[llvm-dev] [CUDA] Lost debug information when compiling CUDA code

[Yuanfeng Peng via llvm-dev]

Hi Tom,


Thanks for the response!  I wonder whether there's any other way that I can get the source level information when using cuda-gdb to debug a binary compiled by LLVM? Or is there any way to feed the IR files to NVCC and get a binary with the debug info I need?


Thanks!
Yuanfeng




------------------ Original ------------------
From:  "Tom Stellard";<tstellar at redhat.com>;
Send time: Wednesday, Jun 14, 2017 9:06 PM
To: "Yuanfeng Peng"<yuanfengp at foxmail.com>; "via llvm-dev"<llvm-dev at lists.llvm.org>; 

Subject:  Re: [llvm-dev] [CUDA] Lost debug information when compiling CUDA code



On 06/14/2017 02:59 AM, Yuanfeng Peng via llvm-dev wrote:
> Hi,
> 
> I needed to debug some CUDA code in my project; however, although I used -g when compiling the source code, no source-level information is available in cuda-gdb or cuda-memcheck.  
> 

The NVPTX backend in LLVM does not support DWARF emission.

-Tom

> Specifically, below is what I did:
> 
> 1) For a CUDA file a.cu, generate IR files: clang++ -g -emit-llvm --cuda-gpu-arch=sm_35 -c a.cu;
> 2) Instrument the device code a-cuda-nvptx64-nvidia-cuda-sm_35.bc (generated in the previous step), inserting a call to a hook function before each device memory access.  The hook function is defined in another file, b.cu.  Let's say we get a file named intrumented-a-device.bc after this step;
> 3) Generate IR files for b.cu: clang++ -g -emit-llvm --cuda-gpu-arch=sm_35 -c b.cu;
> 4) Link instrumented-a.device.bc with the device code generated for b.cu: llvm-link intrumented-a-device.bc b-cuda-nvptx64-nvidia-cuda-sm_35.bc -o ab-device.bc;
> 5) Use llc, ptxas & fatbinary on ab-device.bc to get ab-device.ptx, ab-device.o & ab-device.fatbin;
> 6) Call clang again the generate the host object file ab.o, with ab-device.o & ab-device.fatbin embedded;
> 7) Link against libraries and get the final binary: a.out.
> 
> The binary a.out fails with an exception I when run it; but when I try to debug it with cuda-gdb or cuda-memcheck, no source information was available.  Why?
> 
> Thanks!
> Yuanfeng Peng
>  
> 
> 
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