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Re: [PR84620] output symbolic entry_view as data2, not addr
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Alexandre Oliva <aoliva at redhat dot com>
- Cc: Jason Merrill <jason at redhat dot com>, gcc-patches at gcc dot gnu dot org, mjw at redhat dot com
- Date: Thu, 8 Mar 2018 10:39:28 +0100
- Subject: Re: [PR84620] output symbolic entry_view as data2, not addr
- Authentication-results: sourceware.org; auth=none
- References: <orfu5ix62w.fsf@lxoliva.fsfla.org> <orwoypspe0.fsf@lxoliva.fsfla.org> <20180306072848.GV5867@tucnak> <orh8prvsxr.fsf@lxoliva.fsfla.org>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Thu, Mar 08, 2018 at 06:05:04AM -0300, Alexandre Oliva wrote:
> On Mar 6, 2018, Jakub Jelinek <jakub@redhat.com> wrote:
>
> > I'm afraid I haven't understood yet why we need labels instead of compiler
> > assigned numbers for the views,
>
> The compiler can't determine points at which the insn address changes
> reliably (or at all). It's impossible in the general case, considering
> that alignment requests might be fulfilled by an assembler without any
> address change, if the current address was just right, and only the
> assembler would know that.
An upper bound would be fine, count any potential spot where you introduce a
view and if the upper bound fits into 8-bit value, use data1, if into 16-bit
value, use data2, otherwise use data4.
Jakub