This reduces ty::sty from 160 bytes to just 112, and some measurements
eddyb made suggest that the ty_trait variant occurs very
rarely (e.g. ~1% of all sty instances) hence this will result in a large
memory saving, and the cost of the indirection is unlikely to be an
issue.
This also drops support for the managed pointer POISON_ON_FREE feature
as it's not worth adding back the support for it. After a snapshot, the
leftovers can be removed.
Major changes:
- Define temporary scopes in a syntax-based way that basically defaults
to the innermost statement or conditional block, except for in
a `let` initializer, where we default to the innermost block. Rules
are documented in the code, but not in the manual (yet).
See new test run-pass/cleanup-value-scopes.rs for examples.
- Refactors Datum to better define cleanup roles.
- Refactor cleanup scopes to not be tied to basic blocks, permitting
us to have a very large number of scopes (one per AST node).
- Introduce nascent documentation in trans/doc.rs covering datums and
cleanup in a more comprehensive way.
Unique pointers and vectors currently contain a reference counting
header when containing a managed pointer.
This `{ ref_count, type_desc, prev, next }` header is not necessary and
not a sensible foundation for tracing. It adds needless complexity to
library code and is responsible for breakage in places where the branch
has been left out.
The `borrow_offset` field can now be removed from `TyDesc` along with
the associated handling in the compiler.
Closes#9510Closes#11533
Unique pointers and vectors currently contain a reference counting
header when containing a managed pointer.
This `{ ref_count, type_desc, prev, next }` header is not necessary and
not a sensible foundation for tracing. It adds needless complexity to
library code and is responsible for breakage in places where the branch
has been left out.
The `borrow_offset` field can now be removed from `TyDesc` along with
the associated handling in the compiler.
Closes#9510Closes#11533
When performing LTO, the rust compiler has an opportunity to completely strip
all landing pads in all dependent libraries. I've modified the LTO pass to
recognize the -Z no-landing-pads option when also running an LTO pass to flag
everything in LLVM as nothrow. I've verified that this prevents any and all
invoke instructions from being emitted.
I believe that this is one of our best options for moving forward with
accomodating use-cases where unwinding doesn't really make sense. This will
allow libraries to be built with landing pads by default but allow usage of them
in contexts where landing pads aren't necessary.
When performing LTO, the rust compiler has an opportunity to completely strip
all landing pads in all dependent libraries. I've modified the LTO pass to
recognize the -Z no-landing-pads option when also running an LTO pass to flag
everything in LLVM as nothrow. I've verified that this prevents any and all
invoke instructions from being emitted.
I believe that this is one of our best options for moving forward with
accomodating use-cases where unwinding doesn't really make sense. This will
allow libraries to be built with landing pads by default but allow usage of them
in contexts where landing pads aren't necessary.
cc #10780
