversion._analyze import (_analyzeSigs, _analyzeGens, _analyzeTopFunc,
                                        _Ram, _Rom, _enumTypeSet)
 from myhdl._Signal import _WaiterList
@@ -1254,7 +1254,8 @@ class _ConvertVisitor(_ConversionMixin):
 
     def visitSlice(self, node, context=None, *args):
         if isinstance(node.expr, astNode.CallFunc) and \
-           node.expr.node.obj is intbv:
+           node.expr.node.obj is intbv and \
+           _isConstant(node.expr.args[0], self.ast.symdict):
             c = self.getVal(node)._val
             pre, post = "", ""
             if node.vhd.size <= 30:

myhdl/conversion/_toVerilog.py

@@ -46,7 +46,7 @@ from myhdl._always_comb import _AlwaysComb
 from myhdl._always import _Always
 from myhdl._instance import _Instantiator
 from myhdl.conversion._misc import (_error, _access, _kind,_context, 
-                                    _ConversionMixin, _Label, _genUniqueSuffix)
+                                    _ConversionMixin, _Label, _genUniqueSuffix, _isConstant)
 from myhdl.conversion._analyze import (_analyzeSigs, _analyzeGens, _analyzeTopFunc, 
                                        _Ram, _Rom)
             
@@ -632,10 +632,10 @@ class _ConvertVisitor(_ConversionMixin):
             self.write(f.__name__)
         if node.args:
             self.write(opening)
-            self.visit(node.args[0])
+            self.visit(node.args[0], *args)
             for arg in node.args[1:]:
                 self.write(", ")
-                self.visit(arg)
+                self.visit(arg, *args)
             self.write(closing)
         if hasattr(node, 'ast'):
             if node.ast.kind == _kind.TASK:
@@ -956,7 +956,8 @@ class _ConvertVisitor(_ConversionMixin):
 
     def visitSlice(self, node, context=None, *args):
         if isinstance(node.expr, astNode.CallFunc) and \
-           node.expr.node.obj is intbv:
+           node.expr.node.obj is intbv and \
+           _isConstant(node.expr.args[0], self.ast.symdict):
             c = self.getVal(node)
             self.write("%s'h" % c._nrbits)
             self.write("%x" % c._val)