Debian Bug report logs - #775235
use llvm's getCPUTargetFeatures() over getHostCPUName()

Package: libgl1-mesa-dri; Maintainer for libgl1-mesa-dri is Debian X Strike Force <[email protected]>; Source for libgl1-mesa-dri is src:mesa (PTS, buildd, popcon).

Reported by: Steve McIntyre <[email protected]>

Date: Mon, 12 Jan 2015 21:39:01 UTC

Severity: wishlist

Tags: patch

Forwarded to https://patchwork.freedesktop.org/patch/34445/

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From: Michael Gilbert <[email protected]>
Date: Wed, 15 Apr 2015 23:08:11 -0400
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Subject: Re: Bug#775235: Bug#776911: gnome-shell: fails to start on i386 when
 [Mesa was] built with llvm-3.5
To: [email protected]
Content-Type: text/plain; charset=UTF-8
control: severity -1 wishlist
control: forwarded -1 https://freedesktop.org/patch/34445
control: retitle -1 mesa: use llvm's getCPUTargetFeatures() instead of
getHostCPUName()

It turns out that mesa uses llvm's getHostCPUName(), and qemu i386 by
default (correctly) reports itself as pentium2, which is assumed
non-sse2. gnome-shell uses a mesa feature that requires sse2, so it
fails at startup on qemu i386.

On llvm trunk they've implemented getCPUTargetFeatures(), which can be
used to check for specific cpu features like sse2, and that is the
long term solution to the problem:
https://llvm.org/bugs/show_bug.cgi?id=23201

In the meantime, the problem can be worked around by using a
non-default qemu cpu options.  Some examples:

$ qemu -cpu pentium3 test.img
$ kvm -cpu host test.img

Since there workarounds are straightforward I am reducing the severity.

Best wishes,
Mike



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