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Erik Eckstein
541664237c
The pass merges to adjacent borrow scopes in a basic block. ``` %2 = begin_borrow %1 use(%2) end_borrow %2 ... %6 = begin_borrow %1 use(%6) end_borrow %6 ``` -> ``` %2 = begin_borrow %1 use(%2) ... use(%2) end_borrow %2 ``` This helps other optimizations, like common-subexpression-elimination, because the borrow liveranges are larger and not split.
66 lines
1.9 KiB
Swift
66 lines
1.9 KiB
Swift
//===--- MergeBorrowScopes.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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/// Merges to adjacent borrow scopes in a basic block.
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///
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/// ```
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/// %2 = begin_borrow %1
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/// use(%2)
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/// end_borrow %2
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/// ...
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/// %6 = begin_borrow %1
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/// use(%6)
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/// end_borrow %6
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///
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/// ```
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/// ->
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/// ```
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/// %2 = begin_borrow %1
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/// use(%2)
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/// ...
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/// use(%2)
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/// end_borrow %2
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/// ```
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///
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/// This helps other optimizations, like common-subexpression-elimination, because the
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/// borrow liveranges are larger and not split.
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///
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let mergeBorrowScopes = FunctionPass(name: "merge-borrow-scopes") {
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(function: Function, context: FunctionPassContext) in
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for block in function.blocks {
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doMergeBorrowScopes(in: block, context)
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}
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}
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private func doMergeBorrowScopes(in block: BasicBlock, _ context: FunctionPassContext) {
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var endBorrows = Dictionary<ObjectIdentifier, EndBorrowInst>()
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for inst in block.instructions {
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switch inst {
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case let endBorrow as EndBorrowInst:
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if let beginBorrow = endBorrow.borrow as? BeginBorrowInst {
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endBorrows[ObjectIdentifier(beginBorrow.borrowedValue)] = endBorrow
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}
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case let beginBorrow as BeginBorrowInst:
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if let endBorrow = endBorrows[ObjectIdentifier(beginBorrow.borrowedValue)] {
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endBorrows.removeValue(forKey: ObjectIdentifier(beginBorrow.borrowedValue))
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beginBorrow.replace(with: endBorrow.borrow, context)
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context.erase(instruction: endBorrow)
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}
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default:
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break
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}
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}
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}
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