On 07/02/17 23:11, Steve Ellcey wrote:
> This patch was submitted last year by Andrew Pinski, this is a
> resubmit/ping of that patch.
>
> https://gcc.gnu.org/ml/gcc-patches/2016-04/msg01726.html
>
> During the initial submittal James Greenhalgh asked if this was an ABI change.
> I do not believe it is because while it is changing the size of the reg
> structure in _Unwind_Context that structure is opaque to anything outside of
> libunwind and so the change is not visible to user programs. It is not
> changing the type or size of _Unwind_Word which remains as 64 bits but it
> fixes some places where those 64 bits are being truncated to 32 bits. Any
> ILP32 Aarch64 program that uses an unwind library without this change may
> abort because of that truncation.
>
> The other thing that this patch does (by setting REG_VALUE_IN_UNWIND_CONTEXT)
> is change the value of ASSUME_EXTENDED_UNWIND_CONTEXT to 1. That should not
> matter because we are currently setting EXTENDED_CONTEXT_BIT in
> uw_init_context_1 anyway and that basically does the same thing, saying that
> we have the opaque extended unwind context structure which can be changed
> without affecting the ABI. I believe that only pre-G++ 3.0 objects would not
> have the extended opaque context structure and there is no ILP32 Aarch64
> support in a compiler that old.
>
> I am a little confused about why, when ASSUME_EXTENDED_UNWIND_CONTEXT
> is set in unwind-dw2.c, we don't still set the EXTENDED_CONTEXT_BIT in
> uw_init_context_1. I guess it doesn't matter because once we start assuming
> the extended unwind context we will never go back and allowing a mix and match
> with pre 3.0 unextended unwind contexts so it doesn't matter if the bit is set
> or not.
>
> I actually tested this patch without changing ASSUME_EXTENDED_UNWIND_CONTEXT
> and it worked as well as this patch where ASSUME_EXTENDED_UNWIND_CONTEXT is
> changed so that change could be left out out by setting it to 0 in the new
> aarch64 value-unwind.h header file if we thought there was a reason to do
> that.
>
> Steve Ellcey
> sell...@cavium.com
>
>
> 2017-02-07 Andrew Pinski <apin...@cavium.com>
>
> * config/aarch64/value-unwind.h: New file.
> * config.host (aarch64*-*-*): Add aarch64/value-unwind.h
> to tm_file.
>
OK.
R.
>
> unwind.patch
>
>
> diff --git a/libgcc/config.host b/libgcc/config.host
> index 9472a60..8bab369 100644
> --- a/libgcc/config.host
> +++ b/libgcc/config.host
> @@ -1379,4 +1379,8 @@ i[34567]86-*-linux* | x86_64-*-linux*)
> fi
> tm_file="${tm_file} i386/value-unwind.h"
> ;;
> +aarch64*-*-*)
> + # ILP32 needs an extra header for unwinding
> + tm_file="${tm_file} aarch64/value-unwind.h"
> + ;;
> esac
> diff --git a/libgcc/config/aarch64/value-unwind.h
> b/libgcc/config/aarch64/value-unwind.h
> index e69de29..c79e832 100644
> --- a/libgcc/config/aarch64/value-unwind.h
> +++ b/libgcc/config/aarch64/value-unwind.h
> @@ -0,0 +1,25 @@
> +/* Store register values as _Unwind_Word type in DWARF2 EH unwind context.
> + Copyright (C) 2017 Free Software Foundation, Inc.
> +
> + This file is part of GCC.
> +
> + GCC 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.
> +
> + GCC 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.
> +
> + 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/>. */
> +
> +/* Define this macro if the target stores register values as _Unwind_Word
> + type in unwind context. Only enable it for ilp32. */
> +#if defined __aarch64__ && !defined __LP64__
> +# define REG_VALUE_IN_UNWIND_CONTEXT
> +#endif
>
