Summary:
The backend does not generally interpret conditional expressions
specially. Therefore it is logically stronger to hoist them over other
boolean exps, for example normalizing
`e = (c ? t : f)` to `(c ? e = t : e =f)`
This enables the treatment of top-level conditional expressions in
terms of disjunction, conjunction and negation.
Reviewed By: mbouaziz
Differential Revision: D14495815
fbshipit-source-id: 4f2e8053f
Summary:
Eq and Dq expressions are interpreted by Equality and Exp, rather than
being considered uninterpreted functions. Classifying them as
interpreted results in stronger Equality normalization.
Reviewed By: mbouaziz
Differential Revision: D14495817
fbshipit-source-id: 44bb376c0
Summary: Also fix the spec for posix_memalign, and minor cleanup.
Reviewed By: ngorogiannis
Differential Revision: D14403648
fbshipit-source-id: 6b1cb3e3a
Summary:
The SL solver is currently not always able to append segments which
have been split symbolically, that is, at an internal point expressed
using a variable, rather than merely a constant.
Also, existential instantiation, that is, the choice of witnesses
during proof search, is currently sensitive to the order of
subformulas. This can lead to fragile incompleteness.
Reviewed By: mbouaziz
Differential Revision: D14481991
fbshipit-source-id: 80fe2f0a8
Summary:
Strengthen the Sh.seg constructor and Sh.is_false test to account for
the axiom that `null -[_;_)-> ⟨_,_⟩` is inconsistent.
Reviewed By: ngorogiannis
Differential Revision: D14481986
fbshipit-source-id: 7016e7451
Summary:
The dnf implementation dates to before nested existentials were
added. Updating it was overlooked, and it is just wrong.
Reviewed By: ngorogiannis
Differential Revision: D14481988
fbshipit-source-id: 9bba570f0
Summary:
P ∨ (∃x. Q ∨ R) could be simplified to (∃x. P ∨ Q ∨ R) and capture
occurrences of x in P.
Reviewed By: ngorogiannis
Differential Revision: D14481990
fbshipit-source-id: 92b474d59
Summary:
Also minor change to make strlen implementation syntactically closer
to spec.
Reviewed By: ngorogiannis
Differential Revision: D14403647
fbshipit-source-id: 48c771329
Summary:
This diff adds support in symbolic execution for calls to intrinsic
functions, to be used in lieu of adding a separate Llair instruction
for each intrinsic. This involves:
- adding skeleton support in Exec for symbolically execution an
intrinsic function call;
- exposing this in Domain;
- allowing symbolic execution of block terminators (e.g. function
call) to possibly fail; and
- generalizing Report for failing terminators.
Reviewed By: ngorogiannis
Differential Revision: D14403652
fbshipit-source-id: d86d9d1b8
Summary:
Some functions are translated directly to an expression, rather than a
function call. The llvm instructions for calling functions that may
and may not raise exceptions differ (Invoke and Call, resp.). This
diff adds support for the Invoke case.
Reviewed By: jvillard
Differential Revision: D14385596
fbshipit-source-id: 24458d960
Summary:
These tell llvm that contents of memory will not change during
execution of some code, which the analyzer does not need.
Reviewed By: jvillard
Differential Revision: D14385597
fbshipit-source-id: 0ef566a6f
Summary:
The backend has an implicit assumption that the entry block's locals
are all the function locals, not just those that happen to appear in
the entry block.
An alternative would be to collect the inverse renaming substitutions
produced by symbolic execution of jumps, which rename variables to
avoid clashes with the destination block's locals. These inverse
substitutions could be applied upon function return, in inverse
order. The complication with this approach is that it would be
necessary to distinguish between a destination local that clashes
because it has the same name as a local of some function higher in the
call stack versus a clash due to being a previous incarnation of the
same local due to a control-flow cycle. Accumulating unrenamings for
the latter case is expensive and pointless, as well as incongrous with
true interprocedural extensions.
So it seems preferable to exploit the asymmetry between the entry
block and others a bit more.
Reviewed By: jvillard
Differential Revision: D14354530
fbshipit-source-id: 815cdb224
Summary:
Interpreted subexps were not handled correctly: they must not be in
the carrier, but their non-interpreted subexps should.
