From d9f033146b47ceef94c1f041afcd339ef007279e Mon Sep 17 00:00:00 2001 From: Joseph Huber Date: Mon, 24 Apr 2023 18:28:54 -0500 Subject: [PATCH] [libc] Ignore 'errno' on the GPU and support 'atoi' The 'errno' value is most likely not useful on the GPU and it prevents us from providing certain functions on the GPU that depend on it, like `atoi`. This patch makes the necessary changes to support `errno` by simple replacing it with a consumer class. Supporting `errno` on the GPU is possible in some aspects. The first approach would be to use a buffer of shared memory that has enough space for all threads. Another option would be to change code generation to support `thread_local` using `address_space(5)` memory allocated at kernel launch. The former could look like the following, which could be implemented in a later patch: ``` template using SharedBuffer = T[gpu::MAX_THREADS] [[clang::address_space(3)]]; template struct ErrnoSetter { constexpr ErrnoSetter(SharedBuffer &storage) : storage(storage) {} SharedBuffer &storage; void operator=(const T &val) { storage[gpu::get_thread_id()] = val; } }; static SharedBuffer thread_local_buffer [[clang::loader_uninitialized]]; ErrnoSetter __llvmlibc_internal_errno(thread_local_buffer); ``` Reviewed By: sivachandra Differential Revision: https://reviews.llvm.org/D149107 --- libc/config/gpu/entrypoints.txt | 3 +++ libc/config/gpu/headers.txt | 1 + libc/include/errno.h.def | 2 ++ libc/src/errno/libc_errno.cpp | 10 ++++++++++ libc/src/errno/libc_errno.h | 21 +++++++++++++++++++++ 5 files changed, 37 insertions(+) diff --git a/libc/config/gpu/entrypoints.txt b/libc/config/gpu/entrypoints.txt index 4c78b2f..69af9ff 100644 --- a/libc/config/gpu/entrypoints.txt +++ b/libc/config/gpu/entrypoints.txt @@ -53,6 +53,9 @@ set(TARGET_LIBC_ENTRYPOINTS libc.src.string.strstr libc.src.string.strtok libc.src.string.strtok_r + + # stdlib.h entrypoints + libc.src.stdlib.atoi ) set(TARGET_LLVMLIBC_ENTRYPOINTS diff --git a/libc/config/gpu/headers.txt b/libc/config/gpu/headers.txt index 2280244..fd753a4 100644 --- a/libc/config/gpu/headers.txt +++ b/libc/config/gpu/headers.txt @@ -1,4 +1,5 @@ set(TARGET_PUBLIC_HEADERS libc.include.ctype libc.include.string + libc.include.stdlib ) diff --git a/libc/include/errno.h.def b/libc/include/errno.h.def index 580a53f..d8f79dd 100644 --- a/libc/include/errno.h.def +++ b/libc/include/errno.h.def @@ -43,7 +43,9 @@ #include #endif +#if !defined(__AMDGPU__) && !defined(__NVPTX__) extern _Thread_local int __llvmlibc_errno; #define errno __llvmlibc_errno +#endif #endif // LLVM_LIBC_ERRNO_H diff --git a/libc/src/errno/libc_errno.cpp b/libc/src/errno/libc_errno.cpp index b8c276c..26bd9d9 100644 --- a/libc/src/errno/libc_errno.cpp +++ b/libc/src/errno/libc_errno.cpp @@ -6,6 +6,8 @@ // //===----------------------------------------------------------------------===// +#include "src/__support/macros/properties/architectures.h" + namespace __llvm_libc { extern "C" { @@ -18,9 +20,17 @@ extern "C" { // macro defined in LLVM libc's public errno.h header file. // TODO: Use a macro to distinguish full build and overlay build which can be // used to exclude __llvmlibc_errno under overlay build. +#ifdef LIBC_TARGET_ARCH_IS_GPU +ErrnoConsumer __llvmlibc_errno; +#else thread_local int __llvmlibc_errno; +#endif // LIBC_TARGET_ARCH_IS_GPU +#else +#ifdef LIBC_TARGET_ARCH_IS_GPU +ErrnoConsumer __llvmlibc_internal_errno; #else thread_local int __llvmlibc_internal_errno; +#endif // LIBC_TARGET_ARCH_IS_GPU #endif } // extern "C" diff --git a/libc/src/errno/libc_errno.h b/libc/src/errno/libc_errno.h index 28f8d0d..585da15 100644 --- a/libc/src/errno/libc_errno.h +++ b/libc/src/errno/libc_errno.h @@ -9,21 +9,42 @@ #ifndef LLVM_LIBC_SRC_ERRNO_LLVMLIBC_ERRNO_H #define LLVM_LIBC_SRC_ERRNO_LLVMLIBC_ERRNO_H +#include "src/__support/macros/properties/architectures.h" + #include +// If we are targeting the GPU we currently don't support 'errno'. We simply +// consume it. +#ifdef LIBC_TARGET_ARCH_IS_GPU +namespace __llvm_libc { +struct ErrnoConsumer { + void operator=(int) {} +}; +} // namespace __llvm_libc +#endif + // All of the libc runtime and test code should use the "libc_errno" macro. They // should not refer to the "errno" macro directly. #ifdef LIBC_COPT_PUBLIC_PACKAGING +#ifdef LIBC_TARGET_ARCH_IS_GPU +extern "C" __llvm_libc::ErrnoConsumer __llvmlibc_errno; +#define libc_errno __llvmlibc_errno +#else // This macro will resolve to errno from the errno.h file included above. Under // full build, this will be LLVM libc's errno. In overlay build, it will be // system libc's errno. #define libc_errno errno +#endif #else namespace __llvm_libc { +#ifdef LIBC_TARGET_ARCH_IS_GPU +extern "C" ErrnoConsumer __llvmlibc_internal_errno; +#else // LIBC_TARGET_ARCH_IS_GPU extern "C" { extern thread_local int __llvmlibc_internal_errno; } // extern "C" +#endif // TODO: After all of libc/src and libc/test are switched over to use // libc_errno, this header file will be "shipped" via an add_entrypoint_object -- 2.7.4