[clang][ModulesDriver] Add support for Clang modules to -fmodules-driver

clang/lib/Driver/ModulesDriver.cpp

@@ -25,6 +25,7 @@
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/DirectedGraph.h"
+#include "llvm/ADT/PostOrderIterator.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVectorExtras.h"
 #include "llvm/ADT/TypeSwitch.h"
@@ -1528,9 +1529,12 @@ void driver::modules::runModulesDriver(
   // TODO: Install all updated command-lines produced by the dependency scan.
   // TODO: Fix-up command-lines for named module imports.
 
-  // TODO: Sort the graph topologically before adding jobs back to the
-  // Compilation being built.
-  for (auto *N : Graph)
-    if (auto *JN = dyn_cast<JobNode>(N))
-      C.addCommand(std::move(JN->Job));
+  llvm::ReversePostOrderTraversal<CompilationGraph *> TopologicallySortedNodes(
+      &Graph);
+  assert(isa<RootNode>(*TopologicallySortedNodes.begin()) &&
+         "First node in topological order must be the root!");
+  auto TopologicallySortedJobNodes = llvm::map_range(
+      llvm::drop_begin(TopologicallySortedNodes), llvm::CastTo<JobNode>);
+  for (auto *JN : TopologicallySortedJobNodes)
+    C.addCommand(std::move(JN->Job));
 }

clang/test/Driver/modules-driver-clang-modules-only.cpp

@@ -0,0 +1,75 @@
+// Checks that -fmodules-driver correctly handles compilations using Clang modules.
+
+// RUN: split-file %s %t
+// RUN: rm -rf %t/modules-cache
+// RUN: %clang -std=c++23 \
+// RUN: -fmodules-driver -Rmodules-driver \
+// RUN: -fmodules -Rmodule-import \
+// RUN: -fmodule-map-file=%t/module.modulemap \
+// RUN: -fmodules-cache-path=%t/modules-cache \
+// RUN: -fsyntax-only %t/main.cpp 2>&1 \
+// RUN: | sed 's:\\\\\?:/:g' \
+// RUN: | FileCheck -DPREFIX=%/t %s
+
+// The scan itself will also produce [-Rmodule-import] remarks.
+// Let's skip past them, we only care about the final -cc1 commands.
+// CHECK:       clang: remark: printing module dependency graph [-Rmodules-driver]
+// CHECK-NEXT:  digraph "Module Dependency Graph" {
+// CHECK:       }
+
+// CHECK:      [[PREFIX]]/main.cpp:1:2: remark: importing module 'root' from
+// CHECK:      [[PREFIX]]/main.cpp:1:2: remark: importing module 'direct1' into 'root'
+// CHECK:      [[PREFIX]]/main.cpp:1:2: remark: importing module 'transitive1' into 'direct1'
+// CHECK:      [[PREFIX]]/main.cpp:1:2: remark: importing module 'transitive2' into 'direct1'
+// CHECK:      [[PREFIX]]/main.cpp:1:2: remark: importing module 'direct2' into 'root'
+// CHECK:      [[PREFIX]]/main.cpp:1:2: remark: importing module 'transitive2' into 'direct2'
+
+// (Because of missing include guards, this example would also run into
+// redefinition errors when compiling without modules.)
+
+/--- module.modulemap
+module root { header "root.h"}
+module transitive1 { header "transitive1.h" }
+module transitive2 { header "transitive2.h" }
+module direct1 { header "direct1.h" }
+module direct2 { header "direct2.h" }
+
+//--- root.h
+#include "direct1.h"
+#include "direct2.h"
+int fromRoot() {
+  return fromDirect1() + fromDirect2();
+}
+
+//--- direct1.h
+#include "transitive1.h"
+#include "transitive2.h"
+
+int fromDirect1() {
+  return fromTransitive1() + fromTransitive2();
+}
+
+//--- direct2.h
+#include "transitive2.h"
+
+int fromDirect2() {
+  return fromTransitive2() + 2;
+}
+
+//--- transitive1.h
+int fromTransitive1() {
+    return 20;
+}
+
+//--- transitive2.h
+
+int fromTransitive2() {
+    return 10;
+}
+
+//--- main.cpp
+#include "root.h"
+
+int main() {
+ fromRoot();
+}

clang/test/Driver/modules-driver-manifest-input-args.cpp

@@ -26,17 +26,11 @@
 // RUN:   %t/main.cpp \
 // RUN:   -### 2>&1 \
 // RUN:   | sed 's:\\\\\?:/:g' \
-// RUN:   | FileCheck %s -check-prefix=MAIN-CC1 -check-prefix=STDLIB-MOD-CC1 -DPREFIX=%/t
+// RUN:   | FileCheck %s -DPREFIX=%/t
 
-// MAIN-CC1: "-cc1"
-// MAIN-CC1-SAME: "main.cpp"
-// MAIN-CC1-NOT: "-Wno-reserved-module-identifier"
-// MAIN-CC1-NOT: "-internal-isystem" "[[PREFIX]]/Inputs/usr/lib/x86_64-linux-gnu/../share/libc++/v1/"
-
-// STDLIB-MOD-CC1: "-cc1"
-// STDLIB-MOD-CC1-SAME: "[[PREFIX]]/Inputs/usr/lib/x86_64-linux-gnu/../share/libc++/v1/std.cppm"
-// STDLIB-MOD-CC1-SAME: "-Wno-reserved-module-identifier"
-// STDLIB-MOD-CC1-SAME: "-internal-isystem" "[[PREFIX]]/Inputs/usr/lib/x86_64-linux-gnu/../share/libc++/v1/"
+// CHECK: "-cc1" {{.*}} "[[PREFIX]]/Inputs/usr/lib/x86_64-linux-gnu/../share/libc++/v1/std.cppm"
+// CHECK-SAME: "-Wno-reserved-module-identifier"
+// CHECK-SAME: "-internal-isystem" "[[PREFIX]]/Inputs/usr/lib/x86_64-linux-gnu/../share/libc++/v1/"
 
 //--- main.cpp
 import std;