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Small SILValue::getOwnershipValue() fixes #6831

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Merged
merged 3 commits into from
Jan 16, 2017
Merged

Small SILValue::getOwnershipValue() fixes #6831

merged 3 commits into from
Jan 16, 2017

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gottesmm
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This PR contains a few fixes for SILValue::getOwnershipValue() that I discovered as I was cleaning up ownership in SILGen.

Specifically:

  1. thin_to_thick_function should return an owned value even though its input is trivial.
  2. unchecked_bitwise_cast does not return trivial semantics. Instead it has the semantics that:
    a. trivial -> trivial => trivial
    b. trivial -> non-trivial => unowned
    c. non-trivial -> trivial => trivial
    d. non-trivial -> non-trivial => forwarding
  3. objc_{existential_,}metatype_to_object is owned. In SIL metatypes are trivial. We only convert them to full objects on request for usage in objective-c. These instructions convert metatypes to objects. Thus they should return the value as owned. The one interesting part here is that one may think that these should return an unowned value (since we are converting from trivial => non-trivial), but since in objective-c land class types are eternal (with a special retain/release that do nothing), we can avoid needing to do that.

rdar://29791263

@gottesmm
[semantic-sil] thin_to_thick_function should be treated as returning an
8ede336 
@owned value.
@gottesmm
[semantic-sil] Fix semantics of unchecked_bitwise_cast for SILValue::…
8a7e535 
…getOwnershipKind().

This is used in SILGen in a few different cases:

1. trivial -> non-trivial. This should have unowned semantics since one should
retain before use.
2. non-trivial -> trivial. This should have trivial semantics.
3. trivial -> trivial. This should have trivial semantics.
4. non-trivial -> non-trivial. This should have forwarding semantics.
@gottesmm
[semantic-sil] objc_{existential_,}metatype_to_object should be treat…
2f9a90d 
…ed as owned.

Metatypes in SIL are trivial, until we conver them to objects (mainly for cases
where one converts the metatype to an object for use in objc). Thus these
conversion functions must be treated as returning an @owned value.
@gottesmm
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@swift-ci Please smoke test and merge

@gottesmm gottesmm merged commit 554bc78 into swiftlang:master Jan 16, 2017
@gottesmm gottesmm deleted the small_getownershipvalue_fixes branch January 16, 2017 04:22
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