ocaml/asmcomp/amd64/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 Intel 386 assembly code *)

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

(* Tradeoff between code size and code speed *)

let fastcode_flag = ref true

let stack_offset = ref 0

(* Layout of the stack frame *)

let frame_required () =
  !contains_calls || num_stack_slots.(0) > 0 || num_stack_slots.(1) > 0

let frame_size () =                     (* includes return address *)
  let sz = (!stack_offset + 8 * (num_stack_slots.(0) + num_stack_slots.(1)) + 8)
  in Misc.align sz 16

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

(* Symbols *)

let emit_symbol s =
  Emitaux.emit_symbol '$' s

(* Output a label *)

let emit_label lbl =
  emit_string ".L"; emit_int lbl

(* Output a .align directive. *)

let emit_align n =
  `	.align	{emit_int n}\n`
  
let emit_Llabel fallthrough lbl =
  if not fallthrough && !fastcode_flag then emit_align 4;
  emit_label lbl
  
(* Output a pseudo-register *)

let emit_reg = function
    { loc = Reg r } ->
      emit_string (register_name r)
  | { loc = Stack s } as r ->
      let ofs = slot_offset s (register_class r) in
      `{emit_int ofs}(%rsp)`
  | { loc = Unknown } ->
      assert false

(* Output a reference to the lower 8, 16 or 32 bits of a register *)

let reg_low_8_name =
  [| "%al"; "%bl"; "%dil"; "%sil"; "%dl"; "%cl"; "%r8b"; "%r9b"; 
     "%r10b"; "%r11b"; "%bpl"; "%r12b"; "%r13b" |]
let reg_low_16_name =
  [| "%ax"; "%bx"; "%di"; "%si"; "%dx"; "%cx"; "%r8w"; "%r9w"; 
     "%r10w"; "%r11w"; "%bp"; "%r12w"; "%r13w" |]
let reg_low_32_name =
  [| "%eax"; "%ebx"; "%edi"; "%esi"; "%edx"; "%ecx"; "%r8d"; "%r9d"; 
     "%r10d"; "%r11d"; "%ebp"; "%r12d"; "%r13d" |]

let emit_subreg tbl r =
  match r.loc with
    Reg r when r < 13 ->
      emit_string tbl.(r)
  | Stack s ->
      let ofs = slot_offset s (register_class r) in
      `{emit_int ofs}(%rsp)`
  | _ ->
      assert false

let emit_reg8 r = emit_subreg reg_low_8_name r
let emit_reg16 r = emit_subreg reg_low_16_name r
let emit_reg32 r = emit_subreg reg_low_32_name r

(* Output an addressing mode *)

let emit_addressing addr r n =
  match addr with
    Ibased(s, d) ->
      `{emit_symbol s}`;
      if d <> 0 then ` + {emit_int d}`;
      `(%rip)`
  | Iindexed d ->
      if d <> 0 then emit_int d;
      `({emit_reg r.(n)})`
  | Iindexed2 d ->
      if d <> 0 then emit_int d;
      `({emit_reg r.(n)}, {emit_reg r.(n+1)})`
  | Iscaled(2, d) ->
      if d <> 0 then emit_int d;
      `({emit_reg r.(n)}, {emit_reg r.(n)})`
  | Iscaled(scale, d) ->
      if d <> 0 then emit_int d;
      `(, {emit_reg r.(n)}, {emit_int scale})`
  | Iindexed2scaled(scale, d) ->
      if d <> 0 then emit_int d;
      `({emit_reg r.(n)}, {emit_reg r.(n+1)}, {emit_int scale})`

(* 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_label 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;
  lbl

let record_frame live =
  let lbl = record_frame_label live in `{emit_label lbl}:\n`

let emit_frame fd =
  `	.quad	{emit_label fd.fd_lbl}\n`;
  `	.word	{emit_int fd.fd_frame_size}\n`;
  `	.word	{emit_int (List.length fd.fd_live_offset)}\n`;
  List.iter
    (fun n ->
      `	.word	{emit_int n}\n`)
    fd.fd_live_offset;
  emit_align 8

