a more wholistic solution for your viewing pleasure

Author: rauhul

Sources/Build/BuildDescription/SwiftTargetBuildDescription.swift

@@ -74,22 +74,58 @@ public final class SwiftTargetBuildDescription {
         self.target.sources.paths + self.derivedSources.paths + self.pluginDerivedSources.paths
     }
 
+    /// The list of all source files in the target, including the derived ones.
+    private var relativeSources: [RelativePath] {
+        self.target.sources.relativePaths + self.derivedSources.relativePaths + self
+            .pluginDerivedSources.relativePaths
+    }
+
     /// The list of all resource files in the target, including the derived ones.
     public var resources: [Resource] {
         self.target.underlyingTarget.resources + self.pluginDerivedResources
     }
 
-    /// The objects in this target.
+    private var producesBitcodeObjects: Bool {
+        get throws {
+            try self.compileArguments().contains {
+                    // Using -lto=x will result in bitcode generation.
+                    $0.hasPrefix("-lto=")
+                    // Using -embed-bitcode will result in bitcode generation.
+                    || $0 == "-embed-bitcode"
+                }
+        }
+    }
+
+    /// The objects in this target, containing either machine code or bitcode
+    /// depending on the compiler flags used.
     public var objects: [AbsolutePath] {
         get throws {
-            let relativePaths = self.target.sources.relativePaths + self.derivedSources.relativePaths + self
-                .pluginDerivedSources.relativePaths
-            return try relativePaths.map {
+            // Prefer bitcode objects over machine code objects if they are
+            // produced.
+            try self.producesBitcodeObjects
+                ? self.bitcodeObjects
+                : self.machineCodeObjects
+        }
+    }
+
+    /// The machine code objects in this target.
+    private var machineCodeObjects: [AbsolutePath] {
+        get throws {
+            try self.relativeSources.map {
                 try AbsolutePath(validating: "\($0.pathString).o", relativeTo: tempsPath)
             }
         }
     }
 
+    /// The bitcode objects in this target.
+    private var bitcodeObjects: [AbsolutePath] {
+        get throws {
+            try self.relativeSources.map {
+                try AbsolutePath(validating: "\($0.pathString).bc", relativeTo: tempsPath)
+            }
+        }
+    }
+
     /// The path to the swiftmodule file after compilation.
     var moduleOutputPath: AbsolutePath {
         // If we're an executable and we're not allowing test targets to link against us, we hide the module.
@@ -729,14 +765,18 @@ public final class SwiftTargetBuildDescription {
 
 
         // Write out the entries for each source file.
-        let sources = self.target.sources.paths + self.derivedSources.paths + self.pluginDerivedSources.paths
-        for (idx, source) in sources.enumerated() {
-            let object = try objects[idx]
-            let objectDir = object.parentDirectory
+        let sources = self.sources
+        let machineCodeObjects = try self.machineCodeObjects
+        let bitcodeObjects = try self.bitcodeObjects
 
-            let sourceFileName = source.basenameWithoutExt
+        for idx in 0..<sources.count {
+            let source = sources[idx]
+            let machineCodeObject = machineCodeObjects[idx]
+            let bitcodeObject = bitcodeObjects[idx]
 
-            let swiftDepsPath = objectDir.appending(component: sourceFileName + ".swiftdeps")
+            let sourceFileName = source.basenameWithoutExt
+            let partialModulePath = self.tempsPath.appending(component: sourceFileName + "~partial.swiftmodule")
+            let swiftDepsPath = self.tempsPath.appending(component: sourceFileName + ".swiftdeps")
 
             content +=
                 #"""
@@ -745,7 +785,7 @@ public final class SwiftTargetBuildDescription {
                 """#
 
             if !self.buildParameters.useWholeModuleOptimization {
-                let depsPath = objectDir.appending(component: sourceFileName + ".d")
+                let depsPath = self.tempsPath.appending(component: sourceFileName + ".d")
                 content +=
                     #"""
                         "dependencies": "\#(depsPath._nativePathString(escaped: true))",
@@ -755,12 +795,10 @@ public final class SwiftTargetBuildDescription {
             }
 
 
-            let partialModulePath = objectDir.appending(component: sourceFileName + "~partial.swiftmodule")
-
             content +=
                 #"""
-                    "llvm-bc": "\#(object._nativePathString(escaped: true))",
-                    "object": "\#(object._nativePathString(escaped: true))",
+                    "object": "\#(machineCodeObject._nativePathString(escaped: true))",
+                    "llvm-bc": "\#(bitcodeObject._nativePathString(escaped: true))",
                     "swiftmodule": "\#(partialModulePath._nativePathString(escaped: true))",
                     "swift-dependencies": "\#(swiftDepsPath._nativePathString(escaped: true))"
                   }\#((idx + 1) < sources.count ? "," : "")