From: Jeff Law <jlaw@tachyum.com>
To: "H.J. Lu" <hjl.tools@gmail.com>, Jakub Jelinek <jakub@redhat.com>
Cc: Michael Matz <matz@suse.de>, GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: Aligning stack offsets for spills
Date: Tue, 8 Jun 2021 09:18:20 -0600 [thread overview]
Message-ID: <2714d40f-46f5-7039-33b6-e52585569071@tachyum.com> (raw)
In-Reply-To: <CAMe9rOr4Bz1mX-N1Omr29UykUPqo03B3eaLY2pPGzam1d0Yd9g@mail.gmail.com>
On 6/8/2021 9:06 AM, H.J. Lu wrote:
> On Tue, Jun 8, 2021 at 7:56 AM Jakub Jelinek via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
>> On Tue, Jun 08, 2021 at 08:47:26AM -0600, Jeff Law wrote:
>>>> Why is the machinery involving STACK_SLOT_ALIGNMENT and
>>>> spill_slot_alignment() (for spilling) or get_stack_local_alignment() (for
>>>> backing stack slots) not working for you? If everything is setup
>>>> correctly the input alignment to try_fit_stack_local ought to be correct
>>>> already.
>>> We don't need the MEM as a whole aligned, just the offset in the address
>>> calculation due to how we encode those instructions. If I've read that code
>>> correctly, it would arrange for a dynamic realignment of the stack so that
>>> it could then align the slot. None of that is necessary for us and we'd like
>>> to avoid forcing the dynamic stack realignment. Or did I misread the code?
>> I think dynamic stack realignment is done only on x86, no other backend has
> I believe that all pieces of infrastructure to realign the stack are
> in place. You
> just need to properly align the stack in the backend.
As I've stated, we don't need the stack aligned to these higher
boundaries. Nor do we need the slot as a whole aligned. That's
ultimately just wasteful since we don't need them. We just want to get
an aligned offset.
Jeff
next prev parent reply other threads:[~2021-06-08 15:18 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-07 19:00 Jeff Law
2021-06-08 6:56 ` Richard Biener
2021-06-08 15:00 ` Jeff Law
2021-06-08 14:08 ` Michael Matz
2021-06-08 14:47 ` Jeff Law
2021-06-08 14:55 ` Jakub Jelinek
2021-06-08 15:06 ` H.J. Lu
2021-06-08 15:18 ` Jeff Law [this message]
2021-06-08 15:56 ` Michael Matz
2021-06-10 22:49 ` Jeff Law
2021-06-10 19:28 ` Peter Bergner
2021-06-10 21:34 ` Segher Boessenkool
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