diff --git a/clang/lib/Driver/ToolChains/AIX.cpp b/clang/lib/Driver/ToolChains/AIX.cpp
--- a/clang/lib/Driver/ToolChains/AIX.cpp
+++ b/clang/lib/Driver/ToolChains/AIX.cpp
@@ -44,12 +44,6 @@
     CmdArgs.push_back("-a64");
   }
 
-  // Accept an undefined symbol as an extern so that an error message is not
-  // displayed. Otherwise, undefined symbols are flagged with error messages.
-  // FIXME: This should be removed when the assembly generation from the
-  // compiler is able to write externs properly.
-  CmdArgs.push_back("-u");
-
   // Accept any mixture of instructions.
   // On Power for AIX and Linux, this behaviour matches that of GCC for both the
   // user-provided assembler source case and the compiler-produced assembler
diff --git a/clang/test/Driver/aix-as.c b/clang/test/Driver/aix-as.c
--- a/clang/test/Driver/aix-as.c
+++ b/clang/test/Driver/aix-as.c
@@ -9,7 +9,6 @@
 // CHECK-AS32: {{.*}}clang{{(.exe)?}}" "-cc1" "-triple" "powerpc-ibm-aix7.1.0.0"
 // CHECK-AS32: "{{.*}}as{{(.exe)?}}" 
 // CHECK-AS32: "-a32" 
-// CHECK-AS32: "-u" 
 // CHECK-AS32: "-many" 
 
 // Check powerpc64-ibm-aix7.1.0.0, 64-bit.
@@ -20,7 +19,6 @@
 // CHECK-AS64: {{.*}}clang{{(.exe)?}}" "-cc1" "-triple" "powerpc64-ibm-aix7.1.0.0"
 // CHECK-AS64: "{{.*}}as{{(.exe)?}}" 
 // CHECK-AS64: "-a64" 
-// CHECK-AS64: "-u" 
 // CHECK-AS64: "-many"
 
 // Check powerpc-ibm-aix7.1.0.0, 32-bit. -Xassembler <arg> option. 
@@ -32,7 +30,6 @@
 // CHECK-AS32-Xassembler: {{.*}}clang{{(.exe)?}}" "-cc1" "-triple" "powerpc-ibm-aix7.1.0.0"
 // CHECK-AS32-Xassembler: "{{.*}}as{{(.exe)?}}" 
 // CHECK-AS32-Xassembler: "-a32" 
-// CHECK-AS32-Xassembler: "-u" 
 // CHECK-AS32-Xassembler: "-many"
 // CHECK-AS32-Xassembler: "-w"
 
@@ -45,7 +42,6 @@
 // CHECK-AS64-Wa: {{.*}}clang{{(.exe)?}}" "-cc1" "-triple" "powerpc64-ibm-aix7.1.0.0"
 // CHECK-AS64-Wa: "{{.*}}as{{(.exe)?}}" 
 // CHECK-AS64-Wa: "-a64" 
-// CHECK-AS64-Wa: "-u" 
 // CHECK-AS64-Wa: "-many"
 // CHECK-AS64-Wa: "-v"
 // CHECK-AS64-Wa: "-w"
@@ -60,13 +56,10 @@
 // CHECK-AS32-MultiInput-NOT: warning:
 // CHECK-AS32-MultiInput: "{{.*}}as{{(.exe)?}}"
 // CHECK-AS32-MultiInput: "-a32"
-// CHECK-AS32-MultiInput: "-u"
 // CHECK-AS32-MultiInput: "-many"
 // CHECK-AS32-MultiInput: "{{.*}}as{{(.exe)?}}"
 // CHECK-AS32-MultiInput: "-a32"
-// CHECK-AS32-MultiInput: "-u"
 // CHECK-AS32-MultiInput: "-many"
 // CHECK-AS32-MultiInput: "{{.*}}as{{(.exe)?}}"
 // CHECK-AS32-MultiInput: "-a32"
-// CHECK-AS32-MultiInput: "-u"
 // CHECK-AS32-MultiInput: "-many"