ocaml/asmcomp/power/emit.mlp

(***********************************************************************)
(*                                                                     *)
(*                           Objective Caml                            *)
(*                                                                     *)
(*            Xavier Leroy, projet Cristal, INRIA Rocquencourt         *)
(*                                                                     *)
(*  Copyright 1996 Institut National de Recherche en Informatique et   *)
(*  en Automatique.  All rights reserved.  This file is distributed    *)
(*  under the terms of the Q Public License version 1.0.               *)
(*                                                                     *)
(***********************************************************************)

(* $Id$ *)

(* Emission of PowerPC assembly code *)

module StringSet = Set.Make(struct type t = string let compare = compare end)

open Misc
open Cmm
open Arch
open Proc
open Reg
open Mach
open Linearize
open Emitaux

(* Layout of the stack *)

(* In the TOC-based model:
     The bottom 24 bytes of the stack are reserved at all times
     for a standard linkage area.
     In this area, the word at offset +20 is used by glue code and others to
     save the TOC register.
     The bottom two words are used as temporaries and for trap frames.
     The stack is kept 8-aligned.
   In the absolute-address model:
     No reserved space at the bottom of the stack.
     The stack is kept 8-aligned. *)

let stack_linkage_area = if toc then 24 else 0
let trap_frame_size = if toc then 24 else 8

let stack_offset = ref 0

let frame_size () =
  let size =
    stack_linkage_area +                (* The bottom linkage area *)
    !stack_offset +                     (* Trap frame, outgoing parameters *)
    4 * num_stack_slots.(0) + 8 * num_stack_slots.(1) + (* Local variables *)
    (if !contains_calls then 4 else 0) in (* The return address *)
  Misc.align size 8

let slot_offset loc cls =
  match loc with
    Local n ->
      if cls = 0
      then stack_linkage_area + !stack_offset + num_stack_slots.(1) * 8 + n * 4
      else stack_linkage_area + !stack_offset + n * 8
  | Incoming n -> frame_size() + n
  | Outgoing n -> n

(* Output a symbol *)

let emit_symbol =
  match Config.system with
    "aix" | "elf" -> (fun s -> Emitaux.emit_symbol '.' s)
  | "rhapsody"    -> (fun s -> emit_char '_'; Emitaux.emit_symbol '$' s)
  | _ -> assert false

let emit_codesymbol s =
  if toc then emit_char '.';
  emit_symbol s

(* Output a label *)

let label_prefix =
  match Config.system with
    "aix" -> "L.."
  | "elf" -> ".L"
  | "rhapsody" -> "L"
  | _ -> assert false

let emit_label lbl =
  emit_string label_prefix; emit_int lbl

(* Section switching *)

let data_space =
  match Config.system with
    "aix" -> "	.csect  .data[RW]\n"
  | "elf" -> "	.section \".data\"\n"
  | "rhapsody" -> "	.data\n"
  | _ -> assert false

let code_space =
  match Config.system with
    "aix" -> "	.csect  .text[PR]\n"
  | "elf" -> "	.section \".text\"\n"
  | "rhapsody" -> "	.text\n"
  | _ -> assert false

let rodata_space =
  match Config.system with
    "aix" -> "	.csect  .data[RW]\n" (* ?? *)
  | "elf" -> "	.section \".rodata\"\n"
  | "rhapsody" -> "	.const\n"
  | _ -> assert false

(* Output a pseudo-register *)

let emit_reg r =
  match r.loc with
    Reg r -> emit_string (register_name r)
  | _ -> fatal_error "Emit.emit_reg"

let use_full_regnames = 
  Config.system = "rhapsody"

let emit_gpr r =
  if use_full_regnames then emit_char 'r';
  emit_int r

let emit_fpr r =
  if use_full_regnames then emit_char 'f';
  emit_int r

let emit_ccr r =
  if use_full_regnames then emit_string "cr";
  emit_int r

(* Output a stack reference *)

let emit_stack r =
  match r.loc with
    Stack s ->
      let ofs = slot_offset s (register_class r) in `{emit_int ofs}({emit_gpr 1})`
  | _ -> fatal_error "Emit.emit_stack"

(* Split a 32-bit integer constants in two 16-bit halves *)

let low n = n land 0xFFFF
let high n = n asr 16

let nativelow n = Nativeint.to_int n land 0xFFFF
let nativehigh n = Nativeint.to_int (Nativeint.shift_right n 16)

let is_immediate n =
  n <= 32767 && n >= -32768

let is_native_immediate n =
  n <= Nativeint.of_int 32767 && n >= Nativeint.of_int (-32768)

(* Output a "upper 16 bits" or "lower 16 bits" operator
   (for the absolute addressing mode) *)

let emit_upper emit_fun arg =
  match Config.system with
    "elf" ->
      emit_fun arg; emit_string "@ha"
  | "rhapsody" ->
      emit_string "ha16("; emit_fun arg; emit_string ")"
  | _ -> assert false

let emit_lower emit_fun arg =
  match Config.system with
    "elf" ->
      emit_fun arg; emit_string "@l"
  | "rhapsody" ->
      emit_string "lo16("; emit_fun arg; emit_string ")"
  | _ -> assert false

