Re: Computed gotos on Reddit

[Walter Bright]

On 7/25/2012 10:29 AM, Dmitry Olshansky wrote:

Is it possible you could code it up and test it using inline asm?

Mm... I could try. So the trick is to add say this:
Dispatch:
asm{
       ...
      lea EAX,jmp_table[EBX][EBX*4]
      jmp EAX
jmp_table:
       jmp Lcase1;
       jmp Lcase2;
       jmp Lcase3;
}
Lcase1:
     ...
     goto Dispatch
instead of current switch and replace case with labels. Sounds not half bad.

Then I could even replace that one goto Dispatch with same
      lea EAX,jmp_table[EBX][EBX*4]
      jmp EAX

I'll give it a shot. The only thing that worries me is that I will step on
compiler's toes breaking his register allocation scheme (it would have to work
around my inline asm).

Use the same register for both schemes, and it should then give comparable 
results.

Any tips on which spare registers to use (I guess ecx is no go, as there is
'this' pointer present) ?

I wouldn't worry about it. EAX is good.