Index: cfe/trunk/include/clang/Driver/Options.td
===================================================================
--- cfe/trunk/include/clang/Driver/Options.td
+++ cfe/trunk/include/clang/Driver/Options.td
@@ -1311,6 +1311,7 @@
 def mabi_EQ : Joined<["-"], "mabi=">, Group<m_Group>;
 def miamcu : Flag<["-"], "miamcu">, Group<m_Group>, Flags<[DriverOption, CoreOption]>,
   HelpText<"Use Intel MCU ABI">;
+def mno_iamcu : Flag<["-"], "mno-iamcu">, Group<m_Group>, Flags<[DriverOption, CoreOption]>;
 def malign_functions_EQ : Joined<["-"], "malign-functions=">, Group<clang_ignored_m_Group>;
 def malign_loops_EQ : Joined<["-"], "malign-loops=">, Group<clang_ignored_m_Group>;
 def malign_jumps_EQ : Joined<["-"], "malign-jumps=">, Group<clang_ignored_m_Group>;
Index: cfe/trunk/lib/Driver/Driver.cpp
===================================================================
--- cfe/trunk/lib/Driver/Driver.cpp
+++ cfe/trunk/lib/Driver/Driver.cpp
@@ -280,8 +280,9 @@
   }
 
   // Enforce -static if -miamcu is present.
-  if (Args.hasArg(options::OPT_miamcu))
-    DAL->AddFlagArg(0, Opts->getOption(options::OPT_static));
+  if (Arg *Ar = Args.getLastArg(options::OPT_miamcu, options::OPT_mno_iamcu))
+    if (Ar->getOption().matches(options::OPT_miamcu))
+      DAL->AddFlagArg(0, Opts->getOption(options::OPT_static));
 
 // Add a default value of -mlinker-version=, if one was given and the user
 // didn't specify one.
@@ -375,22 +376,24 @@
   }
 
   // Handle -miamcu flag.
-  if (Args.hasArg(options::OPT_miamcu)) {
-    if (Target.get32BitArchVariant().getArch() != llvm::Triple::x86)
-      D.Diag(diag::err_drv_unsupported_opt_for_target) << "-miamcu"
-                                                       << Target.str();
-
-    if (A && !A->getOption().matches(options::OPT_m32))
-      D.Diag(diag::err_drv_argument_not_allowed_with)
-          << "-miamcu" << A->getBaseArg().getAsString(Args);
-
-    Target.setArch(llvm::Triple::x86);
-    Target.setArchName("i586");
-    Target.setEnvironment(llvm::Triple::UnknownEnvironment);
-    Target.setEnvironmentName("");
-    Target.setOS(llvm::Triple::ELFIAMCU);
-    Target.setVendor(llvm::Triple::UnknownVendor);
-    Target.setVendorName("intel");
+  if (Arg *Ar = Args.getLastArg(options::OPT_miamcu, options::OPT_mno_iamcu)) {
+    if (Ar->getOption().matches(options::OPT_miamcu)) {
+      if (Target.get32BitArchVariant().getArch() != llvm::Triple::x86)
+        D.Diag(diag::err_drv_unsupported_opt_for_target) << "-miamcu"
+                                                         << Target.str();
+
+      if (A && !A->getOption().matches(options::OPT_m32))
+        D.Diag(diag::err_drv_argument_not_allowed_with)
+            << "-miamcu" << A->getBaseArg().getAsString(Args);
+
+      Target.setArch(llvm::Triple::x86);
+      Target.setArchName("i586");
+      Target.setEnvironment(llvm::Triple::UnknownEnvironment);
+      Target.setEnvironmentName("");
+      Target.setOS(llvm::Triple::ELFIAMCU);
+      Target.setVendor(llvm::Triple::UnknownVendor);
+      Target.setVendorName("intel");
+    }
   }
 
   return Target;
Index: cfe/trunk/lib/Driver/Tools.cpp
===================================================================
--- cfe/trunk/lib/Driver/Tools.cpp
+++ cfe/trunk/lib/Driver/Tools.cpp
@@ -2243,10 +2243,12 @@
   }
 
   // Set flags to support MCU ABI.
-  if (Args.hasArg(options::OPT_miamcu)) {
-    CmdArgs.push_back("-mfloat-abi");
-    CmdArgs.push_back("soft");
-    CmdArgs.push_back("-mstack-alignment=4");
+  if (Arg *A = Args.getLastArg(options::OPT_miamcu, options::OPT_mno_iamcu)) {
+    if (A->getOption().matches(options::OPT_miamcu)) {
+      CmdArgs.push_back("-mfloat-abi");
+      CmdArgs.push_back("soft");
+      CmdArgs.push_back("-mstack-alignment=4");
+    }
   }
 }
 
Index: cfe/trunk/test/Driver/miamcu-opt.c
===================================================================
--- cfe/trunk/test/Driver/miamcu-opt.c
+++ cfe/trunk/test/Driver/miamcu-opt.c
@@ -4,9 +4,11 @@
 // RUN: %clang -miamcu -no-canonical-prefixes %s -### -o %t.o 2>&1 | FileCheck %s
 // RUN: %clang -miamcu -no-canonical-prefixes -m32 %s -### -o %t.o 2>&1 | FileCheck %s
 // RUN: %clang -miamcu -no-canonical-prefixes -target x86_64-unknown-linux-gnu %s -### -o %t.o 2>&1 | FileCheck %s
+// RUN: %clang -mno-iamcu -miamcu -no-canonical-prefixes %s -### -o %t.o 2>&1 | FileCheck %s
 // RUN: %clang -miamcu -no-canonical-prefixes -m64 %s -### -o %t.o 2>&1 | FileCheck %s -check-prefix=M64
 // RUN: %clang -miamcu -no-canonical-prefixes -dynamic %s -### -o %t.o 2>&1 | FileCheck %s -check-prefix=DYNAMIC
 // RUN: %clang -miamcu -no-canonical-prefixes  -target armv8-eabi %s -### -o %t.o 2>&1 | FileCheck %s -check-prefix=NOT-X86
+// RUN: %clang -miamcu -mno-iamcu -no-canonical-prefixes -target x86_64-unknown-linux-gnu %s -### -o %t.o 2>&1 | FileCheck %s -check-prefix=MNOIAMCU
 
 // M64: error: invalid argument '-miamcu' not allowed with '-m64'
 
@@ -14,6 +16,8 @@
 
 // NOT-X86: error: unsupported option '-miamcu' for target 'armv8---eabi'
 
+// MNOIAMCU-NOT: "-triple" "i586-intel-elfiamcu"
+
 // CHECK: "{{.*}}clang{{.*}}" "-cc1"
 // CHECK: "-triple" "i586-intel-elfiamcu"
 // CHECK: "-static-define"