Coloring: allow to exclude user-specified registers from allocation.

CPragmas (PPC/EABI only): add #pragma reserve_register


git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1314 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e

5 files changed, 131 insertions, 28 deletions

diff --git a/backend/Coloringaux.ml b/backend/Coloringaux.ml
index 9b657697..04cc1ee2 100644
--- a/backend/Coloringaux.ml
+++ b/backend/Coloringaux.ml
@@ -167,6 +167,42 @@ module IntPairSet = Set.Make(struct
     0
   end)
 
+(* Register classes *)
+
+let class_of_type = function Tint -> 0 | Tfloat -> 1
+
+let num_register_classes = 2
+
+let caller_save_registers = Array.make num_register_classes [||]
+
+let callee_save_registers = Array.make num_register_classes [||]
+
+let num_available_registers = Array.make num_register_classes 0
+
+let reserved_registers = ref ([]: mreg list)
+
+let rec remove_reserved = function
+  | [] -> []
+  | hd :: tl ->
+      if List.mem hd !reserved_registers
+      then remove_reserved tl
+      else hd :: remove_reserved tl
+
+let init_regs() =
+  caller_save_registers.(0) <-
+    Array.of_list (remove_reserved Conventions.int_caller_save_regs);
+  caller_save_registers.(1) <-
+    Array.of_list (remove_reserved Conventions.float_caller_save_regs);
+  callee_save_registers.(0) <-
+    Array.of_list (remove_reserved Conventions.int_callee_save_regs);
+  callee_save_registers.(1) <-
+    Array.of_list (remove_reserved Conventions.float_callee_save_regs);
+  for i = 0 to num_register_classes - 1 do
+    num_available_registers.(i) <-
+      Array.length caller_save_registers.(i)
+      + Array.length callee_save_registers.(i)
+  done
+
 (* \subsection{The George-Appel algorithm} *)
 
 (* Below is a straigthforward translation of the pseudo-code at the end
@@ -208,7 +244,7 @@ let nextRegIdent = ref 0
 
 (* Initialization of all global data structures *)
 
-let init() =
+let init_graph() =
   adjSet := IntPairSet.empty;
   nextRegIdent := 0;
   DLinkNode.clear simplifyWorklist;
@@ -268,28 +304,6 @@ let nodeMoves n =
 let moveRelated n =
   List.exists moveIsActiveOrWorklist n.movelist
 
-(* Register classes *)
-
-let class_of_type = function Tint -> 0 | Tfloat -> 1
-
-let num_register_classes = 2
-
-let caller_save_registers = [|
-  Array.of_list Conventions.int_caller_save_regs;
-  Array.of_list Conventions.float_caller_save_regs
-|]
-
-let callee_save_registers = [|
-  Array.of_list Conventions.int_callee_save_regs;
-  Array.of_list Conventions.float_callee_save_regs
-|]
-
-let num_available_registers = 
-  [| Array.length caller_save_registers.(0)
-           + Array.length callee_save_registers.(0);
-     Array.length caller_save_registers.(1)
-           + Array.length callee_save_registers.(1) |]
-
 (*i
 (* Check invariants *)
 
@@ -689,11 +703,12 @@ let spill_costs f = Hashtbl.create 7
 
 let graph_coloring (f: coq_function) (g: graph) (env: regenv) (regs: Regset.t)
                    : (reg -> loc) =
-  init();
+  init_regs();
+  init_graph();
   Array.fill start_points 0 num_register_classes 0;
   let mapping = build g env (spill_costs f) in
   List.iter assign_color (nodeOrder []);
-  init();
+  init_graph();  (* free data structures *)
   fun r ->
     try location_of_node (getAlias (Hashtbl.find mapping r))
     with Not_found -> R IT1 (* any location *)
diff --git a/backend/Coloringaux.mli b/backend/Coloringaux.mli
index c5070f20..7597c7ca 100644
--- a/backend/Coloringaux.mli
+++ b/backend/Coloringaux.mli
@@ -18,3 +18,5 @@ open InterfGraph
 
