[libc] [llvm] [libc] Make RPC server handling header only (PR #131205)
Joseph Huber via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 13 13:07:32 PDT 2025
https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/131205
Summary:
This patch moves the RPC server handling to be a header only utility
stored in the `shared/` directory. This is intended to be shared within
LLVM for the loaders and `offload/` handling.
Generally, this makes it easier to share code without weird
cross-project binaries being plucked out of the build system. It also
allows us to soon move the loader interface out of the `libc` project so
that we don't need to bootstrap those and can build them in LLVM.
>From bc4046e02d7ec073e00b26b361c8cb331d7d3c71 Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Thu, 13 Mar 2025 14:41:27 -0500
Subject: [PATCH] [libc] Make RPC server handling header only
Summary:
This patch moves the RPC server handling to be a header only utility
stored in the `shared/` directory. This is intended to be shared within
LLVM for the loaders and `offload/` handling.
Generally, this makes it easier to share code without weird
cross-project binaries being plucked out of the build system. It also
allows us to soon move the loader interface out of the `libc` project so
that we don't need to bootstrap those and can build them in LLVM.
---
libc/docs/gpu/rpc.rst | 13 +++--
libc/shared/rpc_opcodes.h | 6 ---
.../rpc_server.cpp => shared/rpc_server.h} | 53 +++++++++++++------
libc/utils/gpu/CMakeLists.txt | 1 -
libc/utils/gpu/loader/CMakeLists.txt | 3 ++
libc/utils/gpu/loader/Loader.h | 1 +
libc/utils/gpu/loader/amdgpu/CMakeLists.txt | 8 +--
libc/utils/gpu/loader/nvptx/CMakeLists.txt | 8 +--
libc/utils/gpu/server/CMakeLists.txt | 30 -----------
llvm/cmake/modules/FindLibcCommonUtils.cmake | 19 +++++++
offload/plugins-nextgen/common/CMakeLists.txt | 13 +----
offload/plugins-nextgen/common/src/RPC.cpp | 3 +-
12 files changed, 71 insertions(+), 87 deletions(-)
rename libc/{utils/gpu/server/rpc_server.cpp => shared/rpc_server.h} (92%)
delete mode 100644 libc/utils/gpu/server/CMakeLists.txt
create mode 100644 llvm/cmake/modules/FindLibcCommonUtils.cmake
diff --git a/libc/docs/gpu/rpc.rst b/libc/docs/gpu/rpc.rst
index dde4207df6e49..1d6aaea2adcfe 100644
--- a/libc/docs/gpu/rpc.rst
+++ b/libc/docs/gpu/rpc.rst
@@ -184,6 +184,7 @@ but the following example shows how it can be used by a standard user.
#include <shared/rpc.h>
#include <shared/rpc_opcodes.h>
+ #include <shared/rpc_server.h>
[[noreturn]] void handle_error(cudaError_t err) {
fprintf(stderr, "CUDA error: %s\n", cudaGetErrorString(err));
@@ -230,10 +231,10 @@ but the following example shows how it can be used by a standard user.
// Requires non-blocking CUDA kernels but avoids a separate thread.
do {
auto port = server.try_open(warp_size, /*index=*/0);
- // From libllvmlibc_rpc_server.a in the installation.
if (!port)
continue;
+ // Only available in-tree from the 'libc' sources.
handle_libc_opcodes(*port, warp_size);
port->close();
} while (cudaStreamQuery(stream) == cudaErrorNotReady);
@@ -242,14 +243,16 @@ but the following example shows how it can be used by a standard user.
The above code must be compiled in CUDA's relocatable device code mode and with
the advanced offloading driver to link in the library. Currently this can be
done with the following invocation. Using LTO avoids the overhead normally
-associated with relocatable device code linking. The C library for GPUs is
-linked in by forwarding the static library to the device-side link job.
+associated with relocatable device code linking. The C library for GPU's
+handling is included through the ``shared/`` directory. This is not currently
+installed as it does not use a stable interface.
