Revert "[libc] Add support for creating wrapper headers for offloading in clang"

This reverts commit a4a26374aa. This was causing some problems with the CPU build and CUDA buildbot. Revert until I can figure out what those issues are and fix them. I believe it is just some CMake.
2026-01-27 06:06:34 +08:00 · 2023-07-06 18:25:52 -05:00
parent a8df21f433
commit 6ca6cdb23e
14 changed files with 9 additions and 417 deletions
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -1181,30 +1181,23 @@ void Clang::AddPreprocessingOptions(Compilation &C, const JobAction &JA,

  // If we are compiling for a GPU target we want to override the system headers
  // with ones created by the 'libc' project if present.
+  // FIXME: We need to find a way to make these headers compatible with the
+  // host environment so they can be included from offloading languages. For now
+  // these are only active when targeting the GPU with cross-compilation.
  if (!Args.hasArg(options::OPT_nostdinc) &&
      !Args.hasArg(options::OPT_nogpuinc) &&
      !Args.hasArg(options::OPT_nobuiltininc) &&
+      C.getActiveOffloadKinds() == Action::OFK_None &&
      (getToolChain().getTriple().isNVPTX() ||
       getToolChain().getTriple().isAMDGCN())) {

-    // Without an offloading language we will include these headers directly.
-    // Offloading languages will instead only use the declarations stored in
-    // the resource directory at clang/lib/Headers/llvm_libc_wrappers.
-    if (C.getActiveOffloadKinds() == Action::OFK_None) {
+      // Add include/gpu-none-libc/* to our system include path. This lets us use
+      // GPU-specific system headers first.
      SmallString<128> P(llvm::sys::path::parent_path(D.InstalledDir));
      llvm::sys::path::append(P, "include");
      llvm::sys::path::append(P, "gpu-none-llvm");
      CmdArgs.push_back("-c-isystem");
      CmdArgs.push_back(Args.MakeArgString(P));
-    } else if (C.getActiveOffloadKinds() == Action::OFK_OpenMP) {
-      // TODO: CUDA / HIP include their own headers for some common functions
-      // implemented here. We'll need to clean those up so they do not conflict.
-      SmallString<128> P(D.ResourceDir);
-      llvm::sys::path::append(P, "include");
-      llvm::sys::path::append(P, "llvm_libc_wrappers");
-      CmdArgs.push_back("-internal-isystem");
-      CmdArgs.push_back(Args.MakeArgString(P));
-    }
  }

  // If we are offloading to a target via OpenMP we need to include the
--- a/clang/lib/Headers/CMakeLists.txt
+++ b/clang/lib/Headers/CMakeLists.txt
@@ -298,14 +298,6 @@ set(openmp_wrapper_files
  openmp_wrappers/new
 )

-set(llvm_libc_wrapper_files
-  llvm_libc_wrappers/stdio.h
-  llvm_libc_wrappers/stdlib.h
-  llvm_libc_wrappers/string.h
-  llvm_libc_wrappers/ctype.h
-  llvm_libc_wrappers/inttypes.h
-)
-
 include(GetClangResourceDir)
 get_clang_resource_dir(output_dir PREFIX ${LLVM_LIBRARY_OUTPUT_INTDIR}/.. SUBDIR include)
 set(out_files)
@@ -341,8 +333,7 @@ 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} ${hlsl_files}
-           ${llvm_libc_wrapper_files})
+           ${ppc_wrapper_files} ${openmp_wrapper_files} ${hlsl_files})
  copy_header_to_output_dir(${CMAKE_CURRENT_SOURCE_DIR} ${f})
 endforeach( f )

@@ -436,7 +427,6 @@ add_dependencies("clang-resource-headers"
                 "x86-resource-headers"
                 "opencl-resource-headers"
                 "openmp-resource-headers"
-                 "llvm-libc-resource-headers"
                 "windows-resource-headers"
                 "utility-resource-headers")

