On 2016/11/27 1:25, Alexei Starovoitov wrote:
On Sat, Nov 26, 2016 at 07:03:38AM +0000, Wang Nan wrote:
getBPFObjectFromModule() is introduced to compile LLVM IR(Module)
to BPF object. Add new testcase for it.
Test result:
$ ./buildperf/perf test -v clang
51: Test builtin clang support :
51.1: Test builtin clang compile C source to IR :
--- start ---
test child forked, pid 21822
test child finished with 0
---- end ----
Test builtin clang support subtest 0: Ok
51.2: Test builtin clang compile C source to ELF object :
--- start ---
test child forked, pid 21823
test child finished with 0
---- end ----
Test builtin clang support subtest 1: Ok
Signed-off-by: Wang Nan <wangn...@huawei.com>
...
+ legacy::PassManager PM;
+ if (TargetMachine->addPassesToEmitFile(PM, ostream,
+ TargetMachine::CGFT_ObjectFile))
{
+ llvm::errs() << "TargetMachine can't emit a file of this
type\n";
+ return std::unique_ptr<llvm::SmallVectorImpl<char>>(nullptr);;
+ }
+ PM.run(*Module);
I'm pretty sure you want to add FunctionInlingPass as well otherwise
I think llvm won't be doing much inlining and only very very simple
programs will compile fine. See what we did on bcc side.
Thank you for your information. I though inlining should be done during
C to IR phase, and we have use -O2 for it. Let me check it.
Also did you consider skipping elf generation and using in memory
instead ? That will improve compile/run time.
Maybe in future work? Current design reuse libelf and bpf-loader for
loading BPF code. Skipping ELF generation make compiling faster, but
require another loader to be coexist with bpf-loader.c, or we need
a new libbpf. In my current experience, outputting ELF is not so slow
for both server and smartphone.
Thank you.
