[llvm-dev] instrumenting device code with gpucc

Tue Mar 15 10:51:31 PDT 2016

Gotcha.  Thank you sooooo much for all your invaluable help!

yuanfeng

On Tue, Mar 15, 2016 at 10:48 AM, Jingyue Wu <jingyue at google.com> wrote:

> When you generate axpy-host.bc, you should use "clang -cc1 ..." with the
> "-fcuda-include-gpubinary" flag. "clang -cc1" invokes the frontend only.
>
> On Tue, Mar 15, 2016 at 6:45 PM, Yuanfeng Peng <
> yuanfeng.jack.peng at gmail.com> wrote:
>
>> Hi Jingyue,
>>
>> Sorry to ask again, but how exactly could I glue the fatbin with the
>> instrumented host code?  Or does it mean we actually cannot instrument both
>> the host & device code at the same time?
>>
>> Thanks!
>> yuanfeng
>>
>> On Tue, Mar 15, 2016 at 10:09 AM, Jingyue Wu <jingyue at google.com> wrote:
>>
>>> Including fatbin into host code should be done in frontend.
>>>
>>> On Mon, Mar 14, 2016 at 12:13 AM, Yuanfeng Peng <
>>> yuanfeng.jack.peng at gmail.com> wrote:
>>>
>>>> Hey Jingyue,
>>>>
>>>> Thanks for being so responsive!  I finally figured out a way to resolve
>>>> the issue: all I have to do is to use `-only-needed` when merging the
>>>> device bitcodes with llvm-link.
>>>>
>>>> However, since we actually need to instrument the host code as well,  I
>>>> encountered another issue when I tried to glue the instrumented host code
>>>> and fatbin together.  When I only instrumented the device code, I used the
>>>> following cmd to do so:
>>>>
>>>> "/mnt/wtf/tools/bin/clang-3.9" "-cc1" "-triple"
>>>> "x86_64-unknown-linux-gnu" "-aux-triple" "nvptx64-nvidia-cuda"
>>>> "-fcuda-target-overloads" "-fcuda-disable-target-call-checks" "-emit-obj"
>>>> "-disable-free" "-main-file-name" "axpy.cu" "-mrelocation-model"
>>>> "static" "-mthread-model" "posix" "-fmath-errno" "-masm-verbose"
>>>> "-mconstructor-aliases" "-munwind-tables" "-fuse-init-array" "-target-cpu"
>>>> "x86-64" "-momit-leaf-frame-pointer" "-dwarf-column-info"
>>>> "-debugger-tuning=gdb" "-resource-dir"
>>>> "/mnt/wtf/tools/bin/../lib/clang/3.9.0" "-I"
>>>> "/usr/local/cuda-7.0/samples/common/inc" "-internal-isystem"
>>>> "/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8"
>>>> "-internal-isystem"
>>>> "/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/x86_64-linux-gnu/c++/4.8"
>>>> "-internal-isystem"
>>>> "/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/x86_64-linux-gnu/c++/4.8"
>>>> "-internal-isystem"
>>>> "/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/backward"
>>>> "-internal-isystem" "/usr/local/include" "-internal-isystem"
>>>> "/mnt/wtf/tools/bin/../lib/clang/3.9.0/include" "-internal-externc-isystem"
>>>> "/usr/include/x86_64-linux-gnu" "-internal-externc-isystem" "/include"
>>>> "-internal-externc-isystem" "/usr/include" "-internal-isystem"
>>>> "/usr/local/cuda/include" "-include" "__clang_cuda_runtime_wrapper.h" "-O3"
>>>> "-fdeprecated-macro" "-fdebug-compilation-dir"
>>>> "/mnt/wtf/workspace/cuda/gpu-race-detection" "-ferror-limit" "19"
>>>> "-fmessage-length" "291" "-pthread" "-fobjc-runtime=gcc" "-fcxx-exceptions"
>>>> "-fexceptions" "-fdiagnostics-show-option" "-vectorize-loops"
>>>> "-vectorize-slp" "-o" "axpy-host.o" "-x" "cuda" "tests/axpy.cu"
>>>> "-fcuda-include-gpubinary" "axpy-sm_30.fatbin"
>>>>
>>>> which, from my understanding, compiles the host code in tests/axpy.cu
>>>> and link it with axpy-sm_30.fatbin.  However, now that I instrumented the
>>>> IR of the host code (axpy.bc) and did `llc axpy.bc -o axpy.s`, which cmd
>>>> should I use to link axpy.s with axpy-sm_30.fatbin?  I tried to use -cc1as,
