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mutated_ocaml / asmcomp / amd64 / emit_nt.mlp

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(***********************************************************************)
(*                                                                     *)
(*                                OCaml                                *)
(*                                                                     *)
(*            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: emit_nt.mlp 12907 2012-09-08 16:51:03Z xleroy $ *)

(* Emission of x86-64 (AMD 64) assembly code, MASM syntax *)

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

(* 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 *)
  if frame_required() then begin
    let sz =
      (!stack_offset + 8 * (num_stack_slots.(0) + num_stack_slots.(1)) + 8)
    in Misc.align sz 16
  end else
    !stack_offset + 8

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

(* Output a 32 bit integer in hex *)

let emit_int32 n = emit_printf "0%lxh" n

(* Symbols *)

let emit_symbol s =
  Emitaux.emit_symbol '$' s

(* Record symbols used and defined - at the end generate extern for those
   used but not defined *)

let symbols_defined = ref StringSet.empty
let symbols_used = ref StringSet.empty

let add_def_symbol s =
  symbols_defined := StringSet.add s !symbols_defined

let add_used_symbol s =
  symbols_used := StringSet.add s !symbols_used

(* Output a label *)

let emit_label lbl =
  emit_string "L"; emit_int lbl

let emit_data_label lbl =
  emit_string "Ld"; 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; typ = Float } as r ->
      let ofs = slot_offset s (register_class r) in
      `REAL8 PTR {emit_int ofs}[rsp]`
  | { loc = Stack s; typ = _ } as r ->
      let ofs = slot_offset s (register_class r) in
      `QWORD PTR {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";
     "r12b"; "r13b"; "bpl"; "r10b"; "r11b" |]
let reg_low_16_name =
  [| "ax"; "bx"; "di"; "si"; "dx"; "cx"; "r8w"; "r9w";
     "r12w"; "r13w"; "bp"; "r10w"; "r11w" |]
let reg_low_32_name =
  [| "eax"; "ebx"; "edi"; "esi"; "edx"; "ecx"; "r8d"; "r9d";
     "r12d"; "r13d"; "ebp"; "r10d"; "r11d" |]

let emit_subreg tbl pref 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_string pref} PTR {emit_int ofs}[rsp]`
  | _ ->
      assert false

let emit_reg8 r = emit_subreg reg_low_8_name "BYTE" r
let emit_reg16 r = emit_subreg reg_low_16_name "WORD" r
let emit_reg32 r = emit_subreg reg_low_32_name "DWORD" r

(* Output an addressing mode *)

let emit_signed_int d =
  if d > 0 then emit_char '+';
  if d <> 0 then emit_int d

let emit_addressing addr r n =
  match addr with
    Ibased(s, d) ->
      add_used_symbol s;
      `{emit_symbol s}{emit_signed_int d}`
  | Iindexed d ->
      `[{emit_reg r.(n)}{emit_signed_int d}]`
  | Iindexed2 d ->
      `[{emit_reg r.(n)}+{emit_reg r.(n+1)}{emit_signed_int d}]`
  | Iscaled(2, d) ->
      `[{emit_reg r.(n)}+{emit_reg r.(n)}{emit_signed_int d}]`
  | Iscaled(scale, d) ->
      `[{emit_reg r.(n)}*{emit_int scale}{emit_signed_int d}]`
  | Iindexed2scaled(scale, d) ->
      `[{emit_reg r.(n)}+{emit_reg r.(n+1)}*{emit_int scale}{emit_signed_int d}]`

(* Record live pointers at call points *)

let record_frame_label live dbg =
  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;
      fd_debuginfo = dbg } :: !frame_descriptors;
  lbl

