fwyzard / nvidia_bug_4139266

A simple reproducer for NVIDIA bug #4139266 - fixed in CUDA 12.2.2

This repository contains the preprocessed files to reproduce the NVIDIA bug #4139266 (https://developer.nvidia.com/nvidia_bug/4139266). The problem has been fixed in CUDA 12.2.2.

Description

Including <cub/cub.cuh> and <immintrin.h> breaks compilation with GCC 12, if the SSE2 instruction set is enabled.

Reproducer

Here is a simple reproducer, test.cu:

#include <cub/cub.cuh>
#include <immintrin.h>

__global__
void unused() {}

Compiling with

/usr/local/cuda-12.1/bin/nvcc -ccbin g++-12 --compiler-options "-msse2" test.cu -c -o test.o

fails with

/usr/lib/gcc/x86_64-linux-gnu/12/include/avx512fp16intrin.h(38): error: vector_size attribute requires an arithmetic or enum type
                  __v8hf __attribute__ ((__vector_size__ (16)));
                                         ^

/usr/lib/gcc/x86_64-linux-gnu/12/include/avx512fp16intrin.h(39): error: vector_size attribute requires an arithmetic or enum type
                  __v16hf __attribute__ ((__vector_size__ (32)));
                                          ^

/usr/lib/gcc/x86_64-linux-gnu/12/include/avx512fp16intrin.h(40): error: vector_size attribute requires an arithmetic or enum type
                  __v32hf __attribute__ ((__vector_size__ (64)));

(... 95 more errors ...)

Killed

Discussion

This is caused by:

• the header .../include/cub/cub.cuh indirectly includes the header .../include/cuda/std/detail/__config
• .../include/cuda/std/detail/__config defines _Float16 as

  #define _Float16 __half

• this conflicts with GCC's use of _Float16 on ARM, and x86 systems with SSE2 starting with GCC 12.

Usage of _Float16 with GCC is documented in https://gcc.gnu.org/onlinedocs/gcc-12.3.0/gcc/Floating-Types.html, and it is used in GCC's headers <avx512fp16vlintrin.h> and <avx512fp16intrin.h>, that are included by <immintrin.h>.

---

A simple workaround seems to be to #undef _Float16 after including <cub/cub.cuh>, but this may lead to other conflicts in a more realistic program.

For the simple reproducer above, this:

#include <cub/cub.cuh>
#undef _Float16
#include <immintrin.h>

__global__
void unused() {}

compiles fine.

Update for CUDA 12.2.2

The problem has been fixed in CUDA 12.2.2:

/usr/local/cuda-12.2/bin/nvcc --version
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2023 NVIDIA Corporation
Built on Tue_Aug_15_22:02:13_PDT_2023
Cuda compilation tools, release 12.2, V12.2.140
Build cuda_12.2.r12.2/compiler.33191640_0

/usr/local/cuda-12.2/bin/nvcc -ccbin g++-12 --compiler-options "-msse2" test.cu -c -o test.o

builds correctly.