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[CUDA] add wrapper header for libc++'s __utlility/declval.h#148918
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Sincellvm#116709 more libc++ code relies on std::declval() and it broke some CUDA compilations.The new wrapper adds GPU-side overloads for the declval() helper functionswhich allows it to continue working when used from CUDA sources.
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llvmbot commentedJul 15, 2025 • edited
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@llvm/pr-subscribers-backend-x86 @llvm/pr-subscribers-clang Author: Artem Belevich (Artem-B) ChangesSince #116709 more libc++ code relies on std::declval() and it broke some CUDA compilations. The new wrapper adds GPU-side overloads for the declval() helper functions which allows it to continue working when used from CUDA sources. Full diff:https://github.com/llvm/llvm-project/pull/148918.diff 2 Files Affected:
diff --git a/clang/lib/Headers/CMakeLists.txt b/clang/lib/Headers/CMakeLists.txtindex c96d209c1fc0c..b4618fe4a46da 100644--- a/clang/lib/Headers/CMakeLists.txt+++ b/clang/lib/Headers/CMakeLists.txt@@ -347,6 +347,10 @@ set(cuda_wrapper_bits_files cuda_wrappers/bits/basic_string.tcc )+set(cuda_wrapper_utility_files+ cuda_wrappers/__utility/declval.h+)+ set(ppc_wrapper_files ppc_wrappers/mmintrin.h ppc_wrappers/xmmintrin.h@@ -443,8 +447,9 @@ endfunction(clang_generate_header) # Copy header files from the source directory to the build directory foreach( f ${files} ${cuda_wrapper_files} ${cuda_wrapper_bits_files}- ${ppc_wrapper_files} ${openmp_wrapper_files} ${zos_wrapper_files} ${hlsl_files}- ${llvm_libc_wrapper_files} ${llvm_offload_wrapper_files})+ ${cuda_wrapper_utility_files} ${ppc_wrapper_files} ${openmp_wrapper_files}+ ${zos_wrapper_files} ${hlsl_files} ${llvm_libc_wrapper_files}+ ${llvm_offload_wrapper_files}) copy_header_to_output_dir(${CMAKE_CURRENT_SOURCE_DIR} ${f}) endforeach( f )@@ -553,7 +558,7 @@ add_header_target("arm-common-resource-headers" "${arm_common_files};${arm_commo # Architecture/platform specific targets add_header_target("arm-resource-headers" "${arm_only_files};${arm_only_generated_files}") add_header_target("aarch64-resource-headers" "${aarch64_only_files};${aarch64_only_generated_files}")-add_header_target("cuda-resource-headers" "${cuda_files};${cuda_wrapper_files};${cuda_wrapper_bits_files}")+add_header_target("cuda-resource-headers" "${cuda_files};${cuda_wrapper_files};${cuda_wrapper_bits_files};${cuda_wrapper_utility_files}") add_header_target("hexagon-resource-headers" "${hexagon_files}") add_header_target("hip-resource-headers" "${hip_files}") add_header_target("loongarch-resource-headers" "${loongarch_files}")@@ -600,6 +605,11 @@ install( DESTINATION ${header_install_dir}/cuda_wrappers/bits COMPONENT clang-resource-headers)+install(+ FILES ${cuda_wrapper_utility_files}+ DESTINATION ${header_install_dir}/cuda_wrappers/__utility+ COMPONENT clang-resource-headers)+ install( FILES ${ppc_wrapper_files} DESTINATION ${header_install_dir}/ppc_wrappers@@ -663,6 +673,12 @@ install( EXCLUDE_FROM_ALL COMPONENT cuda-resource-headers)+install(+ FILES ${cuda_wrapper_utility_files}+ DESTINATION ${header_install_dir}/cuda_wrappers/__utility+ EXCLUDE_FROM_ALL+ COMPONENT cuda-resource-headers)+ install( FILES ${cuda_files} DESTINATION ${header_install_dir}diff --git a/clang/lib/Headers/cuda_wrappers/__utility/declval.h b/clang/lib/Headers/cuda_wrappers/__utility/declval.hnew file mode 100644index 0000000000000..b16311e849fa4--- /dev/null+++ b/clang/lib/Headers/cuda_wrappers/__utility/declval.h@@ -0,0 +1,31 @@+#ifndef __CUDA_WRAPPERS_UTILITY_DECLVAL_H__+#define __CUDA_WRAPPERS_UTILITY_DECLVAL_H__++#include_next <__utility/declval.h>++// The stuff below is the exact copy of the <__utility/declval.h>,+// but with __device__ attribute applied to the functions, so it works on a GPU.++_LIBCPP_BEGIN_NAMESPACE_STD++// Suppress deprecation notice for volatile-qualified return type resulting+// from volatile-qualified types _Tp.+_LIBCPP_SUPPRESS_DEPRECATED_PUSH+template <class _Tp>+__attribute__((device))+_Tp&& __declval(int);+template <class _Tp>+__attribute__((device))+_Tp __declval(long);+_LIBCPP_SUPPRESS_DEPRECATED_POP++template <class _Tp>+__attribute__((device))+_LIBCPP_HIDE_FROM_ABI decltype(std::__declval<_Tp>(0)) declval() _NOEXCEPT {+ static_assert(!__is_same(_Tp, _Tp),+ "std::declval can only be used in an unevaluated context. "+ "It's likely that your current usage is trying to extract a value from the function.");+}++_LIBCPP_END_NAMESPACE_STD+#endif // __CUDA_WRAPPERS_UTILITY_DECLVAL_H__ |
github-actionsbot commentedJul 15, 2025 • edited
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✅ With the latest revision this PR passed the C/C++ code formatter. |
LGTM. I would like it if the new file were formatted, but I suppose it's intentional in order to be more of an exact copy of the libc++ file? |
7f2bcd9 intollvm:main 9 checks passed
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LLVM Buildbot has detected a new failure on builder Full details are available at:https://lab.llvm.org/buildbot/#/builders/88/builds/13968 Here is the relevant piece of the build log for the reference |
LLVM Buildbot has detected a new failure on builder Full details are available at:https://lab.llvm.org/buildbot/#/builders/153/builds/38242 Here is the relevant piece of the build log for the reference |
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backend:X86clang:headersHeaders provided by Clang, e.g. for intrinsics clangClang issues not falling into any other category
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Since#116709 more libc++ code relies on std::declval() and it broke some CUDA compilations.
The new wrapper adds GPU-side overloads for the declval() helper functions which allows it to continue working when used from CUDA sources.