On 7/12/19 12:12 AM, Pip Cet wrote:

> I don't understand why this would improve performance this
> significantly (maybe because it allows 8-bit offsets to be used rather
> than 32-bit ones?).

Yes, that's my guess too. For the record, my benchmark platform was my old work 
desktop (AMD Phenom II X4 910e, circa 2010) running Fedora 30 x86-64, with plain 
'make compile-always' (no -j). I really should get that upgraded.

> Maybe it would be a good idea to make Vdead a symbol (or a tagged NULL
> pointer) and treat it similarly, if this actually improves
> performance.

It does speed up GC a bit. I installed the attached. Thanks for the suggestion.

>> +      static char const commonsym[][8]
> 
> I'm curious, why isn't this simply "static char *commonsym[]"?

Old performance habits that don't matter here. Besides, that alternative should 
be 'static char const *const commonsym[]" which is not obviously simpler....