>>>> but the flag '-fcuda-include-gpubinary' was not recognized.
>>>>
>>>> Thanks!
>>>>
>>>> yuanfeng
>>>>
>>>> On Sat, Mar 12, 2016 at 12:05 AM, Jingyue Wu <jingyue at google.com>
>>>> wrote:
>>>>
>>>>> I've no idea. Without instrumentation, nvvm_reflect_anchor doesn't
>>>>> appear in the final PTX, right? If that's the case, some pass in llc must
>>>>> have deleted the anchor and you should be able to figure out which one.
>>>>>
>>>>> On Fri, Mar 11, 2016 at 4:56 PM, Yuanfeng Peng <
>>>>> yuanfeng.jack.peng at gmail.com> wrote:
>>>>>
>>>>>> Hey Jingyue,
>>>>>>
>>>>>> Though I tried `opt -nvvm-reflect` on both bc files, the nvvm reflect
>>>>>> anchor didn't go away; ptxas is still complaining about the duplicate
>>>>>> definition of of function '_ZL21__nvvm_reflect_anchorv' .  Did I misused
>>>>>> the nvvm-reflect pass?
>>>>>>
>>>>>> Thanks!
>>>>>> yuanfeng
>>>>>>
>>>>>> On Fri, Mar 11, 2016 at 10:10 AM, Jingyue Wu <jingyue at google.com>
>>>>>> wrote:
>>>>>>
>>>>>>> According to the examples you sent, I believe the linking issue was
>>>>>>> caused by nvvm reflection anchors. I haven't played with that, but I guess
>>>>>>> running nvvm-reflect on an IR removes the nvvm reflect anchors. After that,
>>>>>>> you can llvm-link the two bc/ll files.
>>>>>>>
>>>>>>> Another potential issue is that your cuda_hooks-sm_30.ll is
>>>>>>> unoptimized. This could cause the instrumented code to run super slow.
>>>>>>>
>>>>>>> On Fri, Mar 11, 2016 at 9:40 AM, Yuanfeng Peng <
>>>>>>> yuanfeng.jack.peng at gmail.com> wrote:
>>>>>>>
>>>>>>>> Hey Jingyue,
>>>>>>>>
>>>>>>>> Attached are the .ll files.  Thanks!
>>>>>>>>
>>>>>>>> yuanfeng
>>>>>>>>
>>>>>>>> On Fri, Mar 11, 2016 at 3:47 AM, Jingyue Wu <jingyue at google.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Looks like we are getting closer!
>>>>>>>>>
>>>>>>>>> On Thu, Mar 10, 2016 at 5:21 PM, Yuanfeng Peng <
>>>>>>>>> yuanfeng.jack.peng at gmail.com> wrote:
>>>>>>>>>
>>>>>>>>>> Hi Jingyue,
>>>>>>>>>>
>>>>>>>>>> Thank you so much for the helpful response!  I didn't know that
>>>>>>>>>> PTX assembly cannot be linked; that's likely the reason for my issue.
>>>>>>>>>>
>>>>>>>>>> So I did the following as you suggested(axpy-sm_30.bc is the
>>>>>>>>>> instrumented bitcode, and cuda_hooks-sm_30.bc contains the hook functions):
>>>>>>>>>>
>>>>>>>>>> *llvm-link axpy-sm_30.bc cuda_hooks-sm_30.bc  -o
>>>>>>>>>> inst_axpy-sm_30.bc*
>>>>>>>>>>
>>>>>>>>>> *llc inst_axpy-sm_30.bc -o axpy-sm_30.s*
>>>>>>>>>>
>>>>>>>>>> *"/usr/local/cuda/bin/ptxas" "-m64" "-O3" -c "--gpu-name" "sm_30"
>>>>>>>>>> "--output-file" axpy-sm_30.o axpy-sm_30.s*
>>>>>>>>>>
>>>>>>>>>> However, I got the following error from ptxas:
>>>>>>>>>>
>>>>>>>>>> *ptxas axpy-sm_30.s, line 106; error   : Duplicate definition of
>>>>>>>>>> function '_ZL21__nvvm_reflect_anchorv'*
>>>>>>>>>>
>>>>>>>>>> *ptxas axpy-sm_30.s, line 106; fatal   : Parsing error near '.2':
>>>>>>>>>> syntax error*
>>>>>>>>>>
>>>>>>>>>> *ptxas fatal   : Ptx assembly aborted due to errors*
>>>>>>>>>>
>>>>>>>>>> Looks like some cuda function definitions are in both bitcode
>>>>>>>>>> files which caused duplicate definition... what am I supposed to do to
>>>>>>>>>> resolve this issue?
>>>>>>>>>>
>>>>>>>>> Can you attach axpy-sm_30.ll and cuda_hooks-sm_30.ll? The
>>>>>>>>> duplication may be caused by how nvvm reflection works, but I'd like to see
>>>>>>>>> a concrete example.
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Thanks!
>>>>>>>>>>
>>>>>>>>>> yuanfeng
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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