+
.. code-block:: sh
$> clang++ -x cuda rpc.cpp --offload-arch=native -fgpu-rdc -lcudart \
- -I<install-path>include -L<install-path>/lib -lllvmlibc_rpc_server \
- -Xoffload-linker -lc -O3 -foffload-lto -o hello
+ -I<install-path>include -L<install-path>/lib -Xoffload-linker -lc \
+ -O3 -foffload-lto -o hello
$> ./hello
Hello world!
diff --git a/libc/shared/rpc_opcodes.h b/libc/shared/rpc_opcodes.h
index 270c35dec28b8..6de41cd1899e7 100644
--- a/libc/shared/rpc_opcodes.h
+++ b/libc/shared/rpc_opcodes.h
@@ -50,10 +50,4 @@ typedef enum {
#undef LLVM_LIBC_OPCODE
-namespace rpc {
-// The implementation of this function currently lives in the utility directory
-// at 'utils/gpu/server/rpc_server.cpp'.
-rpc::Status handle_libc_opcodes(rpc::Server::Port &port, uint32_t num_lanes);
-} // namespace rpc
-
#endif // LLVM_LIBC_SHARED_RPC_OPCODES_H
diff --git a/libc/utils/gpu/server/rpc_server.cpp b/libc/shared/rpc_server.h
similarity index 92%
rename from libc/utils/gpu/server/rpc_server.cpp
rename to libc/shared/rpc_server.h
index caffc0aee772b..6d1f52b69c02f 100644
--- a/libc/utils/gpu/server/rpc_server.cpp
+++ b/libc/shared/rpc_server.h
@@ -1,4 +1,4 @@
-//===-- Shared memory RPC server instantiation ------------------*- C++ -*-===//
+//===-- RPC server handling -----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
@@ -6,11 +6,25 @@
//
//===----------------------------------------------------------------------===//
+#ifndef LLVM_LIBC_SHARED_RPC_SERVER_H
+#define LLVM_LIBC_SHARED_RPC_SERVER_H
+
// Workaround for missing __has_builtin in < GCC 10.
#ifndef __has_builtin
#define __has_builtin(x) 0
#endif
+// Configs for using the LLVM libc writer interface.
+#define LIBC_COPT_USE_C_ASSERT
+#define LIBC_COPT_MEMCPY_USE_EMBEDDED_TINY
+#define LIBC_COPT_ARRAY_ARG_LIST
+#define LIBC_COPT_PRINTF_DISABLE_WRITE_INT
+#define LIBC_COPT_PRINTF_DISABLE_INDEX_MODE
+#define LIBC_COPT_PRINTF_DISABLE_STRERROR
+
+// The 'long double' type is 8 byte
+#define LIBC_TYPES_LONG_DOUBLE_IS_FLOAT64
+
#include "shared/rpc.h"
#include "shared/rpc_opcodes.h"
@@ -24,6 +38,7 @@
#include <stdlib.h>
namespace LIBC_NAMESPACE {
+namespace internal {
// Minimal replacement for 'std::vector' that works for trivial types.
template <typename T> class TempVector {
@@ -88,15 +103,15 @@ struct TempStorage {
TempVector<char *> storage;
};
-enum Stream {
- File = 0,
- Stdin = 1,
- Stdout = 2,
- Stderr = 3,
-};
-
// Get the associated stream out of an encoded number.
