diff --git a/i/clang/lib/Driver/ToolChains/Arch/X86.cpp b/clang/lib/Driver/ToolChains/Arch/X86.cpp
--- a/i/clang/lib/Driver/ToolChains/Arch/X86.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/X86.cpp
@@ -73,12 +73,15 @@
   if (Triple.isOSDarwin()) {
     if (Triple.getArchName() == "x86_64h")
       return "core-avx2";
-    // macosx10.12 drops support for all pre-Penryn Macs.
-    // Simulators can still run on 10.11 though, like Xcode.
-    if (Triple.isMacOSX() && !Triple.isOSVersionLT(10, 12))
-      return "penryn";
     // The oldest x86_64 Macs have core2/Merom; the oldest x86 Macs have Yonah.
-    return Is64Bit ? "core2" : "yonah";
+    // The simulators (i.e. Darwin but not macOS) can still run on older Macs.
+    // macosx10.12 requires Penryn.
+    if (!Triple.isMacOSX() || Triple.isOSVersionLT(10, 12))
+      return Is64Bit ? "core2" : "yonah";
+    // macosx10.14 requires Ivy Bridge.
+    if (Triple.isOSVersionLT(10, 14))
+      return "penryn";
+    return "ivybridge";
   }
 
   // Set up default CPU name for PS4 compilers.