Reviewed By: jvillard
Differential Revision: D14344291
fbshipit-source-id: 995896640
Summary:
In case the starting locations of two heap segments are
related (provably equal up to some offset), add equations between
their enclosing block to the goal. In these cases, the enclosing
blocks must be the same, so no completeness is lost. This has the
effect of instantiating existentials in the enclosing block prior to
others, which can avoid incomplete instantiation guesses.
Reviewed By: mbouaziz
Differential Revision: D14323550
fbshipit-source-id: 89a34a2c8
Summary: An initial set of basic sanity checks for frame inference.
Reviewed By: mbouaziz
Differential Revision: D14323549
fbshipit-source-id: d7cd4235f
Summary:
`('a, exn) result` is a more widely used type than with something
custom in place of `exn`, e.g. by the `Result` operations.
Reviewed By: mbouaziz
Differential Revision: D14322627
fbshipit-source-id: e2ed167ed
Summary:
- Change representation of Concat expressions from curried binary
operator to an nary one. This enables normalizing Concat expressions
with respect to associativity.
- Generalize Exp.solve to return a map rather than a pair of exps, to
enable expressing cases where solving an equation yields multiple
equations.
- Strengthen solver with implied equalities between sums of sizes of
concatenations of byte arrays.
Reviewed By: ngorogiannis
Differential Revision: D14297865
fbshipit-source-id: b40871559
Summary:
This patch adds an embarrassingly inefficient implementation of a
decision procedure for equality in the theories of uninterpreted
functions and linear arithmetic. A Shostak-style approach, where a
single congruence closure structure is shared by all theories, is
used. This is mostly based on the corrected variant of Shostak's
algorithm from:
Harald Rueβ and Natarajan Shankar. 2001. Deconstructing Shostak. In
Proceedings of the 16th Annual IEEE Symposium on Logic in Computer
Science (LICS '01).
Reviewed By: jvillard
Differential Revision: D14251655
fbshipit-source-id: 8a080145f
Summary:
Now with rational coefficients, dividing a polynomial by an integer
can be simplified.
Reviewed By: jvillard
Differential Revision: D14251656
fbshipit-source-id: 01094bc61
Summary:
Exp simplification must not generate fresh subexpressions in its
output that do not appear in its input, lest congruence closure gets
confused. Previously this check only considered immediate
subexpressions, which is overly restrictive.
Reviewed By: ngorogiannis
Differential Revision: D14251653
fbshipit-source-id: f8d5d9756
Summary:
Trace.report is essentially redundant with Trace.fail, and does not
behave as well wrt flushing when raising exceptions.
Reviewed By: ngorogiannis
Differential Revision: D14251657
fbshipit-source-id: 69a61c915
Summary:
Represent Add and Mul directly as associative and commutative nary
operations, rather than have Add and Mul operators and a separate AppN
nary application.
Reviewed By: ngorogiannis
Differential Revision: D14231544
fbshipit-source-id: 4fb7a06cf
Summary:
- Add nary expressions implemented using a form of multisets which
support any integer multiplicity
- Reimplement polynomials using new nary expressions
- Move the decomposition of exps into "base plus offset" form into
Exp, to enforce simplification invariants
- Revise expression simplification to cooperate with congruence
closure (mainly: simplification should not invent new
subexpressions)
- Reimplement congruence closure plus integer offsets to
+ cope with new representation of polynomials using nary expression forms
+ be diligent about maintaining which expressions are in the relation
+ add lots of invariant checking for the correlations between the
componnents of the congruence closure data structures
Reviewed By: jvillard
Differential Revision: D14075512
fbshipit-source-id: 2dbaf3d11
Summary:
Even pretty-printed congruence relations are verbose, and most
operations do not change much of the relation. So on return, print
only the symmetric difference between input and output relations.
Reviewed By: mbouaziz
Differential Revision: D14075513
fbshipit-source-id: b1f0ae6d0
Summary:
This is significant for operations involving the NULL pointer, which
is an integer of pointer type.
Reviewed By: mbouaziz
Differential Revision: D14075516
fbshipit-source-id: b727cb4c8
Summary:
Trace.parse is exposed across a module boundary, so handle its own
exceptions and return an `error`.
Reviewed By: mbouaziz
Differential Revision: D14081602
fbshipit-source-id: 4087c5d5b
Summary:
This allows exposing `Trace.parse`, which can be used to call
`Trace.init` in test code.
