Re: [PATCH] alpha: Remove s_ceil{f} and s_floor{f} implementation (BZ#22665)

[Richard Henderson <rth@twiddle.net>]

On 01/03/2018 10:03 AM, Adhemerval Zanella wrote:
> As discussed in libc-alpha [1], alpha ceil{f} and floor{f}
> implementation uses cvttq/svm and although the Alpha Architecture
> Handbook version 3 states that that CVTfi OUTPUT Exceptions
> (B.3 Mapping to IEEE Standard) should not generate Inexact if INE
> bit is set on fpcr, the Alpha 21264 [1] chip manual (A.8 IEEE
> Floating-Point Conformance) states that CVTfi and CVTif OUTPUT
> does generate inexact exception for inexact result regardless.
> 
> As Joseph noted [2] to correctly fix it on alpha we need to either
> avoid the instruction or avoid any inexact bit from it being set
> on return from the function (while preserving the inexact bit that
> might be set on the entry to the function).  The later will result
> mf_fpcr followed by a mt_fpcr to get and set the fpcr which will
> defeat the optimization itself.
> 
> So the patch just remove the alpha optimized and rely on generic
> implementation.  It fixes the math/test-*-{ceil,floor} on alpha.
> 
> 	[BZ #15479]
> 	[BZ #22665]
> 	* sysdeps/alpha/fpu/s_ceil.c: Remove file.
> 	* sysdeps/alpha/fpu/s_ceilf.c: Likewise.
> 	* sysdeps/alpha/fpu/s_floor.c: Likewise.
> 	* sysdeps/alpha/fpu/s_floorf.c: Likewise.

ACK.


r~