zSystem port: revise addressing modes

- Ibased addressing is removed.  The code generated for an Ibased load/store is no better than the code we generate for an Iindexed load/store preceded by a Iconst_symbol instruction that loads the address of the global variable.  Plus, we now get opportunities for CSE of the Iconst_symbol.

- Iindexed2 addressing is extended with a constant displacement, to take full advantage of the ofs(%r1, %r2) addressing mode of the processor.

- During selection instruction, make sure that the constant displacement of Iindexed and Iindexed2 is within range (20 bit signed).

asmcomp/s390x/arch.ml

@@ -35,17 +35,13 @@ type specific_operation =
 (* Addressing modes *)
 
 type addressing_mode =
-    Ibased of string * int              (* symbol + displ *)
   | Iindexed of int                     (* reg + displ *)
-  | Iindexed2                           (* reg + reg *)
+  | Iindexed2 of int                    (* reg + reg + displ *)
 
 (* Sizes, endianness *)
 
 let big_endian = true
 
-let s390x =
-  match Config.model with "s390x" -> true | _ -> false
-
 let size_addr = 8
 let size_int = size_addr
 let size_float = 8
@@ -62,27 +58,23 @@ let identity_addressing = Iindexed 0
 
 let offset_addressing addr delta =
   match addr with
-    Ibased(s, n) -> Ibased(s, n + delta)
   | Iindexed n -> Iindexed(n + delta)
-  | Iindexed2 -> assert false
+  | Iindexed2 n -> Iindexed2(n + delta)
 
 let num_args_addressing = function
-    Ibased(s, n) -> 0
   | Iindexed n -> 1
-  | Iindexed2 -> 2
+  | Iindexed2 n -> 2
 
 (* Printing operations and addressing modes *)
 
 let print_addressing printreg addr ppf arg =
   match addr with
-  | Ibased(s, n) ->
-      let idx = if n <> 0 then Printf.sprintf " + %i" n else "" in
-      fprintf ppf "\"%s\"%s" s idx
   | Iindexed n ->
       let idx = if n <> 0 then Printf.sprintf " + %i" n else "" in
       fprintf ppf "%a%s" printreg arg.(0) idx
-  | Iindexed2 ->
-      fprintf ppf "%a + %a" printreg arg.(0) printreg arg.(1)
+  | Iindexed2 n ->
+      let idx = if n <> 0 then Printf.sprintf " + %i" n else "" in
+      fprintf ppf "%a + %a%s" printreg arg.(0) printreg arg.(1) idx
 
 let print_specific_operation printreg op ppf arg =
   match op with

asmcomp/s390x/emit.mlp

@@ -112,32 +112,16 @@ let emit_load_store instr addressing_mode addr n arg =
 if (compare instr "stey") = 0 then begin
   `	ledbr	{emit_fpr 15}, {emit_reg arg}\n`;
   match addressing_mode with
-    Ibased(s, d) ->
-    if !pic_code then begin
-      `	lg	{emit_gpr 1}, {emit_symbol s}@GOT({emit_gpr 12})\n`;
-      `	{emit_string instr}	{emit_fpr 15},{emit_int d}({emit_gpr 1})\n`
-    end else begin
-      `	larl	{emit_gpr 1}, {emit_symbol_offset (s,d)}\n`;
-      `	{emit_string instr}	{emit_fpr 15},0({emit_gpr 1})\n`
-    end
   | Iindexed ofs ->
       `	{emit_string instr}	{emit_fpr 15}, {emit_int ofs}({emit_reg addr.(n)})\n`
-  | Iindexed2 ->
-      `	{emit_string instr}	{emit_fpr 15}, 0({emit_reg addr.(n)},{emit_reg addr.(n+1)})\n`
+  | Iindexed2 ofs ->
+      `	{emit_string instr}	{emit_fpr 15}, {emit_int ofs}({emit_reg addr.(n)},{emit_reg addr.(n+1)})\n`
 end else begin
   match addressing_mode with
-    Ibased(s, d) ->
-    if !pic_code then begin
-      `	lg	{emit_gpr 1}, {emit_symbol s}@GOT({emit_gpr 12})\n`;
-      `	{emit_string instr}	{emit_reg arg},{emit_int d}({emit_gpr 1})\n`
-    end else begin
-      `	larl	{emit_gpr 1}, {emit_symbol_offset (s,d)}\n`;
-      `	{emit_string instr}	{emit_reg arg},0({emit_gpr 1})\n`
-    end
   | Iindexed ofs ->
       `	{emit_string instr}	{emit_reg arg}, {emit_int ofs}({emit_reg addr.(n)})\n`
-  | Iindexed2 ->
-      `	{emit_string instr}	{emit_reg arg}, 0({emit_reg addr.(n)},{emit_reg addr.(n+1)})\n`
+  | Iindexed2 ofs ->
+      `	{emit_string instr}	{emit_reg arg}, {emit_int ofs}({emit_reg addr.(n)},{emit_reg addr.(n+1)})\n`
 end
 
 (* After a comparison, extract the result as 0 or 1 *)

asmcomp/s390x/scheduling.ml

@@ -46,8 +46,6 @@ method reload_retaddr_latency = 12
 
 method oper_issue_cycles = function
     Iconst_float _ | Iconst_symbol _ -> 2
-  | Iload(_, Ibased(_, _)) -> 2
-  | Istore(_, Ibased(_, _), _) -> 2
   | Ialloc _ -> 4
   | Iintop(Imod) -> 40 (* assuming full stall *)
   | Iintop(Icomp _) -> 4

asmcomp/s390x/selection.ml

@@ -23,18 +23,15 @@ open Mach
 exception Use_default
 
 type addressing_expr =
-    Asymbol of string
   | Alinear of expression
   | Aadd of expression * expression
 
 let rec select_addr = function
-    Cconst_symbol s ->
-      (Asymbol s, 0)
-  | Cop((Caddi | Cadda), [arg; Cconst_int m]) ->
+  | Cop((Caddi | Cadda | Caddv), [arg; Cconst_int m]) ->
       let (a, n) = select_addr arg in (a, n + m)
-  | Cop((Caddi | Cadda), [Cconst_int m; arg]) ->
+  | Cop((Caddi | Cadda | Caddv), [Cconst_int m; arg]) ->
       let (a, n) = select_addr arg in (a, n + m)
-  | Cop((Caddi | Cadda), [arg1; arg2]) ->
+  | Cop((Caddi | Cadda | Caddv), [arg1; arg2]) ->
       begin match (select_addr arg1, select_addr arg2) with
           ((Alinear e1, n1), (Alinear e2, n2)) ->
               (Aadd(e1, e2), n1 + n2)
@@ -65,15 +62,14 @@ inherit Selectgen.selector_generic as super
 method is_immediate n = (n <= 2147483647) && (n >= -2147483648)
 
 method select_addressing chunk exp =
-  match select_addr exp with
-    (Asymbol s, d) ->
-      (Ibased(s, d), Ctuple [])
-  | (Alinear e, d) ->
-      (Iindexed d, e)
-  | (Aadd(e1, e2), d) ->
-      if d = 0
-      then (Iindexed2, Ctuple[e1; e2])
-      else (Iindexed d, Cop(Cadda, [e1; e2]))
+  let (a, d) = select_addr exp in
+  (* 20-bit signed displacement *)
+  if d < 0x80000 && d >= -0x80000 then begin
+    match a with
+    | Alinear e -> (Iindexed d, e)
+    | Aadd(e1, e2) -> (Iindexed2 d, Ctuple [e1; e2])
+  end else
+    (Iindexed 0, exp)
 
 method! select_operation op args =
   match (op, args) with