Arguments that can't be safely referenced will be implicitly copied.
(Warnings for expensive copies will be forthcoming.)
This will allow us to get rid of most of the ampersands in function
signatures. See [1].
[1] https://mail.mozilla.org/pipermail/rust-dev/2011-September/000759.html
trans::type_of now has a constraint saying that its type argument
is statically sized. This eliminates the "impossible happened" case
in type_of. Yay!
I note that this change decreased translation time for stage2/rustc
from 16.1 s to 14.0 s. I also think many of the remaining checks
could be eliminated with some mildly clever use of constrained types
and further preconditions. Future work!
Experimenting with adding typestate constraints in the compiler.
Added a constraint to GEP_tag that says the variant index is in
bounds. Added necessary checks.
Having it in the alias pass was slightly more efficient (finding
expression roots has to be done in both passes), but further muddled
up the already complex alias checker.
Also factors out some duplication in the mutability-checking code.
The uniformity doesn't seem to be worth the extra noise and pointless
code being generated. If something doesn't produce a value, don't make
it return one. (For now, trans_[exprtype] things are left in the result-
returning form, even when they never return anything useful, since in
that case uniformity is arguably helpful.)
Vectors are now similar to our old, pre-internal vectors, except that
they are uniquely owned, not refcounted.
Their name should probably change too, then. I've renamed them to vec
in the runtime, will do so throughout the compiler later.
The glue-calling will spill the values again anyway. This should
prevent a lot of load/spill junk in the output. It is also necessary
to be able to have unique vecs be immediate values (take must know the
actual address to be able to duplicate).
You now do
bld::Ret(bcx, someval)
where you used to say
bcx.build.Ret(someval)
Two fewer boxes are allocated for each block context, and build calls
no longer go through a vtable.
This makes it easier for the caller to optimize the take/drop away for
temporary values, and opens up new possibilities for alias handling.
Breaks tail calls.