(* Record calls to the GC -- we've moved them out of the way *)

type gc_call =
  { gc_lbl: label;                      (* Entry label *)
    gc_return_lbl: label;               (* Where to branch after GC *)
    gc_frame: label }                   (* Label of frame descriptor *)

let call_gc_sites = ref ([] : gc_call list)

let emit_call_gc gc =
  `{emit_label gc.gc_lbl}:	call	{emit_symbol "caml_call_gc"}\n`;
  `{emit_label gc.gc_frame}:	jmp	{emit_label gc.gc_return_lbl}\n`

(* Names for instructions *)

let instr_for_intop = function
    Iadd -> "addq"
  | Isub -> "subq"
  | Imul -> "imulq"
  | Iand -> "andq"
  | Ior -> "orq"
  | Ixor -> "xorq"
  | Ilsl -> "salq"
  | Ilsr -> "shrq"
  | Iasr -> "sarq"
  | _ -> assert false

let instr_for_floatop = function
    Iaddf -> "addsd"
  | Isubf -> "subsd"
  | Imulf -> "mulsd"
  | Idivf -> "divsd"
  | _ -> assert false

let instr_for_floatarithmem = function
    Ifloatadd -> "addsd"
  | Ifloatsub -> "subsd"
  | Ifloatmul -> "mulsd"
  | Ifloatdiv -> "divsd"

let name_for_cond_branch = function
    Isigned Ceq -> "e"     | Isigned Cne -> "ne"
  | Isigned Cle -> "le"     | Isigned Cgt -> "g"
  | Isigned Clt -> "l"     | Isigned Cge -> "ge"
  | Iunsigned Ceq -> "e"   | Iunsigned Cne -> "ne"
  | Iunsigned Cle -> "be"  | Iunsigned Cgt -> "a"
  | Iunsigned Clt -> "b"  | Iunsigned Cge -> "ae"
    
(* Output an = 0 or <> 0 test. *)

let output_test_zero arg =
  match arg.loc with
    Reg r -> `	testq	{emit_reg arg}, {emit_reg arg}\n`
  | _     -> `	cmpq	$0, {emit_reg arg}\n`

(* Output a floating-point compare and branch *)

let emit_float_test cmp neg arg lbl =
  begin match cmp with
  | Ceq | Cne -> `	ucomisd	`
  | _         -> `	comisd	`
  end;
  `{emit_reg arg.(1)}, {emit_reg arg.(0)}\n`;
  let (branch_opcode, need_jp) =
    match (cmp, neg) with
      (Ceq, false) -> ("je", true)
    | (Ceq, true)  -> ("jne", true)
    | (Cne, false) -> ("jne", true)
    | (Cne, true)  -> ("je", true)
    | (Clt, false) -> ("jb", true)
    | (Clt, true)  -> ("jae", true)
    | (Cle, false) -> ("jbe", true)
    | (Cle, true)  -> ("ja", true)
    | (Cgt, false) -> ("ja", false)
    | (Cgt, true)  -> ("jbe", false)
    | (Cge, false) -> ("jae", true)
    | (Cge, true)  -> ("jb", false) in
  let branch_if_not_comparable =
    if cmp = Cne then not neg else neg in
  if need_jp then
    if branch_if_not_comparable then begin
      `	jp	{emit_label lbl}\n`;
      `	{emit_string branch_opcode}	{emit_label lbl}\n`
    end else begin
      let next = new_label() in
      `	jp	{emit_label next}\n`;
      `	{emit_string branch_opcode}	{emit_label lbl}\n`;
      `{emit_label next}:\n`
    end
  else begin
    `	{emit_string branch_opcode}	{emit_label lbl}\n`
  end

(* Deallocate the stack frame before a return or tail call *)

let output_epilogue () =
  if frame_required() then begin
    let n = frame_size() - 8 in
    `	addq	${emit_int n}, %rsp\n`
  end

(* Output the assembly code for an instruction *)

