bug#11657: 24.1.50; Byte compiler is a lot slower now, when run interpreted

[Stefan Monnier]

>> > Another would be to add some instrumentation code to the `pcase' macro,
>> > to output a message everytime the cache misses.  E.g. use the patch below.
>> I tried that and found that the `pcase-let' macro was not memoized (it
>> goes through `pcase' but pcase's memoization fails in that case).
>> I added explicit memoization to pcase-let, which should
>> help significantly.
>> Please try it and tell me if it was the only source of slowdown.
> Unfortunately, I see no improvement at all, with trunk revision
> 108559: I still get the same 16.5 sec compiling org.el.

I think I see another cause for slowdown: macroexp now ends up preloaded
in bootstrap-emacs, so byte-compiling it from COMPILE_FIRST is
ineffective (BTW, we can remove subr.el from makefile-w32.in's
COMPILE_FIRST, since it's useless there).


        Stefan