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Re: [PATCH] Introduce abi_word_mode
- From: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- To: iant at google dot com (Ian Lance Taylor)
- Cc: mark at codesourcery dot com (Mark Mitchell), geoffk at apple dot com (Geoffrey Keating), Andreas dot Krebbel at de dot ibm dot com (Andreas Krebbel), gcc-patches at gcc dot gnu dot org
- Date: Tue, 10 Oct 2006 00:34:22 +0200 (CEST)
- Subject: Re: [PATCH] Introduce abi_word_mode
(I apologize for duplicate messages, I used a broken mailer ...)
Ian Lance Taylor <email@example.com> wrote on 10/09/2006 10:31:02 PM:
> The use in unwind-generic.h most likely does have to be the size of a
> register. The requirement for ABI compliance in this case when the
> size of a register changes has already led to the introduction of the
> undocumented target hook TARGET_EH_RETURN_FILTER_MODE, which would be
> subsumed by Andreas's proposed patch.
Yes, except that TARGET_EH_RETURN_FILTER_MODE only takes are of one
side of the ABI interface -- it allows to compile the application
in 64-bit mode, but it doesn't allow to compile libgcc in 64-bit mode.
Anyway, that's actually a good example, since the use of mode (word)
in the unwind code reflects the *size* of a general purpose register
for unwind purposes, i.e. what's the size of a saved register on the
stack, in the DWARF-2 structures etc.
Now all of *this* is defined by the ABI, and is IMO perfectly
described as "size of a general purpose register according to
the ABI". This may well be different from the actual size of
a general purpose register on the machine.
Dr. Ulrich Weigand
Linux on zSeries Development