[clang][deps] Remove unintentional `move`

[jansvoboda11]

Summary

This is a fix related to D135414. The original intention was to keep BaseFS as a member of the worker and conditionally overlay it with local in-memory FS. The move of ref-counted BaseFS was not intended, and it's a bug.

Disabling parallelism in the "by-module-name" test reliably reproduces this, and the test itself doesn't *need* parallelism. (I think -j 4 was cargo culted from another test.) Reusing that test to check for correct behavior...

[DavidSpickett]

clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp

400

Is this equivalent?

auto OverlayFS = BaseFS;

Given that BaseFS is already IntrusiveRefCntPtr.

clang/test/ClangScanDeps/modules-full-by-mod-name.cpp

18

Would it help to have one be j1 and one j4, any extra coverage by doing that?

[jansvoboda11]

clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp

400

It's not, because BaseFS is pointer to the llvm::vfs::FileSystem interface. Here we need to call members of llvm::vfs::OverlayFileSystem specifically.

[jansvoboda11]

Use both -j 1 and -j 4 in tests.

[jansvoboda11]

clang/test/ClangScanDeps/modules-full-by-mod-name.cpp

18

Technically that does give us extra coverage. Let's do it if you feel more comfortable that way.

[DavidSpickett]

LGTM

As it happens the bot that found this has been moved to silent for other reasons. I'll let you know if we see any further issues.

clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp

bool DependencyScanningWorker::computeDependencies(
   BaseFS->setCurrentWorkingDirectory(WorkingDirectory);
 
   Optional<std::vector<std::string>> ModifiedCommandLine;
   llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> ModifiedFS;
   if (ModuleName) {
     ModifiedCommandLine = CommandLine;
     ModifiedCommandLine->emplace_back(*ModuleName);
 
-    auto OverlayFS = llvm::makeIntrusiveRefCnt<llvm::vfs::OverlayFileSystem>(
-        std::move(BaseFS));
+    auto OverlayFS =
+        llvm::makeIntrusiveRefCnt<llvm::vfs::OverlayFileSystem>(BaseFS);
     auto InMemoryFS =
         llvm::makeIntrusiveRefCnt<llvm::vfs::InMemoryFileSystem>();
     InMemoryFS->setCurrentWorkingDirectory(WorkingDirectory);
     InMemoryFS->addFile(*ModuleName, 0, llvm::MemoryBuffer::getMemBuffer(""));
     OverlayFS->pushOverlay(InMemoryFS);
     ModifiedFS = OverlayFS;
   }
 

clang/test/ClangScanDeps/modules-full-by-mod-name.cpp

 // UNSUPPORTED: powerpc64-ibm-aix
 // RUN: rm -rf %t.dir
 // RUN: rm -rf %t.cdb
 // RUN: mkdir -p %t.dir
 // RUN: cp %s %t.dir/modules_cdb_input.cpp
 // RUN: cp %s %t.dir/modules_cdb_input2.cpp
 // RUN: mkdir %t.dir/Inputs
 // RUN: cp %S/Inputs/header.h %t.dir/Inputs/header.h
 // RUN: cp %S/Inputs/header2.h %t.dir/Inputs/header2.h
 // RUN: cp %S/Inputs/module.modulemap %t.dir/Inputs/module.modulemap
 // RUN: sed -e "s|DIR|%/t.dir|g" %S/Inputs/modules_cdb_by_mod_name.json > %t.cdb
 // RUN: sed -e "s|DIR|%/t.dir|g" %S/Inputs/modules_cdb_clangcl_by_mod_name.json > %t_clangcl.cdb
 //
-// RUN: clang-scan-deps -compilation-database %t.cdb -j 4 -format experimental-full \
+// RUN: clang-scan-deps -compilation-database %t.cdb -j 1 -format experimental-full \
 // RUN:   -mode preprocess-dependency-directives -module-name=header1 > %t.result
 // RUN: cat %t.result | sed 's:\\\\\?:/:g' | FileCheck -DPREFIX=%/t.dir --check-prefixes=CHECK %s
 //
 // RUN: clang-scan-deps -compilation-database %t_clangcl.cdb -j 4 -format experimental-full \
 // RUN:   -mode preprocess-dependency-directives -module-name=header1 > %t_clangcl.result
 // RUN: cat %t_clangcl.result | sed 's:\\\\\?:/:g' | FileCheck -DPREFIX=%/t.dir --check-prefixes=CHECK %s
 
 // CHECK:      {
 // CHECK-NEXT:   "modules": [
 // CHECK-NEXT:     {
 // CHECK-NEXT:       "clang-module-deps": [
 // CHECK-NEXT:         {