-LIBC_INLINE ::FILE *to_stream(uintptr_t f) {
+static inline ::FILE *to_stream(uintptr_t f) {
+ enum Stream {
+ File = 0,
+ Stdin = 1,
+ Stdout = 2,
+ Stderr = 3,
+ };
+
::FILE *stream = reinterpret_cast<FILE *>(f & ~0x3ull);
Stream type = static_cast<Stream>(f & 0x3ull);
if (type == Stdin)
@@ -109,7 +124,8 @@ LIBC_INLINE ::FILE *to_stream(uintptr_t f) {
}
template <bool packed, uint32_t num_lanes>
-static void handle_printf(rpc::Server::Port &port, TempStorage &temp_storage) {
+static inline void handle_printf(rpc::Server::Port &port,
+ TempStorage &temp_storage) {
FILE *files[num_lanes] = {nullptr};
// Get the appropriate output stream to use.
if (port.get_opcode() == LIBC_PRINTF_TO_STREAM ||
@@ -282,7 +298,7 @@ static void handle_printf(rpc::Server::Port &port, TempStorage &temp_storage) {
}
template <uint32_t num_lanes>
-rpc::Status handle_port_impl(rpc::Server::Port &port) {
+static inline rpc::Status handle_port_impl(rpc::Server::Port &port) {
TempStorage temp_storage;
switch (port.get_opcode()) {
@@ -498,21 +514,24 @@ rpc::Status handle_port_impl(rpc::Server::Port &port) {
return rpc::RPC_SUCCESS;
}
+} // namespace internal
} // namespace LIBC_NAMESPACE
namespace rpc {
-// The implementation of this function currently lives in the utility directory
-// at 'utils/gpu/server/rpc_server.cpp'.
-rpc::Status handle_libc_opcodes(rpc::Server::Port &port, uint32_t num_lanes) {
+// Handles any opcode generated from the 'libc' client code.
+static inline rpc::Status handle_libc_opcodes(rpc::Server::Port &port,
+ uint32_t num_lanes) {
switch (num_lanes) {
case 1:
- return LIBC_NAMESPACE::handle_port_impl<1>(port);
+ return LIBC_NAMESPACE::internal::handle_port_impl<1>(port);
case 32:
- return LIBC_NAMESPACE::handle_port_impl<32>(port);
+ return LIBC_NAMESPACE::internal::handle_port_impl<32>(port);
case 64:
- return LIBC_NAMESPACE::handle_port_impl<64>(port);
+ return LIBC_NAMESPACE::internal::handle_port_impl<64>(port);
default:
return rpc::RPC_ERROR;
}
}
} // namespace rpc
+
+#endif // LLVM_LIBC_SHARED_RPC_SERVER_H
diff --git a/libc/utils/gpu/CMakeLists.txt b/libc/utils/gpu/CMakeLists.txt
index 7c15f36052cf3..e529646a1206e 100644
--- a/libc/utils/gpu/CMakeLists.txt
+++ b/libc/utils/gpu/CMakeLists.txt
@@ -1,2 +1 @@
-add_subdirectory(server)
add_subdirectory(loader)
diff --git a/libc/utils/gpu/loader/CMakeLists.txt b/libc/utils/gpu/loader/CMakeLists.txt
index 60597a67ce57a..9b3bd009dc0f1 100644
--- a/libc/utils/gpu/loader/CMakeLists.txt
+++ b/libc/utils/gpu/loader/CMakeLists.txt
@@ -1,5 +1,8 @@
add_library(gpu_loader OBJECT Main.cpp)
+include(FindLibcCommonUtils)
+target_link_libraries(gpu_loader PUBLIC llvm-libc-common-utilities)
