As a preparation for implementing the temporary-move optimization for
argument passing. The optimization itself isn't in yet, since it
mysteriously corrupts memory.
This adds support for dropping cleanups for temporary values when they
are moved somewhere else. It then adds wraps most copy operations
(return, put in data structure, box, etc) in a way that will fall back
to a move when it is safe.
This saves a lot of taking/dropping, shaving over a megabyte off the
stage2/rustc binary size.
In some cases, most notably function returns, we could detect that the
returned value is a local variable, and can thus be safely moved even
though it is not a temporary. This will require putting some more
information in lvals.
I did not yet handle function arguments, since the logic for passing
them looked too convoluted to touch. I'll probably try that in the
near future, since it's bound to be a big win.
The duplication of upcalls is due to the fact that the runtime is
shared between stage0/rustc and stage1/rustc. Once snapshots are
updated, they should be de-duplicated.
If a closure inside a case alternative (for example, a for each loop)
referenced a pattern-bound variable, this would cause an assertion
failure in trans. Changed trans::collect_upvars to handle pattern-bound
vars correctly.
Incidentally, eliminated all direct uses of option::get in trans.
src/comp/syntax is currently just a sub-module of rustc, but it will,
in the near future, be its own crate. This includes:
- The AST data structure
- The parser
- The pretty-printer
- Visit, walk, and fold
- The syntax extension system
- Some utility stuff that should be in the stdlib*
*) Stdlib extensions currently require a snapshot before they can be
used, and the win build is very broken right now. This is temporary
and will be cleaned up when one of those problems goes away.
A lot of code was moved by this patch, mostly towards a more organized
layout. Some package paths did get longer, and I guess the new layout
will take some getting used to. Sorry about that!
Please try not to re-introduce any dependencies in syntax/ on any of
the other src/comp/ subdirs.
An expression like:
foo(1, fail, 2)
was failing to parse, because the parser was interpreting the comma
as the start of an expression that was an argument to fail, rather
than recognizing that the fail here has no arguments
Fixed this by using can_begin_expr to determine whether the next
token after a fail token suggests that this is a nullary fail or a
unary fail.
In addition, when translating calls, check before translating each
argument that the block still isn't terminated. This has the effect
that if an argument list includes fail, the back-end won't keep trying
to generate code for successive arguments and trip the !*terminated
assertion.
The code for translating a fail (for example) would call
Unreachable(), which terminates the block; if a fail appeared as an
argument, this would cause an LLVM assertion failure. Changed
trans_call to handle this situation correctly.
(Using the * operator.)
This makes tags more useful as nominal 'newtype' types, since you no
longer have to copy out their contents (or construct a cumbersome
boilerplate alt) to access them.
I could have gone with a scheme where you could dereference individual
arguments of an n-ary variant with ._0, ._1, etc, but opted not to,
since we plan to move to a system where all variants are unary (or, I
guess, nullary).
This is a preparation for tags-as-nominal-types. A tag that has only a
single variant is now represented, at run-time, as simply a tuple of
the variant's parameters, with the variant id left off.
This is important since we are going to be making functions noncopyable
soon, which means we'll be seeing a lot of boxed functions.
(*f)(...) is really just too heavyweight.
Doing the autodereferencing was a very little bit tricky since
trans_call works with an *lval* of the function whereas existing
autoderef code was not for lvals.
Tydescs are currently re-created for each compilation unit (and I
guess for structural types, they have to be, though the duplication
still bothers me). This means a destructor can not be inlined in the
drop glue for a resource type, since other crates don't have access to
the destructor body.
Destructors are now compiled as separate functions with an external
symbol that can be looked up in the crate (under the resource type's
def_id), and called from the drop glue.
