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Now it just returns the actual arguments and a separate function
calculates the start index when required.
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Previously union types could have no-argument constructors, for
example the option type was previously:
union option ('a : Type) = {
Some : 'a,
None
}
Now every union constructor must have a type, so option becomes:
union option ('a : Type) = {
Some : 'a,
None : unit
}
The reason for this is because previously these two different types of
constructors where very different in the AST, constructors with
arguments were used the E_app AST node, and no-argument constructors
used the E_id node. This was particularly awkward, because it meant
that E_id nodes could have polymorphic types, i.e. every E_id node
that was also a union constructor had to be annotated with a type
quantifier, in constrast with all other identifiers that have
unquantified types. This became an issue when monomorphising types,
because the machinery for figuring out function instantiations can't
be applied to identifier nodes. The same story occurs in patterns,
where previously unions were split across P_id and P_app nodes - now
the P_app node alone is used solely for unions.
This is a breaking change because it changes the syntax for union
constructors - where as previously option was matched as:
function is_none opt = match opt {
Some(_) => false,
None => true
}
it is now matched as
function is_none opt = match opt {
Some(_) => false,
None() => true
}
note that constructor() is syntactic sugar for constructor(()), i.e. a
one argument constructor with unit as it's value. This is exactly the
same as for functions where a unit-function can be called as f() and
not as f(()). (This commit also makes exit() work consistently in the
same way) An attempt to pattern match a variable with the same name as
a union-constructor now gives an error as a way to guard against
mistakes made because of this change.
There is probably an argument for supporting the old syntax via some
syntactic sugar, as it is slightly prettier that way, but for now I
have chosen to keep the implementation as simple as possible.
The RISCV spec, ARM spec, and tests have been updated to account for
this change. Furthermore the option type can now be included from
$SAIL_DIR/lib/ using
$include <option.sail>
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Architecture-specific lemmas about concrete registers and types are generated
and written to a file <prefix>_lemmas.thy, generic lemmas are in the
theories *_extras.thy in lib/isabelle. In particular, State_extras contains
simplification lemmas about the lifting from prompt to state monad.
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Generate only one Lem model based on the prompt monad (instead of two models
with different monads), and add a lifting from prompt to state monad. Add some
Isabelle lemmas about the monad lifting.
Also drop the "_embed" and "_sequential" suffixes from names of generated
files.
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- Use simplified monad type (e.g., without the with_aux constructors that are
not needed by the shallow embedding).
- Add support for registers with arbitrary types (e.g., records, enumerations,
vectors of vectors). Instead of using bit lists as the common representation
of register values at the monad interface, use a register_value type that is
generated per spec as a union of all register types that occur in the spec.
Conversion functions between register_value and concrete types are generated.
- Use the same representation of register references as the state monad, in
preparation of rebasing the state monad onto the prompt monad.
- Split out those types from sail_impl_base.lem that are used by the shallow
embedding into a new module sail_instr_kinds.lem, and import that. Removing
the dependency on Sail_impl_base from the shallow embedding avoids name clashes
between the different monad types.
Not yet done:
- Support for reading/writing register slices. Currently, a rewriting pass
pushes register slices in l-expressions to the right-hand side, turning a
write to a register slice into a read-modify-write. For interfacing with the
concurreny model, we will want to be more precise than that (in particular
since some specs represent register files as big single registers containing a
vector of bitvectors).
- Lemmas about the conversion functions to/from register_value should be
generated automatically.
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