diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -727,8 +727,15 @@
 include(config-ix)
 
 # By default, we target the host, but this can be overridden at CMake
-# invocation time.
-set(LLVM_DEFAULT_TARGET_TRIPLE "${LLVM_HOST_TRIPLE}" CACHE STRING
+# invocation time. Except on 64-bit AIX, where the system toolchain
+# expect 32-bit objects by default.
+if("${LLVM_HOST_TRIPLE}" MATCHES "^powerpc64-ibm-aix")
+  string(REGEX REPLACE "^powerpc64" "powerpc" LLVM_DEFAULT_TARGET_TRIPLE_default "${LLVM_HOST_TRIPLE}")
+else()
+  set(LLVM_DEFAULT_TARGET_TRIPLE_default "${LLVM_HOST_TRIPLE}")
+endif()
+
+set(LLVM_DEFAULT_TARGET_TRIPLE "${LLVM_DEFAULT_TARGET_TRIPLE_default}" CACHE STRING
   "Default target for which LLVM will generate code." )
 set(TARGET_TRIPLE "${LLVM_DEFAULT_TARGET_TRIPLE}")
 message(STATUS "LLVM host triple: ${LLVM_HOST_TRIPLE}")