usb-tools/amaranth
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

hdl.dsl: cases wider than switch test value are unreachable.

Browse source 
In 3083c1d6 they were erroneously fixed via truncation.
This commit is contained in:
whitequark 2019-01-13 08:51:49 +00:00
parent 3083c1d6dd
commit 664b4bcb3a
3 changed files with 13 additions and 11 deletions
Download patch file Download diff file Expand all files Collapse all files

8
nmigen/hdl/dsl.py
View file

@ -219,17 +219,19 @@ class Module(_ModuleBuilderRoot):
if isinstance(value, str) and len(value) != len(switch_data["test"]):
raise SyntaxError("Case value '{}' must have the same width as test (which is {})"
.format(value, len(switch_data["test"])))
omit_case = False
if isinstance(value, int) and bits_for(value) > len(switch_data["test"]):
warnings.warn("Case value '{:b}' is wider than test (which has width {}); "
"comparison will be made against truncated value"
"comparison will never be true"
.format(value, len(switch_data["test"])), SyntaxWarning, stacklevel=3)
value &= (1 << len(switch_data["test"])) - 1
omit_case = True
try:
_outer_case, self._statements = self._statements, []
self._ctrl_context = None
yield
self._flush_ctrl()
switch_data["cases"][value] = self._statements
if not omit_case:
switch_data["cases"][value] = self._statements
finally:
self._ctrl_context = "Switch"
self._statements = _outer_case