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Date: Tue, 10 Sep 2013 18:16:01 +0200
From: Tijl Coosemans <tijl@FreeBSD.org>
To: toolchain@FreeBSD.org
Subject: i386 clang optimisation problem with stack alignment
Message-ID: <20130910181601.2e89af87@kalimero.tijl.coosemans.org>
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Hi,

I've attached a small test program extracted from multimedia/gstreamer-ffmp=
eg
(libavcodec/h264_cabac.c:ff_h264_init_cabac_states(H264Context *h)).

When you compile and run it like this on FreeBSD/i386, it results in a
SIGBUS:

% cc -o paddd paddd.c -O3 -msse2 -fPIE -fomit-frame-pointer=20
% ./paddd
Bus error

The reason is this instruction where %esp isn't 16-byte aligned:
paddd   (%esp), %xmm7

Is this an upstream bug or is this because of local changes (to make the
stack 4 byte aligned by default or something)?

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