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Make PrunedLiveness ownership-friendly #61371

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Merged
merged 19 commits into from
Oct 4, 2022
Merged

Make PrunedLiveness ownership-friendly #61371

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ca503b5
Redesign PrunedLiveness APIs, introducing live ranges
atrick Sep 17, 2022
40e03ef
Update passes to use SSAPrunedLiveness or MultiDefPrunedLiveness
atrick Sep 25, 2022
464e353
Fix ScopedAddressValue::computeLiveness.
atrick Sep 26, 2022
4ef7f85
Fix findTransitiveUsesForAddress to handle incomplete scopes
atrick Sep 27, 2022
da4f1b9
Add InnerBorrowKind and AddressUseKind to PrunedLiveness API
atrick Sep 29, 2022
619a638
ScopedAddressUtils - clarify the API used for transitive liveness.
atrick Sep 29, 2022
376483d
Add a test case for generic specialization with borrow scope fixup.
atrick Sep 24, 2022
11ef752
Add an OSSLifetimeAnalysis utility pass
atrick Sep 29, 2022
6daebfd
Add ossa lifetime analysis tests
atrick Sep 29, 2022
3b5e198
Add OSSA liveness tests for incomplete lifetimes
atrick Sep 29, 2022
52b87c2
Temporarily disable a SILVerifier unit test.
atrick Sep 29, 2022
d98ccb0
Fix a comment merge error
atrick Oct 3, 2022
2244875
Add a clarifying comment to updateTransitiveLiveness
atrick Oct 3, 2022
6346bf5
Rename areUsesWithinTransitiveScope to ...ExtendedScope
atrick Oct 3, 2022
6861b31
Make PrunedLiveness::computeSimple one-level transitive
atrick Oct 3, 2022
9e0b615
Add a comment on liveness terminology
atrick Oct 3, 2022
98b6e09
Add a transitive liveness test case
atrick Oct 3, 2022
8f34d9c
Add a comment regarding an optimizer rule for self-loops.
atrick Oct 4, 2022
755bce2
Remove complexity in findBoundariesInBlock
atrick Oct 4, 2022
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42 changes: 37 additions & 5 deletions include/swift/SIL/OwnershipUtils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,36 @@
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
///
/// Terminology:
///
/// Simple liveness:
/// - Ends at lifetime-ending operations.
/// - Transitively follows guaranteed forwarding operations and address uses
/// within the current scope.
/// - Assumes inner scopes are complete, including borrow and address scopes
/// - Rarely returns AddressUseKind::PointerEscape.
/// - Per-definition dominance holds
/// - Insulates outer scopes from inner scope details. Maintains the
/// invariant that inlining cannot pessimize optimization.
///
/// Transitive liveness
/// - Transitively follows uses within inner scopes, including forwarding
/// operations and address uses.
/// - Much more likely to returns AddressUseKind::PointerEscape
/// - Per-definition dominance holds
/// - Does not assume that any scopes are complete.
///
/// Extended liveness (copy-extension and reborrow-extension)
/// - Extends a live range across lifetime-ending operations
/// - Depending on context: owned values are extended across copies or
/// guaranteed values are extended across reborrows
/// - Copy-extension is used to canonicalize an OSSA lifetime
/// - Reborrow-extension is used to check borrow scopes relative to its inner
/// uses and outer lifetime
/// - Per-definition dominance does not hold
///
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Thanks for writing this down

//===----------------------------------------------------------------------===//

#ifndef SWIFT_SIL_OWNERSHIPUTILS_H
#define SWIFT_SIL_OWNERSHIPUTILS_H
Expand All @@ -30,7 +60,7 @@ class SILInstruction;
class SILModule;
class SILValue;
class DeadEndBlocks;
class PrunedLiveness;
class MultiDefPrunedLiveness;
struct BorrowedValue;

/// Returns true if v is an address or trivial.
Expand Down Expand Up @@ -566,8 +596,10 @@ struct BorrowedValue {

bool isLocalScope() const { return kind.isLocalScope(); }

/// Add this scopes live blocks into the PrunedLiveness result.
void computeLiveness(PrunedLiveness &liveness) const;
/// Add this scope's live blocks into the PrunedLiveness result. This
/// includes reborrow scopes that are reachable from this borrow scope but not
/// necessarilly dominated by the borrow scope.
void computeTransitiveLiveness(MultiDefPrunedLiveness &liveness) const;

/// Returns true if \p uses are completely within this borrow introducer's
/// local scope.
Expand All @@ -580,8 +612,8 @@ struct BorrowedValue {
///
/// \p deadEndBlocks is optional during transition. It will be completely
/// removed in an upcoming commit.
bool areUsesWithinTransitiveScope(ArrayRef<Operand *> uses,
DeadEndBlocks *deadEndBlocks) const;
bool areUsesWithinExtendedScope(ArrayRef<Operand *> uses,
DeadEndBlocks *deadEndBlocks) const;

/// Given a local borrow scope introducer, visit all non-forwarding consuming
/// users. This means that this looks through guaranteed block arguments. \p
Expand Down
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