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Re: [Qemu-arm] [Qemu-devel] [PATCH 5/7] target-arm: Add isread parameter

From: Alex Bennée
Subject: Re: [Qemu-arm] [Qemu-devel] [PATCH 5/7] target-arm: Add isread parameter to CPAccessFns
Date: Fri, 05 Feb 2016 16:43:42 +0000
User-agent: mu4e 0.9.17; emacs

Peter Maydell <address@hidden> writes:

> On 5 February 2016 at 16:17, Alex Bennée <address@hidden> wrote:
>> Peter Maydell <address@hidden> writes:
>>> I haven't measured, no, but since there are only 3 arguments the
>>> third argument is going to be in a register on any host architecture
>>> we care about, which means the overhead is just going to be a single
>>> "load constant 0 or 1 into register before the call". I think that's
>>> going to be lost in the noise compared to actually having to make
>>> the function call at all, the work the function call does, and then
>>> the second function call later to do the read or write.
>> I was thinking of knock on effects on spilling other registers in the
>> TCG code. I guess this depends on how complex the code is around system
>> register access.
> The register in question is going to be caller-saves anyway, so no
> effect on spilling in the TCG code I think.

Well my only remaining objection is the additional line-wrapping looks
ugly which I don't think is a valid objection ;-)

Reviewed-by: Alex Bennée <address@hidden>

> thanks
> -- PMM

Alex Bennée

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