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Canonicalize a `fix_lifetime` from an address to a `load` + `fix_lifetime`: ``` %1 = alloc_stack $T ... fix_lifetime %1 ``` -> ``` %1 = alloc_stack $T ... %2 = load %1 fix_lifetime %2 ``` This transformation is done for `alloc_stack` and `store_borrow` (which always has an `alloc_stack` operand). The benefit of this transformation is that it enables other optimizations, like mem2reg. This peephole optimization was already done in SILCombine, but it didn't handle store_borrow. A good opportunity to make an instruction simplification out of it. This is part of fixing regressions when enabling OSSA modules: rdar://140229560
56 lines
1.8 KiB
Swift
56 lines
1.8 KiB
Swift
//===--- SimplifyFixLifetime.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 - 2024 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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/// Canonicalize a `fix_lifetime` from an address to a `load` + `fix_lifetime`:
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/// ```
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/// %1 = alloc_stack $T
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/// ...
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/// fix_lifetime %1
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/// ```
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/// ->
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/// ```
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/// %1 = alloc_stack $T
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/// ...
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/// %2 = load %1
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/// fix_lifetime %2
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/// ```
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///
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/// This transformation is done for `alloc_stack` and `store_borrow` (which always has an `alloc_stack`
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/// operand).
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/// The benefit of this transformation is that it enables other optimizations, like mem2reg.
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///
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extension FixLifetimeInst : Simplifyable, SILCombineSimplifyable {
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func simplify(_ context: SimplifyContext) {
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let opValue = operand.value
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guard opValue is AllocStackInst || opValue is StoreBorrowInst,
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opValue.type.isLoadable(in: parentFunction)
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else {
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return
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}
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let builder = Builder(before: self, context)
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let loadedValue: Value
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if !parentFunction.hasOwnership {
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loadedValue = builder.createLoad(fromAddress: opValue, ownership: .unqualified)
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} else if opValue.type.isTrivial(in: parentFunction) {
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loadedValue = builder.createLoad(fromAddress: opValue, ownership: .trivial)
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} else {
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loadedValue = builder.createLoadBorrow(fromAddress: opValue)
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Builder(after: self, context).createEndBorrow(of: loadedValue)
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}
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operand.set(to: loadedValue, context)
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}
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}
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