diff --git a/Sources/Build/Command.compile(ClangModule).swift b/Sources/Build/Command.compile(ClangModule).swift
index 9ddfe0fab65..72cef232ab9 100644
--- a/Sources/Build/Command.compile(ClangModule).swift
+++ b/Sources/Build/Command.compile(ClangModule).swift
@@ -12,25 +12,19 @@ import PackageType
 import Utility
 import POSIX
 
-//FIXME: Incremental builds
-
-extension Command {
-    static func compile(clangModule module: ClangModule, externalModules: Set<Module>, configuration conf: Configuration, prefix: String, CC: String) -> (Command, Command) {
-
-        let wd = Path.join(prefix, "\(module.c99name).build")
-        let mkdir = Command.createDirectory(wd)
-
-        let inputs = module.dependencies.map{ $0.targetName } + module.sources.paths + [mkdir.node]
-        let productPath = Path.join(prefix, module.type == .Library ? "lib\(module.c99name).so" : module.c99name)
-
+private extension ClangModule {
+    var basicArgs: [String] {
         var args: [String] = []
-    #if os(Linux)
-        args += ["-fPIC"]
-    #endif
-        args += ["-fmodules", "-fmodule-name=\(module.name)"]
-        args += ["-L\(prefix)"]
+        #if os(Linux)
+            args += ["-fPIC"]
+        #endif
+        args += ["-fmodules", "-fmodule-name=\(name)"]
+        return args
+    }
 
-        for case let dep as ClangModule in module.dependencies {
+    func includeFlagsWithExternalModules(externalModules: Set<Module>) -> [String] {
+        var args: [String] = []
+        for case let dep as ClangModule in dependencies {
             let includeFlag: String
             //add `-iquote` argument to the include directory of every target in the package in the
             //transitive closure of the target being built allowing the use of `#include "..."`
@@ -39,32 +33,89 @@ extension Command {
 
             includeFlag = externalModules.contains(dep) ? "-I" : "-iquote"
             args += [includeFlag, dep.path]
-            args += ["-l\(dep.c99name)"] //FIXME: giving path to other module's -fmodule-map-file is not linking that module
         }
+        return args
+    }
+
+    var linkFlags: [String] {
+        var args: [String] = []
+        for case let dep as ClangModule in dependencies {
+            args += ["-l\(dep.c99name)"]
+        }
+        return args
+    }
 
+    func optimizationFlags(conf: Configuration) -> [String] {
         switch conf {
         case .Debug:
-            args += ["-g", "-O0"]
+            return ["-g", "-O0"]
         case .Release:
-            args += ["-O2"]
+            return ["-O2"]
         }
+    }
+}
+
+private extension Sources {
+    func compilePathsForBuildDir(wd: String) -> [(filename: String, source: String, object: String, deps: String)] {
+        return relativePaths.map { source in
+            let path = Path.join(root, source)
+            let object = Path.join(wd, "\(source).o")
+            let deps = Path.join(wd, "\(source).d")
+            return (source, path, object, deps)
+        }
+    }
+}
+
+extension Command {
+    static func compile(clangModule module: ClangModule, externalModules: Set<Module>, configuration conf: Configuration, prefix: String, CC: String) -> ([Command], Command) {
+
+        let wd = Path.join(prefix, "\(module.c99name).build")
+        let mkdir = Command.createDirectory(wd)
+
+        ///------------------------------ Compile -----------------------------------------
+        var compileCommands = [Command]()
+        let dependencies = module.dependencies.map{ $0.targetName }
+        let basicArgs = module.basicArgs + module.includeFlagsWithExternalModules(externalModules) + module.optimizationFlags(conf)
+        for path in module.sources.compilePathsForBuildDir(wd) {
+            var args = basicArgs
+            args += ["-MD", "-MT", "dependencies", "-MF", path.deps]
+            args += ["-c", path.source, "-o", path.object]
+
+            let clang = ClangTool(desc: "Compiling \(module.name) \(path.filename)",
+                                  inputs: dependencies + [path.source, mkdir.node],
+                                  outputs: [path.object],
+                                  args: [CC] + args,
+                                  deps: path.deps)
+
+            let command = Command(node: path.object, tool: clang)
+
+            compileCommands.append(command)
+        }
+
+
+        ///FIXME: This probably doesn't belong here
+        ///------------------------------ Product -----------------------------------------
+
+        var args = module.basicArgs
+        args += module.optimizationFlags(conf)
+        args += ["-L\(prefix)"]
+        args += module.linkFlags
+        args += module.sources.compilePathsForBuildDir(wd).map{$0.object}
 
-        args += module.sources.paths
-        
         if module.type == .Library {
             args += ["-shared"]
         }
-        
-        args += ["-o", productPath]
 
-        let clang = ShellTool(
-            description: "Compiling \(module.name)",
-            inputs: inputs,
-            outputs: [productPath, module.targetName],
-            args: [CC] + args)
-
-        let command = Command(node: module.targetName, tool: clang)
+        let productPath = Path.join(prefix, module.type == .Library ? "lib\(module.c99name).so" : module.c99name)
+        args += ["-o", productPath]
+        
+        let shell = ShellTool(description: "Linking \(module.name)",
+                              inputs: dependencies + compileCommands.map{$0.node} + [mkdir.node],
+                              outputs: [productPath, module.targetName],
+                              args: [CC] + args)
+        
+        let command = Command(node: module.targetName, tool: shell)
 
-        return (command, mkdir)
+        return (compileCommands + [command], mkdir)
     }
 }
diff --git a/Sources/Build/ToolProtocol.swift b/Sources/Build/ToolProtocol.swift
index 8736c8222fc..f6a95348abf 100644
--- a/Sources/Build/ToolProtocol.swift
+++ b/Sources/Build/ToolProtocol.swift
@@ -110,3 +110,26 @@ struct MkdirTool: ToolProtocol {
         return yaml
     }
 }
+
+struct ClangTool: ToolProtocol {
+    let desc: String
+    let inputs: [String]
+    let outputs: [String]
+    let args: [String]
+    let deps: String?
+
+    var name: String { return "clang" }
+
+    var YAMLDescription: String {
+        var yaml = ""
+        yaml += "    tool: " + name.YAML + "\n"
+        yaml += "    description: " + desc.YAML + "\n"
+        yaml += "    inputs: " + inputs.YAML + "\n"
+        yaml += "    outputs: " + outputs.YAML + "\n"
+        yaml += "    args: " + args.joined(separator: " ").YAML + "\n"
+        if let deps = deps {
+            yaml += "    deps: " + deps.YAML + "\n"
+        }
+        return yaml
+    }
+}
diff --git a/Sources/Build/describe().swift b/Sources/Build/describe().swift
index 3246042c67f..6779d119d04 100644
--- a/Sources/Build/describe().swift
+++ b/Sources/Build/describe().swift
@@ -54,9 +54,9 @@ public func describe(prefix: String, _ conf: Configuration, _ modules: [Module],
             }
 
             let (compile, mkdir) = Command.compile(clangModule: module, externalModules: externalModules, configuration: conf, prefix: prefix, CC: CC)
-            commands.append(compile)
+            commands += compile
             commands.append(mkdir)
-            targets.main.cmds.append(compile)
+            targets.main.cmds += compile
 
         case is CModule:
             continue