(* Name of current function *)
let function_name = ref ""
(* Entry point for tail recursive calls *)
let tailrec_entry_point = ref 0
(* Label of trap for out-of-range accesses *)
let range_check_trap = ref 0

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

let emit_instr fallthrough i =
    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
          if src.typ = Float then
            `	movsd	{emit_reg src}, {emit_reg dst}\n`
          else
              `	movq	{emit_reg src}, {emit_reg dst}\n`
        end
    | Lop(Iconst_int n) ->
        if n = 0n then begin
          match i.res.(0).loc with
            Reg n -> `	xorq	{emit_reg i.res.(0)}, {emit_reg i.res.(0)}\n`
          | _     -> `	movq	$0, {emit_reg i.res.(0)}\n`
        end else if n <= 0x7FFFFFFFn && n >= -0x80000000n then
          `	movq	${emit_nativeint n}, {emit_reg i.res.(0)}\n`
        else
          `	movabsq	${emit_nativeint n}, {emit_reg i.res.(0)}\n`
    | Lop(Iconst_float s) ->
        let f = float_of_string s in
        if f = 0.0 then
          `	xorpd	{emit_reg i.res.(0)}, {emit_reg i.res.(0)}\n`
        else begin
          let lbl = new_label() in
          float_constants := (lbl, s) :: !float_constants;
          `	movlpd	{emit_label lbl}(%rip), {emit_reg i.res.(0)}\n`
        end
    | Lop(Iconst_symbol s) ->
        `	movq	${emit_symbol s}, {emit_reg i.res.(0)}\n`
    | Lop(Icall_ind) ->
        `	call	*{emit_reg i.arg.(0)}\n`;
        record_frame i.live
    | Lop(Icall_imm s) ->
        `	call	{emit_symbol s}\n`;
        record_frame i.live
    | Lop(Itailcall_ind) ->
        output_epilogue();
        `	jmp	*{emit_reg i.arg.(0)}\n`
    | Lop(Itailcall_imm s) ->
        if s = !function_name then
          `	jmp	{emit_label !tailrec_entry_point}\n`
        else begin
          output_epilogue();
          `	jmp	{emit_symbol s}\n`
        end
    | Lop(Iextcall(s, alloc)) ->
        if alloc then begin
          `	movq	${emit_symbol s}, %rax\n`;
          `	call	{emit_symbol "caml_c_call"}\n`;
          record_frame i.live
        end else begin
          `	call	{emit_symbol s}\n`
        end
    | Lop(Istackoffset n) ->
        if n < 0
        then `	addq	${emit_int(-n)}, %rsp\n`
        else `	subq	${emit_int(n)}, %rsp\n`;
        stack_offset := !stack_offset + n
    | Lop(Iload(chunk, addr)) ->
        let dest = i.res.(0) in
        begin match chunk with
          | Word ->
              `	movq	{emit_addressing addr i.arg 0}, {emit_reg dest}\n`
          | Byte_unsigned ->
              `	movzbq	{emit_addressing addr i.arg 0}, {emit_reg dest}\n`
          | Byte_signed ->
              `	movsbq	{emit_addressing addr i.arg 0}, {emit_reg dest}\n`
          | Sixteen_unsigned ->
              `	movzwq	{emit_addressing addr i.arg 0}, {emit_reg dest}\n`
          | Sixteen_signed ->
