Fix lld detection in standalone compiler-rt.

[eugenis]

Summary

Right now all hwasan tests on Android are silently disabled because they
require "has_lld" and standalone compiler-rt can not (and AFAIK was
never able to) set it.

[eugenis]

As it turns out, hwasan has not been tested on Android for the past two months.
It was broken by this change (which went in without code review, btw, not cool):

http://llvm.org/viewvc/llvm-project?rev=368242&view=rev

The change may look trivial, but nothing in CMake ever is.

Now, this can not go in right now, because, naturally, most of the stuff we have committed over the past two months does not pass on Android.
It looks like it is almost all Peter.
One thing that I've noticed is that __hwasan_personality_wrapper has neither extern"C" or public visibility, so it is not exported from the shared runtime library.

compiler-rt/CMakeLists.txt

500

I believe all the stuff above this line is necessary for non-standalone case, when the linker flag check would run before the linker itself is built.

[pcc]

compiler-rt/CMakeLists.txt

500

Shouldn't this be ${COMPILER_RT_HAS_FUSE_LD_LLD_FLAG}?

[dyung]

Sorry for breaking this, I thought the change would be trivial, guess it was not. From what I can remember, Peter's change was causing our internal testing to break because we don't build/use LLD for our platform.

[eugenis]

Add missing ${}

compiler-rt/CMakeLists.txt

500

It definitely should!

[pcc]

LGTM

[dyung]

I tried applying this to our internal sources and it worked, so LGTM as well.

[eugenis]

I've applied a workaround for the last remaining regression in r375471.
Time to land this change.

[morehouse]

This appears to have broken the standalone compiler-rt build: http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux/builds/23986

CMake Error at /b/sanitizer-x86_64-linux/build/llvm_build64/lib/cmake/llvm/AddLLVM.cmake:1422 (add_dependencies):
  The dependency target "lld" of target "check-compiler-rt" does not exist.
Call Stack (most recent call first):
  test/CMakeLists.txt:86 (add_lit_target)


CMake Error at /b/sanitizer-x86_64-linux/build/llvm_build64/lib/cmake/llvm/AddLLVM.cmake:1422 (add_dependencies):
  The dependency target "lld" of target "check-ubsan" does not exist.
Call Stack (most recent call first):
  /b/sanitizer-x86_64-linux/build/llvm_build64/lib/cmake/llvm/AddLLVM.cmake:1443 (add_lit_target)
  test/ubsan/CMakeLists.txt:131 (add_lit_testsuite)


CMake Error at /b/sanitizer-x86_64-linux/build/llvm_build64/lib/cmake/llvm/AddLLVM.cmake:1422 (add_dependencies):
  The dependency target "lld" of target "check-msan" does not exist.
Call Stack (most recent call first):
  /b/sanitizer-x86_64-linux/build/llvm_build64/lib/cmake/llvm/AddLLVM.cmake:1443 (add_lit_target)
  test/msan/CMakeLists.txt:56 (add_lit_testsuite)

[peter.smith]

I've just taken over buildbot monitoring duty and it looks like our http://lab.llvm.org:8011/builders/clang-cmake-thumbv7-full-sh/builds/3006 is still failing even with the latest fix.

I can reproduce on an x86_64 machine. It looks like specific problem is when the compiler has -fuse-ld=lld, but lld is not in the LLVM_ENABLE_PROJECTS list. If I add it then the cmake step will complete.

CC=/path/to/clang CXX=/path/to/clang++ \
  cmake -GNinja ../../llvm \
      -DLLVM_ENABLE_PROJECTS="clang;compiler-rt" \
      -DCMAKE_BUILD_TYPE=Release

Can you take a look?

[eugenis]

Hi Peter, it appears that I've missed some of the compiler-rt subprojects. This commit should fix it:
https://github.com/llvm/llvm-project/commit/3f345732b4f88e8d0d302470929cbe33d65a7435

compiler-rt/CMakeLists.txt

 set(COMPILER_RT_LLD_PATH ${LLVM_MAIN_SRC_DIR}/tools/lld)
 if(EXISTS ${COMPILER_RT_LLD_PATH}/ AND LLVM_TOOL_LLD_BUILD)
   set(COMPILER_RT_HAS_LLD TRUE)
 else()
   set(COMPILER_RT_LLD_PATH ${LLVM_MAIN_SRC_DIR}/../lld)
   if(EXISTS ${COMPILER_RT_LLD_PATH}/ AND LLVM_TOOL_LLD_BUILD)
     set(COMPILER_RT_HAS_LLD TRUE)
   else()
-    set(COMPILER_RT_HAS_LLD FALSE)
+    set(COMPILER_RT_HAS_LLD ${COMPILER_RT_HAS_FUSE_LD_LLD_FLAG})
   endif()
 endif()
 pythonize_bool(COMPILER_RT_HAS_LLD)
 
 add_subdirectory(lib)
 
 if(COMPILER_RT_INCLUDE_TESTS)
   add_subdirectory(unittests)

compiler-rt/cmake/config-ix.cmake

if (ANDROID AND COMPILER_RT_HAS_LIBDL)
   # Android's libstdc++ has a dependency on libdl.
   list(APPEND CMAKE_REQUIRED_LIBRARIES dl)
 endif()
 check_library_exists(c++ __cxa_throw "" COMPILER_RT_HAS_LIBCXX)
 check_library_exists(stdc++ __cxa_throw "" COMPILER_RT_HAS_LIBSTDCXX)
 
 # Linker flags.
 check_linker_flag("-Wl,-z,text" COMPILER_RT_HAS_Z_TEXT)
+check_linker_flag("-fuse-ld=lld" COMPILER_RT_HAS_FUSE_LD_LLD_FLAG)
 
 if(ANDROID)
   check_linker_flag("-Wl,-z,global" COMPILER_RT_HAS_Z_GLOBAL)
   check_library_exists(log __android_log_write "" COMPILER_RT_HAS_LIBLOG)
 endif()
 
 # Architectures.