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Re: [PATCH] Update assertion in sched-ebb.c to cope with table jumps
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Jeff Law <law at redhat dot com>
- Cc: David Malcolm <dmalcolm at redhat dot com>, Alexander Monakov <amonakov at ispras dot ru>, Andrey Belevantsev <abel at ispras dot ru>, gcc-patches at gcc dot gnu dot org
- Date: Tue, 26 Mar 2019 12:52:14 -0500
- Subject: Re: [PATCH] Update assertion in sched-ebb.c to cope with table jumps
- References: <alpine.LNX.2.20.13.1901231642120.22415@monopod.intra.ispras.ru> <1548256275-42315-1-git-send-email-dmalcolm@redhat.com> <4ad1f9b7-343f-c1e2-3903-af6e43c2b611@redhat.com>
On Mon, Mar 25, 2019 at 05:12:05PM -0600, Jeff Law wrote:
> To touch on one of the issues I raised. AFAICT the schedulers don't use
> SCHED_GROUP_P for dealing with tablejumps. They're used for
> cc0-user/setter, fused insns and the like. That's a bit of a surprise.
>
> Given that the table isn't actually associated with the block with the
> tablejump, SCHED_GROUP_P might actually create a whole new set of problems.
>
> Why oh why is the jump table data not actually attached to the tablejump
> insn itself. Nearly 30 years of working on GCC and I can't answer that one.
It somewhat makes sense for targets where the jump table is emitted in the
text section; we then need to know its size for jumps over it, etc.
Segher