@@ -463,7 +453,6 @@ add_header_target("x86-resource-headers" "${x86_files}")
 # Other header groupings
 add_header_target("hlsl-resource-headers" ${hlsl_files})
 add_header_target("opencl-resource-headers" ${opencl_files})
-add_header_target("llvm-libc-resource-headers" ${llvm_libc_wrapper_files})
 add_header_target("openmp-resource-headers" ${openmp_wrapper_files})
 add_header_target("windows-resource-headers" ${windows_only_files})
 add_header_target("utility-resource-headers" ${utility_files})
@@ -492,11 +481,6 @@ install(
  DESTINATION ${header_install_dir}/ppc_wrappers
  COMPONENT clang-resource-headers)

-install(
-  FILES ${llvm_libc_wrapper_files}
-  DESTINATION ${header_install_dir}/llvm_libc_wrappers
-  COMPONENT clang-resource-headers)
-
 install(
  FILES ${openmp_wrapper_files}
  DESTINATION ${header_install_dir}/openmp_wrappers
@@ -652,12 +636,6 @@ install(
  EXCLUDE_FROM_ALL
  COMPONENT openmp-resource-headers)

-install(
-  FILES ${openmp_wrapper_files}
-  DESTINATION ${header_install_dir}/openmp_wrappers
-  EXCLUDE_FROM_ALL
-  COMPONENT openmp-resource-headers)
-
 install(
  FILES ${utility_files}
  DESTINATION ${header_install_dir}
--- a/clang/lib/Headers/llvm_libc_wrappers/ctype.h
+++ b/clang/lib/Headers/llvm_libc_wrappers/ctype.h
@@ -1,85 +0,0 @@
-//===-- Wrapper for C standard ctype.h declarations on the GPU ------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef __CLANG_LLVM_LIBC_WRAPPERS_CTYPE_H__
-#define __CLANG_LLVM_LIBC_WRAPPERS_CTYPE_H__
-
-#if !defined(_OPENMP) && !defined(__HIP__) && !defined(__CUDA__)
-#error "This file is for GPU offloading compilation only"
-#endif
-
-#include_next <ctype.h>
-
-#if __has_include(<llvm-libc-decls/ctype.h>)
-
-#if defined(__HIP__) || defined(__CUDA__)
-#define __LIBC_ATTRS __attribute__((device))
-#endif
-
-// The GNU headers like to provide these as macros, we need to undefine them so
-// they do not conflict with the following definitions for the GPU.
-
-#pragma push_macro("isalnum")
-#pragma push_macro("isalpha")
-#pragma push_macro("isblank")
-#pragma push_macro("iscntrl")
-#pragma push_macro("isdigit")
-#pragma push_macro("isgraph")
-#pragma push_macro("islower")
-#pragma push_macro("isprint")
-#pragma push_macro("ispunct")
-#pragma push_macro("isspace")
-#pragma push_macro("isupper")
-#pragma push_macro("isxdigit")
-#pragma push_macro("tolower")
-#pragma push_macro("toupper")
-
-#undef isalnum
-#undef isalpha
-#undef iscntrl
-#undef isdigit
-#undef islower
-#undef isgraph
-#undef isprint
-#undef ispunct
-#undef isspace
-#undef isupper
-#undef isblank
-#undef isxdigit
-#undef tolower
-#undef toupper
-
-#pragma omp begin declare target
-
-#include <llvm-libc-decls/ctype.h>
-
-#pragma omp end declare target
-
-// Restore the original macros when compiling on the host.
-#if !defined(__NVPTX__) && !defined(__AMDGPU__)
-#pragma pop_macro("isalnum")
-#pragma pop_macro("isalpha")
-#pragma pop_macro("isblank")
-#pragma pop_macro("iscntrl")
-#pragma pop_macro("isdigit")
-#pragma pop_macro("isgraph")
-#pragma pop_macro("islower")
-#pragma pop_macro("isprint")
-#pragma pop_macro("ispunct")
-#pragma pop_macro("isspace")
-#pragma pop_macro("isupper")
-#pragma pop_macro("isxdigit")
-#pragma pop_macro("tolower")
-#pragma pop_macro("toupper")
-#endif
-
-#undef __LIBC_ATTRS
-
-#endif
-
-#endif // __CLANG_LLVM_LIBC_WRAPPERS_CTYPE_H__
--- a/clang/lib/Headers/llvm_libc_wrappers/inttypes.h
+++ b/clang/lib/Headers/llvm_libc_wrappers/inttypes.h
@@ -1,34 +0,0 @@
-//===-- Wrapper for C standard inttypes.h declarations on the GPU ---------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef __CLANG_LLVM_LIBC_WRAPPERS_INTTYPES_H__
-#define __CLANG_LLVM_LIBC_WRAPPERS_INTTYPES_H__
-
-#if !defined(_OPENMP) && !defined(__HIP__) && !defined(__CUDA__)
-#error "This file is for GPU offloading compilation only"
-#endif
-
-#include_next <inttypes.h>
-
-#if __has_include(<llvm-libc-decls/inttypes.h>)
-
-#if defined(__HIP__) || defined(__CUDA__)
-#define __LIBC_ATTRS __attribute__((device))
-#endif
-