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

(* 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`

(* Record calls to caml_ml_array_bound_error.
   In -g mode, we maintain one call to caml_ml_array_bound_error
   per bound check site.  Without -g, we can share a single call. *)

type bound_error_call =
  { bd_lbl: label;                      (* Entry label *)
    bd_frame: label }                   (* Label of frame descriptor *)

let bound_error_sites = ref ([] : bound_error_call list)
let bound_error_call = ref 0

let bound_error_label dbg =
  if !Clflags.debug then begin
    let lbl_bound_error = new_label() in
    let lbl_frame = record_frame_label Reg.Set.empty dbg in
    bound_error_sites :=
     { bd_lbl = lbl_bound_error; bd_frame = lbl_frame } :: !bound_error_sites;
   lbl_bound_error
 end else begin
   if !bound_error_call = 0 then bound_error_call := new_label();
   !bound_error_call
 end

let emit_call_bound_error bd =
  `{emit_label bd.bd_lbl}:	call	caml_ml_array_bound_error\n`;
  `{emit_label bd.bd_frame}:\n`

let emit_call_bound_errors () =
  List.iter emit_call_bound_error !bound_error_sites;
  if !bound_error_call > 0 then
    `{emit_label !bound_error_call}:	call	caml_ml_array_bound_error\n`

(* Names for instructions *)

let instr_for_intop = function
    Iadd -> "add"
  | Isub -> "sub"
  | Imul -> "imul"
  | Iand -> "and"
  | Ior -> "or"
  | Ixor -> "xor"
  | Ilsl -> "sal"
  | Ilsr -> "shr"
  | Iasr -> "sar"
  | _ -> 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 -> `	test	{emit_reg arg}, {emit_reg arg}\n`
  | _     -> `	cmp	{emit_reg arg}, 0\n`

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

let emit_float_test cmp neg arg lbl =
  (* Effect of comisd on flags and conditional branches:
                     ZF PF CF  cond. branches taken
        unordered     1  1  1  je, jb, jbe, jp
        >             0  0  0  jne, jae, ja
        <             0  0  1  jne, jbe, jb
        =             1  0  0  je, jae, jbe.
     If FP traps are on (they are off by default),
     comisd traps on QNaN and SNaN but ucomisd traps on SNaN only.
  *)
  match (cmp, neg) with
  | (Ceq, false) | (Cne, true) ->
      let next = new_label() in
      `	ucomisd	{emit_reg arg.(0)}, {emit_reg arg.(1)}\n`;
      `	jp	{emit_label next}\n`;    (* skip if unordered *)
      `	je	{emit_label lbl}\n`;     (* branch taken if x=y *)
      `{emit_label next}:\n`
  | (Cne, false) | (Ceq, true) ->
      `	ucomisd	{emit_reg arg.(0)}, {emit_reg arg.(1)}\n`;
      `	jp	{emit_label lbl}\n`;     (* branch taken if unordered *)
      `	jne	{emit_label lbl}\n`      (* branch taken if x<y or x>y *)
  | (Clt, _) ->
      ` comisd	{emit_reg arg.(1)}, {emit_reg arg.(0)}\n`;  (* swap compare *)
      if not neg then
      `	ja	{emit_label lbl}\n`     (* branch taken if y>x i.e. x<y *)
      else
      `	jbe	{emit_label lbl}\n` (* taken if unordered or y<=x i.e. !(x<y) *)
  | (Cle, _) ->
      ` comisd	{emit_reg arg.(1)}, {emit_reg arg.(0)}\n`;  (* swap compare *)
      if not neg then
      `	jae	{emit_label lbl}\n`     (* branch taken if y>=x i.e. x<=y *)
      else
      `	jb	{emit_label lbl}\n` (* taken if unordered or y<x i.e. !(x<=y) *)
  | (Cgt, _) ->
      ` comisd	{emit_reg arg.(0)}, {emit_reg arg.(1)}\n`;
      if not neg then
      `	ja	{emit_label lbl}\n`     (* branch taken if x>y *)
      else
      `	jbe	{emit_label lbl}\n` (* taken if unordered or x<=y i.e. !(x>y) *)
  | (Cge, _) ->
      ` comisd	{emit_reg arg.(0)}, {emit_reg arg.(1)}\n`;  (* swap compare *)
      if not neg then
      `	jae	{emit_label lbl}\n`     (* branch taken if x>=y *)
      else
      `	jb	{emit_label lbl}\n` (* taken if unordered or x<y i.e. !(x>=y) *)

