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[PATCH 03/14] perf tools: Add feature detection for LLVM

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Check if basic LLVM compiling environment is ready.

Use llvm-config to detect include and library directories. Avoid using
'llvm-config --cxxflags' because its result contain some unwanted flags
like --sysroot (if LLVM is built by yocto).

Use '?=' to set LLVM_CONFIG, so explicitly passing LLVM_CONFIG to make
would override it.

Use 'llvm-config --libs BPF' to check if BPF backend is compiled in.
Since now BPF bytecode is the only required backend, no need to waste
time linking llvm and clang if BPF backend is missing. This
also introduce an implicit requirement that LLVM should be new enough.
Old LLVM doesn't support BPF backend.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: 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>
---
 tools/build/feature/Makefile      | 8 ++++++++
 tools/build/feature/test-llvm.cpp | 8 ++++++++
 2 files changed, 16 insertions(+)
 create mode 100644 tools/build/feature/test-llvm.cpp

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index ac9c477..fd2f3e2 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -54,6 +54,7 @@ FILES := $(addprefix $(OUTPUT),$(FILES))
 CC := $(CROSS_COMPILE)gcc -MD
 CXX := $(CROSS_COMPILE)g++ -MD
 PKG_CONFIG := $(CROSS_COMPILE)pkg-config
+LLVM_CONFIG ?= llvm-config
 
 all: $(FILES)
 
@@ -225,6 +226,13 @@ $(OUTPUT)test-sdt.bin:
 $(OUTPUT)test-cxx.bin:
 	$(BUILDXX) -std=gnu++11
 
+$(OUTPUT)test-llvm.bin:
+	$(BUILDXX) -std=gnu++11 					\
+		-I$(shell $(LLVM_CONFIG) --includedir) 		\
+		-L$(shell $(LLVM_CONFIG) --libdir)		\
+		$(shell $(LLVM_CONFIG) --libs Core BPF)		\
+		$(shell $(LLVM_CONFIG) --system-libs)
+
 -include $(OUTPUT)*.d
 
 ###############################
diff --git a/tools/build/feature/test-llvm.cpp b/tools/build/feature/test-llvm.cpp
new file mode 100644
index 0000000..d8d2cee
--- /dev/null
+++ b/tools/build/feature/test-llvm.cpp
@@ -0,0 +1,8 @@
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/raw_ostream.h"
+int main()
+{
+	llvm::errs() << "Hello World!\n";
+	llvm::llvm_shutdown();
+	return 0;
+}
-- 
1.8.3.4

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[PATCH 00/14] perf clang: Support compiling BPF script use builtin clang Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 03/14] perf tools: Add feature detection for LLVM Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 01/14] tools build: Support compiling C++ source file Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
    Re: [PATCH 01/14] tools build: Support compiling C++ source file Jiri Olsa <jolsa@redhat.com> - 2016-09-28 16:40 +0200
  [PATCH 04/14] perf tools: Add feature detection for clang Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 09/14] perf clang: Update test case to use real BPF script Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 08/14] perf clang: Allow passing CFLAGS to builtin clang Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 13/14] perf clang: Pass fill path compiler Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 12/14] perf bpf: Compile BPF script use builtin cflags support Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 02/14] perf tools: Add feature detection for g++ Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 11/14] perf tools: Extract kernel build option detector as utils Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 06/14] perf clang: Add builtin clang support ant test case Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 05/14] perf build: Add clang and llvm compile and linking support Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 07/14] perf clang: Use real file system for #include Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 14/14] perf clang: Pass correct CFLAGS to builtin clang Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  [PATCH 10/14] perf clang: Support compile IR to BPF object and add testcase Wang Nan <wangnan0@huawei.com> - 2016-09-23 15:00 +0200
  Re: [PATCH 00/14] perf clang: Support compiling BPF script use  builtin clang Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-09-24 17:20 +0200
    Re: [PATCH 00/14] perf clang: Support compiling BPF script use  builtin clang "Wangnan (F)" <wangnan0@huawei.com> - 2016-09-26 04:00 +0200
      Re: [PATCH 00/14] perf clang: Support compiling BPF script use  builtin clang Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-09-27 01:50 +0200
        Re: [PATCH 00/14] perf clang: Support compiling BPF script use  builtin clang "Wangnan (F)" <wangnan0@huawei.com> - 2016-09-27 04:00 +0200

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