(* Output a load or store operation *)

let emit_symbol_offset (s, d) =
  emit_symbol s;
  if d > 0 then `+`;
  if d <> 0 then emit_int d

let emit_load_store instr addressing_mode addr n arg =
  match addressing_mode with
    Ibased(s, d) ->
      (* Only relevant in the absolute model *)
      `	addis	{emit_gpr 11}, 0, {emit_upper emit_symbol_offset (s,d)}\n`;
      `	{emit_string instr}	{emit_reg arg}, {emit_lower emit_symbol_offset (s,d)}({emit_gpr 11})\n`
  | Iindexed ofs ->
      if is_immediate ofs then
        `	{emit_string instr}	{emit_reg arg}, {emit_int ofs}({emit_reg addr.(n)})\n`
      else begin
        `	lis	{emit_gpr 0}, {emit_int(high ofs)}\n`;
        if low ofs <> 0 then
          `	ori	{emit_gpr 0}, {emit_gpr 0}, {emit_int(low ofs)}\n`;
        `	{emit_string instr}x	{emit_reg arg}, {emit_reg addr.(n)}, {emit_gpr 0}\n`
      end
  | Iindexed2 ->
      `	{emit_string instr}x	{emit_reg arg}, {emit_reg addr.(n)}, {emit_reg addr.(n+1)}\n`

(* After a comparison, extract the result as 0 or 1 *)

let emit_set_comp cmp res =
  `	mfcr	{emit_gpr 0}\n`;
  let bitnum =
    match cmp with
      Ceq | Cne -> 2
    | Cgt | Cle -> 1
    | Clt | Cge -> 0 in
`	rlwinm	{emit_reg res}, {emit_gpr 0}, {emit_int(bitnum+1)}, 31, 31\n`;
  begin match cmp with
    Cne | Cle | Cge -> `	xori	{emit_reg res}, {emit_reg res}, 1\n`
  | _ -> ()
  end

(* Record live pointers at call points *)

type frame_descr =
  { fd_lbl: int;                        (* Return address *)
    fd_frame_size: int;                 (* Size of stack frame *)
    fd_live_offset: int list }          (* Offsets/regs of live addresses *)

let frame_descriptors = ref([] : frame_descr list)

let record_frame live =
  let lbl = new_label() in
  let live_offset = ref [] in
  Reg.Set.iter
    (function
        {typ = Addr; loc = Reg r} ->
          live_offset := (r lsl 1) + 1 :: !live_offset
      | {typ = Addr; loc = Stack s} as reg ->
          live_offset := slot_offset s (register_class reg) :: !live_offset
      | _ -> ())
    live;
  frame_descriptors :=
    { fd_lbl = lbl;
      fd_frame_size = frame_size();
      fd_live_offset = !live_offset } :: !frame_descriptors;
  `{emit_label lbl}:`

let emit_frame fd =
  `	.long	{emit_label fd.fd_lbl} + 4\n`;
  `	.short	{emit_int fd.fd_frame_size}\n`;
  `	.short	{emit_int (List.length fd.fd_live_offset)}\n`;
  List.iter
    (fun n ->
      `	.short	{emit_int n}\n`)
    fd.fd_live_offset;
  `	.align	2\n`

(* Record symbols and floating-point constants (for the TOC model).
   These will go in the toc section. *)

let label_constant table constant =
  try
    Hashtbl.find table constant
  with Not_found ->
    let lbl = new_label() in
    Hashtbl.add table constant lbl;
    lbl

let symbol_constants = (Hashtbl.create 17 : (string, int) Hashtbl.t)
let float_constants = (Hashtbl.create 11 : (string, int) Hashtbl.t)

let label_symbol s = label_constant symbol_constants s
let label_float  s = label_constant float_constants s

let emit_symbol_constant symb lbl =
  `{emit_label lbl}:	.tc	{emit_symbol symb}[TC], {emit_symbol symb}\n`

let emit_float_constant float lbl =
  `{emit_label lbl}:	.tc	FD_`;
  for i = 0 to 7 do
    emit_printf "%02x" (Char.code (String.unsafe_get float i))
  done;
  `[TC], 0x`;
  for i = 0 to 3 do
    emit_printf "%02x" (Char.code (String.unsafe_get float i))
  done;
  `, 0x`;
  for i = 4 to 7 do
     emit_printf "%02x" (Char.code (String.unsafe_get float i))
  done;
  `\n`

(* Record floating-point literals (for the ELF model) *)

let float_literals = ref ([] : (string * int) list)

(* Record external C functions to be called in a position-independent way
   (for Rhapsody) *)

let pic_externals = (Config.system = "rhapsody")

let external_functions = ref StringSet.empty

let emit_external s =
  `	.non_lazy_symbol_pointer\n`;
  `L{emit_symbol s}$non_lazy_ptr:\n`;
  `	.indirect_symbol {emit_symbol s}\n`;
  `	.long	0\n`

