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- /* Copyright (C) 2001-2022 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 (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
- #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 @
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