[llvm-dev] instrumenting device code with gpucc

Thu Mar 10 13:19:19 PST 2016

It's hard to tell what is wrong without a concrete example. E.g., what is
the program you are instrumenting? What is the definition of the hook
function? How did you link that definition with the binary?

One thing suspicious to me is that you may have linked the definition of
_Cool_MemRead_Hook as a host function instead of a device function. AFAIK,
PTX assembly cannot be linked. So, if you want that hook function called
from your device code, you should merge the IR of the hook function and the
IR of your device code into one IR (via linking or direct IR emitting)
before the IR to PTX.

On Wed, Mar 9, 2016 at 4:31 PM, Yuanfeng Peng <yuanfeng.jack.peng at gmail.com>
wrote:

> Hi Jingyue,
>
> Thanks for the instructions! I instrumented the device code and got a
> binary of axpy.cu; however, the resulting executable always fails on the
> first cudaMalloc call in host code (the kernel had not even been launched
> yet), with the error code being 30 (cudaErrorUnknown).  In my
> instrumentation pass, I only inserted a hook function upon each access  to
> device memory, with their signatures being: "__device__ void
> _Cool_MemRead_Hook(uint64_t addr)".  I've compiled these hooks functions
>  into a shared object, and linked the axpy binary with it.
>
> I'm really sorry to bother you again, but I wonder whether any step I did
> was apparently wrong, or there's any gpucc-specific step I need to do when
> instrumenting a kernel?
>
> Thanks!
> yuanfeng
>
>
>
> On Fri, Mar 4, 2016 at 7:56 PM, Jingyue Wu <jingyue at google.com> wrote:
>
>>
>>
>> On Fri, Mar 4, 2016 at 5:50 PM, Yuanfeng Peng <
>> yuanfeng.jack.peng at gmail.com> wrote:
>>
>>> Hi Jingyue,
>>>
>>> My name is Yuanfeng Peng, I'm a PhD student at UPenn.  I'm sorry to
>>> bother you, but I'm having trouble with gpucc in my project, and I would be
>>> really grateful for your help!
>>>
>>> Currently we're trying to instrument CUDA code using LLVM 3.9, and I've
>>> written a pass to insert hook functions for certain function calls and
>>> memory accesses.  For example, given a CUDA program, say, axpy.cu, I
>>> first compile it with
>>>
>>>  clang++ -emit-llvm -c axpy.cu,
>>>
>>> which gives me two bitcode files, axpy.bc and axpy-sm_20.bc.  Then I use
>>> opt to load my pass and insert the hook functions to axpy.bc, which works
>>> fine.  After inspecting the instrumented axpy.bc, I noticed that the kernel
>>> code was not there; rather, it lived inside axpy-sm_20.bc, so I also load
>>> my pass to instrument axpy-sm_20.bc.
>>>
>>
>> Expected. axpy.bc contains host code, and axpy-sm_??.bc contains device
>> code. If you only want to instrument the device side, you don't need to
>> modify axpy.bc.
>>
>>
>>>
>>>  However, after instrumenting axpy-sm_20.bc, I don't know how could I
>>> combine the host bitcode & device bitcode into a single binary... When I
>>> used llc to compile axpy-sm_20.bc into native code, I always got a bunch of
>>> errors; if I only do llc axpy.bc -o axpy.s and then link axpy.s with the
>>> necessary libraries, I got a working binary, but only the host code was
>>> instrumented.
>>>
>>> So what should I do to get a binary where the device code is also
>>> instrumented?
>>>
>>
>>
>> To link the modified axpy-sm_20.bc to the final binary, you need several
>> extra steps:
>> 1. Compile axpy-sm_20.bc to PTX assembly using llc: llc axpy-sm_20.bc -o
>> axpy-sm_20.ptx -march=<nvptx or nvptx64>
>> 2. Compile the PTX assembly to SASS using ptxas
>> 3. Make the SASS a fat binary using NVIDIA's fatbinary tool
>> 4. Link the fat binary to the host code using ld.
>>
>> Clang does step 2-4 by invoking subcommands. Therefore, you can use
>> "clang -###" to dump all the subcommands, and then find the ones for step
>> 2-4. For example,
>>
>> $ clang++ -### -O3 axpy.cu -I/usr/local/cuda/samples/common/inc
>> -L/usr/local/cuda/lib64 -lcudart_static -lcuda -ldl -lrt -pthread
>> --cuda-gpu-arch=sm_35