Reviewed By: mbouaziz
Differential Revision: D14075522
fbshipit-source-id: 4715c643f
Summary:
This makes it convenient to call
`Trace.init ~margin:70 ~config:all ()`
in test modules.
Reviewed By: mbouaziz
Differential Revision: D14075515
fbshipit-source-id: 3d3940eb1
Summary:
Comparison operations always return Typ.bool, and Add/Mul/Integer exps
are typed. Use these types to check that arguments are type correct up
to Typ.castable.
Reviewed By: mbouaziz
Differential Revision: D12854504
fbshipit-source-id: fff1426d5
Summary:
Require Exp clients to provide the type of the result of arithmetic
operations.
Reviewed By: mbouaziz
Differential Revision: D12854511
fbshipit-source-id: cc91a39ca
Summary:
Previously only the arguments of binary operations on integers were
clamped to the given bitwidth, but the results could overflow. This
was incorrect.
Also, use a clamped version of equality to simplify equality
expressions. This was previously overlooked.
Reviewed By: mbouaziz
Differential Revision: D12854502
fbshipit-source-id: 8786b4217
Summary:
Types of integer constants, in particular their bit-width, are
necessary for:
- correctly interpreting bitwise operations (e.g. `-1 xor 1` at type
`i1` is `0` while without the type the result is `-2`), and;
- distinguishing between integers and booleans, which are one-bit
integers, since booleans admit stronger algebraic simplification.
Note that code does genuinely treat 1-bit integers interchangeably as
booleans and integers, e.g. with expressions such as `e + (b != 42)`.
Therefore a lighter-weight early syntactic distinction between boolean
and bitwise operations is nontrivial/impossible to make robust.
This patch:
- adds the type to the representation of Exp.Integer;
- adds checks that Integer values fit within their specified bit-width
- factors out code handling 1-bit integers as booleans into `Z`, as it
is easy to make mistakes when forgetting that `-1`, not `1`, is the
representation of `true`;
- corrects the treatment of Exp.Convert in some cases involving
treating negative integers as unsigned;
- corrects and strengthens Exp simplification based on the bit-width
information;
- removes the `e - e ==> 0` simplification, due to not having the type
for `0`.
Reviewed By: mbouaziz
Differential Revision: D10488407
fbshipit-source-id: ff4320a29
Summary:
The main motivation is to factor out the code that determines the test
condition, e.g. to uniformly test `!= 0` vs `= 1`.
Also a convenience, and there are enough uses to make it worthwhile
and a readability improvement.
Reviewed By: mbouaziz
Differential Revision: D10488408
fbshipit-source-id: 520e843f3
Summary:
Just a convenience, but there are enough uses to make it worthwhile,
and a readability improvement.
Reviewed By: mbouaziz
Differential Revision: D10488404
fbshipit-source-id: 30cca06d5
Summary:
`sledge -c foo.bc` generates a binary file `foo.bc.llair` which can be
analyzed with `sledge foo.bc.llair`, and converted to textual form
with `sledge -c foo.bc.llair -o foo.llair`. Binary files are not
compatible between debug and release builds.
Reviewed By: mbouaziz
Differential Revision: D10389473
fbshipit-source-id: dfcabf33b
Summary:
Also for debugging support, note that analysis can be stopped after
reporting an attempt to call an unknown function with `sledge
-tReport.unknown_call` and likewise for invalid memory accesses with
`sledge -tReport.invalid_access`.
Reviewed By: mbouaziz
Differential Revision: D10389474
fbshipit-source-id: b006480d3
Summary:
Call __cxa_demangle from libstdc++ using Ctypes instead of the
wrapper in Llvm.
Reviewed By: mbouaziz
Differential Revision: D9939682
fbshipit-source-id: a9f02fff5
Summary:
Change the license of the source code from BSD + PATENTS to MIT.
Change `checkCopyright` to reflect the new license and learn some new file
types.
Generated with:
```
git grep BSD | xargs -n 1 ./scripts/checkCopyright -i
```
Reviewed By: jeremydubreil, mbouaziz, jberdine
Differential Revision: D8071249
fbshipit-source-id: 97ca23a
Summary:
Upgrade ocamlformat, and base which needs to be done in sync in order to build
ocamlformat, and the other deps can come for the ride.
Reviewed By: jvillard
Differential Revision: D7663537
fbshipit-source-id: 3e90970
Josh Berdine
Mehdi Bouaziz
Jules Villard