search for: optmisations

On Feb 26, 2011, at 1:36 PM, Joerg Sonnenberger wrote: > On Sat, Feb 26, 2011 at 01:07:39PM -0800, Jakob Stoklund Olesen wrote: >> >> You may want to consider using xorl+decl instead. It is also three >> bytes, and there are no false dependencies. The xor idiom is recognized >> by processors as old as Pentium 4 as having no dependencies. > > Any examples of how

...d to not reorder stores [2]: "Stores Are Seen in a Consistent Order by Other Processors". We rely on both these facts and don't use barrier in the virtq code. However I do agree that we'll have to put barriers once we switch to other architectures and/or LuaJIT implements ordering optmisations. Finally, I checked the virtio 1.0 spec again and didn't see any explicit mentioning of memory barriers regarding the device side of the spec. There are several places where memory barriers are mentioned and these all are about the driver. Maybe they are omitted because they are implicit someh...

On Sat, Feb 26, 2011 at 01:07:39PM -0800, Jakob Stoklund Olesen wrote: > > On Feb 25, 2011, at 7:27 PM, Joerg Sonnenberger wrote: > > > I'm trying to add a X86 pattern to turn > > movl $-1, %eax > > into > > orl $-1, $eax > > Please make sure to measure the performance impact of doing this. You > are creating a false dependency on the last

...s having no dependencies. > > > > Any examples of how to create more than one instructions for a given > > pattern? There are some other cases I could use this for. > > def : Pat<(i32 -1), (DEC32r (MOV32r0))>; Hm. Right. This gives the me first set of size peep hole optmisations as attached. I didn't add the above rule for 64bit builds, since it is larger than the to-be-figured out OR32rmi8 / OR64rmi8. Joerg -------------- next part -------------- A non-text attachment was scrubbed... Name: X86InstrCompiler.td.diff Type: text/x-diff Size: 876 bytes Desc: not available...

On 14 March 2012 at 23:09, Simon Urbanek wrote: | I thought I'll post this here since I could not find an answer anywhere I searched: how to setup R with threaded BLAS on Debian/Ubuntu. | | First, neither Debian nor Ubuntu come with optimized ATLAS binaries, simply because by definition they need to be optimized for a particular machine. The good news: it is easy to build: | | apt-get source

Hi Nikolay, I poked at src/lib/virtio/virtq.lua a bit - I was surprised to find no explicit CPU memory barriers in the virtq implementation. These are typically required when using virtio on smp machines - the spec actually mention where barriers are necessary. Are the barriers implicit somehow for lua? I'd be curious to learn. Thanks, -- MST

Hi Nikolay, I poked at src/lib/virtio/virtq.lua a bit - I was surprised to find no explicit CPU memory barriers in the virtq implementation. These are typically required when using virtio on smp machines - the spec actually mention where barriers are necessary. Are the barriers implicit somehow for lua? I'd be curious to learn. Thanks, -- MST