(* Names for conditional branches after comparisons *)

let branch_for_comparison = function
    Ceq -> "beq" | Cne -> "bne"
  | Cle -> "ble" | Cgt -> "bgt"
  | Cge -> "bge" | Clt -> "blt"

let name_for_int_comparison = function
    Isigned cmp -> ("cmpw", branch_for_comparison cmp)
  | Iunsigned cmp -> ("cmplw", branch_for_comparison cmp)

(* Names for various instructions *)

let name_for_intop = function
    Iadd -> "add"
  | Imul -> "mullw"
  | Idiv -> if powerpc then "divw" else "divs"
  | Iand -> "and"
  | Ior  -> "or"
  | Ixor -> "xor"
  | Ilsl -> "slw"
  | Ilsr -> "srw"
  | Iasr -> "sraw"
  | _ -> Misc.fatal_error "Emit.Intop"

let name_for_intop_imm = function
    Iadd -> "addi"
  | Imul -> "mulli"
  | Iand -> "andi."
  | Ior  -> "ori"
  | Ixor -> "xori"
  | Ilsl -> "slwi"
  | Ilsr -> "srwi"
  | Iasr -> "srawi"
  | _ -> Misc.fatal_error "Emit.Intop_imm"

let name_for_floatop1 = function
    Inegf -> "fneg"
  | Iabsf -> "fabs"
  | _ -> Misc.fatal_error "Emit.Iopf1"

let name_for_floatop2 = function
    Iaddf -> "fadd"
  | Isubf -> "fsub"
  | Imulf -> "fmul"
  | Idivf -> "fdiv"
  | _ -> Misc.fatal_error "Emit.Iopf2"

let name_for_specific = function
    Imultaddf -> "fmadd"
  | Imultsubf -> "fmsub"

(* Name of current function *)
let function_name = ref ""
(* Entry point for tail recursive calls *)
let tailrec_entry_point = ref 0
(* Names of functions defined in the current file *)
let defined_functions = ref StringSet.empty
(* Label of glue code for calling the GC *)
let call_gc_label = ref 0
(* Label of jump table *)
let lbl_jumptbl = ref 0
(* List of all labels in jumptable (reverse order) *)
let jumptbl_entries = ref []
(* Number of jumptable entries *)
let num_jumptbl_entries = ref 0

(* Output the assembly code for an instruction *)