              `	movswq	{emit_addressing addr i.arg 0}, {emit_reg dest}\n`
          | Thirtytwo_unsigned ->
              `	movl	{emit_addressing addr i.arg 0}, {emit_reg32 dest}\n`
          | Thirtytwo_signed ->
              `	movslq	{emit_addressing addr i.arg 0}, {emit_reg dest}\n`
          | Single ->
            `	cvtss2sd {emit_addressing addr i.arg 0}, {emit_reg dest}\n`
          | Double | Double_u ->
            `	movlpd	{emit_addressing addr i.arg 0}, {emit_reg dest}\n`
        end
    | Lop(Istore(chunk, addr)) ->
        begin match chunk with
          | Word ->
            `	movq	{emit_reg i.arg.(0)}, {emit_addressing addr i.arg 1}\n`
          | Byte_unsigned | Byte_signed ->
            `	movb	{emit_reg8 i.arg.(0)}, {emit_addressing addr i.arg 1}\n`
          | Sixteen_unsigned | Sixteen_signed ->
            `	movw	{emit_reg16 i.arg.(0)}, {emit_addressing addr i.arg 1}\n`
          | Thirtytwo_signed | Thirtytwo_unsigned ->
            `	movl	{emit_reg32 i.arg.(0)}, {emit_addressing addr i.arg 1}\n`
          | Single ->
            `	cvtsd2ss {emit_reg i.arg.(0)}, %xmm15\n`;
            `	movss	%xmm15, {emit_addressing addr i.arg 1}\n`
          | Double | Double_u ->
            `	movlpd	{emit_reg i.arg.(0)}, {emit_addressing addr i.arg 1}\n`
        end
    | Lop(Ialloc n) ->
        if !fastcode_flag then begin
          let lbl_redo = new_label() in
          `{emit_label lbl_redo}:	subq	${emit_int n}, %r15\n`;
          `	cmpq	{emit_symbol "caml_young_limit"}(%rip), %r15\n`;
          let lbl_call_gc = new_label() in
          let lbl_frame = record_frame_label i.live in
          `	jb	{emit_label lbl_call_gc}\n`;
          `	leaq	8(%r15), {emit_reg i.res.(0)}\n`;
          call_gc_sites :=
            { gc_lbl = lbl_call_gc;
              gc_return_lbl = lbl_redo;
              gc_frame = lbl_frame } :: !call_gc_sites
        end else begin
          begin match n with
            16  -> `	call	{emit_symbol "caml_alloc1"}\n`
          | 24 -> `	call	{emit_symbol "caml_alloc2"}\n`
          | 32 -> `	call	{emit_symbol "caml_alloc3"}\n`
          | _  -> `	movq	${emit_int n}, %rax\n`;
                  `	call	{emit_symbol "caml_allocN"}\n`
          end;
          `{record_frame i.live}	leaq	8(%r15), {emit_reg i.res.(0)}\n`
        end
    | Lop(Iintop(Icomp cmp)) ->
        `	cmpq	{emit_reg i.arg.(1)}, {emit_reg i.arg.(0)}\n`;
        let b = name_for_cond_branch cmp in
        `	set{emit_string b}	%al\n`;
        `	movzbq	%al, {emit_reg i.res.(0)}\n`
    | Lop(Iintop_imm(Icomp cmp, n)) ->
        `	cmpq	${emit_int n}, {emit_reg i.arg.(0)}\n`;
        let b = name_for_cond_branch cmp in
        `	set{emit_string b}	%al\n`;
        `	movzbq	%al, {emit_reg i.res.(0)}\n`
    | Lop(Iintop Icheckbound) ->
        if !range_check_trap = 0 then range_check_trap := new_label();
        `	cmpq	{emit_reg i.arg.(1)}, {emit_reg i.arg.(0)}\n`;
