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smtbmc: Add --track-assumes and --minimize-assumes options

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The --track-assumes option makes smtbmc keep track of which assumptions
were used by the solver when reaching an unsat case and to output that
set of assumptions. This is particularly useful to debug PREUNSAT
failures.

The --minimize-assumes option can be used in addition to --track-assumes
which will cause smtbmc to spend additional solving effort to produce a
minimal set of assumptions that are sufficient to cause the unsat
result.
This commit is contained in:
Jannis Harder 2024-03-07 13:27:03 +01:00
parent e4f11eb0a0
commit 42122e240e
3 changed files with 219 additions and 24 deletions
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61
backends/smt2/smtio.py
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@ -114,6 +114,7 @@ class SmtModInfo:
self.clocks = dict()
self.cells = dict()
self.asserts = dict()
self.assumes = dict()
self.covers = dict()
self.maximize = set()
self.minimize = set()
@ -141,6 +142,7 @@ class SmtIo:
self.recheck = False
self.smt2cache = [list()]
self.smt2_options = dict()
self.smt2_assumptions = dict()
self.p = None
self.p_index = solvers_index
solvers_index += 1
@ -602,6 +604,12 @@ class SmtIo:
else:
self.modinfo[self.curmod].covers["%s_c %s" % (self.curmod, fields[2])] = fields[3]
if fields[1] == "yosys-smt2-assume":
if len(fields) > 4:
self.modinfo[self.curmod].assumes["%s_u %s" % (self.curmod, fields[2])] = f'{fields[4]} ({fields[3]})'
else:
self.modinfo[self.curmod].assumes["%s_u %s" % (self.curmod, fields[2])] = fields[3]
if fields[1] == "yosys-smt2-maximize":
self.modinfo[self.curmod].maximize.add(fields[2])
@ -785,8 +793,13 @@ class SmtIo:
return stmt
def check_sat(self, expected=["sat", "unsat", "unknown", "timeout", "interrupted"]):
if self.smt2_assumptions:
assume_exprs = " ".join(self.smt2_assumptions.values())
check_stmt = f"(check-sat-assuming ({assume_exprs}))"
else:
check_stmt = "(check-sat)"
if self.debug_print:
print("> (check-sat)")
print(f"> {check_stmt}")
if self.debug_file and not self.nocomments:
print("; running check-sat..", file=self.debug_file)
self.debug_file.flush()
@ -800,7 +813,7 @@ class SmtIo:
for cache_stmt in cache_ctx:
self.p_write(cache_stmt + "\n", False)
self.p_write("(check-sat)\n", True)
self.p_write(f"{check_stmt}\n", True)
if self.timeinfo:
i = 0
@ -868,7 +881,7 @@ class SmtIo:
if self.debug_file:
print("(set-info :status %s)" % result, file=self.debug_file)
print("(check-sat)", file=self.debug_file)
print(check_stmt, file=self.debug_file)
self.debug_file.flush()
if result not in expected:
@ -945,6 +958,48 @@ class SmtIo:
def bv2int(self, v):
return int(self.bv2bin(v), 2)
def get_raw_unsat_assumptions(self):
self.write("(get-unsat-assumptions)")
exprs = set(self.unparse(part) for part in self.parse(self.read()))
unsat_assumptions = []
for key, value in self.smt2_assumptions.items():
# normalize expression
value = self.unparse(self.parse(value))
if value in exprs:
exprs.remove(value)
unsat_assumptions.append(key)
return unsat_assumptions
def get_unsat_assumptions(self, minimize=False):
if not minimize:
return self.get_raw_unsat_assumptions()
required_assumptions = {}
while True:
candidate_assumptions = {}
for key in self.get_raw_unsat_assumptions():
if key not in required_assumptions:
candidate_assumptions[key] = self.smt2_assumptions[key]
while candidate_assumptions:
candidate_key, candidate_assume = candidate_assumptions.popitem()
self.smt2_assumptions = {}
for key, assume in candidate_assumptions.items():
self.smt2_assumptions[key] = assume
for key, assume in required_assumptions.items():
self.smt2_assumptions[key] = assume
result = self.check_sat()
if result == 'unsat':
candidate_assumptions = None
else:
required_assumptions[candidate_key] = candidate_assume
if candidate_assumptions is not None:
return list(required_assumptions)
def get(self, expr):
self.write("(get-value (%s))" % (expr))
return self.parse(self.read())[0][1]