diff --git a/clang/lib/Driver/ToolChains/Arch/ARM.cpp b/clang/lib/Driver/ToolChains/Arch/ARM.cpp
--- a/clang/lib/Driver/ToolChains/Arch/ARM.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/ARM.cpp
@@ -524,6 +524,10 @@
         }
       }
     }
+
+    // Accept but warn.
+    if (Arg *A = Args.getLastArgNoClaim(options::OPT_mabi_EQ))
+      A->ignoreTargetSpecific();
   }
 
   if (getReadTPMode(D, Args, Triple, ForAS) == ReadTPMode::TPIDRURW)
diff --git a/clang/test/Driver/arm-abi.c b/clang/test/Driver/arm-abi.c
--- a/clang/test/Driver/arm-abi.c
+++ b/clang/test/Driver/arm-abi.c
@@ -61,3 +61,8 @@
 // CHECK-APCS-GNU: "-target-abi" "apcs-gnu"
 // CHECK-AAPCS: "-target-abi" "aapcs"
 // CHECK-AAPCS-LINUX: "-target-abi" "aapcs-linux"
+
+// RUN: %clang --target=arm---gnueabi -mabi=aapcs -x assembler %s -### -o /dev/null 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-ASM %s
+
+// CHECK-ASM: warning: argument unused during compilation: '-mabi={{.*}}'