5.9: [MoveOnlyAddressChecker] Maximize lifetimes. #66736
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According to language rules, such lifetimes are fixed and the relative order of their deinits is guaranteed. rdar://110913116
The members were declared but undefined.
Its storage vector is intended to be of some type like `std::vector<std::pair<Key, Optional<Value>>>`, i.e., some collection of pairs whose `second` is an `Optional<Value>`. So when constructing a default instance of that pair, just construct an Optional in the None case.
FieldSensitivePrunedLiveness is used as a vectorization of
PrunedLiveness. An instance of FSPL with N elements needs to be able to
represent the same states as N instances of PL.
Previously, it failed to do that in two significant ways:
(1) It attempted to save space for which elements were live by using
a range. This failed to account for instructions which are users of
non-contiguous fields of an aggregate.
apply(
@owned (struct_element_addr %s, #S.f1),
@owned (struct_element_addr %s, #S.f3)
)
(2) It used a single bit to represent whether the instruction was
consuming. This failed to account for instructions which consumed
some fields and borrowed others.
apply(
@owned (struct_element_addr %s, #S.f1),
@guaranteed (struct_element_addr %s, #S.f2)
)
The fix for (1) is to use a bit vector to represent which elements
are used by the instruction. The fix for (2) is to use a second bit
vector to represent which elements are _consumed_ by the instruction.
Adapted the move-checker to use the new representation.
rdar://110909290
Dumped more info and called llvm_unreachable on bad state.
Previously, the checker inserted destroys after each last use. Here, extend the lifetimes of fields as far as possible within their original (unchecked) limits. rdar://99681073
It's always the first line of the function, so try to do better.
Passing ``` -Xllvm -move-only-address-checker-disable-lifetime-extension=true ``` will skip the maximization of unconsumed field lifetimes.
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Removed some duplicated tests caused by cherry-picking the same commit twice. |
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@swift-ci please test |
tbkka
approved these changes
Jun 19, 2023
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Description: Language rules specify that non-consumed move-only values' lifetimes extend within their scope as far as they can (i.e. without incurring copies).
That was already done for values via the lifetime extension in CanonicalizeOSSALifetime used by the move-only value checker, but was not done for addresses. Here, it is done for addresses.
Risk: Low. This is a port/vectorization of the existing, well-understood, lifetime extension algorithm from CanonicalizeOSSALifetime to the move-only address checker. Additionally a new flag is added to disable the extension.
Scope: Narrow. This only affects move-only types.
Original PR: #66585
Reviewed By: Andrew Trick ( @atrick )
Testing: Added filecheck tests that exhibit the expected SIL and execution tests that exhibit the correct behavior.
Resolves: rdar://99681073