[libc] Make the errno macro resolve to the thread local variable directly.

With modern architectures having a thread pointer and language supporting
thread locals, there is no reason to use a function intermediary to access
the thread local errno value.

The entrypoint corresponding to errno has been replaced with an object
library as there is no formal entrypoint for errno anymore.

Reviewed By: jeffbailey, michaelrj

Differential Revision: https://reviews.llvm.org/D120920

libc/config/linux/aarch64/entrypoints.txt

@@ -17,9 +17,6 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.tolower
     libc.src.ctype.toupper
     
-    # errno.h entrypoints
-    libc.src.errno.__errno_location
-
     # fcntl.h entrypoints
     libc.src.fcntl.creat
     libc.src.fcntl.open

libc/config/linux/api.td

@@ -44,11 +44,8 @@ def NullMacro : MacroDef<"NULL"> {
 
 def ErrnoMacro : MacroDef<"errno"> {
   let Defn = [{
-    #ifdef __cplusplus
-    extern "C"
-    #endif
-    int *__errno_location();
-    #define errno (*__errno_location())
+    extern _Thread_local int __llvmlibc_errno;
+    #define errno __llvmlibc_errno
   }];
 }
 

libc/config/linux/x86_64/entrypoints.txt

@@ -17,9 +17,6 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.tolower
     libc.src.ctype.toupper
 
-    # errno.h entrypoints
-    libc.src.errno.__errno_location
-
     # fcntl.h entrypoints
     libc.src.fcntl.creat
     libc.src.fcntl.open

libc/include/__llvm-libc-common.h

@@ -29,6 +29,9 @@
 #undef _Alignof
 #define _Alignof alignof
 
+#undef _Thread_local
+#define _Thread_local thread_local
+
 #else // not __cplusplus
 
 #undef __BEGIN_C_DECLS

libc/spec/llvm_libc_ext.td

@@ -33,24 +33,8 @@ def LLVMLibcExt : StandardSpec<"llvm_libc_ext"> {
       ]
   >;
 
-  HeaderSpec Errno = HeaderSpec<
-      "errno.h",
-      [], // Macros
-      [], // Types
-      [], // Enumerations
-      [
-          FunctionSpec<
-              "__errno_location",
-              RetValSpec<IntPtr>,
-              [ArgSpec<VoidType>]
-
-          >,
-      ]
-  >;
-
   let Headers = [
     String,
     Assert,
-    Errno,
   ];
 }

libc/src/__support/CMakeLists.txt

@@ -22,7 +22,7 @@ add_header_library(
   DEPENDS
     .ctype_utils
     libc.include.errno
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.__support.CPP.standalone_cpp
 )
 
@@ -43,7 +43,7 @@ add_header_library(
     .ctype_utils
     .high_precision_decimal
     libc.include.errno
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.__support.CPP.standalone_cpp
     libc.src.__support.FPUtil.fputil
 )

libc/src/__support/FPUtil/CMakeLists.txt

@@ -21,7 +21,7 @@ add_header_library(
     libc.include.fenv
     libc.src.__support.common
     libc.src.__support.CPP.standalone_cpp
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_header_library(

libc/src/__support/File/CMakeLists.txt

@@ -5,5 +5,6 @@ add_object_library(
   HDRS
     file.h
   DEPENDS
-    libc.src.errno.__errno_location
+    libc.include.errno
+    libc.src.errno.errno
 )

libc/src/errno/CMakeLists.txt

@@ -1,15 +1,14 @@
 if (LLVM_LIBC_FULL_BUILD)
-add_entrypoint_object(
-  __errno_location
+add_object_library(
+  errno
   SRCS
-    __errno_location.cpp
+    errno.cpp
   HDRS
-    __errno_location.h
     llvmlibc_errno.h
 )
 else()
-add_entrypoint_object(
-  __errno_location
+add_object_library(
+  errno
   SRCS
     dummy_errno.cpp
   HDRS

libc/src/errno/__errno_location.cpp

@@ -1,22 +0,0 @@
-//===-- Implementation of __errno_location --------------------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-#include "src/errno/__errno_location.h"
-
-#include "src/__support/common.h"
-
-namespace __llvm_libc {
-
-static thread_local int errno = 0;
-
-// __errno_location is not really an entry point but we still want it to behave
-// like an entry point because the errno macro resolves to the C symbol
-// "__errno_location".
-LLVM_LIBC_FUNCTION(int *, __errno_location, ()) { return &errno; }
-
-} // namespace __llvm_libc

