From: Jeff Law <law@redhat.com>
To: Armin Rigo <arigo@tunes.org>, David Malcolm <dmalcolm@redhat.com>
Cc: Basile Starynkevitch <basile@starynkevitch.net>,
jit@gcc.gnu.org, GCC Development <gcc@gcc.gnu.org>
Subject: Re: GCC/JIT and precise garbage collection support?
Date: Thu, 01 Jan 2015 00:00:00 -0000 [thread overview]
Message-ID: <55A01062.8000301@redhat.com> (raw)
In-Reply-To: <CAMSv6X3kfoydJAJ1AJXvcDqCaLrSFGp4a=Cqsqxo==iqP1Tj=w@mail.gmail.com>
On 07/10/2015 09:04 AM, Armin Rigo wrote:
> Hi David,
>
> On 10 July 2015 at 16:11, David Malcolm <dmalcolm@redhat.com> wrote:
>> AIUI, we have CALL_INSN instructions all the way through the RTL phase
>> of the backend, so we can identify which locations in the generated code
>> are calls; presumably we'd need at each CALL_INSN to determine somehow
>> which RTL expressions tagged as being GC-aware are live (perhaps a
>> mixture of registers and fp-offset expressions?)
>>
>> So presumably we could use that information (maybe in the final pass) to
>> write out some metadata describing for each %pc callsite the relevant GC
>> roots.
>>
>> Armin: does this sound like what you need?
>
> Not quite. I can understand that you're trying to find some solution
> with automatic discovery of the live variables of a "GC pointer" type
> and so on. This is more than we need, and if
> we had that, then we'd need to work harder to remove the extra stuff.
> We only want the end result: attach to each CALL_INSN a list of
> variables which should be stored in the stack map for that call, and
> be ready to see these locations be modified from outside across the
> call if a GC occurs.
I wonder how much overlap there is between this need and what we're
going to need to do for resumable functions which are being discussed in
the ISO C++ standards meetings.
jeff
next prev parent reply other threads:[~2015-07-10 18:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-01 0:00 Basile Starynkevitch
2015-01-01 0:00 ` Andrew Haley
2015-01-01 0:00 ` David Malcolm
2015-01-01 0:00 ` Armin Rigo
2015-01-01 0:00 ` David Malcolm
2015-01-01 0:00 ` Armin Rigo
2015-01-01 0:00 ` Jeff Law [this message]
2015-01-01 0:00 ` Trevor Saunders
2015-01-01 0:00 ` Andrew Haley
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