let rec emit_instr i dslot =
    match i.desc with
      Lend -> ()
    | Lop(Imove | Ispill | Ireload) ->
        let src = i.arg.(0) and dst = i.res.(0) in
        if src.loc <> dst.loc then begin
           match (src, dst) with
              {loc = Reg rs; typ = (Int | Addr)}, {loc = Reg rd} ->
                `	mr	{emit_reg dst}, {emit_reg src}\n`
            | {loc = Reg rs; typ = Float}, {loc = Reg rd; typ = Float} ->
                `	fmr	{emit_reg dst}, {emit_reg src}\n`
            | {loc = Reg rs; typ = (Int | Addr)}, {loc = Stack sd} ->
                `	stw	{emit_reg src}, {emit_stack dst}\n`
            | {loc = Reg rs; typ = Float}, {loc = Stack sd} ->
                `	stfd	{emit_reg src}, {emit_stack dst}\n`
            | {loc = Stack ss; typ = (Int | Addr)}, {loc = Reg rd} ->
                `	lwz	{emit_reg dst}, {emit_stack src}\n`
            | {loc = Stack ss; typ = Float}, {loc = Reg rd} ->
                `	lfd	{emit_reg dst}, {emit_stack src}\n`
            | (_, _) ->
                fatal_error "Emit: Imove"
        end
    | Lop(Iconst_int n) ->
        if is_native_immediate n then
          `	li	{emit_reg i.res.(0)}, {emit_nativeint n}\n`
        else begin
          `	lis	{emit_reg i.res.(0)}, {emit_int(nativehigh n)}\n`;
          if nativelow n <> 0 then
            `	ori	{emit_reg i.res.(0)}, {emit_reg i.res.(0)}, {emit_int(nativelow n)}\n`
        end
    | Lop(Iconst_float s) ->
        if toc then begin
          let repr = (Obj.magic (float_of_string s) : string) in
          let lbl = label_float repr in
          `	lfd	{emit_reg i.res.(0)}, {emit_label lbl}(2) # {emit_string s}\n`
        end else begin
          let lbl = new_label() in
          float_literals := (s, lbl) :: !float_literals;
          `	addis	{emit_gpr 11}, 0, {emit_upper emit_label lbl}\n`;
          `	lfd	{emit_reg i.res.(0)}, {emit_lower emit_label lbl}({emit_gpr 11})\n`
        end
    | Lop(Iconst_symbol s) ->
        if toc then begin
          let lbl = label_symbol s in
          `	lwz	{emit_reg i.res.(0)}, {emit_label lbl}(2) # {emit_symbol s}\n`
        end else begin
          `	addis	{emit_reg i.res.(0)}, 0, {emit_upper emit_symbol s}\n`;
          `	addi	{emit_reg i.res.(0)}, {emit_reg i.res.(0)}, {emit_lower emit_symbol s}\n`
        end
    | Lop(Icall_ind) ->
        if toc then begin
          `	lwz	0, 0({emit_reg i.arg.(0)})\n`;
          `	stw	2, 20(1)\n`;
          `	mtlr	0\n`;
          `	lwz	2, 4({emit_reg i.arg.(0)})\n`;
          record_frame i.live;
          `	blrl\n`;
          `	lwz	2, 20(1)\n`
        end else begin
          `	mtlr	{emit_reg i.arg.(0)}\n`;
          record_frame i.live;
          `	blrl\n`
        end
    | Lop(Icall_imm s) ->
        record_frame i.live;
        `	bl	{emit_codesymbol s}\n`;
        if toc && not (StringSet.mem s !defined_functions) then
          `	cror	31, 31, 31\n`      (* nop *)
    | Lop(Itailcall_ind) ->
        let n = frame_size() in
        if toc then begin
          `	lwz	0, 0({emit_reg i.arg.(0)})\n`;
          `	lwz	2, 4({emit_reg i.arg.(0)})\n`;
          `	mtctr	0\n`
        end else begin
          `	mtctr	{emit_reg i.arg.(0)}\n`
        end;
        if !contains_calls then begin
          `	lwz	{emit_gpr 11}, {emit_int(n - 4)}({emit_gpr 1})\n`;
          `	addi	{emit_gpr 1}, {emit_gpr 1}, {emit_int n}\n`;
          `	mtlr	{emit_gpr 11}\n`
        end else begin
          if n > 0 then
            `	addi	{emit_gpr 1}, {emit_gpr 1}, {emit_int n}\n`
        end;
        `	bctr\n`
    | Lop(Itailcall_imm s) ->
        if s = !function_name then
          `	b	{emit_label !tailrec_entry_point}\n`
        else if not toc || StringSet.mem s !defined_functions then begin
          let n = frame_size() in
          if !contains_calls then begin
            `	lwz	{emit_gpr 11}, {emit_int(n - 4)}({emit_gpr 1})\n`;
            `	addi	{emit_gpr 1}, {emit_gpr 1}, {emit_int n}\n`;
            `	mtlr	{emit_gpr 11}\n`
          end else begin
            if n > 0 then
              `	addi	{emit_gpr 1}, {emit_gpr 1}, {emit_int n}\n`
          end;
          `	b	{emit_codesymbol s}\n`
        end else begin
          (* Tailcalling a function that has a possibly different TOC
             is difficult, because the callee's TOC must be loaded in r2,
             but ours must not be stored in 20(r1), which would overwrite
             our caller's saved TOC. Hence we can't go through the
             standard glue code. Here, we just proceed as in tailcall_ind. *)
          let lbl = label_symbol s in
          let n = frame_size() in
          `	lwz	12, {emit_label lbl}(2) # {emit_symbol s}\n`;
          if !contains_calls then begin
            `	lwz	11, {emit_int(n - 4)}(1)\n`;
            `	lwz	0, 0(12)\n`;
            `	lwz	2, 4(12)\n`;
            `	mtctr	0\n`;
            `	addi	1, 1, {emit_int n}\n`;
            `	mtlr	11\n`
          end else begin
            `	lwz	0, 0(12)\n`;
            `	lwz	2, 4(12)\n`;
            `	mtctr	0\n`;
            if n > 0 then
              `	addi	1, 1, {emit_int n}\n`
          end;
          `	bctr\n`
        end
    | Lop(Iextcall(s, alloc)) ->
        if alloc then begin
          if toc then begin
            let lbl = label_symbol s in
            `	lwz	11, {emit_label lbl}(2) # {emit_symbol s}\n`
          end else if pic_externals then begin
            external_functions := StringSet.add s !external_functions;
            `	addis	{emit_gpr 11}, 0, ha16(L{emit_symbol s}$non_lazy_ptr)\n`;