+
target_include_directories(gpu_loader PUBLIC
${CMAKE_CURRENT_SOURCE_DIR}
${LIBC_SOURCE_DIR}/include
diff --git a/libc/utils/gpu/loader/Loader.h b/libc/utils/gpu/loader/Loader.h
index 8e86f63969326..d30a7c0c9669f 100644
--- a/libc/utils/gpu/loader/Loader.h
+++ b/libc/utils/gpu/loader/Loader.h
@@ -13,6 +13,7 @@
#include "shared/rpc.h"
#include "shared/rpc_opcodes.h"
+#include "shared/rpc_server.h"
#include <cstddef>
#include <cstdint>
diff --git a/libc/utils/gpu/loader/amdgpu/CMakeLists.txt b/libc/utils/gpu/loader/amdgpu/CMakeLists.txt
index 80c5ae357416a..17878daf0b6fe 100644
--- a/libc/utils/gpu/loader/amdgpu/CMakeLists.txt
+++ b/libc/utils/gpu/loader/amdgpu/CMakeLists.txt
@@ -7,10 +7,4 @@ set(LLVM_LINK_COMPONENTS
)
add_llvm_executable(amdhsa-loader amdhsa-loader.cpp)
-
-target_link_libraries(amdhsa-loader
- PRIVATE
- hsa-runtime64::hsa-runtime64
- gpu_loader
- llvmlibc_rpc_server
-)
+target_link_libraries(amdhsa-loader PRIVATE hsa-runtime64::hsa-runtime64 gpu_loader)
diff --git a/libc/utils/gpu/loader/nvptx/CMakeLists.txt b/libc/utils/gpu/loader/nvptx/CMakeLists.txt
index 21453b9ca0348..42510ac31dad4 100644
--- a/libc/utils/gpu/loader/nvptx/CMakeLists.txt
+++ b/libc/utils/gpu/loader/nvptx/CMakeLists.txt
@@ -6,10 +6,4 @@ set(LLVM_LINK_COMPONENTS
)
add_llvm_executable(nvptx-loader nvptx-loader.cpp)
-
-target_link_libraries(nvptx-loader
- PRIVATE
- gpu_loader
- llvmlibc_rpc_server
- CUDA::cuda_driver
-)
+target_link_libraries(nvptx-loader PRIVATE gpu_loader CUDA::cuda_driver)
diff --git a/libc/utils/gpu/server/CMakeLists.txt b/libc/utils/gpu/server/CMakeLists.txt
deleted file mode 100644
index 7ca101e42a0af..0000000000000
--- a/libc/utils/gpu/server/CMakeLists.txt
+++ /dev/null
@@ -1,30 +0,0 @@
-add_library(llvmlibc_rpc_server STATIC rpc_server.cpp)
-
-# Include the RPC implemenation from libc.
-target_include_directories(llvmlibc_rpc_server PRIVATE ${LIBC_SOURCE_DIR})
-target_include_directories(llvmlibc_rpc_server PUBLIC ${LIBC_SOURCE_DIR}/include)
-target_include_directories(llvmlibc_rpc_server PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
-
-# Ignore unsupported clang attributes if we're using GCC.
-target_compile_options(llvmlibc_rpc_server PUBLIC
- $<$<CXX_COMPILER_ID:Clang>:-Wno-c99-extensions>
- $<$<CXX_COMPILER_ID:GNU>:-Wno-attributes>)
-target_compile_definitions(llvmlibc_rpc_server PUBLIC
- LIBC_COPT_USE_C_ASSERT
- LIBC_COPT_MEMCPY_USE_EMBEDDED_TINY
- LIBC_TYPES_LONG_DOUBLE_IS_FLOAT64
- LIBC_COPT_ARRAY_ARG_LIST
- LIBC_COPT_PRINTF_DISABLE_WRITE_INT
- LIBC_COPT_PRINTF_DISABLE_INDEX_MODE
- LIBC_COPT_PRINTF_DISABLE_STRERROR
- LIBC_NAMESPACE=${LIBC_NAMESPACE})
-
-# Install the server and associated header.