-#pragma omp begin declare target
-
-#include <llvm-libc-decls/inttypes.h>
-
-#pragma omp end declare target
-
-#undef __LIBC_ATTRS
-
-#endif
-
-#endif // __CLANG_LLVM_LIBC_WRAPPERS_INTTYPES_H__
--- a/clang/lib/Headers/llvm_libc_wrappers/llvm-libc-decls/README.txt
+++ b/clang/lib/Headers/llvm_libc_wrappers/llvm-libc-decls/README.txt
@@ -1,6 +0,0 @@
-LLVM libc declarations
-======================
-
-This directory will be filled by the `libc` project with declarations that are
-availible on the device. Each declaration will use the `__LIBC_ATTRS` attribute
-to control emission on the device side.
--- a/clang/lib/Headers/llvm_libc_wrappers/stdio.h
+++ b/clang/lib/Headers/llvm_libc_wrappers/stdio.h
@@ -1,34 +0,0 @@
-//===-- Wrapper for C standard stdio.h declarations on the GPU ------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef __CLANG_LLVM_LIBC_WRAPPERS_STDIO_H__
-#define __CLANG_LLVM_LIBC_WRAPPERS_STDIO_H__
-
-#if !defined(_OPENMP) && !defined(__HIP__) && !defined(__CUDA__)
-#error "This file is for GPU offloading compilation only"
-#endif
-
-#include_next <stdio.h>
-
-#if __has_include(<llvm-libc-decls/stdio.h>)
-
-#if defined(__HIP__) || defined(__CUDA__)
-#define __LIBC_ATTRS __attribute__((device))
-#endif
-
-#pragma omp begin declare target
-
-#include <llvm-libc-decls/stdio.h>
-
-#pragma omp end declare target
-
-#undef __LIBC_ATTRS
-
-#endif
-
-#endif // __CLANG_LLVM_LIBC_WRAPPERS_STDIO_H__
--- a/clang/lib/Headers/llvm_libc_wrappers/stdlib.h
+++ b/clang/lib/Headers/llvm_libc_wrappers/stdlib.h
@@ -1,42 +0,0 @@
-//===-- Wrapper for C standard stdlib.h declarations on the GPU -----------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef __CLANG_LLVM_LIBC_WRAPPERS_STDLIB_H__
-#define __CLANG_LLVM_LIBC_WRAPPERS_STDLIB_H__
-
-#if !defined(_OPENMP) && !defined(__HIP__) && !defined(__CUDA__)
-#error "This file is for GPU offloading compilation only"
-#endif
-
-#include_next <stdlib.h>
-
-#if __has_include(<llvm-libc-decls/stdlib.h>)
-
-#if defined(__HIP__) || defined(__CUDA__)
-#define __LIBC_ATTRS __attribute__((device))
-#endif
-
-#pragma omp begin declare target
-
-// The LLVM C library uses this type so we forward declare it.
-typedef void (*__atexithandler_t)(void);
-
-// Enforce ABI compatibility with the structs used by the LLVM C library.
-_Static_assert(__builtin_offsetof(div_t, quot) == 0, "ABI mismatch!");
-_Static_assert(__builtin_offsetof(ldiv_t, quot) == 0, "ABI mismatch!");
-_Static_assert(__builtin_offsetof(lldiv_t, quot) == 0, "ABI mismatch!");
-
-#include <llvm-libc-decls/stdlib.h>
-
-#pragma omp end declare target
-
-#undef __LIBC_ATTRS
-
-#endif
-
-#endif // __CLANG_LLVM_LIBC_WRAPPERS_STDLIB_H__
--- a/clang/lib/Headers/llvm_libc_wrappers/string.h
+++ b/clang/lib/Headers/llvm_libc_wrappers/string.h
@@ -1,48 +0,0 @@
-//===-- Wrapper for C standard string.h declarations on the GPU -----------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef __CLANG_LLVM_LIBC_WRAPPERS_STRING_H__
-#define __CLANG_LLVM_LIBC_WRAPPERS_STRING_H__
-
-#if !defined(_OPENMP) && !defined(__HIP__) && !defined(__CUDA__)
-#error "This file is for GPU offloading compilation only"
-#endif
-
-// The GNU headers provide non C-standard headers when in C++ mode. Manually
-// undefine it here so that the definitions agree with the C standard for our
-// purposes.
-#ifdef __cplusplus
-extern "C" {
-#pragma push_macro("__cplusplus")
-#undef __cplusplus
-#endif
-
-#include_next <string.h>
-
-#pragma pop_macro("__cplusplus")
-#ifdef __cplusplus
-}
-#endif
-
-#if __has_include(<llvm-libc-decls/string.h>)
-
-#if defined(__HIP__) || defined(__CUDA__)
-#define __LIBC_ATTRS __attribute__((device))
-#endif
-
-#pragma omp begin declare target
-
-#include <llvm-libc-decls/string.h>
-
-#pragma omp end declare target
-
-#undef __LIBC_ATTRS
-
-#endif
-
-#endif // __CLANG_LLVM_LIBC_WRAPPERS_STRING_H__
--- a/clang/test/Driver/gpu-libc-headers.c
+++ b/clang/test/Driver/gpu-libc-headers.c
@@ -1,14 +1,6 @@
 // REQUIRES: nvptx-registered-target
 // REQUIRES: amdgpu-registered-target

