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Remove redundant variables in boolean existentials. A situation can occur
during re-writing when patterns are re-written into simpler guarded
patterns, with the guard containing a large conjunction. Often those
individual conjuncts have no meaning for flow typing, but we'll still
generate a large conjunct bool('p & 'q & 'r & 's ...) for the guard. Now
we can simplify that return type by combining all the type variables
that don't give us any information into a single one, which improves
performance as we can avoid passing all those variables to the
constraint solver.
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This ensures that mappings round-trip through the pretty-printer and
parser unchanged
Remove guarded_pats rewrite from C compilation. It causes a large
increase in compilation time due to how it interacts with flow
typing/pattern literal re-writing/and sizeof-rewriting
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Add an extra argument for Type_check.prove for the location of the prove
call (as prove __POS__) to help debug SMT related issues
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Simply constraints further before calling Z3 to improve performance of
sizeof re-writing.
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Type variables can now be lexically scoped and shadow each other like normal variables,
rather than being required to be unique. This means we can use identifier names to
choose names for type variables in a way where we can assume they remain consistent
between type-checker runs. This means that re-writer steps can lift types out of
annotations in E_aux constructors and put them directly as syntactic annotations in the
AST - this should enable more robust rewrite steps.
Also fix RISC-V lem build w/ flow typing changes
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This reverts commit 4d8a4078990a00ffdc018bc8f5d4d5e3dcf6527d.
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This results in much better error messages, as we can pick readable
names that make sense, and should hopefully make the re-writer more
robust.
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Fixes some re-writer issues that was preventing RISC-V from building
with new flow-typing constraints. Unfortunately because the flow
typing now understands slightly more about boolean variables, the very
large nested case statements with matches predicates produced by the
string-matching end up causing a huge blowup in the overall
compilation time.
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have to recompute it, which can be very expensive for very large
specifications
Also additional flow typing and fixes for boolean type variables
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Also output termination measures in Sail printer
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Add a file nl_flow.ml which can analyse a block of Sail expressions
and insert constraints for flow-typing rules which do not follow the
lexical structure of the code (and therefore the syntax-directed
typing rules can't do any flow-typing for). A common case found in ASL
translated Sail would be something like
function decode(Rt: bits(4)) = {
if Rt == 0xF then {
throw(Error_see("instruction"));
};
let t = unsigned(Rt);
execute(t)
}
which would currently fail is execute has a 0 <= t <= 14 constraint
for a register it writes to. However if we spot this pattern and add
an assertion automatically:
let t = unsigned(Rt);
assert(t != 15);
execute(t)
Then everything works, because the assertion is in the correct place
for regular flow typing. Currently it only works for this specific
use-case, and is turned on using the -non_lexical_flow flag
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Some of the output from the tests scripts is odd on Jenkins, try to
fix this by flushing stdout more regularly in the test scripts
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bool_of_bit and bit_of_bool in sail_lib
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subrange_subrange_concat does a zero extension internally, so another
zero extension of its result is redundant and can lead to a type error
in Lem (because Lem's type system cannot calculate the length of the
intermediate result of subrange_subrange_concat).
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Sizeof-rewriting could introduce extra arguments to functions that
instantiate_simple_equations could fill in with overly complicated
types, causing unification to fail when building lem.
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Now all ARM, RISC-V, and CHERI-MIPS all build successfully with
type-checking changes. All typechecker/c/ocaml/lem/builtin/riscv/arm
tests are now working as well.
Now the python test scripts can run sequentially with TEST_PAR=1 there's
no reason to keep the old shell versions around anymore.
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Spawning a process for every test and running every test in parallel
is quite RAM intensive (up to about 8gb) especially when running
valgrind on every test in parallel. Now we only run up to TEST_PAR
tests in parallel (default 4).
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It now includes updating the effects so that morally pure recursive
functions can be turned into this impure termination-by-assertion form.
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test/typecheck/pass/tautology.sail constaints tests of various boolean
properties, e.g.
// de Morgan
_prove(constraint(not('p | 'q) <--> not('p) & not('q)));
_prove(constraint(not('p & 'q) <--> not('p) | not('q)));
introduce a new _not_prove case which allows us to assert in tests
that a constraint is not provable. This test essentially tests that
constraints map to sensible problems in the SMT solver, without
testing flow typing or any other features.
Add a script test/typecheck/update_errors.sh, which regenerates the
expected error messages. Testing that type-checking failures is
important, but can be brittle when the error messages change for
inconsequential reasons. This script automates fixing this.
Also ensure that this test case works correctly in Lem
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We should infer type variable kinds better in initial_check.ml, but we really don't want to have to deal
with that everywhere, especially when we can no longer easily cheat and assume KOpt_none implies K_int.
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Remove some dead code in Pretty_print_common
Start thinking a bit about Minisail-esque syntactic sugar in initial_check
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This only applies to recursive functions and uses the termination measure
merely as a limit to the recursive call depth, rather than proving the
measure correct.
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* Improve type inference for numeric if statements (if_infer test)
* Correctly handle constraints for existentially quantified constructors (constraint_ctor test)
* Canonicalise all numeric types in function arguments, which
triggers some weird edge cases between parametric polymorphism and
subtyping of numeric arguments
* Because of this eq_int, eq_range, and eq_atom etc become identical
* Avoid duplicating destruct_exist in Env
* Handle some odd subtyping cases better
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Change Typ_arg_ to A_. We use it a lot more now typ_arg is used instead of
uvar as the result of unify. Plus A_ could either stand for argument, or
Any/A type which is quite appropriate in most use cases.
Restore instantiation info in infer_funapp'. Ideally we would save this
instead of recomputing it ever time we need it. However I checked and
there are over 300 places in the code that would need to be changed to add
an extra argument to E_app. Still some issues causing specialisation to
fail however.
