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/* Copyright (C) 2001, 2002, 2011 Free Software Foundation, Inc.
   Contributed by Hans-Peter Nilsson <hp@bitrange.com>

This file is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 3, or (at your option) any
later version.

This file is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

% This is the crt0 equivalent for mmix-knuth-mmixware, for setting up
% things for compiler-generated assembly-code and for setting up things
% between where the simulator calls and main, and shutting things down on
% the way back.  There's an actual crt0.o elsewhere, but that's a dummy.

% This file and the GCC output are supposed to be *reasonably*
% mmixal-compatible to enable people to re-use output with Knuth's mmixal.
% However, forward references are used more freely: we are using the
% binutils tools.  Users of mmixal beware; you will sometimes have to
% re-order things or use temporary variables.

% Users of mmixal will want to set up 8H and 9H to be .text and .data
% respectively, so the compiler can switch between them pretending they're
% segments.

% This little treasure is here so the 32 lowest address bits of user data
% will not be zero.  Because of truncation, that would cause testcase
% gcc.c-torture/execute/980701-1.c to incorrectly fail.

        .data   ! mmixal:= 8H LOC Data_Segment
        .p2align 3
        LOC @+(8-@)@7
        OCTA 2009

        .text   ! mmixal:= 9H LOC 8B; LOC #100
        .global Main

% The __Stack_start symbol is provided by the link script.
stackpp OCTA __Stack_start

% "Main" is the magic symbol the simulator jumps to.  We want to go
% on to "main".
% We need to set rG explicitly to avoid hard-to-debug situations.
Main    SETL    $255,32
        PUT     rG,$255

% Initialize the stack pointer.  It is supposedly made a global
% zero-initialized (allowed to change) register in crtn.S; we use the
% explicit number.
        GETA    $255,stackpp
        LDOU    $254,$255,0

% Make sure we get more than one mem, to simplify counting cycles.
        LDBU    $255,$1,0
        LDBU    $255,$1,1

        PUSHJ   $2,_init

#ifdef __MMIX_ABI_GNU__
% Copy argc and argv from their initial position to argument registers
% where necessary.
        SET     $231,$0
        SET     $232,$1
#else
% For the mmixware ABI, we need to move arguments.  The return value will
% appear in $0.
        SET     $2,$1
        SET     $1,$0
#endif

        PUSHJ   $0,main
        JMP     exit

% Provide the first part of _init and _fini.  Save the return address on the
% register stack.  We eventually ignore the return address of these
% PUSHJ:s, so it doesn't matter that whether .init and .fini code calls
% functions or where they store rJ.  We shouldn't get there, so die
% (TRAP Halt) if that happens.

        .section .init,"ax",@progbits
        .global _init
_init:
        GET     $0,:rJ
        PUSHJ   $1,0F
        SETL    $255,255
        TRAP    0,0,0
0H      IS      @

% Register _fini to be executed as the last atexit function.
#ifdef __MMIX_ABI_GNU__
        GETA    $231,_fini
#else
        GETA    $1,_fini
#endif
        PUSHJ   $0,atexit

        .section .fini,"ax",@progbits
        .global _fini
_fini:
        GET     $0,:rJ
        PUSHJ   $1,0F
        SETL    $255,255
        TRAP    0,0,0
0H      IS      @