-// RUN:   %clang -### --target=x86_64-unknown-linux-gnu -fopenmp=libomp --sysroot=./ \
-// RUN:     -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa --offload-arch=gfx908  \
-// RUN:     -nogpulib %s 2>&1 | FileCheck %s --check-prefix=CHECK-HEADERS
-// RUN:   %clang -### --target=x86_64-unknown-linux-gnu -fopenmp=libomp --sysroot=./ \
-// RUN:     -fopenmp-targets=nvptx64-nvidia-cuda -Xopenmp-target=nvptx64-nvidia-cuda --offload-arch=sm_70  \
-// RUN:     -nogpulib %s 2>&1 | FileCheck %s --check-prefix=CHECK-HEADERS
-// CHECK-HEADERS: "-cc1"{{.*}}"-internal-isystem" "{{.*}}include{{.*}}llvm_libc_wrappers"{{.*}}"-isysroot" "./"
-
 // RUN:   %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx1030 -nogpulib \
 // RUN:     -nogpuinc %s 2>&1 | FileCheck %s --check-prefix=CHECK-HEADERS-DISABLED
 // RUN:   %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx1030 -nogpulib \
--- a/libc/cmake/modules/LLVMLibCHeaderRules.cmake
+++ b/libc/cmake/modules/LLVMLibCHeaderRules.cmake
@@ -131,23 +131,6 @@ function(add_gen_header target_name)
            ${hdrgen_deps}
  )

