[CMake][compiler-rt] Provide a dedicated option for LLVM unwinder

This allows configuring LLVM unwinder separately from the C++ library
matching how we configure it in libcxx.

This also applies changes made to libunwind+libcxxabi+libcxx in D113253
to compiler-rt.

Differential Revision: https://reviews.llvm.org/D115674

clang/cmake/caches/Fuchsia-stage2.cmake

@@ -112,6 +112,7 @@ foreach(target aarch64-unknown-linux-gnu;armv7-unknown-linux-gnueabihf;i386-unkn
     set(RUNTIMES_${target}_CMAKE_MODULE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_EXE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_COMPILER_RT_USE_BUILTINS_LIBRARY ON CACHE BOOL "")
+    set(RUNTIMES_${target}_COMPILER_RT_USE_LLVM_UNWINDER ON CACHE BOOL "")
     set(RUNTIMES_${target}_COMPILER_RT_CAN_EXECUTE_TESTS ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_ENABLE_SHARED OFF CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
@@ -179,6 +180,7 @@ if(FUCHSIA_SDK)
     set(RUNTIMES_${target}_CMAKE_EXE_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")
     set(RUNTIMES_${target}_COMPILER_RT_USE_BUILTINS_LIBRARY ON CACHE BOOL "")
+    set(RUNTIMES_${target}_COMPILER_RT_USE_LLVM_UNWINDER ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_HIDE_SYMBOLS ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_INSTALL_STATIC_LIBRARY OFF CACHE BOOL "")

compiler-rt/CMakeLists.txt

@@ -31,6 +31,7 @@ endif()
 include(SetPlatformToolchainTools)
 include(base-config-ix)
 include(CompilerRTUtils)
+include(CMakeDependentOption)
 
 option(COMPILER_RT_BUILD_BUILTINS "Build builtins" ON)
 mark_as_advanced(COMPILER_RT_BUILD_BUILTINS)
@@ -211,6 +212,11 @@ set(CXXLIBS none default libstdc++ libc++)
 set_property(CACHE SANITIZER_TEST_CXX PROPERTY STRINGS ;${CXXLIBS})
 handle_default_cxx_lib(SANITIZER_TEST_CXX)
 
+option(COMPILER_RT_USE_LLVM_UNWINDER "Use the LLVM unwinder." OFF)
+cmake_dependent_option(COMPILER_RT_ENABLE_STATIC_UNWINDER
+  "Statically link the LLVM unwinder." OFF
+  "COMPILER_RT_USE_LLVM_UNWINDER" OFF)
+
 set(DEFAULT_SANITIZER_USE_STATIC_LLVM_UNWINDER OFF)
 if (FUCHSIA)
   set(DEFAULT_SANITIZER_USE_STATIC_LLVM_UNWINDER ON)
@@ -504,6 +510,15 @@ string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}
 list(APPEND COMPILER_RT_COMMON_CFLAGS ${stdlib_flag})
 list(APPEND COMPILER_RT_COMMON_LINK_FLAGS ${stdlib_flag})
 
+if(COMPILER_RT_USE_LLVM_UNWINDER)
+  if (COMPILER_RT_ENABLE_STATIC_UNWINDER)
+    set(unwinder_target unwind_static)
+  else()
+    set(unwinder_target unwind_shared)
+  endif()
+  list(APPEND SANITIZER_CXX_ABI_LIBRARIES "$<$<TARGET_EXISTS:${unwinder_target}>:$<TARGET_LINKER_FILE:${unwinder_target}>>")
+endif()
+
 macro(append_libcxx_libs var)
   if (${var}_INTREE)
     if (SANITIZER_USE_STATIC_LLVM_UNWINDER AND (TARGET unwind_static OR HAVE_LIBUNWIND))

compiler-rt/cmake/config-ix.cmake

@@ -4,9 +4,19 @@ include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 include(CheckIncludeFiles)
 include(CheckLibraryExists)
+include(LLVMCheckCompilerLinkerFlag)
 include(CheckSymbolExists)
 include(TestBigEndian)
 
+# The compiler driver may be implicitly trying to link against libunwind.
+# This is normally ok (libcxx relies on an unwinder), but if libunwind is
+# built in the same cmake invocation as compiler-rt and we're using the
+# in tree version of runtimes, we'd be linking against the just-built
+# libunwind (and the compiler implicit -lunwind wouldn't succeed as the newly
+# built libunwind isn't installed yet). For those cases, it'd be good to
+# link with --uwnindlib=none. Check if that option works.
+llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
+
 check_library_exists(c fopen "" COMPILER_RT_HAS_LIBC)
 if (COMPILER_RT_USE_BUILTINS_LIBRARY)
   include(HandleCompilerRT)

compiler-rt/lib/scudo/standalone/CMakeLists.txt

@@ -36,6 +36,7 @@ list(APPEND SCUDO_LINK_FLAGS -ffunction-sections -fdata-sections -Wl,--gc-sectio
 
 # We don't use the C++ standard library, so avoid including it by mistake.
 append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ SCUDO_LINK_FLAGS)
+append_list_if(CXX_SUPPORTS_UNWINDLIB_NONE_FLAG --unwindlib=none SCUDO_LINK_FLAGS)
 
 if(ANDROID)
   list(APPEND SCUDO_CFLAGS -fno-emulated-tls)