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Open Source Swift
Workshop
1 — Open Source Swift Workshop, try! Swift Tokyo 2024, @kitasuke
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Open Source Swift Swiftc
Workshop
2 — Open Source Swift Workshop, try! Swift Tokyo 2024, @kitasuke
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Table of Contents
→ Overview of Swift Compiler
→ Getting Started
→ Making Contributions
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Overview of Swift
Compiler
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Swift Compiler
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Parse
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AST
$ swiftc -dump-parse a.swift
// let i = 1
(source_file "a.swift"
(top_level_code_decl range=[a.swift:1:1 - line:1:9]
(brace_stmt implicit range=[a.swift:1:1 - line:1:9]
(pattern_binding_decl range=[a.swift:1:1 - line:1:9]
(pattern_named 'i')
Original init:
(integer_literal_expr type='' value=1 builtin_initializer=**NULL** initializer=**NULL**)
Processed init:
(integer_literal_expr type='' value=1 builtin_initializer=**NULL** initializer=**NULL**))
))
(var_decl range=[a.swift:1:5 - line:1:5] "i" let))
7 — Open Source Swift Workshop, try! Swift Tokyo 2024, @kitasuke
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Sema
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Type-checked AST
$ swiftc -dump-ast a.swift
// let i = 1
(source_file "a.swift"
(top_level_code_decl range=[a.swift:1:1 - line:1:9]
(brace_stmt implicit range=[a.swift:1:1 - line:1:9]
(pattern_binding_decl range=[a.swift:1:1 - line:1:9]
(pattern_named type='Int' 'i')
Original init:
(integer_literal_expr type='Int' location=a.swift:1:9 range=[a.swift:1:9 - line:1:9] value=1
builtin_initializer=Swift.(file).Int.init(_builtinIntegerLiteral:) initializer=**NULL**)
Processed init:
(integer_literal_expr type='Int' location=a.swift:1:9 range=[a.swift:1:9 - line:1:9] value=1
builtin_initializer=Swift.(file).Int.init(_builtinIntegerLiteral:) initializer=**NULL**))
))
(var_decl range=[a.swift:1:5 - line:1:5] "i" interface type='Int'
access=internal let readImpl=stored immutable))
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SILGen
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SIL
$ swiftc -emit-sil a.swift
// let i = 1
sil_stage canonical
import Builtin
import Swift
import SwiftShims
@_hasStorage @_hasInitialValue let i: Int { get }
// i
sil_global hidden [let] @$s1a1iSivp : $Int
// main
sil @main : $@convention(c) (Int32, UnsafeMutablePointer>>) -> Int32 {
[%1: noescape **]
[global: read,write,copy,deinit_barrier]
bb0(%0 : $Int32, %1 : $UnsafeMutablePointer>>):
alloc_global @$s1a1iSivp // id: %2
%3 = global_addr @$s1a1iSivp : $*Int // user: %6
%4 = integer_literal $Builtin.Int64, 1 // user: %5
%5 = struct $Int (%4 : $Builtin.Int64) // user: %6
store %5 to %3 : $*Int // id: %6
%7 = integer_literal $Builtin.Int32, 0 // user: %8
%8 = struct $Int32 (%7 : $Builtin.Int32) // user: %9
return %8 : $Int32 // id: %9
} // end sil function 'main'
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IRGen
12 — Open Source Swift Workshop, try! Swift Tokyo 2024, @kitasuke
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LLVM IR
$ swiftc -emit-ir a.swift
// let i = 1
; ModuleID = ''
source_filename = ""
target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
target triple = "arm64-apple-macosx14.0.0"
%TSi = type <{ i64 }>
@"$s1a1iSivp" = hidden global %TSi zeroinitializer, align 8
@"\01l_entry_point" = private constant { i32, i32 } { i32 trunc (i64 sub (i64 ptrtoint (ptr @main to i64), i64 ptrtoint (ptr @"\01l_entry_point" to
i64)) to i32), i32 0 }, section "__TEXT, __swift5_entry, regular, no_dead_strip", align 4
@__swift_reflection_version = linkonce_odr hidden constant i16 3
@llvm.used = appending global [3 x ptr] [ptr @main, ptr @"\01l_entry_point", ptr @__swift_reflection_version], section "llvm.metadata"
define i32 @main(i32 %0, ptr %1) #0 {
entry:
store i64 1, ptr @"$s1a1iSivp", align 8
ret i32 0
}
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LLVM
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Packages in Swift
→ swift-driver
→ SwiftParser
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SwiftParser
SwiftParser produces a SwiftSyntax syntax tree from
Swift source code mainly used for Swift Macros
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Syntax Tree
$ swift-parser-cli print-tree a.swift
// let i = 1
SourceFileSyntax
├─statements: CodeBlockItemListSyntax
│ ╰─[0]: CodeBlockItemSyntax
│ ╰─item: VariableDeclSyntax
│ ├─attributes: AttributeListSyntax
│ ├─modifiers: DeclModifierListSyntax
│ ├─bindingSpecifier: keyword(SwiftSyntax.Keyword.let)
│ ╰─bindings: PatternBindingListSyntax
│ ╰─[0]: PatternBindingSyntax
│ ├─pattern: IdentifierPatternSyntax
│ │ ╰─identifier: identifier("i")
│ ╰─initializer: InitializerClauseSyntax
│ ├─equal: equal
│ ╰─value: IntegerLiteralExprSyntax
│ ╰─literal: integerLiteral("1")
╰─endOfFileToken: endOfFile
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Getting Started
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Clone swift
$ git clone [email protected]:apple/swift.git swift
$ cd swift
$ utils/update-checkout --clone-with-ssh
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Build using Ninja
$ utils/build-script --skip-build-benchmarks \
--skip-ios --skip-watchos --skip-tvos \
--swift-darwin-supported-archs "$(uname -m)" \
--sccache --release-debuginfo --swift-disable-dead-stripping \
--bootstrapping=hosttools
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Using Ninja with Xcode
$ utils/build-script --swift-darwin-supported-archs "$(uname -m)" \
--xcode --clean
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Debugging issues
# optimized Stdlib + debug Swiftc + optimized Clang/LLVM
$ utils/build-script --release-debuginfo --debug-swift
22 — Open Source Swift Workshop, try! Swift Tokyo 2024, @kitasuke
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Testing Swift
Primary testsuites is LLVM lit-based and write in
Swift for a Swift language feature, write in SIL for a
SIL optimization
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Running tests
# Rebuild all test dependencies and run all tests under test/.
$ utils/run-test --lit ../llvm-project/llvm/utils/lit/lit.py \
../build/Ninja-RelWithDebInfoAssert/swift-macosx-$(uname -m)/test-macosx-$(uname -m)
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Making Contributions
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Reporting Bugs
It's a great way for anyone to help improve Swift on
GitHub issue or Apple's bug reporter instead if Xcode
related or NDA associated.
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Finding Issues
Good first issues are bugs, ideas, and tasks that are
intended to be accessible for contributors that are
new to working on the Swift project
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Swift Evolution
Shaping the future of Swift is a community effort
that anyone can participate in via the Evolution
section of the Swift forums
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Swift Mentorship Program
It's designed to encourage developers to actively
participate in the Swift open source community
through direct mentorship with experienced
developers
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References
→ https://github.com/apple/swift/blob/main/docs/
→ https://forums.swift.org/c/evolution/
→ https://www.swift.org/contributing/
→ https://www.swift.org/mentorship/
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