From: Ian Lance Taylor <ian@airs.com>
To: Vasanth <geekvasanth@gmail.com>
Cc: gcc@gcc.gnu.org
Subject: Re: dw2 frame unwinder - unaligned access
Date: Tue, 19 Jul 2005 06:04:00 -0000 [thread overview]
Message-ID: <m3d5pfxrfs.fsf@gossamer.airs.com> (raw)
In-Reply-To: <89acfbb605071822335c0e58a4@mail.gmail.com>
Vasanth <geekvasanth@gmail.com> writes:
> What is the recommended way to do DW2 frame unwinding based exception
> handling for targets that do not support unaligned accesses in
> hardware? I did see the documentation about UNALIGNED_INT_ASM_OP, but
> not sure if that is meant to generate a directive to the assembler to
> produce an aligned int (the name indicates otherwise). Also, I see
> UNALIGNED_INT_ASM_OP being used only in the VMS debugging source file.
> So I am unsure how it relates to DW2 based frame unwinding.
UNALIGNED_INT_ASM_OP tells the assembler to not do any automatic
alignment before emitting the value. In current development sources
this is TARGET_ASM_UNALIGNED_SI_OP, and it is defined in a number of
config/*/*.c files.
It should not matter that your target does not support unaligned
access in hardware. The code in read_encoded_value_with_base in
unwind-pe.h should do the right thing, by using a packed union. On a
target which does not support unaligned access, it will use byte
reads.
If you really do want to insist that all accesses be aligned, it
should work to define ASM_PREFERRED_EH_DATA_FORMAT to be
DW_EH_PE_aligned.
Ian
prev parent reply other threads:[~2005-07-19 6:04 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-19 5:34 Vasanth
2005-07-19 6:04 ` Ian Lance Taylor [this message]
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