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

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

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
          match src.typ, src.loc, dst.loc with
            Float, Reg _, Reg _ ->
              `	movapd	{emit_reg dst}, {emit_reg src}\n`
          | Float, _, _ ->
              `	movsd	{emit_reg dst}, {emit_reg src}\n`
          | _ ->
              `	mov	{emit_reg dst}, {emit_reg src}\n`
        end
    | Lop(Iconst_int n) ->
        if n = 0n then begin
          match i.res.(0).loc with
            Reg n -> `	xor	{emit_reg i.res.(0)}, {emit_reg i.res.(0)}\n`
          | _     -> `	mov	{emit_reg i.res.(0)}, 0\n`
        end else if n >= -0x80000000n && n <= 0x7FFFFFFFn then
          `	mov	{emit_reg i.res.(0)}, {emit_nativeint n}\n`
        else if n >= 0x80000000n && n <= 0xFFFFFFFFn  then
	  (* work around bug in ml64 *)
          `	mov	{emit_reg32 i.res.(0)}, {emit_nativeint n}\n`
        else
	  (* force ml64 to use mov reg, imm64 instruction *)
          `	mov	{emit_reg i.res.(0)}, {emit_printf "0%nxH" n}\n`
    | Lop(Iconst_float s) ->
        begin match Int64.bits_of_float (float_of_string s) with
        | 0x0000_0000_0000_0000L ->       (* +0.0 *)
          `	xorpd	{emit_reg i.res.(0)}, {emit_reg i.res.(0)}\n`
        | _ ->
          let lbl = new_label() in
          float_constants := (lbl, s) :: !float_constants;
          `	movsd	{emit_reg i.res.(0)}, {emit_label lbl}\n`
        end
    | Lop(Iconst_symbol s) ->
        add_used_symbol s;
        if !pic_code then
          `	lea	{emit_reg i.res.(0)}, {emit_symbol s}\n`
        else
          `	mov	{emit_reg i.res.(0)}, OFFSET {emit_symbol s}\n`
    | Lop(Icall_ind) ->
        `	call	{emit_reg i.arg.(0)}\n`;
        record_frame i.live i.dbg
    | Lop(Icall_imm s) ->
        add_used_symbol s;
        `	call	{emit_symbol s}\n`;
        record_frame i.live i.dbg
    | 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
          add_used_symbol s;
          output_epilogue();
          `	jmp	{emit_symbol s}\n`
        end
    | Lop(Iextcall(s, alloc)) ->
        add_used_symbol s;
        if alloc then begin
          `	lea	rax, {emit_symbol s}\n`;
          `	call	{emit_symbol "caml_c_call"}\n`;
          record_frame i.live i.dbg
        end else begin
          `	call	{emit_symbol s}\n`
        end
    | Lop(Istackoffset n) ->
        if n < 0
        then `	add	rsp, {emit_int(-n)}\n`
        else `	sub	rsp, {emit_int(n)}\n`;
        stack_offset := !stack_offset + n
    | Lop(Iload(chunk, addr)) ->
        let dest = i.res.(0) in
        begin match chunk with
          | Word ->
              `	mov	{emit_reg dest}, QWORD PTR {emit_addressing addr i.arg 0}\n`
          | Byte_unsigned ->
              `	movzx	{emit_reg dest}, BYTE PTR {emit_addressing addr i.arg 0}\n`
          | Byte_signed ->
              `	movsx	{emit_reg dest}, BYTE PTR {emit_addressing addr i.arg 0}\n`
          | Sixteen_unsigned ->
              `	movzx	{emit_reg dest}, WORD PTR {emit_addressing addr i.arg 0}\n`
          | Sixteen_signed ->
              `	movsx	{emit_reg dest}, WORD PTR {emit_addressing addr i.arg 0}\n`
          | Thirtytwo_unsigned ->
              (* load to low 32 bits sets high 32 bits to 0 *)
              `	mov	{emit_reg32 dest}, DWORD PTR {emit_addressing addr i.arg 0}\n`
          | Thirtytwo_signed ->
              `	movsxd	{emit_reg dest}, DWORD PTR {emit_addressing addr i.arg 0}\n`
          | Single ->
            `	cvtss2sd {emit_reg dest}, REAL4 PTR {emit_addressing addr i.arg 0}\n`
