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

lib.fifo: formally verify FIFO contract.

Browse source
This commit is contained in:
whitequark 2019-01-19 00:52:56 +00:00
parent b50b47d984
commit 97b990272e
3 changed files with 110 additions and 31 deletions
Download patch file Download diff file Expand all files Collapse all files

35
nmigen/lib/fifo.py
View file

@ -173,16 +173,31 @@ class SyncFIFO(FIFOInterface):
m.d.sync += self.level.eq(self.level - 1)
if platform == "formal":
m.d.comb += [
Assert(produce < self.depth),
Assert(consume < self.depth),
]
with m.If(produce == consume):
m.d.comb += Assert((self.level == 0) | (self.level == self.depth))
with m.If(produce > consume):
m.d.comb += Assert(self.level == (produce - consume))
with m.If(produce < consume):
m.d.comb += Assert(self.level == (self.depth + produce - consume))
# TODO: move this logic to SymbiYosys
initstate = Signal()
m.submodules += Instance("$initstate", o_Y=initstate)
with m.If(initstate):
m.d.comb += [
Assume(produce < self.depth),
Assume(consume < self.depth),
]
with m.If(produce == consume):
m.d.comb += Assume((self.level == 0) | (self.level == self.depth))
with m.If(produce > consume):
m.d.comb += Assume(self.level == (produce - consume))
with m.If(produce < consume):
m.d.comb += Assume(self.level == (self.depth + produce - consume))
with m.Else():
m.d.comb += [
Assert(produce < self.depth),
Assert(consume < self.depth),
]
with m.If(produce == consume):
m.d.comb += Assert((self.level == 0) | (self.level == self.depth))
with m.If(produce > consume):
m.d.comb += Assert(self.level == (produce - consume))
with m.If(produce < consume):
m.d.comb += Assert(self.level == (self.depth + produce - consume))
return m.lower(platform)