Index: lib/tsan/CMakeLists.txt
===================================================================
--- lib/tsan/CMakeLists.txt
+++ lib/tsan/CMakeLists.txt
@@ -154,6 +154,14 @@
         LANGUAGE C)
    elseif(arch MATCHES "powerpc64|powerpc64le")
      set(TSAN_ASM_SOURCES rtl/tsan_rtl_ppc64.S)
+     # On PPC64, when using clang with sibling-call-optimization to build
+     # tsan library, sibling-call (tail-call) to PrintCurrentStackSlow breaks
+     # distance assumption between StackTrace::GetCurrentPc() and
+     # BufferedStackTrace::Unwind(), so we turn off sco to work around it.
+     # See https://llvm.org/bugs/show_bug.cgi?id=27280#c1
+     if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+       set(TSAN_RTL_CFLAGS ${TSAN_RTL_CFLAGS} -mllvm -disable-ppc-sco=true)
+     endif ()
      # Pass ASM file directly to the C++ compiler.
      set_source_files_properties(${TSAN_ASM_SOURCES} PROPERTIES
        LANGUAGE C)