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brrt | \o | 09:36 | |
nwc10 | o/ | 09:37 | |
brrt: morepypy.blogspot.co.at/2015/10/pow...r-jit.html | |||
URL says enough :-) | |||
also, gcc.gnu.org/wiki/CompileFarm now has aarch64 | 09:38 | ||
and we build fine on it | |||
but, page imples that IBM paid for Power | |||
so, grant application to IBM soon? :-) | |||
timotimo | i hope our jit will reach speedups of 50x at some point ... | 09:39 | |
for things bigger than an empty loop :) | |||
brrt | oh, let's see | 09:46 | |
cool stuff | |||
i'll have to write a 'porting' document | 09:47 | ||
one day or another | |||
i have a new topic for a talk at some conference in the future | |||
'how to make a JIT on the cheap' or 'how to make building a JIT so simple it can be done in < 1 person-year' | |||
timotimo | hah | ||
brrt | but, cool progress for pypy :-) | 09:48 | |
i have a decent guess as to why the performance gain on powerpc exceeds that of the relative gain on x86_64 | 09:49 | ||
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brrt | a): x86_64 these days have impressively good branch prediction, and that helps the interpreter | 09:49 | |
b): 9.3 to 9.7 is noise, when we're considering we're talking about an average *factor* | 09:50 | ||
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brrt | (i'm not sure, because i haven't calculated it, whether that is calculated as a geometric average, but let's ignore that for now) | 09:51 | |
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timotimo | it says geometric average | 09:52 | |
under that table, they also say the thing about branch prediction | |||
brrt | aha | 09:53 | |
c): powerpc, being a RISC architecture, is 'easier' to write a good code generator for | |||
oh, i fixed a few bugs on the bus here... but i have a question for you to ponder | 10:00 | ||
it so happens that i sometimes load a 1-or-2 byte value from memory, and then try to use it as a 4 or 8 byte value | 10:01 | ||
however, x86 does not clear the upper bytes of a register if you load it word or byte mode | |||
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Ven_ | should it? | 10:07 | |
don't you have the "zbl" variants for that? | |||
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brrt | actually, you do | 11:50 | |
good point | |||
no, the question is just that when we're loading smaller values and using them as indices, the fact that the higher bytes are not cleared yields a segfault | 11:55 | ||
my question is really a design question | 11:56 | ||
should i, when using a smaller-byte value in a larger-byte context - and i know the sizes of my operands, they're encoded througout the expression tree, a): automatically zero-extend all values and not care b): have an explicit 'scale' node to do so | 11:57 | ||
and b.a): should i explicitly insert it everywhere or b.b): should this be done automatically, and b.b.b: if that is the case, how do i know ahead of time which operations are signed and unsigend | 11:58 | ||
always design questions :-) | 12:00 | ||
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konobi | jnthn: ping | 19:25 | |
TimToady | on his honeymoon this week | 19:28 | |
konobi | ah yes | 19:29 | |
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