Consts of such enums are aligned correctly, so we could either misalign
them to match the type_of, or fix the type_of. The latter seems like a
better idea.
`simplify_type` was bogus, as there was no way for it to handle enums
properly. It was also slow, because it created many Rust types at runtime. In
general creating Rust types during trans is a source of slowness, and I'd like
to avoid doing it as much as possible. (It is probably not possible to
eliminate it entirely, due to `subst`, but we should get rid of as much of it
as we can.) So this patch replaces `simplify_type` with `sizing_type_of`,
which creates a size-equivalent LLVM type directly without going through a
Rust type first.
Because this is causing an ICE in Servo, I'm rubber stamping it.
Issue #3869
review? @nikomatsakis
Convert all uses of vec::slice to vec::view Issue #3869
Rename const_view to const_slice
Renamed mut_view to mut_slice
Fix windows build error. `buf` is borrowed by the call to
`as_mut_buf()` and so we must invoke `slice()` outside of that
call.
This patch finishes removing inner vector mutability from the vast majority of the compiler. Exceptions:
* core::dvec: ideally this entire type will be able to be replaced by `~[]`, but Niko asked me to hold off on removing Dvecs until he makes some fixes to borrowed pointers.
* liveness: liveness.rs is an impenetrable neutron star of deprecated semantics.
* compile-fail: I'm not sure if a lot of these tests are testing inner mutability or mutability in general. I figure that RIMOVing this folder should wait until this syntax is removed from the parser.
I also took this chance to remove many of the inner-mutability-related functions from core::vec, or as many uses of those functions as possible where still necessary. consume_mut and append_mut have been axed. cast_to_mut and cast_from_mut are still needed in a few places.
If an enum is isomorphic to unit, there's no need to use any bits to
represent it. The only obvious reason this wasn't the case was because
the enum could be C-like and have a user-specified discriminant -- but
that value is constant, so it doesn't need to be stored.
This change means that all newtype-like enums have the same size (and
layout) as their underlying type, which might be a useful property to
have, at least in terms of making programs' low-level behavior less
surprising.
The number of operands of the LLVM node initializing the array
underlying a const vector isn't always the array length -- if the
array is of a sufficiently primitive type and all the elements' values
are known (or something like that), LLVM uses a specialized Constant
subclass that stores the data packed, and thus has no operands. Oops.
But, because llsize_of now gives us a ConstantInt, we can just fix
mozilla/rust#3169 and this all goes away.
This is wasted space if the const is just an enum, but optimizing that
case without breaking everything else is an issue that can be addressed
separately.
