[PATCH] D151013: [CMake] Add option to link LLVM/subproject executables

[Aiden Grossman via Phabricator via llvm-commits]

aidengrossman updated this revision to Diff 526304.
aidengrossman edited the summary of this revision.
aidengrossman added a comment.

Changed from building libc as a project and linking against that to linking against the LLVM libc overaly if available from the system. This prevents building something that should be built as a runtime as a project, ensuring that we have an up to date compiler.

In order to effectively do multi-stage builds https://reviews.llvm.org/D151624 needs to land.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D151013/new/

https://reviews.llvm.org/D151013

Files:
  llvm/cmake/modules/AddLLVM.cmake
  llvm/cmake/modules/HandleLLVMOptions.cmake
  llvm/docs/CMake.rst


Index: llvm/docs/CMake.rst
===================================================================
--- llvm/docs/CMake.rst
+++ llvm/docs/CMake.rst
@@ -509,6 +509,11 @@
   passed to invocations of both so that the project is built using libc++
   instead of stdlibc++. Defaults to OFF.
 
+**LLVM_ENABLE_LLVM_LIBC**: BOOL
+  If the LLVM libc overlay is installed in a location where the host linker
+  can access it, all built executables will be linked against the LLVM libc
+  overlay before linking against the system libc. Defaults to OFF.
+
 **LLVM_ENABLE_LIBPFM**:BOOL
   Enable building with libpfm to support hardware counter measurements in LLVM
   tools.
Index: llvm/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -1300,3 +1300,13 @@
 
 set(LLVM_THIRD_PARTY_DIR  ${CMAKE_CURRENT_SOURCE_DIR}/../third-party CACHE STRING
     "Directory containing third party software used by LLVM (e.g. googletest)")
+
+set(LLVM_ENABLE_LLVM_LIBC OFF CACHE BOOL "Set to on to link all LLVM executables against LLVM libc, assuming it is accessible by the host compiler")
+
+if(LLVM_ENABLE_LLVM_LIBC)
+  include(CheckCXXCompilerFlag)
+  llvm_check_linker_flag(CXX "-lllvmlibc" CXX_LINKER_SUPPORTS_LLVM_LIBC)
+  if(NOT CXX_LINKER_SUPPORTS_LLVM_LIBC)
+    message(WARNING "Unable to link against LLVM libc. LLVM will be built without linking against the LLVM libc overlay.")
+  endif()
+endif()
Index: llvm/cmake/modules/AddLLVM.cmake
===================================================================
--- llvm/cmake/modules/AddLLVM.cmake
+++ llvm/cmake/modules/AddLLVM.cmake
@@ -1029,6 +1029,10 @@
     target_link_libraries(${name} PRIVATE ${LLVM_PTHREAD_LIB})
   endif()
 
+  if(CXX_LINKER_SUPPORTS_LLVM_LIBC)
+    target_link_libraries(${name} PRIVATE llvmlibc)
+  endif()
+
   llvm_codesign(${name} ENTITLEMENTS ${ARG_ENTITLEMENTS} BUNDLE_PATH ${ARG_BUNDLE_PATH})
 endmacro(add_llvm_executable name)
 


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