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, 10 deletions

diff --git a/ia32/SelectOp.vp b/ia32/SelectOp.vp
index 74e3fbd7..bd3a4850 100644
--- a/ia32/SelectOp.vp
+++ b/ia32/SelectOp.vp
@@ -507,17 +507,19 @@ Nondetfunction addressing (chunk: memory_chunk) (e: expr) :=
   | _ => (Aindexed Int.zero, e:::Enil)
   end.
 
-(** ** Arguments of annotations *)
+(** ** Arguments of builtins *)
 
-Nondetfunction annot_arg (e: expr) :=
+Nondetfunction builtin_arg (e: expr) :=
   match e with
-  | Eop (Ointconst n) Enil => AA_int n
-  | Eop (Olea (Aglobal id ofs)) Enil => AA_addrglobal id ofs
-  | Eop (Olea (Ainstack ofs)) Enil => AA_addrstack ofs
+  | Eop (Ointconst n) Enil => BA_int n
+  | Eop (Olea (Aglobal id ofs)) Enil => BA_addrglobal id ofs
+  | Eop (Olea (Ainstack ofs)) Enil => BA_addrstack ofs
   | Eop Omakelong (Eop (Ointconst h) Enil ::: Eop (Ointconst l) Enil ::: Enil) =>
-        AA_long (Int64.ofwords h l)
-  | Eop Omakelong (h ::: l ::: Enil) => AA_longofwords (AA_base h) (AA_base l)
-  | Eload chunk (Aglobal id ofs) Enil => AA_loadglobal chunk id ofs
-  | Eload chunk (Ainstack ofs) Enil => AA_loadstack chunk ofs
-  | _ => AA_base e
+        BA_long (Int64.ofwords h l)
+  | Eop Omakelong (h ::: l ::: Enil) => BA_longofwords (BA h) (BA l)
+  | Eload chunk (Aglobal id ofs) Enil => BA_loadglobal chunk id ofs
+  | Eload chunk (Ainstack ofs) Enil => BA_loadstack chunk ofs
+  | _ => BA e
   end.
+
+Definition builtin_function_const (id: ident) := false.