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/* Copyright (C) 2001-2021 Free Software Foundation, Inc.
Contributed by Hans-Peter Nilsson <>
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
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
<>. */
% 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 (some contents) is required 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
dstart 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
crtstxt OCTA _init % Assumed to be the lowest executed address.
OCTA __etext % Assumed to be beyond the highest executed address.
crtsdat OCTA dstart % Assumed to be the lowest accessed address.
OCTA _end % Assumed to be beyond the highest accessed address.
% "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
% Make sure we have valid memory for addresses in .text and .data (and
% .bss, but we include this in .data), for the benefit of mmo-using
% simulators that require validation of addresses for which contents
% is not present. Due to its implicit-zero nature, zeros in contents
% may be left out in the mmo format, but we don't know the boundaries
% of those zero-chunks; for mmo files from binutils, they correspond
% to the beginning and end of sections in objects before linking. We
% validate the contents by executing PRELD (0; one byte) on each
% 2048-byte-boundary of our .text .data, and we assume this size
% matches the magic lowest-denominator chunk-size for all
% validation-requiring simulators. The effect of the PRELD (any size)
% is assumed to be the same as initial loading of the contents, as
% long as the PRELD happens before the first PUSHJ/PUSHGO. If it
% happens after that, we'll need to distinguish between
% access-for-execution and read/write access.
GETA $255,crtstxt
LDOU $2,$255,0
ANDNL $2,#7ff % Align the start at a 2048-boundary.
LDOU $3,$255,8
SETL $4,2048
0H PRELD 0,$2,0
ADDU $2,$2,$4
CMP $255,$2,$3
BN $255,0B
GETA $255,crtsdat
LDOU $2,$255,0
ANDNL $2,#7ff
LDOU $3,$255,8
0H PRELD 0,$2,0
ADDU $2,$2,$4
CMP $255,$2,$3
BN $255,0B
% 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
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
% For the mmixware ABI, we need to move arguments. The return value will
% appear in $0.
SET $2,$1
SET $1,$0
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
GET $0,:rJ
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
GETA $1,_fini
PUSHJ $0,atexit
.section .fini,"ax",@progbits
.global _fini
GET $0,:rJ
SETL $255,255
TRAP 0,0,0
0H IS @