Refactoring of builtins and annotations in the back-end.

Before, the back-end languages had distinct instructions
- Iannot for annotations, taking structured expressions (annot_arg)
  as arguments, and producing no results'
- Ibuiltin for other builtins, using simple pseudoregs/locations/registers
  as arguments and results.

This branch enriches Ibuiltin instructions so that they take structured
expressions (builtin_arg and builtin_res) as arguments and results.
This way,
- Annotations fit the general pattern of builtin functions,
  so Iannot instructions are removed.
- EF_vload_global and EF_vstore_global become useless, as the
  same optimization can be achieved by EF_vload/vstore taking
  a structured argument of the "address of global" kind.
- Better code can be generated for builtin_memcpy between stack locations,
  or volatile accesses to stack locations.

Finally, this commit also introduces a new kind of external function,
EF_debug, which is like EF_annot but produces no observable events.
It will be used later to transport debug info through the back-end,
without preventing optimizations.

1 files changed, 12 insertions, 9 deletions

diff --git a/backend/Inlining.v b/backend/Inlining.v
index 4f17d59c..98436bf5 100644
--- a/backend/Inlining.v
+++ b/backend/Inlining.v
@@ -203,15 +203,21 @@ Definition sop (ctx: context) (op: operation) :=
 Definition saddr (ctx: context) (addr: addressing) :=
   shift_stack_addressing (Int.repr ctx.(dstk)) addr.
 
-Fixpoint sannotarg (ctx: context) (a: annot_arg reg) : annot_arg reg :=
+Fixpoint sbuiltinarg (ctx: context) (a: builtin_arg reg) : builtin_arg reg :=
   match a with
-  | AA_base x => AA_base (sreg ctx x)
-  | AA_loadstack chunk ofs => AA_loadstack chunk (Int.add ofs (Int.repr ctx.(dstk)))
-  | AA_addrstack ofs => AA_addrstack (Int.add ofs (Int.repr ctx.(dstk)))
-  | AA_longofwords hi lo => AA_longofwords (sannotarg ctx hi) (sannotarg ctx lo)
+  | BA x => BA (sreg ctx x)
+  | BA_loadstack chunk ofs => BA_loadstack chunk (Int.add ofs (Int.repr ctx.(dstk)))
+  | BA_addrstack ofs => BA_addrstack (Int.add ofs (Int.repr ctx.(dstk)))
+  | BA_longofwords hi lo => BA_longofwords (sbuiltinarg ctx hi) (sbuiltinarg ctx lo)
   | _ => a
   end.
 
+Definition sbuiltinres (ctx: context) (a: builtin_res reg) : builtin_res reg :=
+  match a with
+  | BR x => BR (sreg ctx x)
+  | _    => BR_none
+  end.
+
 (** The initial context, used to copy the CFG of a toplevel function. *)
 
 Definition initcontext (dpc dreg nreg: positive) (sz: Z) :=
@@ -390,10 +396,7 @@ Definition expand_instr (ctx: context) (pc: node) (i: instruction): mon unit :=
       end          
   | Ibuiltin ef args res s =>
       set_instr (spc ctx pc)
-                (Ibuiltin ef (sregs ctx args) (sreg ctx res) (spc ctx s))
-  | Iannot ef args s =>
-      set_instr (spc ctx pc)
-                (Iannot ef (map (sannotarg ctx) args) (spc ctx s))
+                (Ibuiltin ef (map (sbuiltinarg ctx) args) (sbuiltinres ctx res) (spc ctx s))
   | Icond cond args s1 s2 =>
       set_instr (spc ctx pc)
                 (Icond cond (sregs ctx args) (spc ctx s1) (spc ctx s2))