From b31080c596246bc26d2493cfd5e07f053cf9541c Mon Sep 17 00:00:00 2001
From: Raul Tambre <raul@tambre.ee>
Date: Wed, 21 Jul 2021 20:38:24 +0300
Subject: [PATCH] [compiler-rt][CMake][arm64] Use a custom target for
 symlinking LSE sources

On Apple platforms the builtins may be built for both arm64 and arm64e.
With Makefile generators separate targets are built using Make sub-invocations.
This causes a race when creating the symlink which may sometimes fail.

Work around this by using a custom target that the builtin targets depend on.
This causes any sub-invocations to depend on the symlinks having been created before.

Mailing list thread: https://lists.llvm.org/pipermail/llvm-dev/2021-July/151822.html

Reviewed By: thakis, steven_wu

Differential Revision: https://reviews.llvm.org/D106305
---
 .../cmake/Modules/CompilerRTDarwinUtils.cmake   | 14 ++++++++++++++
 compiler-rt/lib/builtins/CMakeLists.txt         | 17 +++++++++++++----
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
index 380ae031a0fea..276fcbb9c0e3c 100644
--- a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
+++ b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
@@ -405,6 +405,18 @@ macro(darwin_add_builtin_libraries)
                       ../profile/InstrProfilingVersionVar.c)
   foreach (os ${ARGN})
     list_intersect(DARWIN_BUILTIN_ARCHS DARWIN_${os}_BUILTIN_ARCHS BUILTIN_SUPPORTED_ARCH)
+
+    if((arm64 IN_LIST DARWIN_BUILTIN_ARCHS OR arm64e IN_LIST DARWIN_BUILTIN_ARCHS) AND NOT TARGET lse_builtin_symlinks)
+      add_custom_target(
+        lse_builtin_symlinks
+        BYPRODUCTS ${lse_builtins}
+        ${arm64_lse_commands}
+      )
+
+      set(deps_arm64 lse_builtin_symlinks)
+      set(deps_arm64e lse_builtin_symlinks)
+    endif()
+
     foreach (arch ${DARWIN_BUILTIN_ARCHS})
       darwin_find_excluded_builtins_list(${arch}_${os}_EXCLUDED_BUILTINS
                               OS ${os}
@@ -419,6 +431,7 @@ macro(darwin_add_builtin_libraries)
       darwin_add_builtin_library(clang_rt builtins
                               OS ${os}
                               ARCH ${arch}
+                              DEPS ${deps_${arch}}
                               SOURCES ${filtered_sources}
                               CFLAGS ${CFLAGS} -arch ${arch}
                               PARENT_TARGET builtins)
@@ -443,6 +456,7 @@ macro(darwin_add_builtin_libraries)
         darwin_add_builtin_library(clang_rt cc_kext
                                 OS ${os}
                                 ARCH ${arch}
+                                DEPS ${deps_${arch}}
                                 SOURCES ${filtered_sources} ${PROFILE_SOURCES}
                                 CFLAGS ${CFLAGS} -arch ${arch} -mkernel
                                 DEFS KERNEL_USE
diff --git a/compiler-rt/lib/builtins/CMakeLists.txt b/compiler-rt/lib/builtins/CMakeLists.txt
index 628fe0558fdc2..59d83631a5f43 100644
--- a/compiler-rt/lib/builtins/CMakeLists.txt
+++ b/compiler-rt/lib/builtins/CMakeLists.txt
@@ -531,10 +531,8 @@ foreach(pat cas swp ldadd ldclr ldeor ldset)
     foreach(model 1 2 3 4)
       if(pat STREQUAL "cas" OR NOT size STREQUAL "16")
         set(helper_asm "${OA_HELPERS_DIR}/outline_atomic_${pat}${size}_${model}.S")
-        add_custom_command(
-          OUTPUT ${helper_asm}
-          COMMAND ${CMAKE_COMMAND} -E ${COMPILER_RT_LINK_OR_COPY} "${CMAKE_CURRENT_SOURCE_DIR}/aarch64/lse.S" "${helper_asm}"
-        )
+        list(APPEND lse_builtins "${helper_asm}")
+        list(APPEND arm64_lse_commands COMMAND ${CMAKE_COMMAND} -E ${COMPILER_RT_LINK_OR_COPY} "${CMAKE_CURRENT_SOURCE_DIR}/aarch64/lse.S" "${helper_asm}")
         set_source_files_properties("${helper_asm}"
           PROPERTIES
           COMPILE_DEFINITIONS "L_${pat};SIZE=${size};MODEL=${model}"
@@ -741,9 +739,20 @@ else ()
         list(APPEND BUILTIN_CFLAGS_${arch} -fforce-enable-int128)
       endif()
 
+      if(arch STREQUAL "aarch64")
+        add_custom_target(
+          lse_builtin_symlinks
+          BYPRODUCTS ${lse_builtins}
+          ${arm64_lse_commands}
+        )
+
+        set(deps_aarch64 lse_builtin_symlinks)
+      endif()
+
       add_compiler_rt_runtime(clang_rt.builtins
                               STATIC
                               ARCHS ${arch}
+                              DEPS ${deps_${arch}}
                               SOURCES ${${arch}_SOURCES}
                               DEFS ${BUILTIN_DEFS}
                               CFLAGS ${BUILTIN_CFLAGS_${arch}}