diakopter timotimo: thanks for the link 00:45
timotimo YW
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nwc10 good *, #moarvm 07:18
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brrt good * #moarvm 07:50
jnthn moarning o/ 08:08
brrt jnthn, how worthwhile do you think it will be to allow the interpreter to get the JIT entry label? 08:30
eh, well, to be exact 08:31
jnthn brrt: Can it not today? :)
brrt very well
:-)
busy day today?
jnthn heh, that wasn't the parse I expected :P
"Can the interpreter not already discover that today?" :) 08:32
->jit_entry_label on frame or so
I should probably have waited for the more exact :) 08:33
brrt oh, that way
yeah, it can
what i mean is, it would be nice if the JIT didn't have to do the bookkeeping, but the interpreter could call a function (downstack from the JIT), which would give you that offset, just from the return address of the function 08:34
i.e. MVM_jit_get_reentry_label(MVMThreadContext *tc, void *jit_code_base, size_t jit_code_size)
the downside is that we would have to compile with -fno-omit-frame-pointer 08:35
and the equivalent in MSVC
i can write that function is assembly easily enough
getting it to link correctly on multiple platforms, that is one minor annoyance
jnthn How much of a saving do you think it would be? 08:36
brrt i don't know. we currently insert 'store reentry labels' every basic block, every invokish, every throwish thing
even if they may not throw or invoke at all 08:37
jnthn I'm assuming -fno-omit-frame-pointer costs a little bit too, though maybe not so much on x64 as on x86...
brrt that is quite a bit of memory traffic
jnthn Since the former is less register starved
brrt agreed
only way to know is to measure i think....
jnthn And since we don't JIT on x86 we could only set the flag on x64
brrt it might hurt the interpreter a bit, but i don't know that 08:38
how much
jnthn Yeah. It's hard to guess these things, but while it may be quite a bit of memory traffic, it's also (a) likely to be a cache hit most of the time, and (b) doens't have a data dep 08:40
brrt also gtrue
same is true for stack walking of course 08:41
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brrt i wonder if there is a practical way to make cross platform c-linkable assembly 09:09
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