Change test coverage generation to use llvm-cov instead of gcov.

Clang doesn't produce gcov compatible coverage files. This
causes lcov to break because it uses gcov by default. This
patch switches lcov to use llvm-cov as the gcov-tool.

Unfortunatly llvm-cov doesn't provide a gcov like interface by
default so it won't work with lcov. However `llvm-cov gcov` does.
For this reason we generate 'llvm-cov-wrapper' script that always
passes the gcov flag.

llvm-svn: 297553
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 2aeac46e845ed4423089912c03f2365eba35b09f
diff --git a/cmake/Modules/CodeCoverage.cmake b/cmake/Modules/CodeCoverage.cmake
index addd10a..1bd3a78 100644
--- a/cmake/Modules/CodeCoverage.cmake
+++ b/cmake/Modules/CodeCoverage.cmake
@@ -3,6 +3,11 @@
   message(FATAL_ERROR "Cannot find lcov...")
 endif()
 
+find_program(CODE_COVERAGE_LLVM_COV llvm-cov)
+if (NOT CODE_COVERAGE_LLVM_COV)
+  message(FATAL_ERROR "Cannot find llvm-cov...")
+endif()
+
 find_program(CODE_COVERAGE_GENHTML genhtml)
 if (NOT CODE_COVERAGE_GENHTML)
   message(FATAL_ERROR "Cannot find genhtml...")
@@ -11,6 +16,14 @@
 set(CMAKE_CXX_FLAGS_COVERAGE "-g -O0 --coverage")
 
 function(setup_lcov_test_target_coverage target_name output_dir capture_dirs source_dirs)
+  if (NOT DEFINED LIBCXX_BINARY_DIR)
+    message(FATAL_ERROR "Variable must be set")
+  endif()
+
+  set(GCOV_TOOL "${LIBCXX_BINARY_DIR}/llvm-cov-wrapper")
+  file(GENERATE OUTPUT ${GCOV_TOOL}
+    CONTENT "#!/usr/bin/env bash\n${CODE_COVERAGE_LLVM_COV} gcov \"$@\"\n")
+
   file(MAKE_DIRECTORY ${output_dir})
 
   set(CAPTURE_DIRS "")
@@ -27,8 +40,9 @@
   message(STATUS "Extract Directories: ${EXTRACT_DIRS}")
 
   add_custom_target(generate-lib${target_name}-coverage
-        COMMAND ${CODE_COVERAGE_LCOV} --capture ${CAPTURE_DIRS} -o test_coverage.info
-        COMMAND ${CODE_COVERAGE_LCOV} --extract test_coverage.info ${EXTRACT_DIRS} -o test_coverage.info
+        COMMAND chmod +x ${GCOV_TOOL}
+        COMMAND ${CODE_COVERAGE_LCOV} --gcov-tool ${GCOV_TOOL} --capture ${CAPTURE_DIRS} -o test_coverage.info
+        COMMAND ${CODE_COVERAGE_LCOV} --gcov-tool ${GCOV_TOOL} --extract test_coverage.info ${EXTRACT_DIRS} -o test_coverage.info
         COMMAND ${CODE_COVERAGE_GENHTML} --demangle-cpp test_coverage.info -o test_coverage
         COMMAND ${CMAKE_COMMAND} -E remove test_coverage.info
         WORKING_DIRECTORY ${output_dir}
diff --git a/cmake/Modules/HandleCompilerRT.cmake b/cmake/Modules/HandleCompilerRT.cmake
new file mode 100644
index 0000000..d7c4247
--- /dev/null
+++ b/cmake/Modules/HandleCompilerRT.cmake
@@ -0,0 +1,43 @@
+function(find_compiler_rt_library name dest)
+  if (NOT DEFINED LIBCXX_COMPILE_FLAGS)
+    message(FATAL_ERROR "LIBCXX_COMPILE_FLAGS must be defined when using this function")
+  endif()
+  set(dest "" PARENT_SCOPE)
+  set(CLANG_COMMAND ${CMAKE_CXX_COMPILER} ${LIBCXX_COMPILE_FLAGS}
+      "--rtlib=compiler-rt" "--print-libgcc-file-name")
+  execute_process(
+      COMMAND ${CLANG_COMMAND}
+      RESULT_VARIABLE HAD_ERROR
+      OUTPUT_VARIABLE LIBRARY_FILE
+  )
+  string(STRIP "${LIBRARY_FILE}" LIBRARY_FILE)
+  string(REPLACE "builtins" "${name}" LIBRARY_FILE "${LIBRARY_FILE}")
+  if (NOT HAD_ERROR AND EXISTS "${LIBRARY_FILE}")
+    message(STATUS "Found compiler-rt library: ${LIBRARY_FILE}")
+    set(${dest} "${LIBRARY_FILE}" PARENT_SCOPE)
+  else()
+    message(STATUS "Failed to find compiler-rt library")
+  endif()
+endfunction()
+
+function(find_compiler_rt_dir dest)
+  if (NOT DEFINED LIBCXX_COMPILE_FLAGS)
+    message(FATAL_ERROR "LIBCXX_COMPILE_FLAGS must be defined when using this function")
+  endif()
+  set(dest "" PARENT_SCOPE)
+  set(CLANG_COMMAND ${CMAKE_CXX_COMPILER} ${LIBCXX_COMPILE_FLAGS}
+      "--rtlib=compiler-rt" "--print-libgcc-file-name")
+  execute_process(
+      COMMAND ${CLANG_COMMAND}
+      RESULT_VARIABLE HAD_ERROR
+      OUTPUT_VARIABLE LIBRARY_FILE
+  )
+  string(STRIP "${LIBRARY_FILE}" LIBRARY_FILE)
+  get_filename_component(LIBRARY_DIR "${LIBRARY_FILE}" DIRECTORY)
+  if (NOT HAD_ERROR AND EXISTS "${LIBRARY_DIR}")
+    message(STATUS "Found compiler-rt directory: ${LIBRARY_DIR}")
+    set(${dest} "${LIBRARY_DIR}" PARENT_SCOPE)
+  else()
+    message(STATUS "Failed to find compiler-rt directory")
+  endif()
+endfunction()