libc/src/errno/__errno_location.h

@@ -1,18 +0,0 @@
-//===-- Implementation header for __errno_location --------------*- C++ -*-===//
-//
-// 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 LLVM_LIBC_SRC_ERRNO_ERRNO_LOCATION_H
-#define LLVM_LIBC_SRC_ERRNO_ERRNO_LOCATION_H
-
-namespace __llvm_libc {
-
-int *__errno_location();
-
-} // namespace __llvm_libc
-
-#endif // LLVM_LIBC_SRC_ERRNO_ERRNO_LOCATION_H

libc/src/errno/errno.cpp

@@ -0,0 +1,9 @@
+//===-- Implementation of __errno_location --------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+thread_local int __llvmlibc_errno = 0;

libc/src/errno/llvmlibc_errno.h

@@ -6,13 +6,12 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "src/errno/__errno_location.h"
-
 #ifndef LLVM_LIBC_SRC_ERRNO_LLVMLIBC_ERRNO_H
 #define LLVM_LIBC_SRC_ERRNO_LLVMLIBC_ERRNO_H
 
 // Internal code should use this and not use the errno macro from the
 // public header.
-#define llvmlibc_errno (*__llvm_libc::__errno_location())
+extern thread_local int __llvmlibc_errno;
+#define llvmlibc_errno __llvmlibc_errno
 
 #endif // LLVM_LIBC_SRC_ERRNO_LLVMLIBC_ERRNO_H

libc/src/fcntl/linux/CMakeLists.txt

@@ -8,7 +8,7 @@ add_entrypoint_object(
     libc.include.errno
     libc.include.fcntl
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -21,7 +21,7 @@ add_entrypoint_object(
     libc.include.errno
     libc.include.fcntl
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -34,5 +34,5 @@ add_entrypoint_object(
     libc.include.errno
     libc.include.fcntl
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )

libc/src/math/generic/CMakeLists.txt

@@ -43,7 +43,7 @@ add_object_library(
   DEPENDS
     libc.include.errno
     libc.include.math
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_object_library(
@@ -65,7 +65,7 @@ add_entrypoint_object(
   DEPENDS
     .sincosf_utils
     libc.include.math
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
   COMPILE_OPTIONS
     -O3
 )
@@ -79,7 +79,7 @@ add_entrypoint_object(
   DEPENDS
     .sincosf_utils
     libc.include.math
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.__support.FPUtil.fputil
   COMPILE_OPTIONS
     -O3
@@ -94,7 +94,7 @@ add_entrypoint_object(
   DEPENDS
     .sincosf_utils
     libc.include.math
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
   COMPILE_OPTIONS
     -O3
 )

libc/src/signal/linux/CMakeLists.txt

@@ -41,7 +41,7 @@ add_entrypoint_object(
     libc.include.signal
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -55,7 +55,7 @@ add_entrypoint_object(
     libc.include.signal
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -68,7 +68,7 @@ add_entrypoint_object(
   DEPENDS
     libc.include.errno
     libc.include.signal
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -81,7 +81,7 @@ add_entrypoint_object(
   DEPENDS
     libc.include.errno
     libc.include.signal
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -106,7 +106,7 @@ add_entrypoint_object(
   DEPENDS
     libc.include.errno
     libc.include.signal
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -119,5 +119,5 @@ add_entrypoint_object(
   DEPENDS
     libc.include.errno
     libc.include.signal
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )

libc/src/sys/mman/linux/CMakeLists.txt

@@ -8,7 +8,7 @@ add_entrypoint_object(
     libc.include.sys_mman
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -21,5 +21,5 @@ add_entrypoint_object(
     libc.include.sys_mman
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )

libc/src/sys/stat/linux/CMakeLists.txt

@@ -9,7 +9,7 @@ add_entrypoint_object(
     libc.include.sys_stat
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -22,5 +22,5 @@ add_entrypoint_object(
     libc.include.sys_stat
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )

libc/src/threads/linux/CMakeLists.txt

@@ -50,7 +50,7 @@ add_entrypoint_object(
     libc.include.threads
     libc.src.__support.common
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.sys.mman.mmap
   COMPILE_OPTIONS
     -O3

libc/src/time/CMakeLists.txt

@@ -7,7 +7,7 @@ add_object_library(
   DEPENDS
     libc.include.errno
     libc.include.time
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -64,5 +64,5 @@ add_entrypoint_object(
     .time_utils
     libc.include.errno
     libc.include.time
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )

