diff --git a/clang/lib/Driver/ToolChains/Arch/AArch64.cpp b/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
--- a/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
@@ -260,7 +260,8 @@
         D, getAArch64TargetCPU(Args, Triple, A), Args, Features);
 
   if (!success)
-    D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
+    D.Diag(diag::err_drv_clang_unsupported)
+        << (WaMArch.size() ? "-march=" + WaMArch.str() : A->getAsString(Args));
 
   if (Args.getLastArg(options::OPT_mgeneral_regs_only)) {
     Features.push_back("-fp-armv8");
diff --git a/clang/test/Driver/aarch64-target-as-march.s b/clang/test/Driver/aarch64-target-as-march.s
--- a/clang/test/Driver/aarch64-target-as-march.s
+++ b/clang/test/Driver/aarch64-target-as-march.s
@@ -44,3 +44,12 @@
 // TARGET-FEATURE-3-NOT: "-target-feature" "+v8.4a"
 // TARGET-FEATURE-4: "-target-feature" "+v8.4a"
 // TARGET-FEATURE-4-NOT: "-target-feature" "+v8.3a"
+
+// Invalid -march settings
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Wa,-march=all %s 2>&1 | \
+// RUN: FileCheck --check-prefix=INVALID-ARCH-1 %s
+// RUN: %clang --target=aarch64-linux-gnueabi -### -c -Wa,-march=foobar %s 2>&1 | \
+// RUN: FileCheck --check-prefix=INVALID-ARCH-2 %s
+
+// INVALID-ARCH-1: error: the clang compiler does not support '-march=all'
+// INVALID-ARCH-2: error: the clang compiler does not support '-march=foobar'