-  if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
-    file(MAKE_DIRECTORY ${LIBC_INCLUDE_DIR}/llvm-libc-decls)
-    set(decl_out_file ${LIBC_INCLUDE_DIR}/llvm-libc-decls/${relative_path})
-    add_custom_command(
-      OUTPUT ${decl_out_file}
-      COMMAND ${hdrgen_exe} -o ${decl_out_file}
-              --header ${ADD_GEN_HDR_GEN_HDR} --def ${in_file} --export-decls
-              ${replacement_params} -I ${LIBC_SOURCE_DIR} ${ENTRYPOINT_NAME_LIST_ARG}
-              ${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/api.td
-
-      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
-      DEPENDS ${in_file} ${fq_data_files} ${td_includes}
-              ${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/api.td
-              ${hdrgen_deps}
-    )
-  endif()
-
  if(ADD_GEN_HDR_DEPENDS)
    get_fq_deps_list(fq_deps_list ${ADD_GEN_HDR_DEPENDS})
    # Dependencies of a add_header target can only be another add_gen_header target
@@ -161,14 +144,13 @@ function(add_gen_header target_name)
  endif()
  add_custom_target(
    ${fq_target_name}
-    DEPENDS ${out_file} ${fq_deps_list} ${decl_out_file}
+    DEPENDS ${out_file} ${fq_deps_list}
  )

  set_target_properties(
    ${fq_target_name}
    PROPERTIES
      HEADER_FILE_PATH ${out_file}
-      DECLS_FILE_PATH ${decl_out_file}
      DEPS "${fq_deps_list}"
  )
 endfunction(add_gen_header)
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -3,11 +3,6 @@ set(LIBC_INCLUDE_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})

 include(LLVMLibCHeaderRules)

-# The GPU build wants to install files in the compiler's resource directory.
-if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
-  include(GetClangResourceDir)
-endif()
-
 add_subdirectory(llvm-libc-macros)
 add_subdirectory(llvm-libc-types)

@@ -544,21 +539,4 @@ foreach(target IN LISTS all_install_header_targets)
  install(FILES ${header_file}
          DESTINATION ${LIBC_INSTALL_INCLUDE_DIR}/${nested_dir}
          COMPONENT libc-headers)
-  # The GPU optionally provides the supported declarations externally so
-  # offloading languages like CUDA and OpenMP know what is supported by libc. We
-  # install these in the compiler's resource directory at a preset location.
-  if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
-    get_target_property(decls_file ${target} DECLS_FILE_PATH)
-    if(NOT decls_file)
-      continue()
-    endif()
-    get_clang_resource_dir(resource_dir SUBDIR include)
-    file(RELATIVE_PATH relative_path ${LIBC_INCLUDE_BINARY_DIR} ${decls_file})
-    get_filename_component(nested_dir ${relative_path} DIRECTORY)
-    set(install_dir
-        ${CMAKE_INSTALL_PREFIX}/${resource_dir}/llvm_libc_wrappers/${nested_dir})
-    install(FILES ${decls_file}
-            DESTINATION ${install_dir}
-            COMPONENT libc-headers)
-  endif()
 endforeach()
--- a/libc/utils/HdrGen/Generator.cpp
+++ b/libc/utils/HdrGen/Generator.cpp
@@ -10,7 +10,6 @@

 #include "IncludeFileCommand.h"
 #include "PublicAPICommand.h"
-#include "utils/LibcTableGenUtil/APIIndexer.h"

 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -117,78 +116,4 @@ void Generator::generate(llvm::raw_ostream &OS, llvm::RecordKeeper &Records) {
  }
 }

