Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -1033,6 +1033,9 @@
 def finline_hint_functions: Flag<["-"], "finline-hint-functions">, Group<f_clang_Group>, Flags<[CC1Option]>,
   HelpText<"Inline functions which are (explicitly or implicitly) marked inline">;
 def finline : Flag<["-"], "finline">, Group<clang_ignored_f_Group>;
+def fexperimental_isel : Flag<["-"], "fexperimental-isel">,
+  Group<f_clang_Group>, Flags<[CC1Option]>,
+  HelpText<"Enables the experimental global instruction selector">;
 def fexperimental_new_pass_manager : Flag<["-"], "fexperimental-new-pass-manager">,
   Group<f_clang_Group>, Flags<[CC1Option]>,
   HelpText<"Enables an experimental new pass manager in LLVM.">;
@@ -1244,6 +1247,9 @@
 def fno_gnu_keywords : Flag<["-"], "fno-gnu-keywords">, Group<f_Group>, Flags<[CC1Option]>;
 def fno_inline_functions : Flag<["-"], "fno-inline-functions">, Group<f_clang_Group>, Flags<[CC1Option]>;
 def fno_inline : Flag<["-"], "fno-inline">, Group<f_clang_Group>, Flags<[CC1Option]>;
+def fno_experimental_isel : Flag<["-"], "fno-experimental-isel">,
+  Group<f_clang_Group>, Flags<[CC1Option]>,
+  HelpText<"Disables the experimental global instruction selector">;
 def fno_experimental_new_pass_manager : Flag<["-"], "fno-experimental-new-pass-manager">,
   Group<f_clang_Group>, Flags<[CC1Option]>,
   HelpText<"Disables an experimental new pass manager in LLVM.">;
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -4690,6 +4690,15 @@
     CmdArgs.push_back("-fwhole-program-vtables");
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_fexperimental_isel,
+                               options::OPT_fno_experimental_isel)) {
+    CmdArgs.push_back("-mllvm");
+    if (A->getOption().matches(options::OPT_fexperimental_isel))
+      CmdArgs.push_back("-global-isel=1");
+    else
+      CmdArgs.push_back("-global-isel=0");
+  }
+
   // Finally add the compile command to the compilation.
   if (Args.hasArg(options::OPT__SLASH_fallback) &&
       Output.getType() == types::TY_Object &&
Index: test/Driver/global-isel.c
===================================================================
--- /dev/null
+++ test/Driver/global-isel.c
@@ -0,0 +1,5 @@
+// RUN: %clang -fexperimental-isel -S -### %s 2>&1 | FileCheck -check-prefix=ENABLED %s
+// RUN: %clang -fno-experimental-isel -S -### %s 2>&1 | FileCheck -check-prefix=DISABLED %s
+
+// ENABLED: "-mllvm" "-global-isel=1"
+// DISABLED: "-mllvm" "-global-isel=0"