Hi, all
Recently I'm trying to use LLVM PGO and autoFDO. However I have some
problems in the process.
LLVM source code is updated on April 9th. Operating system is SUSE x86_64
1. Problems in instrumentation based PGO:
clang -O2 -fprofile-instr-generate test.c -o a.out
./a.out (then default.profraw is generated)
clang -O2 -fprofile-instr-use=default.profraw test.c -o a.out
error: pgo data file has malformed function entry
I found that the run-time function "writeFile" in
InstrProfilingFile.cpp didn't write '\n'.
But when parsing the profile data, in CodeGenPGO.cpp line 56, it tried to
find '\n' like below:
CurPtr = strchr(CurPtr, '\n');
if (!CurPtr) {
ReportBadPGOData(CGM, "pgo data file has malformed function
entry");
return;
}
2. Problems in autoFDO:
Actually the problem happened in using create_llvm_prof, transformation is
failed.
clang -O2 -g test.c -o a.out
perf record -b ./a.out (perf version is 0.0.2, "-b" option is not
recognized, why?)
change to: perf record ./a.out (so perf.data is generated)
create_llvm_prof --binary=./a.out --out=code.prof (it read a.out and
perf.data)
error: Malformed .note.gnu.build-id section
no build id found in the binary
it seems that a.out has no build id.
Someone who can help me?
Thanks,
Kaidong Chen
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On Mon, May 12, 2014 at 12:59 PM, 猫妖 <spcatman at qq.com> wrote:> 2. Problems in autoFDO: > Actually the problem happened in using create_llvm_prof, transformation is > failed. > clang -O2 -g test.c -o a.out > perf record -b ./a.out (perf version is 0.0.2, "-b" option is not > recognized, why?) > change to: perf record ./a.out (so perf.data is generated) > create_llvm_prof --binary=./a.out --out=code.prof (it read a.out and > perf.data) > error: Malformed .note.gnu.build-id section > no build id found in the binary > it seems that a.out has no build id.This error message from create_llvm_prof is actually harmless. Dehao will be removing it at some point. The file code.prof should have content and clang will be able to read it. Please try: $ clang -fprofile-sample-use=code.prof -g ... Diego.
On Monday, May 12, 2014, 猫妖 <spcatman at qq.com> wrote:> Hi, all > > Recently I'm trying to use LLVM PGO and autoFDO. However I have some > problems in the process. > LLVM source code is updated on April 9th. Operating system is SUSE > x86_64 > > 1. Problems in instrumentation based PGO: > clang -O2 -fprofile-instr-generate test.c -o a.out > ./a.out (then default.profraw is generated) > clang -O2 -fprofile-instr-use=default.profraw test.c -o a.out > error: pgo data file has malformed function entry > I found that the run-time function "writeFile" in InstrProfilingFile.cpp > didn't write '\n'. > But when parsing the profile data, in CodeGenPGO.cpp line 56, it tried > to find '\n' like below: > CurPtr = strchr(CurPtr, '\n'); > if (!CurPtr) { > ReportBadPGOData(CGM, "pgo data file has malformed function entry"); > return; > } >Sorry that this isn't documented very well. I'm working on some documentation for the instrumentation based profiling that should make this less of a guessing game. You need to run `llvm-profdata merge` on the raw profile data to generate the format that clang understands. Something like: llvm-profdata merge default.profraw -o default.profdata Then use default.profdata as the input to -fprofile-instr-use.> 2. Problems in autoFDO: > Actually the problem happened in using create_llvm_prof, transformation > is failed. > clang -O2 -g test.c -o a.out > perf record -b ./a.out (perf version is 0.0.2, "-b" option is not > recognized, why?) > change to: perf record ./a.out (so perf.data is generated) > create_llvm_prof --binary=./a.out --out=code.prof (it read a.out and > perf.data) > error: Malformed .note.gnu.build-id section > no build id found in the binary > it seems that a.out has no build id. > > Someone who can help me? > > Thanks, > Kaidong Chen > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20140512/471b8cbf/attachment.html>
On Monday, May 12, 2014, 猫妖 <spcatman at qq.com> wrote:
Hi, all
Recently I'm trying to use LLVM PGO and autoFDO. However I have some
problems in the process.
LLVM source code is updated on April 9th. Operating system is SUSE x86_64
1. Problems in instrumentation based PGO:
clang -O2 -fprofile-instr-generate test.c -o a.out
./a.out (then default.profraw is generated)
clang -O2 -fprofile-instr-use=default.profraw test.c -o a.out
error: pgo data file has malformed function entry
I found that the run-time function "writeFile" in
InstrProfilingFile.cpp didn't write '\n'.
But when parsing the profile data, in CodeGenPGO.cpp line 56, it tried to
find '\n' like below:
CurPtr = strchr(CurPtr, '\n');
if (!CurPtr) {
ReportBadPGOData(CGM, "pgo data file has malformed function
entry");
return;
}
>>Sorry that this isn't documented very well. I'm working on some
documentation for the instrumentation
>>based profiling that should make this less of a guessing game.
>>You need to run `llvm-profdata merge` on the raw profile data to
generate the format that clang
>>understands. Something like:
>> llvm-profdata merge default.profraw -o default.profdata
>>Then use default.profdata as the input to -fprofile-instr-use.
It has worked well after I do as you say. Thank you!
And I want to confirm what passes benefits from profdata-guided feedback
currently.
Is the profiledata feeded back to all of basicblock replacement, function
inline, register allocation
and loop-unroll, or only basicblock replacement ?
I'll test performance improvement of PGO on some benchmarks.
I think you already have some test results.
Thanks,
Kaidong Chen
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