[Bug bootstrap/84402] [meta] GCC build system: parallelism bottleneck

[giuliano.belinassi at usp dot br]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84402

--- Comment #32 from Giuliano Belinassi <giuliano.belinassi at usp dot br> ---
(In reply to Eric Gallager from comment #31)
> I think this came up at Cauldron, but I forget what exactly people said
> about it...

Actually this PR comes before Cauldron 2019. One way to fix this issue is to
make the match.pd parser output several smaller gimple-match.c, and add these
to the Makefile. Also repeat this procedure to other big files.

Another solution is to parallelize GCC internals and make GCC communicate with
Make somehow so that when a CPU is idle, it starts compiling some files in
parallel.