mailing list of musl libc
 help / color / mirror / code / Atom feed
From: Damian McGuckin <damianm@esi.com.au>
To: musl@lists.openwall.com
Subject: Re: [musl] Considering x86-64 fenv.s to C
Date: Mon, 20 Jan 2020 16:32:32 +1100 (AEDT)	[thread overview]
Message-ID: <alpine.LRH.2.02.2001201626390.9710@key0.esi.com.au> (raw)
In-Reply-To: <20200117145350.GR30412@brightrain.aerifal.cx>

On Fri, 17 Jan 2020, Rich Felker wrote:

> Note that this approach is not compatible with trapping exceptions, but 
> we don't support them anyway.

When an FNSTENV instruction is executed, all pending exceptions are 
essentially lost (either the x87 FPU status register is cleared or all 
exceptions are masked).

I think that this means either it wipes the exception bits in the status 
register or it wipes out the bits of the control register which handle 
which exceptions are trapped.

Am I wrong.

Because MUSL does not support trapping exceptions, we do not need to
restore the control word.

But do we need to copy the lost exceptions flags in the x87 register
back into the SSE register, well at least where we have an SSE.

Mind you, on an i386 without an SSE, you cannot restore them!

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

  parent reply	other threads:[~2020-01-20  5:32 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 [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=alpine.LRH.2.02.2001201626390.9710@key0.esi.com.au \
    --to=damianm@esi.com.au \
    --cc=musl@lists.openwall.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://git.vuxu.org/mirror/musl/

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).