From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47048) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtGPv-00050U-9k for qemu-devel@nongnu.org; Mon, 02 Nov 2015 09:49:03 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZtGPq-0004ou-AI for qemu-devel@nongnu.org; Mon, 02 Nov 2015 09:49:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51699) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtGPq-0004op-4N for qemu-devel@nongnu.org; Mon, 02 Nov 2015 09:48:58 -0500 References: <1446473134-4330-1-git-send-email-pbonzini@redhat.com> From: Paolo Bonzini Message-ID: <563777D5.6050000@redhat.com> Date: Mon, 2 Nov 2015 15:48:53 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: Blue Swirl , Mark Cave-Ayland , QEMU Developers On 02/11/2015 15:09, Peter Maydell wrote: >> > diff --git a/target-sparc/vis_helper.c b/target-sparc/vis_helper.c >> > index 383cc8b..45fc7db 100644 >> > --- a/target-sparc/vis_helper.c >> > +++ b/target-sparc/vis_helper.c >> > @@ -447,7 +447,7 @@ uint32_t helper_fpackfix(uint64_t gsr, uint64_t rs2) >> > for (word = 0; word < 2; word++) { >> > uint32_t val; >> > int32_t src = rs2 >> (word * 32); >> > - int64_t scaled = src << scale; >> > + int64_t scaled = (int64_t)src << scale; >> > int64_t from_fixed = scaled >> 16; > This will now shift left into the sign bit of a signed integer, > which is undefined behaviour. Why "now"? It would have done the same before. Paolo