in terms of the pattern binding/emission facilities that are currently
used for switches. They are more general (handling all patterns,
not hacked up just for optionals).
This leads to us producing better code for if/let bindings, because we
don't alloc_stack a temporary and deal with memory for non-address-only
types (e.g. the common case of an optional pointer). Instead, the code
emits a select_enum{_addr} on the value.
While this changes the generated code in the compiler, there is no exposed
behavioral change to the developer.
Swift SVN r26142
This doesn't allow 'continue' out of an if statement for the same reason we don't
allow it on switch: we'd prefer people to write loops more explicitly.
Swift SVN r25565
the call instead of during the formal evaluation of the argument.
This is the last major chunk of the semantic changes proposed
in the accessors document. It has two purposes, both related
to the fact that it shortens the duration of the formal access.
First, the change isolates later evaluations (as long as they
precede the call) from the formal access, preventing them from
spuriously seeing unspecified behavior. For example::
foo(&array[0], bar(array))
Here the value passed to bar is a proper copy of 'array',
and if bar() decides to stash it aside, any modifications
to 'array[0]' made by foo() will not spontaneously appear
in the copy. (In contrast, if something caused a copy of
'array' during foo()'s execution, that copy would violate
our formal access rules and would therefore be allowed to
have an arbitrary value at index 0.)
Second, when a mutating access uses a pinning addressor, the
change limits the amount of arbitrary code that falls between
the pin and unpin. For example::
array[0] += countNodes(subtree)
Previously, we would begin the access to array[0] before the
call to countNodes(). To eliminate the pin and unpin, the
optimizer would have needed to prove that countNodes didn't
access the same array. With this change, the call is evaluated
first, and the access instead begins immediately before the call
to +=. Since that operator is easily inlined, it becomes
straightforward to eliminate the pin/unpin.
A number of other changes got bundled up with this in ways that
are hard to tease apart. In particular:
- RValueSource is now ArgumentSource and can now store LValues.
- It is now illegal to use emitRValue to emit an l-value.
- Call argument emission is now smart enough to emit tuple
shuffles itself, applying abstraction patterns in reverse
through the shuffle. It also evaluates varargs elements
directly into the array.
- AllowPlusZero has been split in two. AllowImmediatePlusZero
is useful when you are going to immediately consume the value;
this is good enough to avoid copies/retains when reading a 'var'.
AllowGuaranteedPlusZero is useful when you need a stronger
guarantee, e.g. when arbitrary code might intervene between
evaluation and use; it's still good enough to avoid copies
from a 'let'. The upshot is that we're now a lot smarter
about generally avoiding retains on lets, but we've also
gotten properly paranoid about calling non-mutating methods
on vars.
(Note that you can't necessarily avoid a copy when passing
something in a var to an @in_guaranteed parameter! You
first have to prove that nothing can assign to the var during
the call. That should be easy as long as the var hasn't
escaped, but that does need to be proven first, so we can't
do it in SILGen.)
Swift SVN r24709
Most tests were using %swift or similar substitutions, which did not
include the target triple and SDK. The driver was defaulting to the
host OS. Thus, we could not run the tests when the standard library was
not built for OS X.
Swift SVN r24504
Now the SILLinkage for functions and global variables is according to the swift visibility (private, internal or public).
In addition, the fact whether a function or global variable is considered as fragile, is kept in a separate flag at SIL level.
Previously the linkage was used for this (e.g. no inlining of less visible functions to more visible functions). But it had no effect,
because everything was public anyway.
For now this isFragile-flag is set for public transparent functions and for everything if a module is compiled with -sil-serialize-all,
i.e. for the stdlib.
For details see <rdar://problem/18201785> Set SILLinkage correctly and better handling of fragile functions.
The benefits of this change are:
*) Enable to eliminate unused private and internal functions
*) It should be possible now to use private in the stdlib
*) The symbol linkage is as one would expect (previously almost all symbols were public).
More details:
Specializations from fragile functions (e.g. from the stdlib) now get linkonce_odr,default
linkage instead of linkonce_odr,hidden, i.e. they have public visibility.
The reason is: if such a function is called from another fragile function (in the same module),
then it has to be visible from a third module, in case the fragile caller is inlined but not
the specialized function.
I had to update lots of test files, because many CHECK-LABEL lines include the linkage, which has changed.
The -sil-serialize-all option is now handled at SILGen and not at the Serializer.
This means that test files in sil format which are compiled with -sil-serialize-all
must have the [fragile] attribute set for all functions and globals.
The -disable-access-control option doesn't help anymore if the accessed module is not compiled
with -sil-serialize-all, because the linker will complain about unresolved symbols.
A final note: I tried to consider all the implications of this change, but it's not a low-risk change.
If you have any comments, please let me know.
Swift SVN r22215
