From 792f35ac8fed74904ae08dc48cbbc155b04936c3 Mon Sep 17 00:00:00 2001 From: whitequark Date: Mon, 13 Apr 2020 16:38:36 +0000 Subject: [PATCH] back.rtlil: refuse to create extremely large wires. Such wires are likely to trigger pathological behavior in Yosys and, if applicable, other toolchains that consume Verilog converted from RTLIL. Fixes #341. --- nmigen/back/rtlil.py | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/nmigen/back/rtlil.py b/nmigen/back/rtlil.py index 8433fe2..f683687 100644 --- a/nmigen/back/rtlil.py +++ b/nmigen/back/rtlil.py @@ -10,6 +10,10 @@ from ..hdl import ast, rec, ir, mem, xfrm __all__ = ["convert", "convert_fragment"] +class ImplementationLimit(Exception): + pass + + class _Namer: def __init__(self): super().__init__() @@ -101,6 +105,15 @@ class _ModuleBuilder(_Namer, _BufferedBuilder, _AttrBuilder): self.rtlil._buffer.write(str(self)) def wire(self, width, port_id=None, port_kind=None, name=None, attrs={}, src=""): + # Very large wires are unlikely to work. Verilog 1364-2005 requires the limit on vectors + # to be at least 2**16 bits, and Yosys 0.9 breaks on wires of more than 2**32 bits, so + # those numbers are our hard bounds. Use 2**24 as the arbitrary boundary beyond which + # downstream bugs are more likely than not. + if width > 2 ** 24: + raise ImplementationLimit("Wire created at {} is {} bits wide, which is unlikely to " + "synthesize correctly" + .format(src or "unknown location", width)) + self._attributes(attrs, src=src, indent=1) name = self._make_name(name, local=False) if port_id is None: -- 2.30.2