          | Double | Double_u ->
            `	movsd	{emit_reg dest}, REAL8 PTR {emit_addressing addr i.arg 0}\n`
        end
    | Lop(Istore(chunk, addr)) ->
        begin match chunk with
          | Word ->
            `	mov	QWORD PTR {emit_addressing addr i.arg 1}, {emit_reg i.arg.(0)}\n`
          | Byte_unsigned | Byte_signed ->
            `	mov	BYTE PTR {emit_addressing addr i.arg 1}, {emit_reg8 i.arg.(0)}\n`
          | Sixteen_unsigned | Sixteen_signed ->
            `	mov	WORD PTR {emit_addressing addr i.arg 1}, {emit_reg16 i.arg.(0)}\n`
          | Thirtytwo_signed | Thirtytwo_unsigned ->
            `	mov	DWORD PTR {emit_addressing addr i.arg 1}, {emit_reg32 i.arg.(0)}\n`
          | Single ->
            `	cvtsd2ss xmm15, {emit_reg i.arg.(0)}\n`;
            `	movss	REAL4 PTR {emit_addressing addr i.arg 1}, xmm15\n`
          | Double | Double_u ->
            `	movsd	REAL8 PTR {emit_addressing addr i.arg 1}, {emit_reg i.arg.(0)}\n`
        end
    | Lop(Ialloc n) ->
        if !fastcode_flag then begin
          let lbl_redo = new_label() in
          `{emit_label lbl_redo}:	sub	r15, {emit_int n}\n`;
          `	cmp	r15, {emit_symbol "caml_young_limit"}\n`;
          let lbl_call_gc = new_label() in
          let lbl_frame = record_frame_label i.live Debuginfo.none in
          `	jb	{emit_label lbl_call_gc}\n`;
          `	lea	{emit_reg i.res.(0)}, [r15+8]\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`
          | _  -> `	mov	rax, {emit_int n}\n`;
                  `	call	{emit_symbol "caml_allocN"}\n`
          end;
          `{record_frame i.live Debuginfo.none}	lea	{emit_reg i.res.(0)}, [r15+8]\n`
        end
    | Lop(Iintop(Icomp cmp)) ->
        `	cmp	{emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`;
        let b = name_for_cond_branch cmp in
        `	set{emit_string b}	al\n`;
        `	movzx	{emit_reg i.res.(0)}, al\n`
    | Lop(Iintop_imm(Icomp cmp, n)) ->
        `	cmp	{emit_reg i.arg.(0)}, {emit_int n}\n`;
        let b = name_for_cond_branch cmp in
        `	set{emit_string b}	al\n`;
        `	movzx	{emit_reg i.res.(0)}, al\n`
    | Lop(Iintop Icheckbound) ->
        let lbl = bound_error_label i.dbg in
        `	cmp	{emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\n`;
        `	jbe	{emit_label lbl}\n`
    | Lop(Iintop_imm(Icheckbound, n)) ->
        let lbl = bound_error_label i.dbg in
        `	cmp	{emit_reg i.arg.(0)}, {emit_int n}\n`;
        `	jbe	{emit_label lbl}\n`
    | Lop(Iintop(Idiv | Imod)) ->
        `	cqo\n`;
        `	idiv	{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)}	{emit_reg i.res.(0)}, cl\n`
    | Lop(Iintop op) ->
        (* We have i.arg.(0) = i.res.(0) *)
        `	{emit_string(instr_for_intop op)}	{emit_reg i.res.(0)}, {emit_reg i.arg.(1)}\n`
    | Lop(Iintop_imm(Iadd, n)) when i.arg.(0).loc <> i.res.(0).loc ->
        `	lea	{emit_reg i.res.(0)}, {emit_int n}[{emit_reg i.arg.(0)}]\n`
    | Lop(Iintop_imm(Iadd, 1) | Iintop_imm(Isub, -1)) ->
        `	inc	{emit_reg i.res.(0)}\n`
    | Lop(Iintop_imm(Iadd, -1) | Iintop_imm(Isub, 1)) ->
        `	dec	{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
        `	mov	rax, {emit_reg i.arg.(0)}\n`;
        `	add	{emit_reg i.arg.(0)}, {emit_int(n-1)}\n`;
        `	test	rax, rax\n`;
        `	cmovns	{emit_reg i.arg.(0)}, rax\n`;
        `	sar	{emit_reg i.res.(0)}, {emit_int l}\n`
    | Lop(Iintop_imm(Imod, n)) ->
        (* Note: i.arg.(0) = i.res.(0) = rdx  (cf. selection.ml) *)
        `	mov	rax, {emit_reg i.arg.(0)}\n`;
        `	test	rax, rax\n`;
        `	lea	rax, {emit_int(n-1)}[rax]\n`;
