llvm.20.SwiftCompiler.Compiler-Driver

Swift Compiler Driver

本文基于Swift 5.5的源码: https://github.com/apple/swift/tree/release/5.5

1. Driver Tool

Ref[2] 是Driver命令行工具的CMakeLists.txt文件。

add_swift_host_tool(swift-frontend
  driver.cpp
  autolink_extract_main.cpp
  modulewrap_main.cpp
  swift_api_digester_main.cpp
  swift_indent_main.cpp
  swift_symbolgraph_extract_main.cpp
  swift_api_extract_main.cpp
  SWIFT_COMPONENT compiler
)
target_link_libraries(swift-frontend
                      PRIVATE
                        swiftAPIDigester
                        swiftDriver
                        swiftFrontendTool
                        swiftSymbolGraphGen
                        LLVMBitstreamReader)

1.1 Driver Tool Source Files

Main函数

通过add_swift_host_tool()来定义Driver Tool的源文件，其中driver.cpp为源文件的"入口"，该文件中定义了main()函数。

main()函数的主体逻辑如下所示:

 1 int main(int argc_, const char **argv_) {
 2 // ... ... 
 3 
 4   // Check if this invocation should execute a subcommand.
 5   StringRef ExecName = llvm::sys::path::stem(argv[0]);
 6   SmallString<256> SubcommandName;
 7   bool isRepl = false;
 8   if (shouldRunAsSubcommand(ExecName, SubcommandName, argv, isRepl)) { // Branch-A
 9   // ... ...
10 
11   return 2;
12   }
13 
14   if (isRepl) {
15     // Preserve argv for the stack trace.
16     SmallVector<const char *, 256> replArgs(argv.begin(), argv.end());
17     replArgs.erase(&replArgs[1]);
18     return run_driver(ExecName, replArgs); // Branch-B
19   } else {
20     return run_driver(ExecName, argv); // Branch-C
21   }
22 
23 }

当以"/usr/bin/swiftc --driver-mode=swift -L /Users/zhangchong/SpareTime/DangerUsage/.build/debug -I /Users/zhangchong/SpareTime/DangerUsage/.build/debug -lDanger /var/folders/g0/wz34vwx54616p8q9thj8yyd00000gp/T/_tmp_dangerfile.swift runner"调用swiftc时, main函数会进入到Branch-C。

run_driver函数

在执行"/usr/bin/swiftc --driver-mode=swift -L /Users/zhangchong/SpareTime/DangerUsage/.build/debug -I /Users/zhangchong/SpareTime/DangerUsage/.build/debug -lDanger /var/folders/g0/wz34vwx54616p8q9thj8yyd00000gp/T/_tmp_dangerfile.swift runner"时，run_driver函数实际上执行Part-D部分。

 1 static int run_driver(StringRef ExecName,
 2                        const ArrayRef<const char *> argv) {
 3 
 4   // Part-A: Check the first argument.
 5   // Handle integrated tools.
 6   if (argv.size() > 1) {
 7     StringRef FirstArg(argv[1]);
 8     if (FirstArg == "-frontend") {
 9       return performFrontend(llvm::makeArrayRef(argv.data()+2,
10                                                 argv.data()+argv.size()),
11                              argv[0], (void *)(intptr_t)getExecutablePath);
12     }
13     if (FirstArg == "-modulewrap") {
14       return modulewrap_main(llvm::makeArrayRef(argv.data()+2,
15                                                 argv.data()+argv.size()),
16                              argv[0], (void *)(intptr_t)getExecutablePath);
17     }
18 
19     // Run the integrated Swift frontend when called as "swift-frontend" but
20     // without a leading "-frontend".
21     if (!FirstArg.startswith("--driver-mode=")
22         && ExecName == "swift-frontend") {
23       return performFrontend(llvm::makeArrayRef(argv.data()+1,
24                                                 argv.data()+argv.size()),
25                              argv[0], (void *)(intptr_t)getExecutablePath);
26     }
27   }
28 
29 
30 // ... ...
31   
32   // Part-B: Should we disable the new swift-driver?
33   if (!shouldDisallowNewDriver(ExecName, argv)) {
34     SmallString<256> NewDriverPath(llvm::sys::path::parent_path(Path));
35     if (appendSwiftDriverName(NewDriverPath) &&
36         llvm::sys::fs::exists(NewDriverPath)) {   
37 
38         // ... ... 
39        return 2;
40     }
41   }
42 
43   // Part-C: Select the different tools based on the kind of Driver instance.
44   Driver TheDriver(Path, ExecName, argv, Diags);
45   switch (TheDriver.getDriverKind()) {
46   case Driver::DriverKind::AutolinkExtract:
47     return autolink_extract_main(
48       TheDriver.getArgsWithoutProgramNameAndDriverMode(argv),
49       argv[0], (void *)(intptr_t)getExecutablePath);
50   case Driver::DriverKind::SwiftIndent:
51     return swift_indent_main(
52       TheDriver.getArgsWithoutProgramNameAndDriverMode(argv),
53       argv[0], (void *)(intptr_t)getExecutablePath);
54   case Driver::DriverKind::SymbolGraph:
55       return swift_symbolgraph_extract_main(TheDriver.getArgsWithoutProgramNameAndDriverMode(argv), argv[0], (void *)(intptr_t)getExecutablePath);
56   case Driver::DriverKind::APIExtract:
57     return swift_api_extract_main(
58         TheDriver.getArgsWithoutProgramNameAndDriverMode(argv), argv[0],
59         (void *)(intptr_t)getExecutablePath);
60   case Driver::DriverKind::APIDigester:
61     return swift_api_digester_main(
62         TheDriver.getArgsWithoutProgramNameAndDriverMode(argv), argv[0],
63         (void *)(intptr_t)getExecutablePath);
64   default:
65     break;
66   }
67 
68   // Part-D: Do the real compilation. (ignore the error check.)
69   // Parse the arguments that from the command line.
70   std::unique_ptr<llvm::opt::InputArgList> ArgList =
71     TheDriver.parseArgStrings(ArrayRef<const char*>(argv).slice(1));
72   // Build a ToolChain instance.
73   std::unique_ptr<ToolChain> TC = TheDriver.buildToolChain(*ArgList);
74   // Build a Compilation instance. 
75   std::unique_ptr<Compilation> C =
76       TheDriver.buildCompilation(*TC, std::move(ArgList));
77   if (C) {
78     // Build the task queue from the Compilation instance.
79     std::unique_ptr<sys::TaskQueue> TQ = TheDriver.buildTaskQueue(*C);
80     if (!TQ)
81         return 1;
82     // Run the jobs which are generated from the task queue.
83     return C->performJobs(std::move(TQ)).exitCode;
84   }
85 
86   return 0;  
87 
88 }

