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Erik Eckstein
ec74abb6c9
Add a `raw_pointer_to_ref` instruction simplification which sets the
`immortal` flag if the instruction is used to create an empty collection
singleton, i.e. if the pattern is
%0 = global_addr @_swiftEmptyArrayStorage
%1 = address_to_pointer %0
%2 = raw_pointer_to_ref %1
and the Swift 5.1 runtime is available on the deployment target. Since
Swift 5.1 such statically allocated objects have immortal reference
counts, so retaining and releasing them is a no-op.
This moves the pattern matching out of the strong_retain/strong_release
simplification, which now only needs to check the flag.
49 lines
1.7 KiB
Swift
49 lines
1.7 KiB
Swift
//===--- SimplifyRawPointerToRef.swift ------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2026 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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import SIL
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extension RawPointerToRefInst : OnoneSimplifiable, SILCombineSimplifiable {
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/// Sets the `immortal` flag if used for an Array/Set/Dictionary singleton:
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/// ```
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/// %0 = global_addr @_swiftEmptyArrayStorage
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/// %1 = address_to_pointer %0
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/// %2 = raw_pointer_to_ref %1
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/// ```
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/// ->
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/// ```
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/// %0 = global_addr @_swiftEmptyArrayStorage
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/// %1 = address_to_pointer %0
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/// %2 = raw_pointer_to_ref [immortal] %1
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/// ```
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///
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/// `raw_pointer_to_ref` is only used to implement the `bridgeFromRawPointer`
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/// builtin, which in turn is only used to create the empty COW buffer
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/// singletons (Array, Set, Dictionary) and for the `UnsafeCurrentTask._task`
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/// ABI-compat shim. Since Swift 5.1 those statically allocated objects have
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/// "immortal" reference counts, so retaining and releasing them is a no-op.
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/// This is only true if the Swift 5.1 runtime is available on the deployment
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/// target.
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func simplify(_ context: SimplifyContext) {
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if isImmortal {
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return
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}
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if parentFunction.isSwift51RuntimeAvailable,
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let atp = pointer as? AddressToPointerInst,
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atp.address is GlobalAddrInst
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{
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set(isImmortal: true, context)
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}
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}
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}
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