diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -2486,6 +2486,11 @@
           options::OPT_fvisibility_inlines_hidden_static_local_var,
           options::OPT_fno_visibility_inlines_hidden_static_local_var))
     CC1Args.push_back("-fvisibility-inlines-hidden-static-local-var");
+
+  // If no vector library is specified by the user, default to
+  // Darwin_libsystem_m for iOS based targets.
+  if (isTargetIOSBased() && !DriverArgs.hasArgNoClaim(options::OPT_fveclib))
+    CC1Args.push_back("-fveclib=Darwin_libsystem_m");
 }
 
 DerivedArgList *
diff --git a/clang/test/Driver/darwin-veclib-default.c b/clang/test/Driver/darwin-veclib-default.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Driver/darwin-veclib-default.c
@@ -0,0 +1,24 @@
+// Check default vector library options on Darwin platforms.
+
+// RUN: %clang -target x86_64-apple-darwin -S -### %s -arch x86_64 2>&1 | \
+// RUN:   FileCheck --check-prefix CHECK-MACOS %s
+
+// CHECK-MACOS: "-cc1"
+// CHECK-MACOS-NOT: -fveclib
+
+// RUN: %clang -target arm64-apple-darwinos -S -### %s -arch arm64 2>&1 | \
+// RUN:   FileCheck --check-prefix CHECK-IOS-DEFAULT %s
+
+// RUN: %clang -target arm64-apple-ios -S -### %s -arch arm64 2>&1 | \
+// RUN:   FileCheck --check-prefix CHECK-IOS-DEFAULT %s
+
+// CHECK-IOS-DEFAULT: "-cc1"
+// CHECK-IOS-DEFAULT: "-fveclib=Darwin_libsystem_m"
+
+// RUN: %clang -target arm64-apple-ios -S -### %s -arch arm64 -fveclib=Accelerate 2>&1 | \
+// RUN:   FileCheck --check-prefix CHECK-IOS-ACCELERATE %s
+
+// CHECK-IOS-ACCELERATE: "-cc1"
+// CHECK-IOS-ACCELERATE-NOT: "-fveclib=Darwin_libsystem_m"
+// CHECK-IOS-ACCELERATE: "-fveclib=Accelerate"
+// CHECK-IOS-ACCELERATE-NOT: "-fveclib=Darwin_libsystem_m"