| Issue |
64624
|
| Summary |
[OpenMP][libomptarget][DeviceRTL] Executable hangs when offloading to GPU
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
tavakkoliamirmohammad
|
I have a problem with using OpenMP target offloading on NVIDIA A100.
Here is my build step from the latest cloned LLVM.
```
mkdir build
cd build
cmake -G Ninja ../llvm -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_ENABLE_RUNTIMES="openmp" -DLLVM_TARGETS_TO_BUILD="Native;NVPTX;AMDGPU" -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=ON -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DLLVM_ENABLE_LLD=ON -DLLVM_CCACHE_BUILD=ON
cmake --build . -j 128
```
The build finishes with the follwoing message
`[4047/4047] Completed 'runtimes'
`
Now using the example provided in the [Clang documentation](https://clang.llvm.org/docs/OffloadingDesign.html#offloading-example)
```
#include <complex>
using complex = std::complex<double>;
void zaxpy(complex *X, complex *Y, complex D, std::size_t N) {
#pragma omp target teams distribute parallel for
for (std::size_t i = 0; i < N; ++i)
Y[i] = D * X[i] + Y[i];
}
int main() {
const std::size_t N = 1024;
complex X[N], Y[N], D;
#pragma omp target data map(to:X[0 : N]) map(tofrom:Y[0 : N])
zaxpy(X, Y, D, N);
}
```
Saved as `zaxpy.cpp`
Now compile command
```
./bin/clang++ --libomptarget-nvptx-bc-path=./runtimes/runtimes-bins/openmp/libomptarget/DeviceRTL/ -fopenmp -fopenmp-targets=nvptx64 -O3 zaxpy.cpp -c
```
Also checking the .o file.
```
$ llvm-readelf -WS zaxpy.o
There are 24 section headers, starting at offset 0x90c8:
Section Headers:
[Nr] Name Type Address Off Size ES Flg Lk Inf Al
[ 0] NULL 0000000000000000 000000 000000 00 0 0 0
[ 1] .strtab STRTAB 0000000000000000 008d0c 0003b9 00 0 0 1
[ 2] .text PROGBITS 0000000000000000 000040 00057a 00 AX 0 0 16
[ 3] .rela.text RELA 0000000000000000 0088d0 000318 18 I 23 2 8
[ 4] .rodata.cst16 PROGBITS 0000000000000000 0005c0 000030 10 AM 0 0 16
[ 5] .text.startup PROGBITS 0000000000000000 0005f0 00000a 00 AX 0 0 16
[ 6] .rela.text.startup RELA 0000000000000000 008be8 000018 18 I 23 5 8
[ 7] .rodata.str1.1 PROGBITS 0000000000000000 0005fa 000017 01 AMS 0 0 1
[ 8] .data.rel.ro PROGBITS 0000000000000000 000618 000048 00 WA 0 0 8
[ 9] .rela.data.rel.ro RELA 0000000000000000 008c00 000048 18 I 23 8 8
[10] .rodata PROGBITS 0000000000000000 000660 000001 00 A 0 0 1
[11] .rodata.cst32 PROGBITS 0000000000000000 000670 000040 20 AM 0 0 16
[12] .rodata.str1.16 PROGBITS 0000000000000000 0006b0 00003e 01 AMS 0 0 16
[13] omp_offloading_entries PROGBITS 0000000000000000 0006ee 000020 00 WA 0 0 1
[14] .relaomp_offloading_entries RELA 0000000000000000 008c48 000030 18 I 23 13 8
[15] .init_array.0 INIT_ARRAY 0000000000000000 000710 000008 00 WA 0 0 8
[16] .rela.init_array.0 RELA 0000000000000000 008c78 000018 18 I 23 15 8
[17] .llvm.offloading LLVM_OFFLOADING 0000000000000000 000718 007d18 00 E 0 0 8
[18] .comment PROGBITS 0000000000000000 008430 00006a 01 MS 0 0 1
[19] .note.GNU-stack PROGBITS 0000000000000000 00849a 000000 00 0 0 1
[20] .eh_frame X86_64_UNWIND 0000000000000000 0084a0 000178 00 A 0 0 8
[21] .rela.eh_frame RELA 0000000000000000 008c90 000078 18 I 23 20 8
[22] .llvm_addrsig LLVM_ADDRSIG 0000000000000000 008d08 000004 00 E 23 0 1
[23] .symtab SYMTAB 0000000000000000 008618 0002b8 18 1 15 8
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
R (retain), l (large), p (processor specific)
```
Now compiling with command
```
./bin/clang++ --libomptarget-nvptx-bc-path=./runtimes/runtimes-bins/openmp/libomptarget/DeviceRTL/ -fopenmp -fopenmp-targets=nvptx64 -O3 zaxpy.cpp -o zaxpy
export LD_LIBRARY_PATH=/uufs/chpc.utah.edu/common/home/u1419116/projects/openmp/llvm-project/build/lib:$LD_LIBRARY_PATH
./zaxpy
```
The binary hangs indefinitely!
Also, the tests are failing using the command
```
cmake --build . --target check-openmp
```
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