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From: Damian McGuckin <damianm@esi.com.au>
To: musl@lists.openwall.com
Subject: Re: [musl] Considering x86-64 fenv.s to C
Date: Sun, 23 Feb 2020 19:35:03 +1100 (AEDT)	[thread overview]
Message-ID: <alpine.LRH.2.02.2002231819190.25353@key0.esi.com.au> (raw)
In-Reply-To: <20200223062513.GN1663@brightrain.aerifal.cx>

On Sun, 23 Feb 2020, Rich Felker wrote:

> On Sun, Feb 23, 2020 at 04:41:31PM +1100, Damian McGuckin wrote:
>> On Sat, 22 Feb 2020, Rich Felker wrote:
>>
>>> First comment: I couldn't find (maybe I missed?) what you intend fore
>>> the contents of fenv-generic.c and fenv-trivial.c to be, but I don't
>>> see what you want them for. fenv.c should just use the macros/inlines
>>> the fenv_arch.h defines, naturally collapsing to empty functions when
>>> they do nothing (for softfloat archs).
>>
>> I agree. I was seduced by what I thought was a better way.
>>
>> I assume that I can also have a
>>
>> 	fenv_arch_soft_float.h
>
> I don't follow what this would be for. Presumably 
> arch/generic/fenv_arch.h would be empty and the internal header that 
> includes fenv_arch.h would define dummy fenv accessor helpers in the 
> absence of any defined by fenv_arch.h, or similar.

In
 	arch/generic/bits/fenv.h

You have

 	#define FE_ALL_EXCEPT 0
 	#define FE_TONEAREST  0

 	typedef unsigned long fexcept_t;

 	typedef struct { unsigned long __cw; } fenv_t;

 	#define FE_DFL_ENV      ((const fenv_t *) -1)

If you effectively #include this file into the generic code, it should do 
as you suggest. I think. See below. It does rely on FE_INVALID not being 
defined.

If I fudge it on my X86_64, every routine just does

 	xorl	%eax, %eax
i.e.
 	return 0

except for

fesetround:
.LFB12:
     .cfi_startproc
     cmpl    $1, %edi
     sbbl    %eax, %eax
     notl    %eax
     ret

fegetexceptflag:
.LFB18:
     .cfi_startproc
     movq    $0, (%rdi)
     xorl    %eax, %eax
     ret

Also
 	__flt_rounds()

returns 1 which means round to nearest style which it should.

Regards - Damian

Pacific Engineering Systems International, 277-279 Broadway, Glebe NSW 2037
Ph:+61-2-8571-0847 .. Fx:+61-2-9692-9623 | unsolicited email not wanted here
Views & opinions here are mine and not those of any past or present employer

  reply	other threads:[~2020-02-23  8:35 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16  4:30 Damian McGuckin
2020-01-16 15:11 ` Markus Wichmann
2020-01-16 16:14 ` Rich Felker
2020-01-16 18:56   ` Damian McGuckin
2020-01-16 19:33     ` Rich Felker
2020-01-16 21:31       ` Damian McGuckin
2020-01-17  3:36       ` Damian McGuckin
2020-01-17  3:48         ` Damian McGuckin
2020-01-17  3:53         ` David Edelsohn
2020-01-17 14:13           ` Rich Felker
2020-01-17 14:19             ` David Edelsohn
2020-01-17 14:53         ` Rich Felker
2020-01-18  4:45           ` Damian McGuckin
2020-01-18  5:29             ` Rich Felker
2020-01-19  8:50               ` Damian McGuckin
2020-01-19  9:07           ` Damian McGuckin
2020-01-19 10:42             ` Szabolcs Nagy
2020-01-19 12:25               ` Damian McGuckin
2020-01-20  5:32           ` Damian McGuckin
2020-01-20 17:38             ` Rich Felker
2020-01-20 21:11               ` [musl] Triggering Overflow (or Underflow) without triggering Inexact on i386 Damian McGuckin
2020-01-20 22:32                 ` Szabolcs Nagy
2020-01-21  3:53           ` [musl] Considering x86-64 fenv.s to C Damian McGuckin
2020-01-21  4:22             ` Rich Felker
2020-01-21  4:46               ` Damian McGuckin
2020-01-21  7:26                 ` Damian McGuckin
2020-01-17 16:41         ` Markus Wichmann
2020-01-18  1:15           ` Szabolcs Nagy
2020-01-18  5:03             ` Damian McGuckin
2020-01-18  5:37               ` Rich Felker
2020-01-18  9:40                 ` Szabolcs Nagy
2020-01-24  0:42                   ` Damian McGuckin
2020-01-24  1:11                     ` Rich Felker
2020-01-24  4:13                       ` Damian McGuckin
2020-01-24  4:55                         ` Rich Felker
2020-01-24  6:08                           ` Damian McGuckin
2020-01-24 13:44                             ` Rich Felker
2020-01-24 14:45                               ` Damian McGuckin
2020-01-24 23:59                               ` Damian McGuckin
2020-01-25  0:11                                 ` Rich Felker
2020-01-26  3:28                                   ` Damian McGuckin
2020-01-26  3:28                                   ` Damian McGuckin
2020-01-26  3:30                                   ` Damian McGuckin
2020-01-26  3:32                                   ` Damian McGuckin
2020-01-26  5:25                                   ` Damian McGuckin
2020-01-27  3:32                                   ` Damian McGuckin
2020-01-27  5:39                                   ` Damian McGuckin
2020-02-02  0:47                                   ` Damian McGuckin
2020-02-03  0:54                                   ` Damian McGuckin
2020-02-03  2:09                                     ` Rich Felker
2020-02-03  2:12                                       ` Damian McGuckin
2020-02-22 20:17                                         ` Rich Felker
2020-02-22 20:53                                           ` Damian McGuckin
2020-02-23  5:41                                           ` Damian McGuckin
2020-02-23  6:25                                             ` Rich Felker
2020-02-23  8:35                                               ` Damian McGuckin [this message]
2020-02-07 21:25                                   ` Damian McGuckin
2020-02-07 21:38                                     ` Rich Felker
2020-02-07 23:53                                       ` Damian McGuckin
2020-02-09  5:04                                       ` Damian McGuckin
2020-01-24  7:10                           ` Damian McGuckin
2020-01-18  5:04             ` Markus Wichmann
2020-02-03 14:16 [musl] PPC64(LE) support in musl requires ALTIVEC Romain Naour
2020-02-03 14:50 ` Rich Felker
2020-02-05  1:32   ` [musl] Considering x86-64 fenv.s to C Damian McGuckin

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