[SIL] Simplify debug info generation flow for SIL files

- Now `-g` implies `-Xllvm -sil-print-debuginfo` if the output file
  format is SIL.
- The `-gsil` is renamed into `-sil-based-debuginfo`.

Author: mshockwave

Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift

@@ -240,6 +240,11 @@ extension Driver {
       if shouldSupportAnonymousContextMangledNames {
         commandLine.appendFlag(.enableAnonymousContextMangledNames)
       }
+
+      if compilerOutputType == .sil {
+        commandLine.appendFlag("-Xllvm")
+        commandLine.appendFlag("-sil-print-debuginfo")
+      }
     }
 
     // Pass through any subsystem flags.

Sources/SwiftOptions/Options.swift

@@ -336,7 +336,7 @@ extension Option {
   public static let glineTablesOnly: Option = Option("-gline-tables-only", .flag, attributes: [.frontend], helpText: "Emit minimal debug info for backtraces only", group: .g)
   public static let gnone: Option = Option("-gnone", .flag, attributes: [.frontend], helpText: "Don't emit debug info", group: .g)
   public static let groupInfoPath: Option = Option("-group-info-path", .separate, attributes: [.helpHidden, .frontend, .noDriver], helpText: "The path to collect the group information of the compiled module")
-  public static let debugOnSil: Option = Option("-gsil", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Write the SIL into a file and generate debug-info to debug on SIL  level.")
+  public static let debugOnSil: Option = Option("-sil-based-debuginfo", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Write the SIL into a file and generate debug-info to debug on SIL  level.")
   public static let g: Option = Option("-g", .flag, attributes: [.frontend], helpText: "Emit debug info. This is the preferred setting for debugging with LLDB.", group: .g)
   public static let helpHidden: Option = Option("-help-hidden", .flag, attributes: [.helpHidden, .frontend], helpText: "Display available options, including hidden options")
   public static let helpHidden_: Option = Option("--help-hidden", .flag, alias: Option.helpHidden, attributes: [.helpHidden, .frontend], helpText: "Display available options, including hidden options")

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -421,6 +421,12 @@ final class SwiftDriverTests: XCTestCase {
     try assertDriverDiagnostics(args: "swiftc", "foo.swift", "-emit-module", "-gdwarf-types", "-debug-info-format=codeview") {
       $1.expect(.error("argument '-debug-info-format=codeview' is not allowed with '-gdwarf-types'"))
     }
+
+    try assertNoDriverDiagnostics(args: "swiftc", "foo.swift", "-g", "-emit-sil") { driver in
+        let jobs = try driver.planBuild()
+        XCTAssertTrue(jobs[0].commandLine.contains(.flag("-Xllvm")))
+        XCTAssertTrue(jobs[0].commandLine.contains(.flag("-sil-print-debuginfo")))
+    }
   }
 
   func testCoverageSettings() throws {