Building object files using -c with -lto should respect the output file path (-o) if present

Author: kubamracek

Sources/SwiftDriver/Jobs/CompileJob.swift

@@ -85,7 +85,7 @@ extension Driver {
       } else {
         // When -lto is set, .bc will be used for linking. Otherwise, .bc is
         // top-level output (-emit-bc)
-        return lto == nil
+        return lto == nil || linkerOutputType == nil
       }
     case .swiftModule:
       return compilerMode.isSingleCompilation && moduleOutputInfo.output?.isTopLevel ?? false

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -313,6 +313,27 @@ final class SwiftDriverTests: XCTestCase {
     XCTAssertEqual(driver6.compilerOutputType, .llvmBitcode)
   }
 
+  func testLtoOutputPath() throws {
+    var driver1 = try Driver(args: ["swiftc", "foo.swift", "-lto=llvm-full",
+                                    "-c", "-target", "x86_64-apple-macosx10.9"])
+    XCTAssertEqual(driver1.compilerOutputType, .llvmBitcode)
+    XCTAssertEqual(driver1.linkerOutputType, nil)
+    let jobs1 = try driver1.planBuild()
+    XCTAssertEqual(jobs1.count, 1)
+    XCTAssertEqual(jobs1[0].outputs.count, 1)
+    XCTAssertEqual(jobs1[0].outputs[0].file.basename, "foo.bc")
+
+    var driver2 = try Driver(args: ["swiftc", "foo.swift", "-lto=llvm-full",
+                                    "-c", "-target", "x86_64-apple-macosx10.9",
+                                    "-o", "foo.o"])
+    XCTAssertEqual(driver2.compilerOutputType, .llvmBitcode)
+    XCTAssertEqual(driver2.linkerOutputType, nil)
+    let jobs2 = try driver2.planBuild()
+    XCTAssertEqual(jobs2.count, 1)
+    XCTAssertEqual(jobs2[0].outputs.count, 1)
+    XCTAssertEqual(jobs2[0].outputs[0].file.basename, "foo.o")
+  }
+
   func testPrimaryOutputKindsDiagnostics() throws {
       try assertDriverDiagnostics(args: "swift", "-i") {
         $1.expect(.error("the flag '-i' is no longer required and has been removed; use 'swift input-filename'"))