Re: [PATCH v3 10/30] perf clang: Add builtin clang support ant test case
From: Wangnan (F)
Date: Sun Dec 04 2016 - 23:42:32 EST
On 2016/12/5 10:36, Wangnan (F) wrote:
On 2016/12/2 23:44, Arnaldo Carvalho de Melo wrote:
Em Sat, Nov 26, 2016 at 07:03:34AM +0000, Wang Nan escreveu:
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: Test 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
While testing this I noticed that the perf binary got huge, can't this
be done in some other way, i.e. using dynamic library?
I intentionally use statically linking because it is good for
smartphone: we can simply 'adb push' a statically linked perf
to Android.
The resulting ELF executable would be even larger if LLVM is
built with default setting.
In my setting the resuling 'perf' is less than 60MB:
$ ls -s ~/perf -h
58M /home/wn/perf
$ size ~/perf
text data bss dec hex filename
56931273 2950808 24108632 83990713 50198b9 /home/wn/perf
It is reasonable for me.
I think using dynamic clang and llvm libraries is possible but I
never tried it before. It depend on LLVM compiling. I think if
distro provides shared libraries then perf can utilize them
automatically. Let me check it today.
Good news: it works.
To enable llvm and clang dynamic libraries, we need to build llvm and
clang with
cmake option -DBUILD_SHARED_LIBS=ON. Then apply a trivial patch to perf:
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index dfb20dd..e3054f3 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -346,7 +346,7 @@ LIBS = -Wl,--whole-archive $(PERFLIBS)
-Wl,--no-whole-archive -Wl,--start-group
ifeq ($(USE_CLANG), 1)
CLANGLIBS_LIST = AST Basic CodeGen Driver Frontend Lex Tooling Edit
Sema Analysis Parse Serialization
- LIBCLANG = $(foreach l,$(CLANGLIBS_LIST),$(wildcard $(shell
$(LLVM_CONFIG) --libdir)/libclang$(l).a))
+ LIBCLANG = $(foreach l,$(CLANGLIBS_LIST),$(wildcard $(shell
$(LLVM_CONFIG) --libdir)/libclang$(l).so))
LIBS += -Wl,--start-group $(LIBCLANG) -Wl,--end-group
endif
(replace '.a' to '.so')
Resuling perf executable:
$ ls -s -h ~/perf
26M /home/wn/perf
$ size ~/perf
text data bss dec hex filename
4274339 755032 23959984 28989355 1ba57ab /home/wn/perf
$ strip ~/perf
$ ls -s -h
4.9M /home/wn/perf
$ ldd ~/perf | grep 'LLVM\|clang'
libclangBasic.so => /tmp/oxygen_root/usr/lib64/libclangBasic.so
(0x00007f24da49f000)
libclangCodeGen.so => /tmp/oxygen_root/usr/lib64/libclangCodeGen.so
(0x00007f24d9f72000)
libclangFrontend.so =>
/tmp/oxygen_root/usr/lib64/libclangFrontend.so (0x00007f24d9c64000)
libclangTooling.so => /tmp/oxygen_root/usr/lib64/libclangTooling.so
(0x00007f24d9a01000)
libLLVMBPFCodeGen.so =>
/tmp/oxygen_root/usr/lib64/libLLVMBPFCodeGen.so (0x00007f24d97e2000)
libLLVMBPFDesc.so => /tmp/oxygen_root/usr/lib64/libLLVMBPFDesc.so
(0x00007f24d95da000)
....
As I said, if distro provides dynamic libraries then everything would be
fine.
If you are okay with the above conclusion, in next version I'll use
'-lclangBasic'
style linking options so it works for both dynamic and static
LLVM/clang, then let's
wait for distro's action.
Thank you.