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
@@ -25,6 +25,16 @@
   return Triple.isOSDarwin();
 }
 
+static bool isPreA12AppleCPU(StringRef CPU) {
+  return llvm::StringSwitch<bool>(CPU)
+      .Case("apple-a11", true)
+      .Case("apple-a10", true)
+      .Case("apple-a9", true)
+      .Case("apple-a8", true)
+      .Case("apple-a7", true)
+      .Default(false);
+};
+
 /// getAArch64TargetCPU - Get the (LLVM) name of the AArch64 cpu we are
 /// targeting. Set \p A to the Arg corresponding to the -mcpu argument if it is
 /// provided, or to nullptr otherwise.
@@ -40,7 +50,18 @@
   // Handle CPU name is 'native'.
   if (CPU == "native")
     return std::string(llvm::sys::getHostCPUName());
-  else if (CPU.size())
+
+  if (Triple.isTargetMachineMac() &&
+      Triple.getArch() == llvm::Triple::aarch64) {
+    // Honor -mcpu as long it doesn't specify an older CPU than "apple-a12".
+    if (CPU.size() && !isPreA12AppleCPU(CPU))
+      return CPU;
+
+    // Apple Silicon macs default to A12 CPUs.
+    return "apple-a12";
+  }
+
+  if (CPU.size())
     return CPU;
 
   // Make sure we pick the appropriate Apple CPU if -arch is used or when
diff --git a/clang/test/Driver/aarch64-mac-cpus.c b/clang/test/Driver/aarch64-mac-cpus.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Driver/aarch64-mac-cpus.c
@@ -0,0 +1,24 @@
+// arm64 Mac-based targets default to Apple A12.
+
+// RUN: %clang -target arm64-apple-macos             -### -c %s 2>&1 | FileCheck %s
+// RUN: %clang -target arm64-apple-ios-macabi        -### -c %s 2>&1 | FileCheck %s
+// RUN: %clang -target arm64-apple-ios-simulator     -### -c %s 2>&1 | FileCheck %s
+// RUN: %clang -target arm64-apple-watchos-simulator -### -c %s 2>&1 | FileCheck %s
+// RUN: %clang -target arm64-apple-tvos-simulator    -### -c %s 2>&1 | FileCheck %s
+
+// RUN: %clang -target arm64-apple-macos -arch arm64 -### -c %s 2>&1 | FileCheck %s
+
+// RUN: %clang -target arm64-apple-macos -mcpu=apple-a11 -### -c %s 2>&1 | FileCheck --check-prefix=INFER-A12 %s
+// RUN: %clang -target arm64-apple-macos -mcpu=apple-a10 -### -c %s 2>&1 | FileCheck --check-prefix=INFER-A12 %s
+// RUN: %clang -target arm64-apple-macos -mcpu=apple-a9  -### -c %s 2>&1 | FileCheck --check-prefix=INFER-A12 %s
+// RUN: %clang -target arm64-apple-macos -mcpu=apple-a8  -### -c %s 2>&1 | FileCheck --check-prefix=INFER-A12 %s
+// RUN: %clang -target arm64-apple-macos -mcpu=apple-a7  -### -c %s 2>&1 | FileCheck --check-prefix=INFER-A12 %s
+
+// RUN: %clang -target arm64-apple-macos -mcpu=apple-a13 -### -c %s 2>&1 | FileCheck --check-prefix=EXPLICT-A13 %s
+
+// CHECK: "-cc1"{{.*}} "-triple" "arm64{{.*}}" "-target-cpu" "apple-a12"
+// CHECK-SAME: "-target-feature" "+v8.3a"
+
+// INFER-A12: "-cc1"{{.*}} "-triple" "arm64{{.*}}" "-target-cpu" "apple-a12"
+
+// EXPLICT-A13: "-cc1"{{.*}} "-triple" "arm64{{.*}}" "-target-cpu" "apple-a13"
diff --git a/llvm/include/llvm/ADT/Triple.h b/llvm/include/llvm/ADT/Triple.h
--- a/llvm/include/llvm/ADT/Triple.h
+++ b/llvm/include/llvm/ADT/Triple.h
@@ -484,6 +484,12 @@
     return getEnvironment() == Triple::MacABI;
   }
 
+  /// Returns true for targets that run on a macOS machine.
+  bool isTargetMachineMac() const {
+    return isMacOSX() || (isOSDarwin() && (isSimulatorEnvironment() ||
+                                           isMacCatalystEnvironment()));
+  }
+
   bool isOSNetBSD() const {
     return getOS() == Triple::NetBSD;
   }