IRGen: Set a "not bitwise borrowable" bit in value witnesses for @_rawLayout types.
#76688
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@swift-ci Please test |
…awLayout` types. For types like `Atomic` and `Mutex`, we want to know that even though they are technically bitwise-takable, they differ from other bitwise-takable types until this point because they are not also "bitwise-borrowable"; while borrowed, they are pinned in memory, so they cannot be passed by value as a borrowed parameter, unlike copyable bitwise-takable types. Add a bit to the value witness table flags to record this. Note that this patch does not include any accompanying runtime support for propagating the flag into runtime-instantiated type metadata. There isn't yet any runtime functionality that varies based on this flag, so that can be implemented separately. rdar://136396806
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@swift-ci Please test |
| @@ -3927,8 +3927,8 @@ namespace { | |||
| } else if (allSingleRefcount | |||
| && ElementsWithNoPayload.size() <= 1) { | |||
| CopyDestroyKind = TaggedRefcounted; | |||
| } else if (this->EnumImplStrategy::BitwiseTakable == IsBitwiseTakable && | |||
| Copyable == IsCopyable) { | |||
| } else if (this->EnumImplStrategy::BitwiseTakable == IsBitwiseTakableAndBorrowable | |||
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At first glance, I 'm not sure why CopyDestroyKind would be affected by BitwiseBorrowable.
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I was thinking that it isn't possible for a type to be Copyable and BitwiseTakable without being BitwiseBorrowable, so it didn't really matter which value I compared against here.
| @@ -87,7 +87,8 @@ StructLayout::StructLayout(IRGenModule &IGM, std::optional<CanType> type, | |||
| if (rawLayout && type) { | |||
| auto sd = cast<StructDecl>(decl); | |||
| IsKnownTriviallyDestroyable = triviallyDestroyable; | |||
| IsKnownBitwiseTakable = bitwiseTakable; | |||
| // Raw layout types are never bitwise-borrowable. | |||
| IsKnownBitwiseTakable = bitwiseTakable & IsBitwiseTakableOnly; | |||
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Would this be more logically written
IsKnownBitwiseTakable = bitwiseTakable >= IsBitwiseTakableOnly?
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I was trying to keep the patch size down, but now that IsBitwiseTakable_t is a tristate, I want to rip the Is off of these Is*BitwiseTakable names. The code here is masking out the IsBitwiseTakableAndBorrowable possibility since a raw layout type can be at most bitwise-takable without -borrowable.
| IsKnownBitwiseTakable = likeFixedType->isBitwiseTakable(ResilienceExpansion::Maximal); | ||
| // Raw layout types are still never bitwise-borrowable. | ||
| IsKnownBitwiseTakable = likeFixedType->getBitwiseTakable(ResilienceExpansion::Maximal) | ||
| & IsBitwiseTakableOnly; |
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Would this be more logically written
>= IsBitwiseTakableOnly?
For types like
AtomicandMutex, we want to know that even though they are technically bitwise-takable, they differ from other bitwise-takable types until this point because they are not also "bitwise-borrowable"; while borrowed, they are pinned in memory, so they cannot be passed by value as a borrowed parameter, unlike copyable bitwise-takable types. Add a bit to the value witness table flags to record this.Note that this patch does not include any accompanying runtime support for propagating the flag into runtime-instantiated type metadata. There isn't yet any runtime functionality that varies based on this flag, so that can be implemented separately.
rdar://136396806