diff --git a/clang/tools/clang-shlib/CMakeLists.txt b/clang/tools/clang-shlib/CMakeLists.txt
--- a/clang/tools/clang-shlib/CMakeLists.txt
+++ b/clang/tools/clang-shlib/CMakeLists.txt
@@ -1,3 +1,8 @@
+# In the main branch, LLVM_ABI_REVISION should always be 0.  In the release
+# branches, this should be incremented before each release candidate every
+# time the ABI of libclang-cpp.so changes.
+set(LLVM_ABI_REVISION 0)
+
 # Building libclang-cpp.so fails if LLVM_ENABLE_PIC=Off
 if (NOT LLVM_ENABLE_PIC)
   return()
diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -586,11 +586,14 @@
     # Set SOVERSION on shared libraries that lack explicit SONAME
     # specifier, on *nix systems that are not Darwin.
     if(UNIX AND NOT APPLE AND NOT ARG_SONAME)
+      if (NOT LLVM_ABI_REVISION)
+        set(LLVM_ABI_REVISION 0)
+      endif()
       set_target_properties(${name}
         PROPERTIES
         # Since 4.0.0, the ABI version is indicated by the major version
-        SOVERSION ${LLVM_VERSION_MAJOR}${LLVM_VERSION_SUFFIX}
-        VERSION ${LLVM_VERSION_MAJOR}${LLVM_VERSION_SUFFIX})
+	SOVERSION ${LLVM_VERSION_MAJOR}.${LLVM_ABI_REVISION}
+	VERSION ${LLVM_VERSION_MAJOR}.${LLVM_ABI_REVISION})
     endif()
   endif()
 
diff --git a/llvm/tools/llvm-shlib/CMakeLists.txt b/llvm/tools/llvm-shlib/CMakeLists.txt
--- a/llvm/tools/llvm-shlib/CMakeLists.txt
+++ b/llvm/tools/llvm-shlib/CMakeLists.txt
@@ -2,6 +2,11 @@
 # library is enabled by setting LLVM_BUILD_LLVM_DYLIB=yes on the CMake
 # commandline. By default the shared library only exports the LLVM C API.
 
+# In the main branch, LLVM_ABI_REVISION should always be 0.  In the release
+# branches, this should be incremented before each release candidate every
+# time the ABI of libLLVM.so changes.
+set(LLVM_ABI_REVISION 0)
+
 set(SOURCES
   libllvm.cpp
   )
@@ -67,6 +72,10 @@
     set_property(TARGET LLVM APPEND_STRING PROPERTY
                 LINK_FLAGS
                 " -compatibility_version 1 -current_version ${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}")
+  else()
+    set_target_properties(LLVM
+      PROPERTIES
+      SOVERSION ${LLVM_ABI_REVISION})
   endif()
 
   if(TARGET libLLVMExports)