            `	lwz	{emit_gpr 11}, lo16(L{emit_symbol s}$non_lazy_ptr)({emit_gpr 11})\n`
          end else begin
            `	addis	{emit_gpr 11}, 0, {emit_upper emit_symbol s}\n`;
            `	addi	{emit_gpr 11}, {emit_gpr 11}, {emit_lower emit_symbol s}\n`
          end;
          record_frame i.live;
          `	bl	{emit_codesymbol "caml_c_call"}\n`
        end else begin
          if pic_externals then begin
            external_functions := StringSet.add s !external_functions;
            `	addis	{emit_gpr 11}, 0, ha16(L{emit_symbol s}$non_lazy_ptr)\n`;
            `	lwz	{emit_gpr 11}, lo16(L{emit_symbol s}$non_lazy_ptr)({emit_gpr 11})\n`;
            `	mtlr	{emit_gpr 11}\n`;
            `	blrl\n`
          end else
          `	bl	{emit_codesymbol s}\n`
        end;
        if toc then
          `	cror	31, 31, 31\n`      (* nop *)
    | Lop(Istackoffset n) ->
        `	addi	{emit_gpr 1}, {emit_gpr 1}, {emit_int (-n)}\n`;
        stack_offset := !stack_offset + n
    | Lop(Iload(chunk, addr)) ->
        let loadinstr =
          match chunk with
            Byte_unsigned -> "lbz"
          | Byte_signed -> "lbz"
          | Sixteen_unsigned -> "lhz"
          | Sixteen_signed -> "lha"
          | Single -> "lfs"
          | Double | Double_u -> "lfd"
          | _ -> "lwz" in
        emit_load_store loadinstr addr i.arg 0 i.res.(0);
        if chunk = Byte_signed then
          `	extsb	{emit_reg i.res.(0)}, {emit_reg i.res.(0)}\n`
    | Lop(Istore(chunk, addr)) ->
        let storeinstr =
          match chunk with
            Byte_unsigned | Byte_signed -> "stb"
          | Sixteen_unsigned | Sixteen_signed -> "sth"
          | Single -> "stfs"
          | Double | Double_u -> "stfd"
          | _ -> "stw" in
        emit_load_store storeinstr addr i.arg 1 i.arg.(0)
    | Lop(Ialloc n) ->
        if !call_gc_label = 0 then call_gc_label := new_label();
        `	addi    {emit_gpr 31}, {emit_gpr 31}, {emit_int(-n)}\n`;
        `	cmplw	{emit_gpr 31}, {emit_gpr 30}\n`;
        `	addi	{emit_reg i.res.(0)}, {emit_gpr 31}, 4\n`;
        record_frame i.live;
        `	bltl	{emit_label !call_gc_label}\n`
    | Lop(Iintop Isub) ->               (* subf has swapped arguments *)
        (* Use subfc instead of subf for RS6000 compatibility. *)
        `	subfc	{emit_reg i.res.(0)}, {emit_reg i.arg.(1)}, {emit_reg i.arg.(0)}\n`
    | Lop(Iintop Imod) ->
        if powerpc then begin
          `	divw	{emit_gpr 0}, {emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`;
          `	mullw	{emit_gpr 0}, {emit_gpr 0}, {emit_reg i.arg.(1)}\n`;
          `	subfc	{emit_reg i.res.(0)}, {emit_gpr 0}, {emit_reg i.arg.(0)}\n`
        end else begin
          `	divs	{emit_gpr 0}, {emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`;
          `	mfmq	{emit_reg i.res.(0)}\n`
        end
    | Lop(Iintop(Icomp cmp)) ->
        begin match cmp with
          Isigned c ->
            `	cmpw	{emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`;
            emit_set_comp c i.res.(0)
        | Iunsigned c ->
            `	cmplw	{emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`;
            emit_set_comp c i.res.(0)
        end
    | Lop(Iintop Icheckbound) ->
        `	twlle   {emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`
    | Lop(Iintop op) ->
        let instr = name_for_intop op in
        `	{emit_string instr}	{emit_reg i.res.(0)}, {emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`
    | Lop(Iintop_imm(Isub, n)) ->
        `	addi	{emit_reg i.res.(0)}, {emit_reg i.arg.(0)}, {emit_int(-n)}\n`
    | Lop(Iintop_imm(Idiv, n)) ->       (* n is guaranteed to be a power of 2 *)
        let l = Misc.log2 n in
        `	srawi	{emit_reg i.res.(0)}, {emit_reg i.arg.(0)}, {emit_int l}\n`;
        `	addze	{emit_reg i.res.(0)}, {emit_reg i.res.(0)}\n` 
    | Lop(Iintop_imm(Imod, n)) ->       (* n is guaranteed to be a power of 2 *)
        let l = Misc.log2 n in
        `	srawi	{emit_gpr 0}, {emit_reg i.arg.(0)}, {emit_int l}\n`;
        `	addze	{emit_gpr 0}, {emit_gpr 0}\n`;
        `	slwi	{emit_gpr 0}, {emit_gpr 0}, {emit_int l}\n`;
        `	subfc	{emit_reg i.res.(0)}, {emit_gpr 0}, {emit_reg i.arg.(0)}\n` 
    | Lop(Iintop_imm(Icomp cmp, n)) ->
        begin match cmp with
          Isigned c ->
            `	cmpwi	{emit_reg i.arg.(0)}, {emit_int n}\n`;
            emit_set_comp c i.res.(0)
        | Iunsigned c ->
            `	cmplwi	{emit_reg i.arg.(0)}, {emit_int n}\n`;
            emit_set_comp c i.res.(0)
        end
    | Lop(Iintop_imm(Icheckbound, n)) ->
        `	twllei   {emit_reg i.arg.(0)}, {emit_int n}\n`
    | Lop(Iintop_imm(op, n)) ->
        let instr = name_for_intop_imm op in
        `	{emit_string instr}	{emit_reg i.res.(0)}, {emit_reg i.arg.(0)}, {emit_int n}\n`
    | Lop(Inegf | Iabsf as op) ->
        let instr = name_for_floatop1 op in
        `	{emit_string instr}	{emit_reg i.res.(0)}, {emit_reg i.arg.(0)}\n`
    | Lop(Iaddf | Isubf | Imulf | Idivf as op) ->
        let instr = name_for_floatop2 op in
        `	{emit_string instr}	{emit_reg i.res.(0)}, {emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`
    | Lop(Ifloatofint) ->
        if toc then begin
          let lbl = label_float "\067\048\000\000\128\000\000\000" in
          (* That string above represents 0x4330000080000000 *)
          `	lfd	0, {emit_label lbl}(2)\n`
        end else begin
          let lbl = new_label() in
          float_literals := ("4.503601774854144e15", lbl) :: !float_literals;
          (* That float above also represents 0x4330000080000000 *)
