Reland "[compiler-rt] Simple crtbegin.o and crtend.o implementation"

Clang relies on existence of certain symbols that are normally
provided by crtbegin.o/crtend.o. However, LLVM does not currently
provide implementation of these files, instead relying on either
libgcc or implementations provided as part of the system.

This change provides an initial implementation of crtbegin.o/crtend.o
that can be used on system that don't provide crtbegin.o/crtend.o as
part of their C library.

Differential Revision: https://reviews.llvm.org/D28791

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@359591 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 35 insertions, 17 deletions

diff --git a/cmake/Modules/AddCompilerRT.cmake b/cmake/Modules/AddCompilerRT.cmake
index bed0826ff..8b6518d13 100644
--- a/cmake/Modules/AddCompilerRT.cmake
+++ b/cmake/Modules/AddCompilerRT.cmake
@@ -132,7 +132,7 @@ endmacro()
 # Adds static or shared runtime for a list of architectures and operating
 # systems and puts it in the proper directory in the build and install trees.
 # add_compiler_rt_runtime(<name>
-#                         {STATIC|SHARED}
+#                         {OBJECT|STATIC|SHARED}
 #                         ARCHS <architectures>
 #                         OS <os list>
 #                         SOURCES <source files>
@@ -144,8 +144,8 @@ endmacro()
 #                         PARENT_TARGET <convenience parent target>
 #                         ADDITIONAL_HEADERS <header files>)
 function(add_compiler_rt_runtime name type)
-  if(NOT type MATCHES "^(STATIC|SHARED)$")
-    message(FATAL_ERROR "type argument must be STATIC or SHARED")
+  if(NOT type MATCHES "^(OBJECT|STATIC|SHARED)$")
+    message(FATAL_ERROR "type argument must be OBJECT, STATIC or SHARED")
     return()
   endif()
   cmake_parse_arguments(LIB
@@ -204,7 +204,10 @@ function(add_compiler_rt_runtime name type)
         message(FATAL_ERROR "Architecture ${arch} can't be targeted")
         return()
       endif()
-      if(type STREQUAL "STATIC")
+      if(type STREQUAL "OBJECT")
+        set(libname "${name}-${arch}")
+        set_output_name(output_name_${libname} ${name}${COMPILER_RT_OS_SUFFIX} ${arch})
+      elseif(type STREQUAL "STATIC")
         set(libname "${name}-${arch}")
         set_output_name(output_name_${libname} ${name} ${arch})
       else()
@@ -270,12 +273,34 @@ function(add_compiler_rt_runtime name type)
       set(COMPONENT_OPTION COMPONENT ${libname})
     endif()
 
-    add_library(${libname} ${type} ${sources_${libname}})
-    set_target_compile_flags(${libname} ${extra_cflags_${libname}})
-    set_target_link_flags(${libname} ${extra_link_flags_${libname}})
-    set_property(TARGET ${libname} APPEND PROPERTY
-                COMPILE_DEFINITIONS ${LIB_DEFS})
-    set_target_output_directories(${libname} ${output_dir_${libname}})
+    if(type STREQUAL "OBJECT")
+      string(TOUPPER ${CMAKE_BUILD_TYPE} config)
+      get_property(cflags SOURCE ${sources_${libname}} PROPERTY COMPILE_FLAGS)
+      separate_arguments(cflags)
+      add_custom_command(
+          OUTPUT ${output_dir_${libname}}/${output_name_${libname}}.o
+          COMMAND ${CMAKE_C_COMPILER} ${sources_${libname}} ${cflags} ${extra_cflags_${libname}} -c -o ${output_dir_${libname}}/${output_name_${libname}}.o
+          DEPENDS ${sources_${libname}}
+          COMMENT "Building C object ${output_name_${libname}}.o")
+      add_custom_target(${libname} DEPENDS ${output_dir_${libname}}/${output_name_${libname}}.o)
+      install(FILES ${output_dir_${libname}}/${output_name_${libname}}.o
+        DESTINATION ${install_dir_${libname}}
+        ${COMPONENT_OPTION})
+    else()
+      add_library(${libname} ${type} ${sources_${libname}})
+      set_target_compile_flags(${libname} ${extra_cflags_${libname}})
+      set_target_link_flags(${libname} ${extra_link_flags_${libname}})
+      set_property(TARGET ${libname} APPEND PROPERTY
+                   COMPILE_DEFINITIONS ${LIB_DEFS})
+      set_target_output_directories(${libname} ${output_dir_${libname}})
+      install(TARGETS ${libname}
+        ARCHIVE DESTINATION ${install_dir_${libname}}
+                ${COMPONENT_OPTION}
+        LIBRARY DESTINATION ${install_dir_${libname}}
+                ${COMPONENT_OPTION}
+        RUNTIME DESTINATION ${install_dir_${libname}}
+                ${COMPONENT_OPTION})
+    endif()
     set_target_properties(${libname} PROPERTIES
         OUTPUT_NAME ${output_name_${libname}})
     set_target_properties(${libname} PROPERTIES FOLDER "Compiler-RT Runtime")
@@ -299,13 +324,6 @@ function(add_compiler_rt_runtime name type)
         )
       endif()
     endif()
-    install(TARGETS ${libname}
-      ARCHIVE DESTINATION ${install_dir_${libname}}
-              ${COMPONENT_OPTION}
-      LIBRARY DESTINATION ${install_dir_${libname}}
-              ${COMPONENT_OPTION}
-      RUNTIME DESTINATION ${install_dir_${libname}}
-              ${COMPONENT_OPTION})
 
     # We only want to generate per-library install targets if you aren't using
     # an IDE because the extra targets get cluttered in IDEs.