Lots of experimental changes on this branch

* 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.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/pretty_print_sail2.ml b/src/pretty_print_sail2.ml
index 22b6e9ee..930da39c 100644
--- a/src/pretty_print_sail2.ml
+++ b/src/pretty_print_sail2.ml
@@ -357,6 +357,7 @@ and doc_atomic_exp (E_aux (e_aux, _) as exp) =
      separate space [doc_atomic_exp exp; colon; doc_typ typ]
   | E_lit lit -> doc_lit lit
   | E_id id -> doc_id id
+  | E_ref id -> string "ref" ^^ space ^^ doc_id id
   | E_field (exp, id) -> doc_atomic_exp exp ^^ dot ^^ doc_id id
   | E_sizeof (Nexp_aux (Nexp_var kid, _)) -> doc_kid kid
   | E_sizeof nexp -> string "sizeof" ^^ parens (doc_nexp nexp)
@@ -395,6 +396,7 @@ and doc_lexp (LEXP_aux (l_aux, _) as lexp) =
 and doc_atomic_lexp (LEXP_aux (l_aux, _) as lexp) =
   match l_aux with
   | LEXP_id id -> doc_id id
+  | LEXP_deref exp -> lparen ^^ string "*" ^^ doc_atomic_exp exp ^^ rparen
   | LEXP_tup lexps -> lparen ^^ separate_map (comma ^^ space) doc_lexp lexps ^^ rparen
   | LEXP_field (lexp, id) -> doc_atomic_lexp lexp ^^ dot ^^ doc_id id
   | LEXP_vector (lexp, exp) -> doc_atomic_lexp lexp ^^ brackets (doc_exp exp)