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For example, in
type xlen : Int = 64
type xlenbits = bits(xlen)
rewrite the 'xlen' in the definition of 'xlenbits' to the constant 64 in
order to simplify Lem generation. In order to facilitate this, pass
through the global typing environment to the rewriting steps (in the AST
itself, type definitions don't carry annotations with environments).
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Allow a file sail.json in the same directory as the sail source file
which contains the ordering and options needed for sail files involved
in a specific ISA definition. I have an example for v8.5 in sail-arm.
The interactive Sail process running within emacs then knows about the
relationship between Sail files, so C-c C-l works for files in the ARM
spec. Also added a C-c C-x command to jump to a type error. Requires
yojson library to build interactive Sail.
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Can now use C-c C-s to start an interactive Sail process, C-c C-l to
load a file, and C-c C-q to kill the sail process. Type errors are
highlighted in the emacs buffer (like with merlin for OCaml) with a
tooltip for the type-error, as well as being displayed in the
minibuffer. Need to add a C-c C-x command like merlin to jump to the
error, and figure out how to handle multiple files nicely, as well as
hooking the save function like tuareg/merlin, but this is already
enough to make working with small examples quite a bit more pleasant.
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Work on improving the formatting and quality of error messages
When sail is invoked with sail -i, any type errors now drop the user
down to the interactive prompt, with the interactive environment being
the environment at the point the type error occurred, this means the
typechecker state can be interactively queried in the interpreter to help
diagnose type errors.
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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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* 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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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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- Propagate types more accurately to improve optimization on ANF
representation.
- Add a generic optimization pass to remove redundant variables that
simply alias other variables.
- Modify Sail interactive mode, so it can compile a specification with
the :compile command, view generated intermediate representation via
the :ir <function> command, and step-through the IR with :exec <exp>
(although this is very incomplete)
- Introduce a third bitvector representation, between fast
fixed-precision bitvectors, and variable length large
bitvectors. The bitvector types are now from most efficient to least
* CT_fbits for fixed precision, 64-bit or less bitvectors
* CT_sbits for 64-bit or less, variable length bitvectors
* CT_lbits for arbitrary variable length bitvectors
- Support for generating C code using CT_sbits is currently
incomplete, it just exists in the intermediate representation right
now.
- Include ctyp in AV_C_fragment, so we don't have to recompute it
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The main changes so far are:
* Allow markdown formatting in doc comments. We parse the markdown
using Omd, which is a OCaml library for parsing markdown. The nice
thing about this library is it's pure OCaml and has no dependencies
other the the stdlib. Incidentally it was also developed at OCaml
labs. Using markdown keeps our doc-comments from becoming latex
specfic, and having an actual parser is _much_ nicer than trying to
hackily process latex in doc-comments using OCamls somewhat sub-par
regex support.
* More sane conversion latex identifiers the main approach is to
convert Sail identifiers to lowerCamelCase, replacing numbers with
words, and then add a 'category' code based on the type of
identifier, so for a function we'd have fnlowerCamelCase and for
type synonym typelowerCamelCase etc. Because this transformation is
non-injective we keep track of identifiers we've generated so we end
up with identifierA, identifierB, identifierC when there are
collisions.
* Because we parse markdown in doc comments doc comments can use Sail
identifiers directly in hyperlinks, without having to care about how
they are name-mangled down into TeX compatible things.
* Allow directives to be passed through the compiler to
backends. There are various $latex directives that modify the latex
output. Most usefully there's a
$latex newcommand name markdown
directive that uses the markdown parser to generate latex
commands. An example of why this is useful is bellow. We can also use
$latex noref id
To suppress automatically inserting links to an identifier
* Refactor the latex generator to make the overall generation process
cleaner
* Work around the fact that some operating systems consider
case-sensitive file names to be a good thing
* Fix a bug where latex generation wouldn't occur unless the directory
specified by -o didn't exist
This isn't quite all the requested features for good CHERI
documentation, but new features should be much easier to add now.
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There is no Reporting_complex, so it's not clear what the basic is
intended to signify anyway.
Add a GitHub issue link to any err_unreachable errors (as they are all
bugs)
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Also allow options to be set via a pragma in Sail files
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Interpreter used a re-write (vector concat removal) that is dependent
on the vector_string_to_bit_list rewriting pass. This fixes the
interpreter to work without either vector concat removal, or turning
bitstrings into vector literals like [bitzero, bitzero, bitone]. This
has the upside of reducing the number of steps the interpreter needs
for working with bitvectors so should improve interpreter performance.
We also now test all the C compilation tests behave the same using the
interpreter. Currently the real number tests fail due to limitations
of Lem's rational library (this must be fixed in Lem). This required
supporting configuration registers in the interpreter. As such the
interpreter was refactored to more cleanly process registers when
building an initial global state. The functions are also collected
into the global state, which removes the need to search for them in
the AST every time a function call happens. This should not only
improve performance, but also removes the need to pass an AST into the
interpretation functions.
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Add additional well-formedness check when calling typing rules
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Changes to the interpreter to better support constant folding during
compilation mean it can now throw exceptions to the caller, allow the
caller to handle the error, rather than simply printing an error. This
broke the ARM interpreter test because exit() is handled by throwing
an Exit exception in the interpreter.
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optimizations.
Move the utility functions for graph generation and pretty printing of
intermediate representation instructions into a separate file,
bytecode_util.ml, by analogy with ast_util.ml.
Add an optimization pass that searches for specific patterns of struct
updates and removes uncessary copying of the structs involved. With
this optimisation pass the time taken for u-boot to run approx
57,000,000 instructions goes down from about 11-12 minutes to 8
minutes (about 120,000 IPS).
