Re: LuaJIT with vectors
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- Subject: Re: LuaJIT with vectors
- From: Miles Bader <miles@...>
- Date: 2010年11月19日 11:07:22 +0900
Roberto Ierusalimschy <roberto@inf.puc-rio.br> writes:
>> Check -fno-crossjumping in the GCC manual. But I think there are
>> quite a few rants from Anton Ertl about how every new GCC release
>> messed up the code of his carefully crafted interpreters ...
>
> I guess Anton is right. -fno-crossjumping did not help. Everything
> in the tail code is kept separated for each case, except for the
> final "jmp *%eax" (this is the same result as with -O0). The sequence
>
> ...
> movl %edi, %eax
> andl 63,ドル %eax
> movl disptab.6158(,%eax,4), %eax
> jmp .L462
>
> is repeated 40 times in the code, but all end in the same L462, that do
> the final jump:
>
> .L462:
> jmp *%eax
>
> (This is gcc version 4.4.3.)
If this is a real performance killer, it may be worth posting on the gcc
mailing list, or even filing a gcc bug. They may know ways to avoid the
problem, or good ideas about mechanisms to do so in the future.
-Miles
--
Freebooter, n. A conqueror in a small way of business, whose annexations lack
of the sanctifying merit of magnitude.
- References:
- LuaJIT with vectors, Petri Häkkinen
- Re: LuaJIT with vectors, Mike Pall
- Re: LuaJIT with vectors, Alex Queiroz
- Re: LuaJIT with vectors, David Kastrup
- Re: LuaJIT with vectors, Alex Queiroz
- Re: LuaJIT with vectors, David Kastrup
- Re: LuaJIT with vectors, Mike Pall
- Re: LuaJIT with vectors, Roberto Ierusalimschy
- Re: LuaJIT with vectors, Mike Pall
- Re: LuaJIT with vectors, Roberto Ierusalimschy