From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id 74B5838582B4; Mon, 24 Oct 2022 06:22:53 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 74B5838582B4
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1666592573;
	bh=SGfGpOh81aVyEGL41VncvW+FqagI/bMJ+uT0i0bsx4E=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=jycjMZJg0M6C+kCb+gFjejd/pv/D7hCJurDoLM3DqtGZENIZAD92aEedo9iFRzsNp
	 BaE4X5ZumHF7cdvvaZbj2Qvj6uawediXrNuFE10BfYZaJQ5O/aPs74WQDCChHpr6T2
	 XM8PEXXR6kgyKIyrt6wvyW3pPiJbhAx0AST3BBbk=
From: "jacob at jacob dot remcomp.fr" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/107370] long double precision is wrong in ARM 64
Date: Mon, 24 Oct 2022 06:22:53 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 10.2.1
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jacob at jacob dot remcomp.fr
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-107370-4-KlUf8p5snN@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-107370-4@http.gcc.gnu.org/bugzilla/>
References: <bug-107370-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107370

--- Comment #1 from jacob navia <jacob at jacob dot remcomp.fr> ---
This program produces correct results:
#include <stdio.h>
#include <math.h>
long double nsqrt(long double x)
{
        double m =3D sqrt(x);
        long double r =3D m;

        r =3D (r+x/r)/2.0L;

        r =3D (r+x/r)/2.0L;
        r =3D (r+x/r)/2.0L;
        r =3D (r+x/r)/2.0L;
        r =3D (r+x/r)/2.0L;
        return r;
}

int main(void) { printf("%.30Lg \n",nsqrt(2.0L)); }
produces:
1.41421356237309504880168872421=20
All digits que OK.

jacob=