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From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: David Daney <ddaney@caviumnetworks.com>
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>,
	David Daney <ddaney.cavm@gmail.com>,
	linux-mips@linux-mips.org, Ralf Baechle <ralf@linux-mips.org>,
	Zubair.Kakakhel@imgtec.com, geert+renesas@glider.be,
	peterz@infradead.org, paul.gortmaker@windriver.com,
	chenhc@lemote.com, cl@linux.com, Ingo Molnar <mingo@kernel.org>,
	richard@nod.at, zajec5@gmail.com, james.hogan@imgtec.com,
	keescook@chromium.org, tj@kernel.org, alex@alex-smith.me.uk,
	pbonzini@redhat.com, blogic@openwrt.org, paul.burton@imgtec.com,
	qais.yousef@imgtec.com, linux-kernel@vger.kernel.org,
	markos.chandras@imgtec.com, dengcheng.zhu@imgtec.com,
	manuel.lauss@gmail.com, lars.persson@axis.com,
	David Daney <david.daney@cavium.com>
Subject: Re: [PATCH 2/3] MIPS: Add full ISA emulator.
Date: Thu, 4 Dec 2014 11:49:27 +0000 (GMT)	[thread overview]
Message-ID: <alpine.LFD.2.11.1412040310100.22073@eddie.linux-mips.org> (raw)
In-Reply-To: <547FA8D2.2030703@caviumnetworks.com>

On Wed, 3 Dec 2014, David Daney wrote:

> > but it doesn't support customized instructions,
> 
> GCC will never put these in the delay slot of a FPU branch, so it is not
> needed.
> 
> > multiple ASEs,
> 
> Same as above.  But any instructions that are deemed necessary can easily be
> added.

 GAS will happily schedule any instruction into a branch delay slot as 
long as the instruction is not architecturally forbidden there (e.g. 
ERET), there is no data dependency with the branch that would affect the 
result produced and the instruction is not an explicit exception trap 
operation (BREAK, SYSCALL, TEQ, etc.).  For some reason, unknown to me all 
MT ASE instructions are disallowed too.  Anything else -- free to go in!

 Of course instructions can be scheduled into branch delay slots manually 
too, in handcoded assembly, and that has to continue working.

  Maciej

  parent reply	other threads:[~2014-12-04 11:49 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-03 23:44 [PATCH 0/3] MIPS: Get ready for non-executable stack David Daney
2014-12-03 23:44 ` [PATCH 1/3] MIPS: Add FPU emulator counter for non-FPU instructions emulated David Daney
2014-12-03 23:44 ` [PATCH 2/3] MIPS: Add full ISA emulator David Daney
2014-12-03 23:55   ` Leonid Yegoshin
2014-12-04  0:20     ` David Daney
2014-12-04  0:52       ` Leonid Yegoshin
2014-12-04  1:29         ` David Daney
     [not found]           ` <547FBF63.70802@imgtec.com>
2014-12-04  2:21             ` David Daney
2014-12-04 10:16               ` Paul Burton
2014-12-04 10:45                 ` Qais Yousef
2014-12-04 11:49       ` Maciej W. Rozycki [this message]
2014-12-04 17:40         ` David Daney
2014-12-04 20:32           ` Maciej W. Rozycki
2014-12-03 23:44 ` [PATCH 3/3] MIPS: Use full instruction emulation for FPU emulator delay slot emulation David Daney

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