        `	jbe	{emit_label !range_check_trap}\n`
    | Lop(Iintop_imm(Icheckbound, n)) ->
        if !range_check_trap = 0 then range_check_trap := new_label();
        `	cmpq	${emit_int n}, {emit_reg i.arg.(0)}\n`;
        `	jbe	{emit_label !range_check_trap}\n`
    | Lop(Iintop(Idiv | Imod)) ->
        `	cqto\n`;
        `	idivq	{emit_reg i.arg.(1)}\n`
    | Lop(Iintop(Ilsl | Ilsr | Iasr as op)) ->
        (* We have i.arg.(0) = i.res.(0) and i.arg.(1) = %rcx *)
        `	{emit_string(instr_for_intop op)}	%cl, {emit_reg i.res.(0)}\n`
    | Lop(Iintop op) ->
        (* We have i.arg.(0) = i.res.(0) *)
        `	{emit_string(instr_for_intop op)}	{emit_reg i.arg.(1)}, {emit_reg i.res.(0)}\n`
    | Lop(Iintop_imm(Iadd, n)) when i.arg.(0).loc <> i.res.(0).loc ->
        `	leaq	{emit_int n}({emit_reg i.arg.(0)}), {emit_reg i.res.(0)}\n`
    | Lop(Iintop_imm(Iadd, 1) | Iintop_imm(Isub, -1)) ->
        `	incq	{emit_reg i.res.(0)}\n`
    | Lop(Iintop_imm(Iadd, -1) | Iintop_imm(Isub, 1)) ->
        `	decq	{emit_reg i.res.(0)}\n`
    | Lop(Iintop_imm(Idiv, n)) ->
        (* Note: i.arg.(0) = i.res.(0) = rdx  (cf. selection.ml) *)
        let l = Misc.log2 n in
        `	movq	{emit_reg i.arg.(0)}, %rax\n`;
        `	addq	${emit_int(n-1)}, {emit_reg i.arg.(0)}\n`;
        `	testq	%rax, %rax\n`;
        `	cmovns	%rax, {emit_reg i.arg.(0)}\n`;
        `	sarq	${emit_int l}, {emit_reg i.res.(0)}\n`
    | Lop(Iintop_imm(Imod, n)) ->
        (* Note: i.arg.(0) = i.res.(0) = rdx  (cf. selection.ml) *)
        let l = Misc.log2 n in
        `	movq	{emit_reg i.arg.(0)}, %rax\n`;
        `	testq	%rax, %rax\n`;
        `	leaq	{emit_int(n-1)}(%rax), %rax\n`;
        `	cmovns	{emit_reg i.arg.(0)}, %rax\n`;
        `	andq	${emit_int (-n)}, %rax\n`;
        `	subq	%rax, {emit_reg i.res.(0)}\n`
    | Lop(Iintop_imm(op, n)) ->
        (* We have i.arg.(0) = i.res.(0) *)
        `	{emit_string(instr_for_intop op)}	${emit_int n}, {emit_reg i.res.(0)}\n`
    | Lop(Inegf) ->
        `	xorpd	{emit_symbol "caml_negf_mask"}(%rip), {emit_reg i.res.(0)}\n`
    | Lop(Iabsf) ->
        `	andpd	{emit_symbol "caml_absf_mask"}(%rip), {emit_reg i.res.(0)}\n`
    | Lop(Iaddf | Isubf | Imulf | Idivf as floatop) ->
        `	{emit_string(instr_for_floatop floatop)}	{emit_reg i.arg.(1)}, {emit_reg i.res.(0)}\n`
    | Lop(Ifloatofint) ->
        `	cvtsi2sdq	{emit_reg i.arg.(0)}, {emit_reg i.res.(0)}\n`
    | Lop(Iintoffloat) ->
        `	cvttsd2siq	{emit_reg i.arg.(0)}, {emit_reg i.res.(0)}\n`
    | Lop(Ispecific(Ilea addr)) ->
        `	leaq	{emit_addressing addr i.arg 0}, {emit_reg i.res.(0)}\n`
    | Lop(Ispecific(Istore_int(n, addr))) ->
        `	movq	${emit_nativeint n}, {emit_addressing addr i.arg 0}\n`
    | Lop(Ispecific(Istore_symbol(s, addr))) ->
        `	movq	${emit_symbol s}, {emit_addressing addr i.arg 0}\n`
