fhdl/verilog: support special lowering and overrides

diff --git a/migen/fhdl/verilog.py b/migen/fhdl/verilog.py
index 9e84b31a031fabf23529808542aa4c9670621f3b..502d4d146c08967b6cdaa167856943d70b90b365 100644 (file)
--- a/migen/fhdl/verilog.py
+++ b/migen/fhdl/verilog.py
@@ -208,10 +208,32 @@ def _printsync(f, ns, clock_domains):
                r += "end\n\n"
        return r
 
-def _printspecials(f, ns, clock_domains):
+def _call_special_classmethod(overrides, obj, method, *args, **kwargs):
+       cl = obj.__class__
+       if cl in overrides:
+               cl = overrides[cl]
+       if hasattr(cl, method):
+               return getattr(cl, method)(obj, *args, **kwargs)
+       else:
+               return None
+
+def _lower_specials(overrides, specials):
+       f = Fragment()
+       lowered_specials = set()
+       for special in sorted(specials, key=lambda x: x.huid):
+               impl = _call_special_classmethod(overrides, special, "lower")
+               if impl is not None:
+                       f += impl.get_fragment()
+                       lowered_specials.add(special)
+       return f, lowered_specials
+
+def _printspecials(overrides, specials, ns, clock_domains):
        r = ""
-       for special in sorted(f.specials, key=lambda x: x.huid):
-               r += special.emit_verilog(special, ns, clock_domains)
+       for special in sorted(specials, key=lambda x: x.huid):
+               pr = _call_special_classmethod(overrides, special, "emit_verilog", ns, clock_domains)
+               if pr is None:
+                       raise NotImplementedError("Special " + str(special) + " failed to implement emit_verilog")
+               r += pr
        return r
 
 def _printinit(f, ios, ns):
@@ -230,6 +252,7 @@ def _printinit(f, ios, ns):
 def convert(f, ios=None, name="top",
   clock_domains=None,
   return_ns=False,
+  special_overrides=dict(),
   display_run=False):
        if ios is None:
                ios = set()
@@ -242,6 +265,8 @@ def convert(f, ios=None, name="top",
                        ios.add(cd.rst)
                
        f = lower_arrays(f)
+       fs, lowered_specials = _lower_specials(special_overrides, f.specials)
+       f += fs
 
        ns = build_namespace(list_signals(f) \
                | list_special_ios(f, True, True, True) \
@@ -251,7 +276,7 @@ def convert(f, ios=None, name="top",
        r += _printheader(f, ios, name, ns)
        r += _printcomb(f, ns, display_run)
        r += _printsync(f, ns, clock_domains)
-       r += _printspecials(f, ns, clock_domains)
+       r += _printspecials(special_overrides, f.specials - lowered_specials, ns, clock_domains)
        r += _printinit(f, ios, ns)
        r += "endmodule\n"