libc/src/unistd/linux/CMakeLists.txt

@@ -8,7 +8,7 @@ add_entrypoint_object(
     libc.include.unistd
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -21,7 +21,7 @@ add_entrypoint_object(
     libc.include.unistd
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -34,7 +34,7 @@ add_entrypoint_object(
     libc.include.unistd
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -48,7 +48,7 @@ add_entrypoint_object(
     libc.include.unistd
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -62,7 +62,7 @@ add_entrypoint_object(
     libc.include.unistd
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -76,7 +76,7 @@ add_entrypoint_object(
     libc.include.unistd
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
@@ -89,5 +89,5 @@ add_entrypoint_object(
     libc.include.unistd
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )

libc/test/loader/linux/CMakeLists.txt

@@ -70,6 +70,6 @@ add_loader_test(
 #    libc.include.sys_mman
 #    libc.loader.linux.crt1
 #    libc.src.assert.__assert_fail
-#    libc.src.errno.__errno_location
+#    libc.src.errno.errno
 #    libc.src.sys.mman.mmap
 #)

libc/test/src/__support/File/CMakeLists.txt

@@ -6,6 +6,7 @@ add_libc_unittest(
   SRCS
     file_test.cpp
   DEPENDS
+    libc.include.errno
     libc.include.stdio
     libc.include.stdlib
     libc.src.__support.File.file

libc/test/src/errno/CMakeLists.txt

@@ -11,5 +11,5 @@ add_libc_unittest(
   SRCS
     errno_test.cpp
   DEPENDS
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
 )

libc/test/src/math/CMakeLists.txt

@@ -309,7 +309,7 @@ add_fp_unittest(
   DEPENDS
     libc.include.errno
     libc.include.math
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.fenv.feclearexcept
     libc.src.fenv.feraiseexcept
     libc.src.fenv.fetestexcept
@@ -329,7 +329,7 @@ add_fp_unittest(
   DEPENDS
     libc.include.errno
     libc.include.math
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.fenv.feclearexcept
     libc.src.fenv.feraiseexcept
     libc.src.fenv.fetestexcept
@@ -349,7 +349,7 @@ add_fp_unittest(
   DEPENDS
     libc.include.errno
     libc.include.math
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.fenv.feclearexcept
     libc.src.fenv.feraiseexcept
     libc.src.fenv.fetestexcept
@@ -369,7 +369,7 @@ add_fp_unittest(
   DEPENDS
     libc.include.errno
     libc.include.math
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.fenv.feclearexcept
     libc.src.fenv.feraiseexcept
     libc.src.fenv.fetestexcept
@@ -389,7 +389,7 @@ add_fp_unittest(
   DEPENDS
     libc.include.errno
     libc.include.math
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.fenv.feclearexcept
     libc.src.fenv.feraiseexcept
     libc.src.fenv.fetestexcept
@@ -409,7 +409,7 @@ add_fp_unittest(
   DEPENDS
     libc.include.errno
     libc.include.math
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.fenv.feclearexcept
     libc.src.fenv.feraiseexcept
     libc.src.fenv.fetestexcept

libc/test/src/signal/CMakeLists.txt

@@ -33,7 +33,7 @@ add_libc_unittest(
     sigprocmask_test.cpp
   DEPENDS
     libc.include.errno
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.signal.raise
     libc.src.signal.sigaddset
     libc.src.signal.sigemptyset
@@ -63,7 +63,7 @@ add_libc_unittest(
   DEPENDS
     libc.include.errno
     libc.include.signal
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.signal.raise
     libc.src.signal.signal
     libc.test.errno_setter_matcher

libc/test/src/sys/mman/linux/CMakeLists.txt

@@ -9,7 +9,7 @@ add_libc_unittest(
   DEPENDS
     libc.include.errno
     libc.include.sys_mman
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.sys.mman.mmap
     libc.src.sys.mman.munmap
     libc.test.errno_setter_matcher

libc/test/src/threads/CMakeLists.txt

@@ -26,7 +26,7 @@ add_libc_unittest(
     thrd_test.cpp
   DEPENDS
     libc.include.threads
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.threads.thrd_create
     libc.src.threads.thrd_join
 )
@@ -39,7 +39,7 @@ add_libc_unittest(
     mtx_test.cpp
   DEPENDS
     libc.include.threads
-    libc.src.errno.__errno_location
+    libc.src.errno.errno
     libc.src.threads.mtx_destroy
     libc.src.threads.mtx_init
     libc.src.threads.mtx_lock