1.2 Driver Tool Dependencies

2. swiftDriver library

Ref[1] 是swiftDriver库的CMakeLists.txt文件。

3. Driver Mode

`--driver-mode`的定义在Options.inc文件中, Options.inc文件是生成的。

TODO: 如何生成Options.inc文件?

从https://gist.github.com/vitonzhangtt/7f6f6feaa0e61373d90bbf9291d2b66b#file-options-inc-L322 可以看出

`--driver-mode`的值可以为: swift, 或者swiftc。

3.1 Driver Kind

Driver是整个编译过程的"驱动器"，Driver Kind保存Driver的类型。

Driver Kind有一些作用:

1. 决定Driver对命令行参数的解析

2. 影响OutputInput的生成

https://github1s.com/apple/swift/blob/release/5.5/lib/Driver/Driver.cpp#L1472-L1475

1   
2 // OutputInfo &OI
3 OI.CompilerOutputType = driverKind == DriverKind::Interactive
4                               ? file_types::TY_Nothing
5                               : CompilerOutputType;

3. 影响Compiler Mode

https://github1s.com/apple/swift/blob/release/5.5/lib/Driver/Driver.cpp#L1854-L1857

// const InputFileList &Inputs
  if (driverKind == Driver::DriverKind::Interactive)
    return Inputs.empty() ? OutputInfo::Mode::REPL
                          : OutputInfo::Mode::Immediate;

4. 影响-help选项的输出

https://github1s.com/apple/swift/blob/release/5.5/lib/Driver/Driver.cpp#L3535-L3540

3.2 DriverKind的计算

Driver Mode决定了部分DriverKind的取值。

在Driver的构造函数中，首先进行DriverKind的计算:

 1 Driver::Driver(StringRef DriverExecutable,
 2                StringRef Name,
 3                ArrayRef<const char *> Args,
 4                DiagnosticEngine &Diags)
 5   : Opts(createSwiftOptTable()), Diags(Diags),
 6     Name(Name), DriverExecutable(DriverExecutable),
 7     DefaultTargetTriple(llvm::sys::getDefaultTargetTriple()) {
 8       
 9   // The driver kind must be parsed prior to parsing arguments, since that
10   // affects how arguments are parsed.
11   parseDriverKind(Args.slice(1));
12 }
13 
14 void Driver::parseDriverKind(ArrayRef<const char *> Args) {
15   // The default driver kind is determined by Name.
16   StringRef DriverName = Name;
17 
18   std::string OptName;
19   // However, the driver kind may be overridden if the first argument is
20   // --driver-mode.
21   if (!Args.empty()) {
22     OptName = getOpts().getOption(options::OPT_driver_mode).getPrefixedName();
23 
24     StringRef FirstArg(Args[0]);
25     if (FirstArg.startswith(OptName))
26       DriverName = FirstArg.drop_front(OptName.size());
27   }
28 
29   Optional<DriverKind> Kind =
30       llvm::StringSwitch<Optional<DriverKind>>(DriverName)
31           .Case("swift", DriverKind::Interactive) // --driver-mode=swift
32           .Case("swiftc", DriverKind::Batch).      // --driver-mode=swiftc 
33           .Case("swift-autolink-extract", DriverKind::AutolinkExtract)
34           .Case("swift-indent", DriverKind::SwiftIndent)
35           .Case("swift-symbolgraph-extract", DriverKind::SymbolGraph)
36           .Case("swift-api-extract", DriverKind::APIExtract)
37           .Case("swift-api-digester", DriverKind::APIDigester)
38           .Default(None);
39 
40   if (Kind.hasValue())
41     driverKind = Kind.getValue(); // driverKind is member of Driver Class.
42   else if (!OptName.empty())
43     Diags.diagnose({}, diag::error_invalid_arg_value, OptName, DriverName);
44 }

Interactive: swift --driver-mode=swift

Batch: swift --driver-mode=swiftc

1. --driver-mode=swiftc

swiftc --driver-mode=swiftc hello.swift

编译hello.swift文件，生成可执行文件hello。

2. --driver-mode=swift

swiftc --driver-mode=swift hello.swift

编译并执行hello.swift文件。

Next: swift-driver　

Reference

1. CMakeLists.txt for swiftDriver

https://github.com/apple/swift/blob/release/5.5/lib/Driver/CMakeLists.txt

2. CMakeLists.txt for swift-frontend

https://github.com/apple/swift/blob/release/5.5/tools/driver/CMakeLists.txt

3. Headers file for swiftDriver

https://github.com/apple/swift/tree/release/5.5/include/swift/Driver

4. Options.inc

https://gist.github.com/vitonzhangtt/7f6f6feaa0e61373d90bbf9291d2b66b

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