Fascinating new switch mechanism in assembler

[Walter Bright]

"Dan Lewis" <Dan_member at pathlink.com> wrote in message 
news:dvfnur$a9$1 at digitaldaemon.com...
> Hi guys,
> I've been working on a lexical analyzer for my new scripting engine, and I
> stumbled upon an interesting algorithm.
>
> Essentially:
>
> goto ((charCode << 2)+subroutinePointerArray);
>
> The advantage of this strategy is the elimination of some 90% of the 
> conditional
> testing for each character in a string being interpreted (Yay for code 
> that runs
> in 40% the time!).

Given:

int test(int i)
{
    switch (i)
    {
 case 1:
 case 2:
 case 3:
 case 4:
 case 5:
 case 6:
 case 7:
     return i;
 default:
     return i + 1;
    }
}

The assembler produced is:

?test@@YAHH at Z:
  push EBX
  mov EBX,8[ESP]
  sub EBX,1
  cmp EBX,6
  ja L1A
  jmp dword ptr FLAT:_DATA[00h][EBX*4]
  mov EAX,8[ESP]
  pop EBX
  ret
L1A:  mov EAX,8[ESP]
  inc EAX
  pop EBX
  ret
_TEXT ends
_DATA segment
 dd offset FLAT:?test@@YAHH at Z[014h]
 dd offset FLAT:?test@@YAHH at Z[014h]
 dd offset FLAT:?test@@YAHH at Z[014h]
 dd offset FLAT:?test@@YAHH at Z[014h]
 dd offset FLAT:?test@@YAHH at Z[014h]
 dd offset FLAT:?test@@YAHH at Z[014h]
 dd offset FLAT:?test@@YAHH at Z[014h]
_DATA ends