Author: Gian-Carlo Pascutto
Date: 06:03:57 06/24/04
Go up one level in this thread
On June 24, 2004 at 07:56:32, Anthony Cozzie wrote:
>Bob's code looks like this in assembly:
>
>if(wtm)
>{
> xor eax+0x334, ebx //take memory at eax+0x334 and xor it with ebx
> ...
>
>Your code would look like
>
> xor eax + 8*ecx + 0x334, ebx
> ^--- Index register
>
>Register pressure is one of the biggest problems with bitboards on x86. Just
>having 1 bitboard in registers requires almost 1/3 of the registers.
I don't see how this is possibly a justification:
1) Because of the same register pressure you're talking about, most of the
data in x86 is retried from caches. Duplicating code is not helping
cache pressure.
2) You need to handle the branch too. The cost of that is going to be way
higher than the cost of setting up/restoring a register.
>Switch is _fast_. Again, in assembly:
>
> and eax, 0xF
> jmp table[eax]
An indirect jmp fast?
Are you joking?
Also good luck with getting the compiler to generate that code.
--
GCP
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