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Date: Tue, 21 Mar 2017 12:50:37 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] aarch64: add single instruction math functions
On Sun, Mar 19, 2017 at 05:26:45AM +0100, Szabolcs Nagy wrote:
> this should increase performance and reduce code size on aarch64.
>
> the compiled code was checked against using __builtin_* instead
> of inline asm with gcc-6.2.0.
>
> lrint is two instructions.
>
> c with inline asm is used because it is safer than a pure asm
> implementation, this prevents ll{rint,round} to be an alias
> of l{rint,round} (because the types don't match) and depends
> on gcc style inline asm support.
>
> ceil, floor, round, trunc can either raise inexact on finite
> non-integer inputs or not raise any exceptions. the new
> implementation does not raise exceptions while the generic
> c code does.
>
> on aarch64, the underflow exception is signaled before rounding
> (ieee 754 allows both before and after rounding, but it must be
> consistent), the generic fma c code signals it after rounding
> so using single instruction fixes a slight conformance issue too.
> ---
Thanks, committing.
Rich
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