Improve the error message when we swap how we infer/check an l-expression,
as this could previously cause the actual cause of a type-checking failure
to be effectively hidden.
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On a new branch because it's completely broken everything for now
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Previously the valid constraints had to be carefully restricted to
avoid parser ambiguities between n_constraint and atyp. With the
initial check refactored, we can now parse constraints into atyp using
ATyp_app for the operators, and changing ATyp_constant into a more
general ATyp_lit for true and false. Logically this new structure is
more uniform, as atyp is now the parse representation for all
Bool-kinded things (constraints), Type-kinded things (regular types),
and Int-kinded things (n-expressions), and initial_check.ml now splits
all three into n_constraint, typ, and nexp respectively, rather than
how it was before with initial_check splitting types and nexps, but
constraints already being separate in the parser.
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Mostly this is to change how we desugar types in order to make us more
flexible with what we can parse as a valid constraint as
type. Previously the structure of the initial check forced some
awkward limitations on what was parseable due to how the parse AST is
set up.
As part of this, I've taken the de-scattering of scattered functions
out of the initial check, and moved it to a re-writing step after
type-checking, where I think it logically belongs. This doesn't change
much right now, but opens up some more possibilities in the future:
Since scattered functions are now typechecked normally, any future
module system for Sail would be able to handle them specially, and the
Latex documentation backend can now document scattered functions
explicitly, rather than relying on hackish 'de-scattering' logic to
present documentation as the functions originally appeared.
This has one slight breaking change which is that union clauses must
appear before their uses in scattered functions, so
union ast = Foo : unit
function clause execute(Foo())
is ok, but
function clause execute(Foo())
union ast = Foo : unit
is not. Previously this worked because the de-scattering moved union
clauses upwards before type-checking, but as this now happens after
type-checking they must appear in the correct order. This doesn't
occur in ARM, RISC-V, MIPS, but did appear in Cheri and I submitted a
pull request to re-order the places where it happens.
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This makes dealing with records and field expressions in Sail much
nicer because the constructors are no longer stacked together like
matryoshka dolls with unnecessary layers. Previously to get the fields
of a record it would be either
E_aux (E_record (FES_aux (FES_Fexps (fexps, _), _)), _)
but now it is simply:
E_aux (E_record fexps, _)
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Rather than having K_aux (K_kind [BK_aux (BK_int, _)], _) represent
the Int kind, we now just have K_aux (K_int, _). Since the language is
first order we have no need for fancy kinds in the AST.
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They weren't needed for ASL parser like I thought they would be, and
they increase the complexity of dealing with constraints throughout
Sail, so just remove them.
Also fix some compiler warnings
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- Completely remove the nexp = nexp syntax in favour of nexp ==
nexp. All our existing specs have already switched over. As part of
this fix every test that used the old syntax, and update the
generated aarch64 specs
- Remove the `type when constraint` syntax. It just makes changing the
parser in any way really awkward.
- Change the syntax for declaring new types with multiple type
parameters from:
type foo('a : Type) ('n : Int), constraint = ...
to
type foo('a: Type, 'n: Int), constraint = ...
This makes type declarations mimic function declarations, and makes
the syntax for declaring types match the syntax for using types, as
foo is used as foo(type, nexp). None of our specifications use types
with multiple type parameters so this change doesn't actually break
anything, other than some tests. The brackets around the type
parameters are now mandatory.
- Experiment with splitting Type/Order type parameters from Int type
parameters in the parser.
Currently in a type bar(x, y, z) all of x, y, and z could be either
numeric expressions, orders, or types. This means that in the parser
we are severely restricted in what we can parse in numeric
expressions because everything has to be parseable as a type (atyp)
- it also means we can't introduce boolean type
variables/expressions or other minisail features (like removing
ticks from type variables!) because we are heavily constrained by
what we can parse unambigiously due to how these different type
parameters can be mixed and interleaved.
There is now experimental syntax: vector::<'o, 'a>('n) <-->
vector('n, 'o, 'a) which splits the type argument list into two
between Type/Order-polymorphic arguments and Int-polymorphic
arguments. The exact choice of delimiters isn't set in stone - ::<
and > match generics in Rust. The obvious choices of < and > / [ and
] are ambigious in various ways.
Using this syntax right now triggers a warning.
- Fix undefined behaviour in C compilation when concatenating a
0-length vector with a 64-length vector.
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- Fix pretty printing nested constraints
- Add flow typing for if condition then { throw exn }; ... blocks
- Add optimisations for bitvector concatenation in C
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Essentially all we have to do to make this work is introduce a member of
the Value type, V_attempted_read <reg>, which is returned whenever we
try to read a register value with allow_registers disabled. This defers
the failure from reading the register to the point where the register
value is used (simply because nothing knows how to deal with
V_attempted_read). However, if V_attempted_read is returned directly as
the result of evaluating an expression, then we can replace the
expression with a single direct register read. This optimises some
indirection in the ARM specification.
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Should hopefully fix memory leak in RISC-V.
Also adds an optimization pass that removes copying structs and allows
some structs to simply alias each other and avoid copying their
contents. This requires knowing certain things about the lifetimes of
the structs involved, as can't free the struct if another variable is
referencing it - therefore we conservatively only apply this
optimization for variables that are lifted outside function
definitions, and should therefore never get freed until the model
exits - however this may cause issues outside ARMv8, as there may be
cases where a struct can exist within a variant type (which are not
yet subject to this lifting optimisation), that would break these
assumptions - therefore this optimisation is only enabled with the
-Oexperimental flag.
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This optimisation re-uses variables if possible, rather than
allocating new ones.
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