[PATCH 15/34] perf clang: Use real file system for #include

[Wang Nan]

Utilize clang's OverlayFileSystem facility, allow CompilerInstance to
access real file system.

With this patch '#include' directive can be used.

Add a new getModuleFromSource for real file.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxx>
Cc: He Kuang <hekuang@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/util/c++/clang.cpp | 44 +++++++++++++++++++++++++++++++------------
 tools/perf/util/c++/clang.h   |  3 +++
 2 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/c++/clang.cpp b/tools/perf/util/c++/clang.cpp
index c17b117..cf96199 100644
--- a/tools/perf/util/c++/clang.cpp
+++ b/tools/perf/util/c++/clang.cpp
@@ -15,6 +15,7 @@
 #include "clang/Tooling/Tooling.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Option/Option.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/ManagedStatic.h"
 #include <memory>
 
@@ -27,14 +28,6 @@ static std::unique_ptr<llvm::LLVMContext> LLVMCtx;
 
 using namespace clang;
 
-static vfs::InMemoryFileSystem *
-buildVFS(StringRef& Name, StringRef& Content)
-{
-	vfs::InMemoryFileSystem *VFS = new vfs::InMemoryFileSystem(true);
-	VFS->addFile(Twine(Name), 0, llvm::MemoryBuffer::getMemBuffer(Content));
-	return VFS;
-}
-
 static CompilerInvocation *
 createCompilerInvocation(StringRef& Path, DiagnosticsEngine& Diags)
 {
@@ -60,17 +53,17 @@ createCompilerInvocation(StringRef& Path, DiagnosticsEngine& Diags)
 	return CI;
 }
 
-std::unique_ptr<llvm::Module>
-getModuleFromSource(StringRef Name, StringRef Content)
+static std::unique_ptr<llvm::Module>
+getModuleFromSource(StringRef Path,
+		    IntrusiveRefCntPtr<vfs::FileSystem> VFS)
 {
 	CompilerInstance Clang;
 	Clang.createDiagnostics();
 
-	IntrusiveRefCntPtr<vfs::FileSystem> VFS = buildVFS(Name, Content);
 	Clang.setVirtualFileSystem(&*VFS);
 
 	IntrusiveRefCntPtr<CompilerInvocation> CI =
-		createCompilerInvocation(Name, Clang.getDiagnostics());
+		createCompilerInvocation(Path, Clang.getDiagnostics());
 	Clang.setInvocation(&*CI);
 
 	std::unique_ptr<CodeGenAction> Act(new EmitLLVMOnlyAction(&*LLVMCtx));
@@ -80,6 +73,33 @@ getModuleFromSource(StringRef Name, StringRef Content)
 	return Act->takeModule();
 }
 
+std::unique_ptr<llvm::Module>
+getModuleFromSource(StringRef Name, StringRef Content)
+{
+	using namespace vfs;
+
+	llvm::IntrusiveRefCntPtr<OverlayFileSystem> OverlayFS(
+			new OverlayFileSystem(getRealFileSystem()));
+	llvm::IntrusiveRefCntPtr<InMemoryFileSystem> MemFS(
+			new InMemoryFileSystem(true));
+
+	/*
+	 * pushOverlay helps setting working dir for MemFS. Must call
+	 * before addFile.
+	 */
+	OverlayFS->pushOverlay(MemFS);
+	MemFS->addFile(Twine(Name), 0, llvm::MemoryBuffer::getMemBuffer(Content));
+
+	return getModuleFromSource(Name, OverlayFS);
+}
+
+std::unique_ptr<llvm::Module>
+getModuleFromSource(StringRef Path)
+{
+	IntrusiveRefCntPtr<vfs::FileSystem> VFS(vfs::getRealFileSystem());
+	return getModuleFromSource(Path, VFS);
+}
+
 }
 
 extern "C" {
diff --git a/tools/perf/util/c++/clang.h b/tools/perf/util/c++/clang.h
index f64483b..90aff01 100644
--- a/tools/perf/util/c++/clang.h
+++ b/tools/perf/util/c++/clang.h
@@ -12,5 +12,8 @@ using namespace llvm;
 std::unique_ptr<Module>
 getModuleFromSource(StringRef Name, StringRef Content);
 
+std::unique_ptr<Module>
+getModuleFromSource(StringRef Path);
+
 }
 #endif
-- 
2.10.1