        `	cmovns	rax, {emit_reg i.arg.(0)}\n`;
        `	and	rax, {emit_int (-n)}\n`;
        `	sub	{emit_reg i.res.(0)}, rax\n`
    | Lop(Iintop_imm(op, n)) ->
        (* We have i.arg.(0) = i.res.(0) *)
        `	{emit_string(instr_for_intop op)}	{emit_reg i.res.(0)}, {emit_int n}\n`
    | Lop(Inegf) ->
        `	xorpd	{emit_reg i.res.(0)}, {emit_symbol "caml_negf_mask"}\n`
    | Lop(Iabsf) ->
        `	andpd	{emit_reg i.res.(0)}, {emit_symbol "caml_absf_mask"}\n`
    | Lop(Iaddf | Isubf | Imulf | Idivf as floatop) ->
        `	{emit_string(instr_for_floatop floatop)}	{emit_reg i.res.(0)}, {emit_reg i.arg.(1)}\n`
    | Lop(Ifloatofint) ->
        `	cvtsi2sd	{emit_reg i.res.(0)}, {emit_reg i.arg.(0)}\n`
    | Lop(Iintoffloat) ->
        `	cvttsd2si	{emit_reg i.res.(0)}, {emit_reg i.arg.(0)}\n`
    | Lop(Ispecific(Ilea addr)) ->
        `	lea	{emit_reg i.res.(0)}, {emit_addressing addr i.arg 0}\n`
    | Lop(Ispecific(Istore_int(n, addr))) ->
        `	mov	QWORD PTR {emit_addressing addr i.arg 0}, {emit_nativeint n}\n`
    | Lop(Ispecific(Istore_symbol(s, addr))) ->
        assert (not !pic_code);
	add_used_symbol s;
        `	mov	QWORD PTR {emit_addressing addr i.arg 0}, OFFSET {emit_symbol s}\n`
    | Lop(Ispecific(Ioffset_loc(n, addr))) ->
        `	add	QWORD PTR {emit_addressing addr i.arg 0}, {emit_int n}\n`
    | Lop(Ispecific(Ifloatarithmem(op, addr))) ->
        `	{emit_string(instr_for_floatarithmem op)}	{emit_reg i.res.(0)}, REAL8 PTR {emit_addressing addr i.arg 1}\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 ->
            `	cmp	{emit_reg i.arg.(0)}, {emit_reg i.arg.(1)}\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) ->
            `	cmp	{emit_reg i.arg.(0)}, {emit_int n}\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 ->
            `	test	{emit_reg8 i.arg.(0)}, 1\n`;
            `	jne	{emit_label lbl}\n`
        | Ieventest ->
            `	test	{emit_reg8 i.arg.(0)}, 1\n`;
            `	je	{emit_label lbl}\n`
        end
    | Lcondbranch3(lbl0, lbl1, lbl2) ->
            `	cmp	{emit_reg i.arg.(0)}, 1\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
        (* rax and rdx are clobbered by the Lswitch,
           meaning that no variable that is live across the Lswitch
           is assigned to rax or rdx.  However, the argument to Lswitch
           can still be assigned to one of these two registers, so
           we must be careful not to clobber it before use. *)
        let (tmp1, tmp2) =
          if i.arg.(0).loc = Reg 0 (* rax *)
          then (phys_reg 4 (*rdx*), phys_reg 0 (*rax*))
          else (phys_reg 0 (*rax*), phys_reg 4 (*rdx*)) in
        `	lea	{emit_reg tmp1}, {emit_label lbl}\n`;
        `	movsxd	{emit_reg tmp2}, DWORD PTR [{emit_reg tmp1}+{emit_reg i.arg.(0)}*4]\n`;
        `	add	{emit_reg tmp1}, {emit_reg tmp2}\n`;
        `	jmp	{emit_reg tmp1}\n`;
        emit_align 4;
        `{emit_label lbl}	LABEL DWORD\n`;
        for i = 0 to Array.length jumptbl - 1 do
          `	DWORD	{emit_label jumptbl.(i)} - {emit_label lbl}\n`
        done
    | Lsetuptrap lbl ->
        `	call	{emit_label lbl}\n`
    | Lpushtrap ->
        `	push	r14\n`;
        `	mov	r14, rsp\n`;
        stack_offset := !stack_offset + 16
    | Lpoptrap ->
        `	pop	r14\n`;
        `	add	rsp, 8\n`;
        stack_offset := !stack_offset - 16
    | Lraise ->
        if !Clflags.debug then begin
          `	call	caml_raise_exn\n`;
          record_frame Reg.Set.empty i.dbg
        end else begin
          `	mov	rsp, r14\n`;
          `	pop	r14\n`;
          `	ret\n`
        end

