`enum Token` was 192 bytes (64-bit), as pointed out by pnkfelix; the only
bloating variant being `INTERPOLATED(nonterminal)`.
Updating `enum nonterminal` to use ~ where variants included big types,
shrunk size_of(Token) to 32 bytes (64-bit).
I am unsure if the `nt_ident` variant should have an indirection, with
ast::ident being only 16 bytes (64-bit), but without this, enum Token
would be 40 bytes.
A dumb benchmark says that compilation time is unchanged, while peak
memory usage for compiling std.rs is down 3%
Before::
$ time ./x86_64-unknown-linux-gnu/stage1/bin/rustc --cfg stage1 src/libstd/std.rs
19.00user 0.39system 0:19.41elapsed 99%CPU (0avgtext+0avgdata 627820maxresident)k
0inputs+28896outputs (0major+228665minor)pagefaults 0swaps
$ time ./x86_64-unknown-linux-gnu/stage1/bin/rustc -O --cfg stage1 src/libstd/std.rs
31.64user 0.34system 0:32.02elapsed 99%CPU (0avgtext+0avgdata 629876maxresident)k
0inputs+22432outputs (0major+229411minor)pagefaults 0swaps
After::
$ time ./x86_64-unknown-linux-gnu/stage1/bin/rustc --cfg stage1 src/libstd/std.rs
19.07user 0.45system 0:19.55elapsed 99%CPU (0avgtext+0avgdata 609384maxresident)k
0inputs+28896outputs (0major+221997minor)pagefaults 0swaps
$ time ./x86_64-unknown-linux-gnu/stage1/bin/rustc -O --cfg stage1 src/libstd/std.rs
31.90user 0.34system 0:32.28elapsed 99%CPU (0avgtext+0avgdata 612080maxresident)k
0inputs+22432outputs (0major+223726minor)pagefaults 0swaps
This almost removes the StringRef wrapper, since all strings are
Equiv-alent now. Removes a lot of `/* bad */ copy *`'s, and converts
several things to be &'static str (the lint table and the intrinsics
table).
There are many instances of .to_managed(), unfortunately.
This naming is free now that `oldmap` has finally been removed, so this is a search-and-replace to take advantage of that. It might as well be called `HashMap` instead of being named after the specific implementation, since there's only one.
SipHash distributes keys so well that I don't think there will ever be much need to use anything but a simple hash table with open addressing. If there *is* a better way to do it, it will probably be better in all cases and can just be the default implementation.
A cuckoo-hashing implementation combining a weaker hash with SipHash could be useful, but that won't be as general purpose - you would need to write a separate fast hash function specialized for the type to really take advantage of it (like taking a page from libstdc++/libc++ and just using the integer value as the "hash"). I think a more specific naming for a truly alternative implementation like that would be fine, with the nice naming reserved for the general purpose container.
For bootstrapping purposes, this commit does not remove all uses of
the keyword "pure" -- doing so would cause the compiler to no longer
bootstrap due to some syntax extensions ("deriving" in particular).
Instead, it makes the compiler ignore "pure". Post-snapshot, we can
remove "pure" from the language.
There are quite a few (~100) borrow check errors that were essentially
all the result of mutable fields or partial borrows of `@mut`. Per
discussions with Niko I think we want to allow partial borrows of
`@mut` but detect obvious footguns. We should also improve the error
message when `@mut` is erroneously reborrowed.
