[clang] [clang][modules-driver] Add dependency scan and dependency graph (PR #152770)

[Chuanqi Xu via cfe-commits]

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@@ -1829,6 +1831,53 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
   // Populate the tool chains for the offloading devices, if any.
   CreateOffloadingDeviceToolChains(*C, Inputs);
 
+  modules::StdModuleManifest Manifest;
+  if (C->getArgs().hasFlag(options::OPT_fmodules_driver,
+                           options::OPT_fno_modules_driver, false)) {
+    Diags.Report(diag::remark_performing_driver_managed_module_build);
+    // TODO: Once -fmodules-driver is no longer experimental, move
+    // TODO: The detection logic to implicitly enable -fmodules-driver is kept
+    // here only for diagnostics until the feature is no longer experimental.
+    auto EnableOrErr = modules::shouldUseModulesDriver(Inputs, getVFS(), Diags);
+    if (!EnableOrErr) {
+      llvm::handleAllErrors(
+          EnableOrErr.takeError(), [&](const llvm::FileError &Err) {
+            Diags.Report(diag::err_cannot_open_file)
+                << Err.getFileName() << Err.messageWithoutFileInfo();
+          });
+      return C;
+    }
+
+    // Read the standard modules manifest, and if available, add all discovered
+    // modules to the compilation. Compilation jobs for modules discovered from
+    // the manifest, which are not imported by any other source input, are
+    // pruned later.
+    const auto StdModuleManifestPath =
+        GetStdModuleManifestPath(*C, C->getDefaultToolChain());
+    if (StdModuleManifestPath == "<NOT PRESENT>") {
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ChuanqiXu9 wrote:

nit: maybe we can avoid hardcoding by judging this by if it is a path.

https://github.com/llvm/llvm-project/pull/152770