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 s =
  (* MASM doesn't like floating-point constants such as 2e9.
     Turn them into 2.0e9. *)
  let pos_e = ref (-1) and pos_dot = ref (-1) in
  for i = 0 to String.length s - 1 do
    match s.[i] with
      'e'|'E' -> pos_e := i
    | '.'     -> pos_dot := i
    | _       -> ()
  done;
  if !pos_dot < 0 && !pos_e >= 0 then begin
    emit_string (String.sub s 0 !pos_e);
    emit_string ".0";
    emit_string (String.sub s !pos_e (String.length s - !pos_e))
  end else
    emit_string s

let emit_float_constant (lbl, cst) =
  `{emit_label lbl}     REAL8   {emit_float cst}\n`

(* 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 := [];
  bound_error_sites := [];
  bound_error_call := 0;
  `	.CODE\n`;
  emit_align 16;
  add_def_symbol fundecl.fun_name;
  `	PUBLIC	{emit_symbol fundecl.fun_name}\n`;
  `{emit_symbol fundecl.fun_name}:\n`;
  if frame_required() then begin
    let n = frame_size() - 8 in
    `	sub	rsp, {emit_int n}\n`
  end;
  `{emit_label !tailrec_entry_point}:\n`;
  emit_all true fundecl.fun_body;
  List.iter emit_call_gc !call_gc_sites;
  emit_call_bound_errors();
  if !float_constants <> [] then begin
    `	.DATA\n`;
    List.iter emit_float_constant !float_constants
  end

