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From: Uros Bizjak <ubizjak@gmail.com>
Date: Fri, 14 Apr 2017 12:47:00 -0000
Message-ID: <CAFULd4YwgKAFgoqm97Wh4zMAa4hYbTSzO6Q4T4O0uVCAY_bJhA@mail.gmail.com>
Subject: Re: [PATCH, alpha]: Add earlyclobber to sqrtt/sqrtf insns.
To: Florian Weimer <fw@deneb.enyo.de>
Cc: libc-alpha@sourceware.org, Richard Henderson <rth@twiddle.net>
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On Fri, Apr 14, 2017 at 2:38 PM, Florian Weimer <fw@deneb.enyo.de> wrote:
> * Uros Bizjak:
>
>> Add earlyclobber to sqrtt/sqrtf insns.
>>
>> When using software completions, we have to prevent assembler to match
>> input and output operands of sqrtt/sqrtf insn. Add earlyclobber to
>> output operand to avoid unwanted operand matching.
>
> Is this so that the trap handler can recover the original input?
>
> In this case, please add this to the commit message for those of us
> who are not familiar with the Alpha architecture.

I don't know the low-level details, perhaps Richard can explain these
requirements.

The sqrtt simply returns zero for subnormal operand with software
completions when input and output reg are matched.

Uros.