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We now store the location where type variables were bound, so we can
use this information when printing error messages.
Factor type errors out into type_error.ml. This means that
Type_check.check is now Type_error.check, as it previously it handled
wrapping the type_errors into reporting_basic
errors. Type_check.check' has therefore been renamed to
Type_check.check.
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Also fixes to C backend for compiling MIPS spec to C
- Fix an issue with const correctness in internal_vector_update
functions generated by C backend
- Add builtins for MIPS to sail.h
- Fix an issue where reg_deref didn't work when called on pointers to
large bitvectors, i.e. vectors containing references to large
bitfields as in the MIPS TLB code
- Various bug fixes and changes for running U-boot on ARM model,
including for interpreter and OCaml compilation.
- Fix memory leak issues and incorrect shadowing for foreach loops
- Update C header file. Fixes memory leak in memory read/write
builtins.
- Add aux constructor to ANF representation to hold environment
information.
- Fix undefined behavior caused by optimisation left shifting uint64_t
vectors 64 or more times. Unfortunately there's more issues because
the same happens for X >> 64 right shifts. It would make sense for
this to be zero, because that would guarantee the property that ((X
>> n) >> m) == (X >> (n + m)) but we probably need to do (X >> (n -
1) >> 1) in the optimisation to ensure that we don't cause
UB. Shifting by 63 and then by 1 is well-defined, but shifting by 64
in one go isn't according to the C standard. This issue with
right-shifts only occurs for zero-length vectors, so it's not a huge
deal, but it's still annoying.
- Add versions of print_bits and print_int that print to
stderr. Follows OCaml convention of print/prerr. Should make things
more explicit. Different backends had different ideas about where
print should output to, not every backend needs to have this
(e.g. theorem prover backends don't need to print) but having both
stderr and stdout seperate and clear is useful for executable models
(UART needs to be stdout, debug messages should be stderr).
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Added option -latex that outputs input to a latex document.
Added doc comments that can be attached to certain AST nodes - right now just valspecs and function clauses, e.g.
/*!
Documentation for main
*/
val main : unit -> unit
These comments are kept by the sail pretty printer, and used when generating latex
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Also updated some of the documentation in the sail source code
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This removes all type polymorphism, so we can generate optimized
bitvector code and compile to languages without parametric
polymorphism.
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This change allows the AST to be type-checked after sizeof
re-writing. It modifies the unification algorithm to better support
checking multiplication in constraints, by using division and modulus
SMT operators if they are defined.
Also made sure the typechecker doesn't re-introduce E_constraint
nodes, otherwise re-checking after sizeof-rewriting will re-introduce
constraint nodes.
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Currently doesn't try to compile to lem or use the MIPS spec
All the failing tests have been removed because I intend to handle
them differently - they were very fragile before because there was no
indication of why they failed, so as sail evolved they tended to start
failing for the wrong reasons and not testing what they were supposed
to.
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New testcase for bitfield syntax
Updated to work with latest lem and linksem
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* Changed comment syntax to C-style /* */ and //
* References to registers and mutable variables are never created
implicitly - a reference to a register or variable R is now created
via the expression "ref R". References are assigned like "(*Y) = X",
with "(*ref R) = X" being equivalent to "R = X". Everything is always
explicit now, which simplifies the logic in the typechecker. There's
also now an invariant that every id directly in a LEXP is mutable,
which is actually required for our rewriter steps to be sound.
* More flexible syntax for L-expressions to better support wierd
power-idioms, some syntax sugar means that:
X.GET(a, b, c) ==> _mod_GET(X, a, b, c)
X->GET(a, b, c) ==> _mod_GET(ref X, a, b, c)
for setters, this can be combined with the (still somewhat poorly
named) LEXP_memory construct, such that:
X->SET(a, b, c) = Y ==> _mod_SET(ref X, a, b, c, Y)
Currently I use the _mod_ prefix for these 'modifier' functions, but
we could omit that a la rust.
* The register bits typedef construct no longer exists in the
typechecker. This construct never worked consistently between backends
and inc/dec vectors, and it can be easily replaced by structs with
fancy setters/getters if need be. One can also use custom type operators to mimic the syntax, i.e.
type operator ... ('n : Int) ('m : Int) = slice('n, 'm)
struct cr = {
CR0 : 32 ... 35,
/* 32 : LT; 33 : GT; 34 : EQ; 35 : SO; */
CR1 : 36 ... 39,
/* 36 : FX; 37 : FEX; 38 : VX; 39 : OX; */
CR2 : 40 ... 43,
CR3 : 44 ... 47,
CR4 : 48 ... 51,
CR5 : 52 ... 55,
CR6 : 56 ... 59,
CR7 : 60 ... 63,
}
This greatly simplifies a lot of the logic in the typechecker, as it
means that E_field is no longer ambiguously overloaded between records
and register bit typedefs. This also makes writing semantics for these
constructs much simpler.
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Experimenting with porting riscv model to new typechecker
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Works with the vector branch of asl_parser
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Requires linenoise library (opam install linenoise) for readline
support. Use 'make isail' to build sail with interactive
support. Plain 'make sail' should work as before with no additional
dependencies.
Use 'sail -i <commands>' to run sail interactively, e.g.
sail -new_parser -i test/ocaml/prelude.sail test/ocaml/trycatch/tc.sail
then try some commands for typechecking and evaluation
sail> :t main
sail> main ()
Doesn't use the lem interpreter right now, instead has a small
operational semantics in src/interpreter.ml, but this is not very
complete and will be changed/removed.
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