On 27 February 2013 08:54, David Chisnall <David.Chisnall at cl.cam.ac.uk>wrote:> > People normally care about code size on Cortex-R/M and ARM9 or older, > and in there, not many LLVM users. > > There are a lot of A8 devices around with 256KB (or less) of L2 cache > (32KB of L1 i-cache), and so code density, if not code size, matters a lot > for these. Cache sizes in mobile chips tend to be as small as possible, as > it's very hard to turn off those transistors (there are several projects at > ARM and elsewhere that I'm aware of in this direction, but I don't know of > any in shipping products yet). >I didn't mean to say that code size is not important, especially for ARM, just that the average LLVM user (even ARM users) will not care yet that much. Most benchmarks I've seen around are all platform software, comparing performance with Atom and not a single mention on code size. When I did some benchmarks a few years back, I noticed that LLVM's code was at least twice as big as GCC with the same specs, some times more than 4x bigger, would be good to know how it compares now to see how much people really care about code size. Reed, Will you be able to share your results? I think you'll find that LLVM has indeed progressed in that area, as I've seen some commits going through during the last few years on that area. I'd like to know if we're getting close to GCC. cheers, --renato -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130227/036bf458/attachment.html>
I will surely share some results when I have them. I'm working on mips 16 which is like thumb 1. For mips 16 people only care about size usually. I need to implement a simple version of constant islands which I hope to finish this week and then I should have the tools to start to be competitive. Reed On 02/27/2013 06:23 AM, Renato Golin wrote:> On 27 February 2013 08:54, David Chisnall <David.Chisnall at cl.cam.ac.uk > <mailto:David.Chisnall at cl.cam.ac.uk>> wrote: > > > People normally care about code size on Cortex-R/M and ARM9 or > older, and in there, not many LLVM users. > > There are a lot of A8 devices around with 256KB (or less) of L2 > cache (32KB of L1 i-cache), and so code density, if not code size, > matters a lot for these. Cache sizes in mobile chips tend to be > as small as possible, as it's very hard to turn off those > transistors (there are several projects at ARM and elsewhere that > I'm aware of in this direction, but I don't know of any in > shipping products yet). > > > I didn't mean to say that code size is not important, especially for > ARM, just that the average LLVM user (even ARM users) will not care > yet that much. > > Most benchmarks I've seen around are all platform software, comparing > performance with Atom and not a single mention on code size. When I > did some benchmarks a few years back, I noticed that LLVM's code was > at least twice as big as GCC with the same specs, some times more than > 4x bigger, would be good to know how it compares now to see how much > people really care about code size. > > Reed, > > Will you be able to share your results? I think you'll find that LLVM > has indeed progressed in that area, as I've seen some commits going > through during the last few years on that area. I'd like to know if > we're getting close to GCC. > > cheers, > --renato >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130227/e3edabe2/attachment.html>
On 27 February 2013 16:44, reed kotler <rkotler at mips.com> wrote:> I'm working on mips 16 which is like thumb 1. > For mips 16 people only care about size usually. >So I guess it's on the same level as the M0, makes sense worry more about code size than optimization levels. --renato -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130227/98d17341/attachment.html>