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
@@ -221,7 +221,8 @@
       elseif(${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
         set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                      LINK_FLAGS " -Wl,-z -Wl,discard-unused=sections")
-      elseif(NOT WIN32 AND NOT LLVM_LINKER_IS_GOLD AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "OpenBSD")
+      elseif(NOT WIN32 AND NOT LLVM_LINKER_IS_GOLD AND
+             NOT ${CMAKE_SYSTEM_NAME} MATCHES "OpenBSD|AIX")
         # Object files are compiled with -ffunction-data-sections.
         # Versions of bfd ld < 2.23.1 have a bug in --gc-sections that breaks
         # tools that use plugins. Always pass --gc-sections once we require
@@ -229,6 +230,11 @@
         set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                      LINK_FLAGS " -Wl,--gc-sections")
       endif()
+    else() #LLVM_NO_DEAD_STRIP
+      if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+        set_property(TARGET ${target_name} APPEND_STRING PROPERTY
+                     LINK_FLAGS " -Wl,-bnogc")
+      endif()
     endif()
   endif()
 endfunction(add_link_opts)
diff --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -134,12 +134,32 @@
   set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -Wl,-flat_namespace -Wl,-undefined -Wl,suppress")
 endif()
 
+if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+  if(NOT LLVM_BUILD_32_BITS)
+    if (CMAKE_CXX_COMPILER_ID MATCHES "XL")
+      append("-q64" CMAKE_CXX_FLAGS CMAKE_C_FLAGS)
+    else()
+      append("-maix64" CMAKE_CXX_FLAGS CMAKE_C_FLAGS)
+    endif()
+    set(CMAKE_CXX_ARCHIVE_CREATE "<CMAKE_AR> -X64 qc <TARGET> <LINK_FLAGS> <OBJECTS>")
+    set(CMAKE_CXX_ARCHIVE_APPEND "<CMAKE_AR> -X64 q  <TARGET> <LINK_FLAGS> <OBJECTS>")
+    set(CMAKE_C_ARCHIVE_FINISH "<CMAKE_RANLIB> -X64 <TARGET>")
+    set(CMAKE_CXX_ARCHIVE_FINISH "<CMAKE_RANLIB> -X64 <TARGET>")
+  endif()
+  # -fPIC does not enable the large code model for GCC on AIX but does for XL.
+  if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    append("-mcmodel=large" CMAKE_CXX_FLAGS CMAKE_C_FLAGS)
+  elseif(CMAKE_CXX_COMPILER_ID MATCHES "XL")
+    # XL generates a small number of relocations not of the large model, -bbigtoc is needed.
+    append("-Wl,-bbigtoc"
+           CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
+  endif()
+endif()
+
 # Pass -Wl,-z,defs. This makes sure all symbols are defined. Otherwise a DSO
 # build might work on ELF but fail on MachO/COFF.
-if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin" OR WIN32 OR CYGWIN OR
-        ${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD" OR
-	${CMAKE_SYSTEM_NAME} MATCHES "OpenBSD" OR
-	${CMAKE_SYSTEM_NAME} MATCHES "DragonFly") AND
+if(NOT (${CMAKE_SYSTEM_NAME} MATCHES "Darwin|FreeBSD|OpenBSD|DragonFly|AIX" OR
+        WIN32 OR CYGWIN) AND
    NOT LLVM_USE_SANITIZER)
   set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-z,defs")
 endif()
@@ -219,8 +239,9 @@
   endif()
 endif()
 
-if(NOT WIN32 AND NOT CYGWIN)
+if(NOT WIN32 AND NOT CYGWIN AND NOT (${CMAKE_SYSTEM_NAME} MATCHES "AIX" AND CMAKE_CXX_COMPILER_ID STREQUAL "GNU"))
   # MinGW warns if -fvisibility-inlines-hidden is used.
+  # GCC on AIX warns if -fvisibility-inlines-hidden is used.
   check_cxx_compiler_flag("-fvisibility-inlines-hidden" SUPPORTS_FVISIBILITY_INLINES_HIDDEN_FLAG)
   append_if(SUPPORTS_FVISIBILITY_INLINES_HIDDEN_FLAG "-fvisibility-inlines-hidden" CMAKE_CXX_FLAGS)
 endif()
diff --git a/llvm/include/llvm/Config/abi-breaking.h.cmake b/llvm/include/llvm/Config/abi-breaking.h.cmake
--- a/llvm/include/llvm/Config/abi-breaking.h.cmake
+++ b/llvm/include/llvm/Config/abi-breaking.h.cmake
@@ -34,15 +34,27 @@
 #elif defined(_WIN32) || defined(__CYGWIN__) // Win32 w/o #pragma detect_mismatch
 // FIXME: Implement checks without weak.
 #elif defined(__cplusplus)
+#if !(defined(_AIX) && defined(__GNU__))
+#define LLVM_HIDDEN_VISIBILITY __attribute__ ((visibility("hidden")))
+#else
+// GCC on AIX does not support visibility attributes. Symbols are not
+// exported by default on AIX.
+#define LLVM_HIDDEN_VISIBILITY
+#endif
 namespace llvm {
 #if LLVM_ENABLE_ABI_BREAKING_CHECKS
 extern int EnableABIBreakingChecks;
-__attribute__((weak, visibility ("hidden"))) int *VerifyEnableABIBreakingChecks = &EnableABIBreakingChecks;
+LLVM_HIDDEN_VISIBILITY
+__attribute__((weak)) int *VerifyEnableABIBreakingChecks =
+    &EnableABIBreakingChecks;
 #else
 extern int DisableABIBreakingChecks;
-__attribute__((weak, visibility ("hidden"))) int *VerifyDisableABIBreakingChecks = &DisableABIBreakingChecks;
+LLVM_HIDDEN_VISIBILITY
+__attribute__((weak)) int *VerifyDisableABIBreakingChecks =
+    &DisableABIBreakingChecks;
 #endif
 }
+#undef LLVM_HIDDEN_VISIBILITY
 #endif // _MSC_VER
 
 #endif // LLVM_DISABLE_ABI_BREAKING_CHECKS_ENFORCING