[Simh] simh and jump tables

[Villy Madsen]

Well

the end result of 10 - 12 hours of intensive coding is the discovery that
switch statements in C (well GCC) at least are coded as computed jumps - a 
fact  that I might have realized if I didn't have
this long standing hate relationship with C.


After my recoding and recompiling using mingw, i brought up NetBSD (still 
waiting for my VMS distribution) and ran a math stress test call STREAM.

the good news was that it ran about 2.5x faster with my modified VAX.EXE 
than the distributed exe did (both with Ethernet Support).

the bad news was that it ran marginally slower than a VAX.EXE compiled from 
the original source by mingw.  The only explanation that I could think of 
was that GCC must generate jump tables - and once I discover that a switch 
- case construction only works with integers - everything fell into 
perspective.  As I mentioned in a previous posting, the distributed exe is 
also ~twice the size of the GCC version.

The big question now  is - which compiler was used to generate the 
distribution.

Interesting exercise - if somewhat futile.

Villy



Villy Madsen
www.members.shaw.ca/villy.madsen