mailing list of musl libc
 help / color / mirror / code / Atom feed
From: Alexander Monakov <amonakov@ispras.ru>
To: musl@lists.openwall.com
Cc: "Alex Rønne Petersen" <alex@alexrp.com>
Subject: Re: [musl] [PATCH] configure: prevent compilers from turning a * b + c into fma(a, b, c)
Date: Wed, 28 Aug 2024 22:56:39 +0300 (MSK)	[thread overview]
Message-ID: <e9cbee4c-ca83-dbb5-a29d-be3e3e543f75@ispras.ru> (raw)
In-Reply-To: <20240828152826.826990-1-alex@alexrp.com>

[-- Attachment #1: Type: text/plain, Size: 556 bytes --]


On Wed, 28 Aug 2024, Alex Rønne Petersen wrote:

> I've seen Clang do this for expressions in the fma() implementation itself,
> which of course led to infinite recursion. This happened when targeting
> arm-linux-musleabi with full soft float mode and -march=armv8-a. I imagine

FWIW I can't seem to reproduce this issue. For optionally-fused multiply-add
LLVM IR uses @llvm.fmuladd.f64, which under -mfloat-abi=soft is expanded via
__aeabi_dmul + __aeabi_dadd. I'm quite unsure how you got LLVM to generate a
call to fma in your circumstances.

Alexander

  parent reply	other threads:[~2024-08-28 19:56 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-08-28 15:28 Alex Rønne Petersen
2024-08-28 15:53 ` Alexander Monakov
2024-08-28 16:31   ` Alex Rønne Petersen
2024-08-28 20:15   ` Rich Felker
2024-08-28 20:32     ` Alexander Monakov
2024-08-28 20:47       ` Rich Felker
2024-08-28 21:11         ` Alexander Monakov
2024-08-29 13:37           ` Alex Rønne Petersen
2024-08-28 19:56 ` Alexander Monakov [this message]
2024-08-29 13:36   ` Alex Rønne Petersen
2024-08-29 15:09     ` Alexander Monakov

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=e9cbee4c-ca83-dbb5-a29d-be3e3e543f75@ispras.ru \
    --to=amonakov@ispras.ru \
    --cc=alex@alexrp.com \
    --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).