Re: [Qemu-devel] QEmu TCG SIMD extension?
On Wed, Mar 06, 2013 at 11:47:58AM +0800, Peter Maydell wrote: On 6 March 2013 11:30, 陳韋任 (Wei-Ren Chen) che...@iis.sinica.edu.tw wrote: While searching for QEMU SIMD issues, I found there was a paper presented in 2011 [1], and the source code is also public on [2]. However, it seems this project doesn't make any progress since last year. I update their change to upstream and you can download from here: $ git clone git://github.com/azru0512/qemu.git -b neon-simd Sadly, it can not boot the kernel image provided on [2]. Anyway, I found there was only one thread has discussion on their work [3]. I want to hear more feedback on their idea on adding SIMD TCG IR. I think my opinions are still the same -- interesting idea, but getting it to work with a set of IR ops which aren't target or host specific and getting it to give correct bit-for-bit results, rounding, flags, etc, is likely to be tricky. It would also be important to determine first whether Neon (or other SIMD) emulation performance is truly a major bottleneck. I found the problem and now it can boot the kernel image and run the test. The authors claim they design the general SIMD IR after studying various SIMD ISA. I am not an expert, and only can decide if it's true or not by writing another frontend. Well, one of reasons I am studying their work is to see SIMD IR could benifit our QEMU+LLVM binary translator. ;) Regards, chenwj -- Wei-Ren Chen (陳韋任) Computer Systems Lab, Institute of Information Science, Academia Sinica, Taiwan (R.O.C.) Tel:886-2-2788-3799 #1667 Homepage: http://people.cs.nctu.edu.tw/~chenwj
Re: [Qemu-devel] QEmu TCG SIMD extension?
Il 06/03/2013 04:47, Peter Maydell ha scritto: On 6 March 2013 11:30, 陳韋任 (Wei-Ren Chen) che...@iis.sinica.edu.tw wrote: While searching for QEMU SIMD issues, I found there was a paper presented in 2011 [1], and the source code is also public on [2]. However, it seems this project doesn't make any progress since last year. I update their change to upstream and you can download from here: $ git clone git://github.com/azru0512/qemu.git -b neon-simd Sadly, it can not boot the kernel image provided on [2]. Anyway, I found there was only one thread has discussion on their work [3]. I want to hear more feedback on their idea on adding SIMD TCG IR. I think my opinions are still the same -- interesting idea, but getting it to work with a set of IR ops which aren't target or host specific and getting it to give correct bit-for-bit results, rounding, flags, etc, is likely to be tricky. It would also be important to determine first whether Neon (or other SIMD) emulation performance is truly a major bottleneck. SSE operations, while not a bottleneck, are the top helpers in the profile when booting Linux on x86. Using common code to generate the simplest unrolled SIMD operations (logical operations, add, subtract, compare to zero) would already help a lot, I think. Paolo
Re: [Qemu-devel] QEmu TCG SIMD extension?
On 6 March 2013 16:18, Paolo Bonzini pbonz...@redhat.com wrote: Il 06/03/2013 04:47, Peter Maydell ha scritto: I think my opinions are still the same -- interesting idea, but getting it to work with a set of IR ops which aren't target or host specific and getting it to give correct bit-for-bit results, rounding, flags, etc, is likely to be tricky. It would also be important to determine first whether Neon (or other SIMD) emulation performance is truly a major bottleneck. SSE operations, while not a bottleneck, are the top helpers in the profile when booting Linux on x86. Using common code to generate the simplest unrolled SIMD operations (logical operations, add, subtract, compare to zero) would already help a lot, I think. Yeah, I don't mean to say it's a bad idea, just that there's a long distance between a neat tech demo/research paper and productised code that can be committed to mainline :-) -- PMM
[Qemu-devel] QEmu TCG SIMD extension?
Hi all, While searching for QEMU SIMD issues, I found there was a paper presented in 2011 [1], and the source code is also public on [2]. However, it seems this project doesn't make any progress since last year. I update their change to upstream and you can download from here: $ git clone git://github.com/azru0512/qemu.git -b neon-simd Sadly, it can not boot the kernel image provided on [2]. Anyway, I found there was only one thread has discussion on their work [3]. I want to hear more feedback on their idea on adding SIMD TCG IR. [1] http://adt.cs.upb.de/quf/quf11/quf2011_12.pdf [2] http://tima-sls.imag.fr/www/research/qemu/simd-qemu/ [3] http://lists.gnu.org/archive/html/qemu-devel/2011-03/msg02065.html Regards, chenwj -- Wei-Ren Chen (陳韋任) Computer Systems Lab, Institute of Information Science, Academia Sinica, Taiwan (R.O.C.) Tel:886-2-2788-3799 #1667 Homepage: http://people.cs.nctu.edu.tw/~chenwj
Re: [Qemu-devel] QEmu TCG SIMD extension?
On 6 March 2013 11:30, 陳韋任 (Wei-Ren Chen) che...@iis.sinica.edu.tw wrote: While searching for QEMU SIMD issues, I found there was a paper presented in 2011 [1], and the source code is also public on [2]. However, it seems this project doesn't make any progress since last year. I update their change to upstream and you can download from here: $ git clone git://github.com/azru0512/qemu.git -b neon-simd Sadly, it can not boot the kernel image provided on [2]. Anyway, I found there was only one thread has discussion on their work [3]. I want to hear more feedback on their idea on adding SIMD TCG IR. I think my opinions are still the same -- interesting idea, but getting it to work with a set of IR ops which aren't target or host specific and getting it to give correct bit-for-bit results, rounding, flags, etc, is likely to be tricky. It would also be important to determine first whether Neon (or other SIMD) emulation performance is truly a major bottleneck. -- PMM