    | Lop(Ispecific(Ioffset_loc(n, addr))) ->
        `	addq	${emit_int n}, {emit_addressing addr i.arg 0}\n`
    | Lop(Ispecific(Ifloatarithmem(op, addr))) ->
        `	{emit_string(instr_for_floatarithmem op)}	{emit_addressing addr i.arg 1}, {emit_reg i.res.(0)}\n`
    | Lreloadretaddr ->
        ()
    | Lreturn ->
        output_epilogue();
        `	ret\n`
    | Llabel lbl ->
        `{emit_Llabel fallthrough lbl}:\n`
    | Lbranch lbl ->
        `	jmp	{emit_label lbl}\n`
    | Lcondbranch(tst, lbl) ->
        begin match tst with
          Itruetest ->
            output_test_zero i.arg.(0);
            `	jne	{emit_label lbl}\n`
        | Ifalsetest ->
            output_test_zero i.arg.(0);
            `	je	{emit_label lbl}\n`
        | Iinttest cmp ->
            `	cmpq	{emit_reg i.arg.(1)}, {emit_reg i.arg.(0)}\n`;
            let b = name_for_cond_branch cmp in
            `	j{emit_string b}	{emit_label lbl}\n`
        | Iinttest_imm((Isigned Ceq | Isigned Cne | 
                        Iunsigned Ceq | Iunsigned Cne) as cmp, 0) ->
            output_test_zero i.arg.(0);
            let b = name_for_cond_branch cmp in
            `	j{emit_string b}	{emit_label lbl}\n`
        | Iinttest_imm(cmp, n) ->
            `	cmpq	${emit_int n}, {emit_reg i.arg.(0)}\n`;
            let b = name_for_cond_branch cmp in
            `	j{emit_string b}	{emit_label lbl}\n`
        | Ifloattest(cmp, neg) ->
            emit_float_test cmp neg i.arg lbl
        | Ioddtest ->
            `	testb	$1, {emit_reg8 i.arg.(0)}\n`;
            `	jne	{emit_label lbl}\n`
        | Ieventest ->
            `	testb	$1, {emit_reg8 i.arg.(0)}\n`;
            `	je	{emit_label lbl}\n`
        end
    | Lcondbranch3(lbl0, lbl1, lbl2) ->
            `	cmpq	$1, {emit_reg i.arg.(0)}\n`;
            begin match lbl0 with
              None -> ()
            | Some lbl -> `	jb	{emit_label lbl}\n`
            end;
            begin match lbl1 with
              None -> ()
            | Some lbl -> `	je	{emit_label lbl}\n`
            end;
            begin match lbl2 with
              None -> ()
            | Some lbl -> `	jg	{emit_label lbl}\n`
            end
    | Lswitch jumptbl ->
        let lbl = new_label() in
        `	jmp	*{emit_label lbl}(, {emit_reg i.arg.(0)}, 8)\n`;
        `	.section .rodata\n`;
        emit_align 8;
        `{emit_label lbl}:`;
        for i = 0 to Array.length jumptbl - 1 do
          `	.quad	{emit_label jumptbl.(i)}\n`
        done;
        `	.text\n`
    | Lsetuptrap lbl ->
        `	call	{emit_label lbl}\n`
    | Lpushtrap ->
        `	pushq	%r14\n`;
        `	movq	%rsp, %r14\n`;
        stack_offset := !stack_offset + 16
    | Lpoptrap ->
        `	popq	%r14\n`;
        `	addq	$8, %rsp\n`;
        stack_offset := !stack_offset - 16
    | Lraise ->
        `	movq	%r14, %rsp\n`;
        `	popq	%r14\n`;
        `	ret\n`

