[clang] [clang][ModulesDriver] Add support for Clang modules to -fmodules-driver (PR #187606)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-driver

Author: Naveen Seth Hanig (naveen-seth)

<details>
<summary>Changes</summary>

This PR adds basic support for explicit module builds using Clang modules only, managed natively by the Clang driver.
(Caching of built modules is not included in this PR.)

RFC for driver-managed module builds:
https://discourse.llvm.org/t/rfc-modules-support-simple-c-20-modules-use-from-the-clang-driver-without-a-build-system

---
Full diff: https://github.com/llvm/llvm-project/pull/187606.diff


3 Files Affected:

- (modified) clang/lib/Driver/ModulesDriver.cpp (+9-5) 
- (added) clang/test/Driver/modules-driver-clang-modules-only.cpp (+75) 
- (modified) clang/test/Driver/modules-driver-manifest-input-args.cpp (+5-11) 


``````````diff
diff --git a/clang/lib/Driver/ModulesDriver.cpp b/clang/lib/Driver/ModulesDriver.cpp
index 8740f9615d304..166c7749245c6 100644
--- a/clang/lib/Driver/ModulesDriver.cpp
+++ b/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));
 }
diff --git a/clang/test/Driver/modules-driver-clang-modules-only.cpp b/clang/test/Driver/modules-driver-clang-modules-only.cpp
new file mode 100644
index 0000000000000..e99ce7883afba
--- /dev/null
+++ b/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();
+}
diff --git a/clang/test/Driver/modules-driver-manifest-input-args.cpp b/clang/test/Driver/modules-driver-manifest-input-args.cpp
index 99765a1943faf..6e3c7ac4c3eff 100644
--- a/clang/test/Driver/modules-driver-manifest-input-args.cpp
+++ b/clang/test/Driver/modules-driver-manifest-input-args.cpp
@@ -25,18 +25,12 @@
 // RUN:   -fmodules-cache-path=%t/modules-cache \
 // 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:   | sed 's/\\/\//g' \
+// 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;

``````````

</details>


https://github.com/llvm/llvm-project/pull/187606