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/ast_util.ml b/src/ast_util.ml
index 4407b7f1..7e966bf2 100644
--- a/src/ast_util.ml
+++ b/src/ast_util.ml
@@ -413,6 +413,7 @@ and map_letbind_annot_aux f = function
 and map_lexp_annot f (LEXP_aux (lexp, annot)) = LEXP_aux (map_lexp_annot_aux f lexp, f annot)
 and map_lexp_annot_aux f = function
   | LEXP_id id -> LEXP_id id
+  | LEXP_deref exp -> LEXP_deref (map_exp_annot f exp)
   | LEXP_memory (id, exps) -> LEXP_memory (id, List.map (map_exp_annot f) exps)
   | LEXP_cast (typ, id) -> LEXP_cast (typ, id)
   | LEXP_tup lexps -> LEXP_tup (List.map (map_lexp_annot f) lexps)
@@ -660,6 +661,7 @@ and string_of_pat (P_aux (pat, l)) =
 and string_of_lexp (LEXP_aux (lexp, _)) =
   match lexp with
   | LEXP_id v -> string_of_id v
+  | LEXP_deref exp -> "*(" ^ string_of_exp exp ^ ")"
   | LEXP_cast (typ, v) -> "(" ^ string_of_typ typ ^ ") " ^ string_of_id v
   | LEXP_tup lexps -> "(" ^ string_of_list ", " string_of_lexp lexps ^ ")"
   | LEXP_vector (lexp, exp) -> string_of_lexp lexp ^ "[" ^ string_of_exp exp ^ "]"