-install(FILES ${LIBC_SOURCE_DIR}/shared/rpc.h
- ${LIBC_SOURCE_DIR}/shared/rpc_util.h
- ${LIBC_SOURCE_DIR}/shared/rpc_opcodes.h
- DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/shared
- COMPONENT libc-headers)
-install(TARGETS llvmlibc_rpc_server
- ARCHIVE DESTINATION "lib${LLVM_LIBDIR_SUFFIX}"
- COMPONENT libc)
diff --git a/llvm/cmake/modules/FindLibcCommonUtils.cmake b/llvm/cmake/modules/FindLibcCommonUtils.cmake
new file mode 100644
index 0000000000000..0e65fdff7c34b
--- /dev/null
+++ b/llvm/cmake/modules/FindLibcCommonUtils.cmake
@@ -0,0 +1,19 @@
+#===--------------------------------------------------------------------===//
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for details.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+#===--------------------------------------------------------------------===//
+
+if(NOT TARGET llvm-libc-common-utilities)
+ set(libc_path ${CMAKE_CURRENT_LIST_DIR}/../../../libc)
+ if (EXISTS ${libc_path} AND IS_DIRECTORY ${libc_path})
+ add_library(llvm-libc-common-utilities INTERFACE)
+ # TODO: Reorganize the libc shared section so that it can be included without
+ # adding the root "libc" directory to the include path.
+ target_include_directories(llvm-libc-common-utilities INTERFACE ${libc_path})
+ target_compile_definitions(llvm-libc-common-utilities INTERFACE LIBC_NAMESPACE=__llvm_libc_common_utils)
+ target_compile_features(llvm-libc-common-utilities INTERFACE cxx_std_17)
+ endif()
+endif()
diff --git a/offload/plugins-nextgen/common/CMakeLists.txt b/offload/plugins-nextgen/common/CMakeLists.txt
index de219efc8f79c..ffc431f68dbc5 100644
--- a/offload/plugins-nextgen/common/CMakeLists.txt
+++ b/offload/plugins-nextgen/common/CMakeLists.txt
@@ -21,20 +21,9 @@ if (NOT LLVM_LINK_LLVM_DYLIB)
endforeach()
endif()
-# Include the RPC server from the `libc` project if available.
+# Include the RPC server from the `libc` project.
include(FindLibcCommonUtils)
target_link_libraries(PluginCommon PRIVATE llvm-libc-common-utilities)
-if(TARGET llvmlibc_rpc_server AND ${LIBOMPTARGET_GPU_LIBC_SUPPORT})
- target_link_libraries(PluginCommon PRIVATE llvmlibc_rpc_server)
- target_compile_definitions(PluginCommon PRIVATE LIBOMPTARGET_RPC_SUPPORT)
-elseif(${LIBOMPTARGET_GPU_LIBC_SUPPORT})
- find_library(llvmlibc_rpc_server NAMES llvmlibc_rpc_server
- PATHS ${LIBOMPTARGET_LLVM_LIBRARY_DIR} NO_DEFAULT_PATH)
- if(llvmlibc_rpc_server)
- target_link_libraries(PluginCommon PRIVATE ${llvmlibc_rpc_server})
- target_compile_definitions(PluginCommon PRIVATE LIBOMPTARGET_RPC_SUPPORT)
- endif()
-endif()
# Define the TARGET_NAME and DEBUG_PREFIX.
target_compile_definitions(PluginCommon PRIVATE
diff --git a/offload/plugins-nextgen/common/src/RPC.cpp b/offload/plugins-nextgen/common/src/RPC.cpp
index 70f572923d4b1..670edb5f446ca 100644
--- a/offload/plugins-nextgen/common/src/RPC.cpp
+++ b/offload/plugins-nextgen/common/src/RPC.cpp
@@ -15,6 +15,7 @@
#include "shared/rpc.h"
#include "shared/rpc_opcodes.h"
+#include "shared/rpc_server.h"
using namespace llvm;
using namespace omp;
@@ -88,10 +89,8 @@ static rpc::Status runServer(plugin::GenericDeviceTy &Device, void *Buffer) {
handleOffloadOpcodes(Device, *Port, Device.getWarpSize());
// Let the `libc` library handle any other unhandled opcodes.
-#ifdef LIBOMPTARGET_RPC_SUPPORT
if (Status == rpc::RPC_UNHANDLED_OPCODE)
Status = handle_libc_opcodes(*Port, Device.getWarpSize());
-#endif
Port->close();
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