let rec emit_all fallthrough i =
  match i.desc with
  |  Lend -> ()
  | _ ->
      emit_instr fallthrough i;
      emit_all (Linearize.has_fallthrough i.desc) i.next

(* Emission of the floating-point constants *)

let emit_float_constant (lbl, cst) =
  `{emit_label lbl}:	.double	{emit_string cst}\n`

(* Emission of the profiling prelude -- FIXME *)

let emit_profile () =
  match Config.system with
    "linux_elf" ->
      `	pushl	%eax\n`;
      `	movl	%esp, %ebp\n`;
      `	pushl	%ecx\n`;
      `	pushl	%edx\n`;
      `	call	{emit_symbol "mcount"}\n`;
      `	popl	%edx\n`;
      `	popl	%ecx\n`;
      `	popl	%eax\n`
  | "bsd_elf" ->
      `	pushl	%eax\n`;
      `	movl	%esp, %ebp\n`;
      `	pushl	%ecx\n`;
      `	pushl	%edx\n`;
      `	call	.mcount\n`;
      `	popl	%edx\n`;
      `	popl	%ecx\n`;
      `	popl	%eax\n`
  | _ -> () (*unsupported yet*)

(* Emission of a function declaration *)

let fundecl fundecl =
  function_name := fundecl.fun_name;
  fastcode_flag := fundecl.fun_fast;
  tailrec_entry_point := new_label();
  stack_offset := 0;
  float_constants := [];
  call_gc_sites := [];
  range_check_trap := 0;
  `	.text\n`;
  emit_align 16;
  `	.globl	{emit_symbol fundecl.fun_name}\n`;
  `{emit_symbol fundecl.fun_name}:\n`;
  if !Clflags.gprofile then emit_profile();
  if frame_required() then begin
    let n = frame_size() - 8 in
    `	subq	${emit_int n}, %rsp\n`
  end;
  `{emit_label !tailrec_entry_point}:\n`;
  emit_all true fundecl.fun_body;
  List.iter emit_call_gc !call_gc_sites;
  if !range_check_trap > 0 then
    `{emit_label !range_check_trap}:	call	{emit_symbol "caml_ml_array_bound_error"}\n`;
    (* Never returns, but useful to have retaddr on stack for debugging *)
  if !float_constants <> [] then begin
    `	.section	.rodata.cst8,\"aM\",@progbits,8\n`;
    List.iter emit_float_constant !float_constants
  end

(* Emission of data *)

let emit_item = function
    Cglobal_symbol s ->
      `	.globl	{emit_symbol s}\n`;
  | Cdefine_symbol s ->
      `{emit_symbol s}:\n`
  | Cdefine_label lbl ->
      `{emit_label (100000 + lbl)}:\n`
  | Cint8 n ->
      `	.byte	{emit_int n}\n`
  | Cint16 n ->
      `	.word	{emit_int n}\n`
  | Cint32 n ->
      `	.long	{emit_nativeint n}\n`
  | Cint n ->
      `	.quad	{emit_nativeint n}\n`
  | Csingle f ->
      `	.float	{emit_string f}\n`
  | Cdouble f ->
      `	.double	{emit_string f}\n`
  | Csymbol_address s ->
      `	.quad	{emit_symbol s}\n`
  | Clabel_address lbl ->
      `	.quad	{emit_label (100000 + lbl)}\n`
  | Cstring s ->
      emit_string_directive "	.ascii	" s
  | Cskip n ->
      if n > 0 then `	.space	{emit_int n}\n`
  | Calign n ->
      emit_align n

let data l =
  `	.data\n`;
  List.iter emit_item l

(* Beginning / end of an assembly file *)

let begin_assembly() =
  let lbl_begin = Compilenv.current_unit_name() ^ "__data_begin" in
  `	.data\n`;
  `	.globl	{emit_symbol lbl_begin}\n`;
  `{emit_symbol lbl_begin}:\n`;
  let lbl_begin = Compilenv.current_unit_name() ^ "__code_begin" in
  `	.text\n`;
  `	.globl	{emit_symbol lbl_begin}\n`;
  `{emit_symbol lbl_begin}:\n`

let end_assembly() =
  let lbl_end = Compilenv.current_unit_name() ^ "__code_end" in
  `	.text\n`;
  `	.globl	{emit_symbol lbl_end}\n`;
  `{emit_symbol lbl_end}:\n`;
  `	.data\n`;
  let lbl_end = Compilenv.current_unit_name() ^ "__data_end" in
  `	.globl	{emit_symbol lbl_end}\n`;
  `{emit_symbol lbl_end}:\n`;
  `	.long	0\n`;
  let lbl = Compilenv.current_unit_name() ^ "__frametable" in
  `	.globl	{emit_symbol lbl}\n`;
  `{emit_symbol lbl}:\n`;
  `	.quad	{emit_int (List.length !frame_descriptors)}\n`;
  List.iter emit_frame !frame_descriptors;
  frame_descriptors := []