>>
>> clang version 3.9.0 (http://llvm.org/git/clang.git
>> 4ce165e39e7b185e394aa713d9adffd920288988) (http://llvm.org/git/llvm.git
>> 2550ef485b6f9668bb7a4daa7ab276b6501492df)
>> Target: x86_64-unknown-linux-gnu
>> Thread model: posix
>> InstalledDir: /usr/local/google/home/jingyue/Work/llvm/install/bin
>>  "/usr/local/google/home/jingyue/Work/llvm/install-git/bin/clang-3.7"
>> "-cc1" "-triple" "nvptx64-nvidia-cuda" "-aux-triple"
>> "x86_64-unknown-linux-gnu" "-fcuda-target-overloads"
>> "-fcuda-disable-target-call-checks" "-S" "-disable-free" "-main-file-name" "
>> axpy.cu" "-mrelocation-model" "static" "-mthread-model" "posix"
>> "-mdisable-fp-elim" "-fmath-errno" "-no-integrated-as" "-fcuda-is-device"
>> "-mlink-cuda-bitcode"
>> "/usr/local/cuda/nvvm/libdevice/libdevice.compute_35.10.bc"
>> "-target-feature" "+ptx42" "-target-cpu" "sm_35" "-dwarf-column-info"
>> "-debugger-tuning=gdb" "-resource-dir"
>> "/usr/local/google/home/jingyue/Work/llvm/install-git/bin/../lib/clang/3.9.0"
>> "-I" "/usr/local/cuda/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"
>> "/usr/local/google/home/jingyue/Work/llvm/install-git/bin/../lib/clang/3.9.0/include"
>> "-internal-externc-isystem" "/include" "-internal-externc-isystem"
>> "/usr/include" "-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/cuda/include" "-include"
>> "__clang_cuda_runtime_wrapper.h" "-O3" "-fdeprecated-macro"
>> "-fno-dwarf-directory-asm" "-fdebug-compilation-dir"
>> "/usr/local/google/home/jingyue/Work/cuda" "-ferror-limit" "19"
>> "-fmessage-length" "205" "-pthread" "-fobjc-runtime=gcc" "-fcxx-exceptions"
>> "-fexceptions" "-fdiagnostics-show-option" "-fcolor-diagnostics"
>> "-vectorize-loops" "-vectorize-slp" "-o" "/tmp/axpy-a88a72.s" "-x" "cuda" "
>> axpy.cu"
>>  "/usr/local/cuda/bin/ptxas" "-m64" "-O3" "--gpu-name" "sm_35"
>> "--output-file" "/tmp/axpy-1dbca7.o" "/tmp/axpy-a88a72.s"
>>  "/usr/local/cuda/bin/fatbinary" "--cuda" "-64" "--create"
>> "/tmp/axpy-e6057c.fatbin" "--image=profile=sm_35,file=/tmp/axpy-1dbca7.o"
>> "--image=profile=compute_35,file=/tmp/axpy-a88a72.s"
>>  "/usr/local/google/home/jingyue/Work/llvm/install-git/bin/clang-3.7"
>> "-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"
>> "/usr/local/google/home/jingyue/Work/llvm/install-git/bin/../lib/clang/3.9.0"
>> "-I" "/usr/local/cuda/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"
>> "/usr/local/google/home/jingyue/Work/llvm/install-git/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" "/usr/local/google/home/jingyue/Work/cuda"
>> "-ferror-limit" "19" "-fmessage-length" "205" "-pthread"
>> "-fobjc-runtime=gcc" "-fcxx-exceptions" "-fexceptions"
>> "-fdiagnostics-show-option" "-fcolor-diagnostics" "-vectorize-loops"
>> "-vectorize-slp" "-o" "/tmp/axpy-48f6b5.o" "-x" "cuda" "axpy.cu"
>> "-fcuda-include-gpubinary" "/tmp/axpy-e6057c.fatbin"
>>  "/usr/bin/ld" "-z" "relro" "--hash-style=gnu" "--build-id"
>> "--eh-frame-hdr" "-m" "elf_x86_64" "-dynamic-linker"
>> "/lib64/ld-linux-x86-64.so.2" "-o" "a.out"
>> "/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu/crt1.o"
>> "/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu/crti.o"
>> "/usr/lib/gcc/x86_64-linux-gnu/4.8/crtbegin.o" "-L/usr/local/cuda/lib64"
>> "-L/usr/lib/gcc/x86_64-linux-gnu/4.8"
>> "-L/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu"
>> "-L/lib/x86_64-linux-gnu" "-L/lib/../lib64" "-L/usr/lib/x86_64-linux-gnu"
>> "-L/usr/lib/gcc/x86_64-linux-gnu/4.8/../../.."
>> "-L/usr/local/google/home/jingyue/Work/llvm/install-git/bin/../lib"
>> "-L/lib" "-L/usr/lib" "/tmp/axpy-48f6b5.o" "-lcudart_static" "-lcuda"
>> "-ldl" "-lrt" "-lstdc++" "-lm" "-lgcc_s" "-lgcc" "-lpthread" "-lc"
>> "-lgcc_s" "-lgcc" "/usr/lib/gcc/x86_64-linux-gnu/4.8/crtend.o"
>> "/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu/crtn.o"
>>
>>
>>
>>>
>>> I apologize for the long email and I look forward to hearing from you.
>>>
>>> Thanks!
>>> Yuanfeng Peng
>>>
>>
>>
>
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