          `	addis	{emit_gpr 11}, 0, {emit_upper emit_label lbl}\n`;
          `	lfd	{emit_fpr 0}, {emit_lower emit_label lbl}({emit_gpr 11})\n`
        end;
        `	lis	{emit_gpr 0}, 0x4330\n`;
        `	stwu	{emit_gpr 0}, -8({emit_gpr 1})\n`;
        `	xoris	{emit_gpr 0}, {emit_reg i.arg.(0)}, 0x8000\n`;
        `	stw	{emit_gpr 0}, 4({emit_gpr 1})\n`;
        `	lfd	{emit_reg i.res.(0)}, 0({emit_gpr 1})\n`;
        `	addi	{emit_gpr 1}, {emit_gpr 1}, 8\n`;
        `	fsub	{emit_reg i.res.(0)}, {emit_reg i.res.(0)}, {emit_fpr 0}\n`
    | Lop(Iintoffloat) ->
        `	fctiwz	{emit_fpr 0}, {emit_reg i.arg.(0)}\n`;
        `	stfdu	{emit_fpr 0}, -8({emit_gpr 1})\n`;
        `	lwz	{emit_reg i.res.(0)}, 4({emit_gpr 1})\n`;
        `	addi	{emit_gpr 1}, {emit_gpr 1}, 8\n`
    | Lop(Ispecific sop) ->
        let instr = name_for_specific sop in
        `	{emit_string instr}	{emit_reg i.res.(0)}, {emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}, {emit_reg i.arg.(2)}\n`
    | Lreloadretaddr ->
        let n = frame_size() in
        `	lwz	{emit_gpr 11}, {emit_int(n - 4)}({emit_gpr 1})\n`;
        `	mtlr	{emit_gpr 11}\n`
    | Lreturn ->
        let n = frame_size() in
        if n > 0 then
          `	addi	{emit_gpr 1}, {emit_gpr 1}, {emit_int n}\n`;
        `	blr\n`
    | Llabel lbl ->
        `{emit_label lbl}:\n`
    | Lbranch lbl ->
        `	b	{emit_label lbl}\n`
    | Lcondbranch(tst, lbl) ->
        begin match tst with
          Itruetest ->
            `	cmpwi	{emit_reg i.arg.(0)}, 0\n`;
            emit_delay dslot;
            `	bne	{emit_label lbl}\n`
        | Ifalsetest ->
            `	cmpwi	{emit_reg i.arg.(0)}, 0\n`;
            emit_delay dslot;
            `	beq	{emit_label lbl}\n`
        | Iinttest cmp ->
            let (comp, branch) = name_for_int_comparison cmp in
            `	{emit_string comp}	{emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`;
            emit_delay dslot;
            `	{emit_string branch}	{emit_label lbl}\n`
        | Iinttest_imm(cmp, n) ->
            let (comp, branch) = name_for_int_comparison cmp in
            `	{emit_string comp}i	{emit_reg i.arg.(0)}, {emit_int n}\n`;
            emit_delay dslot;
            `	{emit_string branch}	{emit_label lbl}\n`
        | Ifloattest(cmp, neg) ->
            `	fcmpu	{emit_ccr 0}, {emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`;
            (* bit 0 = lt, bit 1 = gt, bit 2 = eq *)
            let (bitnum, negtst) =
              match cmp with
                Ceq -> (2, neg)
              | Cne -> (2, not neg)
              | Cle -> `	cror	3, 0, 2\n`; (* lt or eq *)
                       (3, neg)
              | Cgt -> (1, neg)
              | Cge -> `	cror	3, 1, 2\n`; (* gt or eq *)
                       (3, neg)
              | Clt -> (0, neg) in
            emit_delay dslot;
            if negtst
            then `	bf	{emit_int bitnum}, {emit_label lbl}\n`
            else `	bt	{emit_int bitnum}, {emit_label lbl}\n`
        | Ioddtest ->
            `	andi.	{emit_gpr 0}, {emit_reg i.arg.(0)}, 1\n`;
            emit_delay dslot;
            `	bne	{emit_label lbl}\n`
        | Ieventest ->
            `	andi.	{emit_gpr 0}, {emit_reg i.arg.(0)}, 1\n`;
            emit_delay dslot;
            `	beq	{emit_label lbl}\n`
        end
    | Lcondbranch3(lbl0, lbl1, lbl2) ->
        `	cmpwi	{emit_reg i.arg.(0)}, 1\n`;
        emit_delay dslot;
        begin match lbl0 with
          None -> ()
        | Some lbl -> `	blt	{emit_label lbl}\n`
        end;
        begin match lbl1 with
          None -> ()
        | Some lbl -> `	beq	{emit_label lbl}\n`
        end;
        begin match lbl2 with
          None -> ()
        | Some lbl -> `	bgt	{emit_label lbl}\n`
        end
    | Lswitch jumptbl ->
        if !lbl_jumptbl = 0 then lbl_jumptbl := new_label();
        if toc then begin
          `	lwz	11, {emit_label !lbl_jumptbl}(2)\n`
        end else begin
          `	addis	{emit_gpr 11}, 0, {emit_upper emit_label !lbl_jumptbl}\n`;
          `	addi	{emit_gpr 11}, {emit_gpr 11}, {emit_lower emit_label !lbl_jumptbl}\n`
        end;
        `	addi	{emit_gpr 0}, {emit_reg i.arg.(0)}, {emit_int !num_jumptbl_entries}\n`;
        `	slwi	{emit_gpr 0}, {emit_gpr 0}, 2\n`;
        `	lwzx	{emit_gpr 0}, {emit_gpr 11}, {emit_gpr 0}\n`;
        `	add	{emit_gpr 0}, {emit_gpr 11}, {emit_gpr 0}\n`;
        `	mtctr	{emit_gpr 0}\n`;
        `	bctr\n`;
        for i = 0 to Array.length jumptbl - 1 do
          jumptbl_entries := jumptbl.(i) :: !jumptbl_entries;
          incr num_jumptbl_entries
        done
    | Lsetuptrap lbl ->
        `	bl	{emit_label lbl}\n`
    | Lpushtrap ->
        stack_offset := !stack_offset + trap_frame_size;
        `	mflr	{emit_gpr 0}\n`;
        `	stwu	{emit_gpr 0}, -{emit_int trap_frame_size}({emit_gpr 1})\n`;
        `	stw	{emit_gpr 29}, 4({emit_gpr 1})\n`;
        if toc then
          `	stw	{emit_gpr 2}, 20({emit_gpr 1})\n`;
        `	mr	{emit_gpr 29}, {emit_gpr 1}\n`
    | Lpoptrap ->
        `	lwz	{emit_gpr 29}, 4({emit_gpr 1})\n`;
        `	addi	{emit_gpr 1}, {emit_gpr 1}, {emit_int trap_frame_size}\n`;
        stack_offset := !stack_offset - trap_frame_size
    | Lraise ->
        `	lwz	{emit_gpr 0}, 0({emit_gpr 29})\n`;
        `	mr	{emit_gpr 1}, {emit_gpr 29}\n`;
        `	mtlr	{emit_gpr 0}\n`;
        `	lwz	{emit_gpr 29}, 4({emit_gpr 1})\n`;
        if toc then
          `	lwz	{emit_gpr 2}, 20({emit_gpr 1})\n`;
        `	addi	{emit_gpr 1}, {emit_gpr 1}, {emit_int trap_frame_size}\n\n`;
        `	blr\n`