 val graph_coloring:
   coq_function -> graph -> regenv -> Regset.t -> (reg -> loc)
+
+val reserved_registers: Machregs.mreg list ref
diff --git a/powerpc/Machregsaux.ml b/powerpc/Machregsaux.ml
new file mode 100644
index 00000000..b729d100
--- /dev/null
+++ b/powerpc/Machregsaux.ml
@@ -0,0 +1,45 @@
+(* *********************************************************************)
+(*                                                                     *)
+(*              The Compcert verified compiler                         *)
+(*                                                                     *)
+(*          Xavier Leroy, INRIA Paris-Rocquencourt                     *)
+(*                                                                     *)
+(*  Copyright Institut National de Recherche en Informatique et en     *)
+(*  Automatique.  All rights reserved.  This file is distributed       *)
+(*  under the terms of the INRIA Non-Commercial License Agreement.     *)
+(*                                                                     *)
+(* *********************************************************************)
+
+(** Auxiliary functions on machine registers *)
+
+open Machregs
+
+let register_names = [
+  ("R3", R3);  ("R4", R4);  ("R5", R5);  ("R6", R6);
+  ("R7", R7);  ("R8", R8);  ("R9", R9);  ("R10", R10);
+  ("R14", R14); ("R15", R15); ("R16", R16);
+  ("R17", R17); ("R18", R18); ("R19", R19); ("R20", R20);
+  ("R21", R21); ("R22", R22); ("R23", R23); ("R24", R24);
+  ("R25", R25); ("R26", R26); ("R27", R27); ("R28", R28);
+  ("R29", R29); ("R30", R30); ("R31", R31);
+  ("F1", F1);  ("F2", F2);  ("F3", F3);  ("F4", F4);
+  ("F5", F5);  ("F6", F6);  ("F7", F7);  ("F8", F8);
+  ("F9", F9);  ("F10", F10); ("F14", F14); ("F15", F15);
+  ("F16", F16); ("F17", F17); ("F18", F18); ("F19", F19);
+  ("F20", F20); ("F21", F21); ("F22", F22); ("F23", F23);
+  ("F24", F24); ("F25", F25); ("F26", F26); ("F27", F27);
+  ("F28", F28); ("F29", F29); ("F30", F30); ("F31", F31);
+  ("R11", IT1); ("R0", IT2);
+  ("F11", FT1); ("F12", FT2); ("F0", FT3)
+]
+
+let register_by_name s =
+  try
+    Some(List.assoc (String.uppercase s) register_names)
+  with Not_found ->
+    None
+
+let can_reserve_register r =
+  List.mem r Conventions.int_callee_save_regs
+  || List.mem r Conventions.float_callee_save_regs
+
diff --git a/powerpc/Machregsaux.mli b/powerpc/Machregsaux.mli
new file mode 100644
index 00000000..6d819882
--- /dev/null
+++ b/powerpc/Machregsaux.mli
@@ -0,0 +1,16 @@
+(* *********************************************************************)
+(*                                                                     *)
+(*              The Compcert verified compiler                         *)
+(*                                                                     *)
+(*          Xavier Leroy, INRIA Paris-Rocquencourt                     *)
+(*                                                                     *)
+(*  Copyright Institut National de Recherche en Informatique et en     *)
+(*  Automatique.  All rights reserved.  This file is distributed       *)
+(*  under the terms of the INRIA Non-Commercial License Agreement.     *)
+(*                                                                     *)
+(* *********************************************************************)
+
+(** Auxiliary functions on machine registers *)
+
+val register_by_name: string -> Machregs.mreg option
+val can_reserve_register: Machregs.mreg -> bool
diff --git a/powerpc/eabi/CPragmas.ml b/powerpc/eabi/CPragmas.ml
index 4bb7786e..3104cc88 100644
--- a/powerpc/eabi/CPragmas.ml
+++ b/powerpc/eabi/CPragmas.ml
@@ -68,6 +68,8 @@ let _ =
                sec_near_access = false}
   ]
 
+(* #pragma section *)
+
 let process_section_pragma classname istring ustring addrmode accmode =
   let old_si =
     try Hashtbl.find section_table classname
@@ -85,6 +87,7 @@ let process_section_pragma classname istring ustring addrmode accmode =
         else (addrmode = "near-code") || (addrmode = "near-data") } in
   Hashtbl.add section_table classname si
 
+(* #pragma use_section *)
 
 let use_section_table : (AST.ident, section_info) Hashtbl.t =
   Hashtbl.create 51
@@ -122,6 +125,19 @@ let define_variable id d =
       if is_small !Clflags.option_small_data then "SDATA" else "DATA" in
   default_use_section id sect
 
+(* #pragma reserve_register *)
+
+let process_reserve_register_pragma name =
+  match Machregsaux.register_by_name name with
+  | None ->
+      C2Clight.error "unknown register in `reserve_register' pragma"
+  | Some r ->
+      if Machregsaux.can_reserve_register r then
+        Coloringaux.reserved_registers :=
+          r :: !Coloringaux.reserved_registers
+      else
+        C2Clight.error "cannot reserve this register (not a callee-save)"
+
 (* Parsing of pragmas using regexps *)
 
 let re_start_pragma_section = Str.regexp "section\\b"
@@ -144,6 +160,11 @@ let re_pragma_use_section = Str.regexp
 
 let re_split_idents = Str.regexp "[ \t,]+"
 
+let re_start_pragma_reserve_register = Str.regexp "reserve_register\\b"
+
+let re_pragma_reserve_register = Str.regexp
+  "reserve_register[ \t]+\\([A-Za-z0-9]+\\)"
+
 let process_pragma name =
   if Str.string_match re_pragma_section name 0 then begin
     process_section_pragma
@@ -162,9 +183,13 @@ let process_pragma name =
     if identlist = [] then C2Clight.warning "vacuous `use_section' pragma";
     List.iter (process_use_section_pragma classname) identlist;
     true
-  end else if Str.string_match re_start_pragma_use_section name 0 then
-    (C2Clight.error "ill-formed `use_section' pragma"; true)
-  else
+  end else if Str.string_match re_start_pragma_use_section name 0 then begin
+    C2Clight.error "ill-formed `use_section' pragma"; true
+  end else if Str.string_match re_pragma_reserve_register name 0 then begin
+    process_reserve_register_pragma (Str.matched_group 1 name); true
+  end else if Str.string_match re_start_pragma_reserve_register name 0 then begin
+    C2Clight.error "ill-formed `reserve_register' pragma"; true
+  end else
     false
 
 let initialize () =