Commit Graph

5 Commits

Author SHA1 Message Date
Shoaib Meenai 5faf6d88e8 Reapply "[Parse] Use CapturedStmt for @finally on MSVC"
This reapplies r334224 and adds explicit triples to some tests to fix
them on Windows (where otherwise they would have run with the default
windows-msvc triple, which I'm changing the behavior for).

Original commit message:
The body of a `@finally` needs to be executed on both exceptional and
non-exceptional paths. On landingpad platforms, this is straightforward:
the `@finally` body is emitted as a normal (non-exceptional) cleanup,
and then a catch-all is emitted which branches to that cleanup (the
cleanup has code to conditionally re-throw based on a flag which is set
by the catch-all).

Unfortunately, we can't use the same approach for MSVC exceptions, where
the catch-all will be emitted as a catchpad. We can't just branch to the
cleanup from within the catchpad, since we can only exit it via a
catchret, at which point the exception is destroyed and we can't
rethrow. We could potentially emit the finally body inside the catchpad
and have the normal cleanup path somehow branch into it, but that would
require some new IR construct that could branch into a catchpad.

Instead, after discussing it with Reid Kleckner, we decided that
frontend outlining was the best approach, similar to how SEH `__finally`
works today. We decided to use CapturedStmt (which was also suggested by
Reid) rather than CaptureFinder (which is what `__finally` uses) since
the latter doesn't handle a lot of cases we care about, e.g. self
accesses, property accesses, block captures, etc. Extending
CaptureFinder to handle those additional cases proved unwieldy, whereas
CapturedStmt already took care of all of those.  In theory `__finally`
could also be moved over to CapturedStmt, which would remove some
existing limitations (e.g. the inability to capture this), although
CaptureFinder would still be needed for SEH filters.

The one case supported by `@finally` but not CapturedStmt (or
CaptureFinder for that matter) is arbitrary control flow out of the
`@finally`, e.g. having a return statement inside a `@finally`. We can
add that support as a follow-up, but in practice we've found it to be
used very rarely anyway.

Differential Revision: https://reviews.llvm.org/D47564

llvm-svn: 334251
2018-06-08 00:30:00 +00:00
Alexander Kornienko 90ff607894 Implement AST dumper for Decls.
http://llvm-reviews.chandlerc.com/D52

Patch by Philip Craig!

llvm-svn: 170634
2012-12-20 02:09:13 +00:00
NAKAMURA Takumi 2538bf111e test/PCH/objc_stmts.m: Suppress stderr to be fed to FileCheck.
llvm-svn: 160720
2012-07-25 11:14:11 +00:00
Anders Carlsson 3320e1575f Make clang -cc1 disable Objective-C exceptions by default, and add a -fobjc-exceptions flag to turn them on.
Update all tests accordingly.

llvm-svn: 126177
2011-02-22 01:52:06 +00:00
Douglas Gregor 96c79498fb Improve the AST representation of Objective-C @try/@catch/@finally
statements. Instead of the @try having a single @catch, where all of
the @catch's were chained (using an O(n^2) algorithm nonetheless),
@try just holds an array of its @catch blocks. The resulting AST is
slightly more compact (not important) and better represents the actual
language semantics (good).

llvm-svn: 102221
2010-04-23 22:50:49 +00:00