-void Generator::generateDecls(llvm::raw_ostream &OS,
-                              llvm::RecordKeeper &Records) {
-
-  OS << "//===-- C standard declarations for " << StdHeader << " "
-     << std::string(80 - (42 + StdHeader.size()), '-') << "===//\n"
-     << "//\n"
-     << "// Part of the LLVM Project, under the Apache License v2.0 with LLVM "
-        "Exceptions.\n"
-     << "// See https://llvm.org/LICENSE.txt for license information.\n"
-     << "// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception\n"
-     << "//\n"
-     << "//"
-        "===-------------------------------------------------------------------"
-        "---===//\n\n";
-
-  std::string HeaderGuard(StdHeader.size(), '\0');
-  llvm::transform(StdHeader, HeaderGuard.begin(), [](const char C) -> char {
-    return !isalnum(C) ? '_' : llvm::toUpper(C);
-  });
-  OS << "#ifndef __LLVM_LIBC_DECLARATIONS_" << HeaderGuard << "\n"
-     << "#define __LLVM_LIBC_DECLARATIONS_" << HeaderGuard << "\n\n";
-
-  OS << "#ifndef __LIBC_ATTRS\n"
-     << "#define __LIBC_ATTRS\n"
-     << "#endif\n\n";
-
-  OS << "#ifdef __cplusplus\n"
-     << "extern \"C\" {\n"
-     << "#endif\n\n";
-
-  APIIndexer G(StdHeader, Records);
-  for (auto &Name : EntrypointNameList) {
-    // Filter out functions not exported by this header.
-    if (G.FunctionSpecMap.find(Name) == G.FunctionSpecMap.end())
-      continue;
-
-    llvm::Record *FunctionSpec = G.FunctionSpecMap[Name];
-    llvm::Record *RetValSpec = FunctionSpec->getValueAsDef("Return");
-    llvm::Record *ReturnType = RetValSpec->getValueAsDef("ReturnType");
-
-    OS << G.getTypeAsString(ReturnType) << " " << Name << "(";
-
-    auto ArgsList = FunctionSpec->getValueAsListOfDefs("Args");
-    for (size_t i = 0; i < ArgsList.size(); ++i) {
-      llvm::Record *ArgType = ArgsList[i]->getValueAsDef("ArgType");
-      OS << G.getTypeAsString(ArgType);
-      if (i < ArgsList.size() - 1)
-        OS << ", ";
-    }
-
-    OS << ") __LIBC_ATTRS;\n\n";
-  }
-
-  // Make another pass over entrypoints to emit object declarations.
-  for (const auto &Name : EntrypointNameList) {
-    if (G.ObjectSpecMap.find(Name) == G.ObjectSpecMap.end())
-      continue;
-    llvm::Record *ObjectSpec = G.ObjectSpecMap[Name];
-    auto Type = ObjectSpec->getValueAsString("Type");
-    OS << "extern " << Type << " " << Name << " __LIBC_ATTRS;\n";
-  }
-
-  // Emit a final newline if we emitted any object declarations.
-  if (llvm::any_of(EntrypointNameList, [&](const std::string &Name) {
-        return G.ObjectSpecMap.find(Name) != G.ObjectSpecMap.end();
-      }))
-    OS << "\n";
-
-  OS << "#ifdef __cplusplus\n"
-     << "}\n"
-     << "#endif\n\n";
-  OS << "#endif\n";
-}
-
 } // namespace llvm_libc
--- a/libc/utils/HdrGen/Generator.h
+++ b/libc/utils/HdrGen/Generator.h
@@ -52,7 +52,6 @@ public:
        ArgMap(Map) {}

  void generate(llvm::raw_ostream &OS, llvm::RecordKeeper &Records);
-  void generateDecls(llvm::raw_ostream &OS, llvm::RecordKeeper &Records);
 };

 } // namespace llvm_libc
--- a/libc/utils/HdrGen/Main.cpp
+++ b/libc/utils/HdrGen/Main.cpp
@@ -32,9 +32,6 @@ llvm::cl::list<std::string> EntrypointNamesOption(
 llvm::cl::list<std::string> ReplacementValues(
    "args", llvm::cl::desc("Command separated <argument name>=<value> pairs."),
    llvm::cl::value_desc("<name=value>[,name=value]"));
-llvm::cl::opt<bool> ExportDecls(
-    "export-decls",
-    llvm::cl::desc("Output a new header containing only the entrypoints."));

 void ParseArgValuePairs(std::unordered_map<std::string, std::string> &Map) {
  for (std::string &R : ReplacementValues) {
@@ -51,10 +48,7 @@ bool HeaderGeneratorMain(llvm::raw_ostream &OS, llvm::RecordKeeper &Records) {
  std::unordered_map<std::string, std::string> ArgMap;
  ParseArgValuePairs(ArgMap);
  Generator G(HeaderDefFile, EntrypointNamesOption, StandardHeader, ArgMap);
-  if (ExportDecls)
-    G.generateDecls(OS, Records);
-  else
-    G.generate(OS, Records);
+  G.generate(OS, Records);

  return false;
 }