[PATCH] D70467: [Distro] Bypass distro detection on Windows

[Alexandre Ganea via Phabricator via cfe-commits]

aganea created this revision.
aganea added reviewers: sylvestre.ledru, rnk.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

This skips distro detection on Windows, thus saving a few `stat` calls for each invocation of `clang.exe`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70467

Files:
  clang/lib/Driver/Distro.cpp
  clang/unittests/Driver/DistroTest.cpp


Index: clang/unittests/Driver/DistroTest.cpp
===================================================================
--- clang/unittests/Driver/DistroTest.cpp
+++ clang/unittests/Driver/DistroTest.cpp
@@ -337,4 +337,37 @@
   ASSERT_TRUE(Gentoo.IsGentoo());
 }
 
+#ifdef _WIN32
+TEST(DistroTest, DetectOnWindows) {
+
+  class CountingFileSystem : public llvm::vfs::ProxyFileSystem {
+  public:
+    CountingFileSystem() : ProxyFileSystem(llvm::vfs::getRealFileSystem()) {}
+
+    llvm::ErrorOr<llvm::vfs::Status> status(const llvm::Twine &Path) override {
+      ++Count;
+      return llvm::vfs::ProxyFileSystem::status(Path);
+    }
+
+    llvm::ErrorOr<std::unique_ptr<llvm::vfs::File>>
+    openFileForRead(const llvm::Twine &Path) override {
+      ++Count;
+      return llvm::vfs::ProxyFileSystem::openFileForRead(Path);
+    }
+
+    unsigned Count{};
+  };
+
+  CountingFileSystem CFileSystem;
+  Distro WinVFS{ CFileSystem };
+  ASSERT_EQ(Distro(Distro::UnknownDistro), WinVFS);
+  ASSERT_GT(CFileSystem.Count, 0U);
+
+  llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> RFS =
+      llvm::vfs::getRealFileSystem();
+  Distro WinRFS{*RFS};
+  ASSERT_EQ(Distro(Distro::UnknownDistro), WinRFS);
+}
+#endif
+
 } // end anonymous namespace
Index: clang/lib/Driver/Distro.cpp
===================================================================
--- clang/lib/Driver/Distro.cpp
+++ clang/lib/Driver/Distro.cpp
@@ -18,6 +18,12 @@
 using namespace clang;
 
 static Distro::DistroType DetectDistro(llvm::vfs::FileSystem &VFS) {
+#ifdef _WIN32
+  IntrusiveRefCntPtr<llvm::vfs::FileSystem> RealFS =
+      llvm::vfs::getRealFileSystem();
+  if (&VFS == RealFS.get())
+    return Distro::UnknownDistro;
+#endif
   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> File =
       VFS.getBufferForFile("/etc/lsb-release");
   if (File) {


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