perf clang: Add builtin clang support ant test case

Add basic clang support in clang.cpp and test__clang() testcase. The
first testcase checks if builtin clang is able to generate LLVM IR.

tests/clang.c is a proxy. Real testcase resides in
utils/c++/clang-test.cpp in c++ and exports C interface to perf test
subsystem.

Test result:

   $ perf test -v clang
   51: builtin clang support                               :
   51.1: Test builtin clang compile C source to IR              :
   --- start ---
   test child forked, pid 13215
   test child finished with 0
   ---- end ----
   Test builtin clang support subtest 0: Ok

Committer note:

Make sure you've enabled CLANG and LLVM builtin support by setting
the LIBCLANGLLVM variable on the make command line, e.g.:

  make LIBCLANGLLVM=1 O=/tmp/build/perf -C tools/perf install-bin

Otherwise you'll get this when trying to do the 'perf test' call above:

  # perf test clang
  51: builtin clang support                      : Skip (not compiled in)
  #

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Joe Stringer <joe@ovn.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/20161126070354.141764-11-wangnan0@huawei.com
[ Removed "Test" from descriptions, redundant and already removed from all the other entries ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

6 files changed, 163 insertions, 0 deletions

diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index bdad82a9812d..3840e3a87057 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -126,6 +126,8 @@ endif
 
 libperf-y += perf-hooks.o
 
+libperf-$(CONFIG_CXX) += c++/
+
 CFLAGS_config.o   += -DETC_PERFCONFIG="BUILD_STR($(ETC_PERFCONFIG_SQ))"
 # avoid compiler warnings in 32-bit mode
 CFLAGS_genelf_debug.o  += -Wno-packed
diff --git a/tools/perf/util/c++/Build b/tools/perf/util/c++/Build
new file mode 100644
index 000000000000..988fef1b11d7
--- /dev/null
+++ b/tools/perf/util/c++/Build
@@ -0,0 +1,2 @@
+libperf-$(CONFIG_CLANGLLVM) += clang.o
+libperf-$(CONFIG_CLANGLLVM) += clang-test.o
diff --git a/tools/perf/util/c++/clang-c.h b/tools/perf/util/c++/clang-c.h
new file mode 100644
index 000000000000..dcde4b564f3b
--- /dev/null
+++ b/tools/perf/util/c++/clang-c.h
@@ -0,0 +1,16 @@
+#ifndef PERF_UTIL_CLANG_C_H
+#define PERF_UTIL_CLANG_C_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern void perf_clang__init(void);
+extern void perf_clang__cleanup(void);
+
+extern int test__clang_to_IR(void);
+
+#ifdef __cplusplus
+}
+#endif
+#endif
diff --git a/tools/perf/util/c++/clang-test.cpp b/tools/perf/util/c++/clang-test.cpp
new file mode 100644
index 000000000000..3da6bfa4bc54
--- /dev/null
+++ b/tools/perf/util/c++/clang-test.cpp
@@ -0,0 +1,31 @@
+#include "clang.h"
+#include "clang-c.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/LLVMContext.h"
+
+class perf_clang_scope {
+public:
+	explicit perf_clang_scope() {perf_clang__init();}
+	~perf_clang_scope() {perf_clang__cleanup();}
+};
+
+extern "C" {
+
+int test__clang_to_IR(void)
+{
+	perf_clang_scope _scope;
+
+	std::unique_ptr<llvm::Module> M =
+		perf::getModuleFromSource("perf-test.c",
+					  "int myfunc(void) {return 1;}");
+
+	if (!M)
+		return -1;
+
+	for (llvm::Function& F : *M)
+		if (F.getName() == "myfunc")
+			return 0;
+	return -1;
+}
+
+}
diff --git a/tools/perf/util/c++/clang.cpp b/tools/perf/util/c++/clang.cpp
new file mode 100644
index 000000000000..c17b1176e25d
--- /dev/null
+++ b/tools/perf/util/c++/clang.cpp
@@ -0,0 +1,96 @@
+/*
+ * llvm C frontend for perf. Support dynamically compile C file
+ *
+ * Inspired by clang example code:
+ * http://llvm.org/svn/llvm-project/cfe/trunk/examples/clang-interpreter/main.cpp
+ *
+ * Copyright (C) 2016 Wang Nan <wangnan0@huawei.com>
+ * Copyright (C) 2016 Huawei Inc.
+ */
+
+#include "clang/CodeGen/CodeGenAction.h"
+#include "clang/Frontend/CompilerInvocation.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Frontend/TextDiagnosticPrinter.h"
+#include "clang/Tooling/Tooling.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Option/Option.h"
+#include "llvm/Support/ManagedStatic.h"
+#include <memory>
+
+#include "clang.h"
+#include "clang-c.h"
+
+namespace perf {
+
+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)
+{
+	llvm::opt::ArgStringList CCArgs {
+		"-cc1",
+		"-triple", "bpf-pc-linux",
+		"-fsyntax-only",
+		"-ferror-limit", "19",
+		"-fmessage-length", "127",
+		"-O2",
+		"-nostdsysteminc",
+		"-nobuiltininc",
+		"-vectorize-loops",
+		"-vectorize-slp",
+		"-Wno-unused-value",
+		"-Wno-pointer-sign",
+		"-x", "c"};
+	CompilerInvocation *CI = tooling::newInvocation(&Diags, CCArgs);
+
+	FrontendOptions& Opts = CI->getFrontendOpts();
+	Opts.Inputs.clear();
+	Opts.Inputs.emplace_back(Path, IK_C);
+	return CI;
+}
+
+std::unique_ptr<llvm::Module>
+getModuleFromSource(StringRef Name, StringRef Content)
+{
+	CompilerInstance Clang;
+	Clang.createDiagnostics();
+
+	IntrusiveRefCntPtr<vfs::FileSystem> VFS = buildVFS(Name, Content);
+	Clang.setVirtualFileSystem(&*VFS);
+
+	IntrusiveRefCntPtr<CompilerInvocation> CI =
+		createCompilerInvocation(Name, Clang.getDiagnostics());
+	Clang.setInvocation(&*CI);
+
+	std::unique_ptr<CodeGenAction> Act(new EmitLLVMOnlyAction(&*LLVMCtx));
+	if (!Clang.ExecuteAction(*Act))
+		return std::unique_ptr<llvm::Module>(nullptr);
+
+	return Act->takeModule();
+}
+
+}
+
+extern "C" {
+void perf_clang__init(void)
+{
+	perf::LLVMCtx.reset(new llvm::LLVMContext());
+}
+
+void perf_clang__cleanup(void)
+{
+	perf::LLVMCtx.reset(nullptr);
+	llvm::llvm_shutdown();
+}
+}
diff --git a/tools/perf/util/c++/clang.h b/tools/perf/util/c++/clang.h
new file mode 100644
index 000000000000..f64483be43d0
--- /dev/null
+++ b/tools/perf/util/c++/clang.h
@@ -0,0 +1,16 @@
+#ifndef PERF_UTIL_CLANG_H
+#define PERF_UTIL_CLANG_H
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include <memory>
+namespace perf {
+
+using namespace llvm;
+
+std::unique_ptr<Module>
+getModuleFromSource(StringRef Name, StringRef Content);
+
+}
+#endif