(* Emission of data *)

let emit_item = function
    Cglobal_symbol s ->
      `	PUBLIC	{emit_symbol s}\n`;
  | Cdefine_symbol s ->
      add_def_symbol s;
      `{emit_symbol s} LABEL QWORD\n`
  | Cdefine_label lbl ->
      `{emit_data_label lbl} LABEL QWORD\n`
  | Cint8 n ->
      `	BYTE	{emit_int n}\n`
  | Cint16 n ->
      `	WORD	{emit_int n}\n`
  | Cint32 n ->
      `	DWORD	{emit_nativeint n}\n`
  | Cint n ->
      `	QWORD	{emit_nativeint n}\n`
  | Csingle f ->
      `	REAL4	{emit_float f}\n`
  | Cdouble f ->
      `	REAL8	{emit_float f}\n`
  | Csymbol_address s ->
      add_used_symbol s;
      `	QWORD	{emit_symbol s}\n`
  | Clabel_address lbl ->
      `	QWORD	{emit_data_label lbl}\n`
  | Cstring s ->
      emit_bytes_directive "	BYTE	" s
  | Cskip n ->
      if n > 0 then `	BYTE	{emit_int n} DUP (?)\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() =
  `	EXTRN caml_young_ptr: QWORD\n`;
  `	EXTRN caml_young_limit: QWORD\n`;
  `	EXTRN caml_exception_pointer: QWORD\n`;
  `	EXTRN caml_absf_mask: QWORD\n`;
  `	EXTRN caml_negf_mask: QWORD\n`;
  `	EXTRN caml_call_gc: NEAR\n`;
  `	EXTRN caml_c_call: NEAR\n`;
  `	EXTRN caml_allocN: NEAR\n`;
  `	EXTRN caml_alloc1: NEAR\n`;
  `	EXTRN caml_alloc2: NEAR\n`;
  `	EXTRN caml_alloc3: NEAR\n`;
  `	EXTRN caml_ml_array_bound_error: NEAR\n`;
  `	EXTRN caml_raise_exn: NEAR\n`;
  let lbl_begin = Compilenv.make_symbol (Some "data_begin") in
  add_def_symbol lbl_begin;
  `	.DATA\n`;
  `	PUBLIC	{emit_symbol lbl_begin}\n`;
  `{emit_symbol lbl_begin} LABEL QWORD\n`;
  let lbl_begin = Compilenv.make_symbol (Some "code_begin") in
  add_def_symbol lbl_begin;
  `	.CODE\n`;
  `	PUBLIC	{emit_symbol lbl_begin}\n`;
  `{emit_symbol lbl_begin} LABEL QWORD\n`

let end_assembly() =
  let lbl_end = Compilenv.make_symbol (Some "code_end") in
  add_def_symbol lbl_end;
  `	.CODE\n`;
  `	PUBLIC	{emit_symbol lbl_end}\n`;
  `{emit_symbol lbl_end} LABEL QWORD\n`;
  `	.DATA\n`;
  let lbl_end = Compilenv.make_symbol (Some "data_end") in
  add_def_symbol lbl_end;
  `	PUBLIC	{emit_symbol lbl_end}\n`;
  `{emit_symbol lbl_end} LABEL QWORD\n`;
  `	QWORD	0\n`;
  let lbl = Compilenv.make_symbol (Some "frametable") in
  add_def_symbol lbl;
  `	PUBLIC	{emit_symbol lbl}\n`;
  `{emit_symbol lbl} LABEL QWORD\n`;
  emit_frames
    { efa_label = (fun l -> `	QWORD	{emit_label l}\n`);
      efa_16 = (fun n -> `	WORD	{emit_int n}\n`);
      efa_32 = (fun n -> `	DWORD	{emit_int32 n}\n`);
      efa_word = (fun n -> `	QWORD	{emit_int n}\n`);
      efa_align = emit_align;
      efa_label_rel = (fun lbl ofs ->
                           `	DWORD	{emit_label lbl} - THIS BYTE + {emit_int32 ofs}\n`);
      efa_def_label = (fun l -> `{emit_label l}	LABEL	QWORD\n`);
      efa_string = (fun s -> emit_bytes_directive  "	BYTE	" (s ^ "\000")) };
  `\n;External functions\n\n`;
  StringSet.iter
    (fun s ->
      if not (StringSet.mem s !symbols_defined) then
        `	EXTRN	{emit_symbol s}: NEAR\n`)
    !symbols_used;
  symbols_used := StringSet.empty;
  symbols_defined := StringSet.empty;
  `END\n`