and emit_delay = function
    None -> ()
  | Some i -> emit_instr i None

(* Checks if a pseudo-instruction expands to instructions
   that do not branch and do not affect CR0 nor R12. *)

let is_simple_instr i =
  match i.desc with
    Lop op ->
      begin match op with
        Icall_imm _ | Icall_ind | Itailcall_imm _ | Itailcall_ind |
        Iextcall(_, _) -> false
      | Ialloc(_) -> false
      | Iintop(Icomp _) -> false
      | Iintop_imm(Iand, _) -> false
      | Iintop_imm(Icomp _, _) -> false
      | _ -> true
      end
  | Lreloadretaddr -> true
  | _ -> false

let no_interference res arg =
  try
    for i = 0 to Array.length arg - 1 do
      for j = 0 to Array.length res - 1 do
        if arg.(i).loc = res.(j).loc then raise Exit
      done
    done;
    true
  with Exit ->
    false

(* Emit a sequence of instructions, trying to fill delay slots for branches *)

let rec emit_all i =
  match i with
    {desc = Lend} -> ()
  | {next = {desc = (Lcondbranch(_, _) | Lcondbranch3(_, _, _))}}
    when is_simple_instr i & no_interference i.res i.next.arg ->
      emit_instr i.next (Some i);
      emit_all i.next.next
  | _ ->
      emit_instr i None;
      emit_all i.next

(* Emission of a function declaration *)

let fundecl fundecl =
  function_name := fundecl.fun_name;
  defined_functions := StringSet.add fundecl.fun_name !defined_functions;
  tailrec_entry_point := new_label();
  stack_offset := 0;
  call_gc_label := 0;
  float_literals := [];
  `	.globl	{emit_symbol fundecl.fun_name}\n`;
  begin match Config.system with
    "aix" ->
      `	.globl	.{emit_symbol fundecl.fun_name}\n`;
      `	.csect	{emit_symbol fundecl.fun_name}[DS]\n`;
      `{emit_symbol fundecl.fun_name}:\n`;
      `	.long	.{emit_symbol fundecl.fun_name}, TOC[tc0], 0\n`
  | "elf" ->
      `	.type	{emit_symbol fundecl.fun_name}, @function\n`
  | _ -> ()
  end;
  emit_string code_space;
  `	.align	2\n`;
  `{emit_codesymbol fundecl.fun_name}:\n`;
  let n = frame_size() in
  if !contains_calls then begin
    `	mflr	{emit_gpr 0}\n`;
    `	addi	{emit_gpr 1}, {emit_gpr 1}, {emit_int(-n)}\n`;
    `	stw	{emit_gpr 0}, {emit_int(n - 4)}({emit_gpr 1})\n`
  end else begin
    if n > 0 then
      `	addi	{emit_gpr 1}, {emit_gpr 1}, {emit_int(-n)}\n`
  end;
  `{emit_label !tailrec_entry_point}:\n`;
  emit_all fundecl.fun_body;
  (* Emit the glue code to call the GC *)
  if !call_gc_label > 0 then begin
    `{emit_label !call_gc_label}:\n`;
    if toc then begin
      `	mflr	0\n`;                  (* Save return address in r0 *)
      `	bl	.caml_call_gc\n`;
      `	cror	31, 31, 31\n`;         (* nop *)
      `	blr\n`                         (* Will re-execute the allocation *)
    end else begin
      `	b	{emit_symbol "caml_call_gc"}\n`
    end
  end;
  (* Emit the floating-point literals *)
  if !float_literals <> [] then begin
    emit_string rodata_space;
    `	.align	3\n`;
    List.iter
      (fun (f, lbl) ->
        `{emit_label lbl}:	.double	0d{emit_string f}\n`)
      !float_literals
  end

