Re: [PATCH] aarch64: add single instruction math functions

[Rich Felker <dalias@libc.org>]

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