Merge pull request #1086 from eeckstein/enable-default-cmo-flag

Explicitly tell the frontend to enable default cross-module-optimization

Author: eeckstein

Sources/SwiftDriver/Jobs/CompileJob.swift

@@ -283,7 +283,13 @@ extension Driver {
     try addCommonFrontendOptions(commandLine: &commandLine, inputs: &inputs)
     // FIXME: MSVC runtime flags
 
-    addDisableCMOOption(commandLine: &commandLine)
+    if Driver.canDoCrossModuleOptimization(parsedOptions: &parsedOptions) &&
+       // For historical reasons, -cross-module-optimization turns on "aggressive" CMO
+       // which is different from "default" CMO.
+       !parsedOptions.hasArgument(.CrossModuleOptimization) {
+      assert(!emitModuleSeparately, "Cannot emit module separately with cross-module-optimization")
+      commandLine.appendFlag("-enable-default-cmo")
+    }
 
     if parsedOptions.hasArgument(.parseAsLibrary, .emitLibrary) {
       commandLine.appendFlag(.parseAsLibrary)

Sources/SwiftDriver/Jobs/EmitModuleJob.swift

@@ -99,8 +99,6 @@ extension Driver {
 
     addCommonModuleOptions(commandLine: &commandLine, outputs: &outputs, isMergeModule: false)
 
-    addDisableCMOOption(commandLine: &commandLine)
-
     try commandLine.appendLast(.emitSymbolGraph, from: &parsedOptions)
     try commandLine.appendLast(.emitSymbolGraphDir, from: &parsedOptions)
     try commandLine.appendLast(.includeSpiSymbols, from: &parsedOptions)
@@ -147,10 +145,9 @@ extension Driver {
                                    default: true)
 
     case .singleCompile:
-      // Non library-evolution builds require a single job, because cross-module-optimization is enabled by default.
-      if !parsedOptions.hasArgument(.enableLibraryEvolution),
-         !parsedOptions.hasArgument(.disableCrossModuleOptimization),
-         let opt = parsedOptions.getLast(in: .O), opt.option != .Onone {
+      // If cross-module-optimization is done, the module must be emitted in the same
+      // swift-frontend invocation which also produces the binary.
+      if canDoCrossModuleOptimization(parsedOptions: &parsedOptions) {
         return false
       }
 
@@ -163,4 +160,13 @@ extension Driver {
       return false
     }
   }
+  
+  static func canDoCrossModuleOptimization(parsedOptions: inout ParsedOptions) -> Bool {
+    if !parsedOptions.hasArgument(.enableLibraryEvolution),
+       !parsedOptions.hasArgument(.disableCrossModuleOptimization),
+       let opt = parsedOptions.getLast(in: .O), opt.option != .Onone {
+      return true
+    }
+    return false
+  }
 }

Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift

@@ -315,14 +315,6 @@ extension Driver {
                                                            driver: self)
   }
 
-  /// Add options to disable cross-module-optimization.
-  mutating func addDisableCMOOption(commandLine: inout [Job.ArgTemplate]) {
-    if parsedOptions.hasArgument(.disableCrossModuleOptimization) {
-      commandLine.appendFlag(.Xllvm)
-      commandLine.appendFlag("-sil-disable-pass=cmo")
-    }
-  }
-
   mutating func addFrontendSupplementaryOutputArguments(commandLine: inout [Job.ArgTemplate],
                                                         primaryInputs: [TypedVirtualPath],
                                                         inputsGeneratingCodeCount: Int,

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -2976,31 +2976,38 @@ final class SwiftDriverTests: XCTestCase {
       var driver = try Driver(args: ["swiftc", "foo.swift", "bar.swift", "-module-name", "Test", "-emit-module-path", rebase("Test.swiftmodule", at: root), "-c", "-o", rebase("test.o", at: root), "-wmo", "-O" ])
       let plannedJobs = try driver.planBuild()
       XCTAssertEqual(plannedJobs.count, 1 + autoLinkExtractJob)
+      XCTAssertTrue(plannedJobs[0].commandLine.contains(.flag("-enable-default-cmo")))
     }
 
     do {
       // library-evolution builds can emit the module in a separate job.
       var driver = try Driver(args: ["swiftc", "foo.swift", "bar.swift", "-module-name", "Test", "-emit-module-path", rebase("Test.swiftmodule", at: root), "-c", "-o", rebase("test.o", at: root), "-wmo", "-O", "-enable-library-evolution" ])
       let plannedJobs = try driver.planBuild()
       XCTAssertEqual(plannedJobs.count, 2 + autoLinkExtractJob)
+      XCTAssertFalse(plannedJobs[0].commandLine.contains(.flag("-enable-default-cmo")))
+      XCTAssertFalse(plannedJobs[1].commandLine.contains(.flag("-enable-default-cmo")))
     }
 
     do {
       // When disabling cross-module-optimization, the module can be emitted in a separate job.
       var driver = try Driver(args: ["swiftc", "foo.swift", "bar.swift", "-module-name", "Test", "-emit-module-path", rebase("Test.swiftmodule", at: root), "-c", "-o", rebase("test.o", at: root), "-wmo", "-O", "-disable-cmo" ])
       let plannedJobs = try driver.planBuild()
       XCTAssertEqual(plannedJobs.count, 2 + autoLinkExtractJob)
+      XCTAssertFalse(plannedJobs[0].commandLine.contains(.flag("-enable-default-cmo")))
+      XCTAssertFalse(plannedJobs[1].commandLine.contains(.flag("-enable-default-cmo")))
     }
 
     do {
       // non optimized builds can emit the module in a separate job.
       var driver = try Driver(args: ["swiftc", "foo.swift", "bar.swift", "-module-name", "Test", "-emit-module-path", rebase("Test.swiftmodule", at: root), "-c", "-o", rebase("test.o", at: root), "-wmo" ])
       let plannedJobs = try driver.planBuild()
       XCTAssertEqual(plannedJobs.count, 2 + autoLinkExtractJob)
+      XCTAssertFalse(plannedJobs[0].commandLine.contains(.flag("-enable-default-cmo")))
+      XCTAssertFalse(plannedJobs[1].commandLine.contains(.flag("-enable-default-cmo")))
     }
 
     do {
-        // Don't use emit-module-separetely as a linker.
+      // Don't use emit-module-separetely as a linker.
       var driver = try Driver(args: ["swiftc", "foo.sil", "bar.sil", "-module-name", "Test", "-emit-module-path", "/foo/bar/Test.swiftmodule", "-emit-library", "-target", "x86_64-apple-macosx10.15", "-wmo", "-emit-module-separately-wmo"],
                                env: envVars)
       let plannedJobs = try driver.planBuild()