(* Emission of data *)

let declare_global_data s =
  `	.globl	{emit_symbol s}\n`;
  if Config.system = "elf" then
    `	.type	{emit_symbol s}, @object\n`

let emit_item = function
    Cdefine_symbol s ->
      `{emit_symbol s}:\n`;
      declare_global_data s
  | Cdefine_label lbl ->
      `{emit_label (lbl + 100000)}:\n`
  | Cint8 n ->
      `	.byte	{emit_int n}\n`
  | Cint16 n ->
      `	.short	{emit_int n}\n`
  | Cint32 n ->
      `	.long	{emit_nativeint n}\n`
  | Cint n ->
      `	.long	{emit_nativeint n}\n`
  | Csingle f ->
      `	.float	0d{emit_string f}\n`
  | Cdouble f ->
      `	.double	0d{emit_string f}\n`
  | Csymbol_address s ->
      `	.long	{emit_symbol s}\n`
  | Clabel_address lbl ->
      `	.long	{emit_label (lbl + 100000)}\n`
  | Cstring s ->
      emit_bytes_directive "	.byte	" s
  | Cskip n ->
      if n > 0 then `	.space	{emit_int n}\n`
  | Calign n ->
      `	.align	{emit_int (Misc.log2 n)}\n`

let data l =
  emit_string data_space;
  List.iter emit_item l

(* Beginning / end of an assembly file *)

let begin_assembly() =
  Hashtbl.clear symbol_constants;
  Hashtbl.clear float_constants;
  defined_functions := StringSet.empty;
  external_functions := StringSet.empty;
  num_jumptbl_entries := 0;
  jumptbl_entries := [];
  lbl_jumptbl := 0;
  (* Emit the beginning of the segments *)
  let lbl_begin = Compilenv.current_unit_name() ^ "_data_begin" in
  emit_string data_space;
  declare_global_data lbl_begin;
  `{emit_symbol lbl_begin}:\n`;
  let lbl_begin = Compilenv.current_unit_name() ^ "_code_begin" in
  emit_string code_space;
  declare_global_data lbl_begin;
  `{emit_symbol lbl_begin}:\n`

let end_assembly() =
  (* Emit the jump table *)
  if !num_jumptbl_entries > 0 then begin
    let lbl_tbl =
      if toc then begin
        let lbl_tbl = new_label() in
        `	.toc\n`;
        `{emit_label !lbl_jumptbl}:	.tc	{emit_label lbl_tbl}[TC], {emit_label lbl_tbl}\n`;
        lbl_tbl
      end else !lbl_jumptbl in
    emit_string code_space;
    `{emit_label lbl_tbl}:\n`;
    List.iter
      (fun lbl -> `	.long	{emit_label lbl} - {emit_label lbl_tbl}\n`)
      (List.rev !jumptbl_entries);
    jumptbl_entries := []
  end;
  if toc then begin
    (* Emit the table of constants *)
    `	.toc\n`;
    Hashtbl.iter emit_symbol_constant symbol_constants;
    Hashtbl.iter emit_float_constant float_constants
  end;
  if pic_externals then
    (* Emit the pointers to external functions *)
    StringSet.iter emit_external !external_functions;
  (* Emit the end of the segments *)
  emit_string code_space;
  let lbl_end = Compilenv.current_unit_name() ^ "_code_end" in
  declare_global_data lbl_end;
  `{emit_symbol lbl_end}:\n`;
  emit_string data_space;
  let lbl_end = Compilenv.current_unit_name() ^ "_data_end" in
  declare_global_data lbl_end;
  `{emit_symbol lbl_end}:\n`;
  `	.long	0\n`;
  (* Emit the frame descriptors *)
  emit_string rodata_space;
  let lbl = Compilenv.current_unit_name() ^ "_frametable" in
  declare_global_data lbl;
  `{emit_symbol lbl}:\n`;
  `	.long	{emit_int (List.length !frame_descriptors)}\n`;
  List.iter emit_frame !frame_descriptors;
  frame_descriptors := []