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Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support
From: |
Marek Vasut |
Subject: |
Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support |
Date: |
Wed, 19 Oct 2016 04:31:00 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.4.0 |
On 10/19/2016 03:24 AM, Richard Henderson wrote:
> On 10/18/2016 03:05 PM, Marek Vasut wrote:
>>>> Thanks, I hope this is fixed now, although I mostly special-case the
>>>> R_ZERO handling throughout the code. Any writes to R_ZERO are now
>>>> ignored and any usage is converted to mov/movi instructions where
>>>> applicable.
>>>
>>> We've done that in the past, but in the end it is much cleaner to
>>> minimize the number of places in which you have to check for R_ZERO.
>>
>> Isn't it a bit more performant if you generate as little TCG
>> instructions as possible ?
>
> Well, yes and no.
>
> We're always going to run the tcg optimizers, so the resulting code
> should be the same either way.
I see, I'd have to dig deeper into the TCG.
> Processing a little more data can be preferable to fewer branch
> prediction failures. And the best way to avoid those is to not have the
> branch at all. Especially when it's unlikely that the data will be
> created in the first place.
OK, but I need to make sure stores to ZERO register are ignored, right ?
--
Best regards,
Marek Vasut
- Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support, Marek Vasut, 2016/10/17
- Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support, Richard Henderson, 2016/10/18
- Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support, Marek Vasut, 2016/10/18
- Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support, Richard Henderson, 2016/10/18
- Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support, Marek Vasut, 2016/10/18
- Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support, Richard Henderson, 2016/10/18
- Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support,
Marek Vasut <=
- Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support, Richard Henderson, 2016/10/19
- Re: [Qemu-devel] [PATCH 2/7] nios2: Add architecture emulation support, Marek Vasut, 2016/10/19