Index: cfe/trunk/include/clang/Driver/Options.td
===================================================================
--- cfe/trunk/include/clang/Driver/Options.td
+++ cfe/trunk/include/clang/Driver/Options.td
@@ -1292,6 +1292,8 @@
 def m64 : Flag<["-"], "m64">, Group<m_Group>, Flags<[DriverOption, CoreOption]>;
 def mx32 : Flag<["-"], "mx32">, Group<m_Group>, Flags<[DriverOption, CoreOption]>;
 def mabi_EQ : Joined<["-"], "mabi=">, Group<m_Group>;
+def miamcu : Flag<["-"], "miamcu">, Group<m_Group>, Flags<[DriverOption, CoreOption]>,
+  HelpText<"Use Intel MCU ABI">;
 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
@@ -278,6 +278,10 @@
     DAL->append(A);
   }
 
+  // Enforce -static if -miamcu is present.
+  if (Args.hasArg(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.
 #if defined(HOST_LINK_VERSION)
@@ -296,7 +300,8 @@
 ///
 /// This routine provides the logic to compute a target triple from various
 /// args passed to the driver and the default triple string.
-static llvm::Triple computeTargetTriple(StringRef DefaultTargetTriple,
+static llvm::Triple computeTargetTriple(const Driver &D,
+                                        StringRef DefaultTargetTriple,
                                         const ArgList &Args,
                                         StringRef DarwinArchName = "") {
   // FIXME: Already done in Compilation *Driver::BuildCompilation
@@ -341,8 +346,9 @@
     return Target;
 
   // Handle pseudo-target flags '-m64', '-mx32', '-m32' and '-m16'.
-  if (Arg *A = Args.getLastArg(options::OPT_m64, options::OPT_mx32,
-                               options::OPT_m32, options::OPT_m16)) {
+  Arg *A = Args.getLastArg(options::OPT_m64, options::OPT_mx32,
+                           options::OPT_m32, options::OPT_m16);
+  if (A) {
     llvm::Triple::ArchType AT = llvm::Triple::UnknownArch;
 
     if (A->getOption().matches(options::OPT_m64)) {
@@ -367,6 +373,25 @@
       Target.setArch(AT);
   }
 
+  // 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");
+  }
+
   return Target;
 }
 
@@ -501,8 +526,8 @@
   DerivedArgList *TranslatedArgs = TranslateInputArgs(*UArgs);
 
   // Owned by the host.
-  const ToolChain &TC =
-      getToolChain(*UArgs, computeTargetTriple(DefaultTargetTriple, *UArgs));
+  const ToolChain &TC = getToolChain(
+      *UArgs, computeTargetTriple(*this, DefaultTargetTriple, *UArgs));
 
   // The compilation takes ownership of Args.
   Compilation *C = new Compilation(*this, TC, UArgs.release(), TranslatedArgs);
@@ -1981,9 +2006,9 @@
     const char *ArchName = BAA->getArchName();
 
     if (ArchName)
-      TC = &getToolChain(
-          C.getArgs(),
-          computeTargetTriple(DefaultTargetTriple, C.getArgs(), ArchName));
+      TC = &getToolChain(C.getArgs(),
+                         computeTargetTriple(*this, DefaultTargetTriple,
+                                             C.getArgs(), ArchName));
     else
       TC = &C.getDefaultToolChain();
 
Index: cfe/trunk/lib/Driver/Tools.cpp
===================================================================
--- cfe/trunk/lib/Driver/Tools.cpp
+++ cfe/trunk/lib/Driver/Tools.cpp
@@ -2137,6 +2137,13 @@
           << A->getOption().getName() << Value;
     }
   }
+
+  // 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");
+  }
 }
 
 void Clang::AddHexagonTargetArgs(const ArgList &Args,
Index: cfe/trunk/test/Driver/miamcu-opt.c
===================================================================
--- cfe/trunk/test/Driver/miamcu-opt.c
+++ cfe/trunk/test/Driver/miamcu-opt.c
@@ -0,0 +1,21 @@
+// RUN: %clang -miamcu %s -### -o %t.o 2>&1 | FileCheck %s
+// RUN: %clang -miamcu -m32 %s -### -o %t.o 2>&1 | FileCheck %s
+// RUN: %clang -miamcu -target x86_64-unknown-linux-gnu %s -### -o %t.o 2>&1 | FileCheck %s
+// RUN: %clang -miamcu -m64 %s -### -o %t.o 2>&1 | FileCheck %s -check-prefix=M64
+// RUN: %clang -miamcu -dynamic %s -### -o %t.o 2>&1 | FileCheck %s -check-prefix=DYNAMIC
+// RUN: %clang -miamcu -target armv8-eabi %s -### -o %t.o 2>&1 | FileCheck %s -check-prefix=NOT-X86
+
+// M64: error: invalid argument '-miamcu' not allowed with '-m64'
+
+// DYNAMIC: error: invalid argument '-dynamic' not allowed with '-static'
+
+// NOT-X86: error: unsupported option '-miamcu' for target 'armv8---eabi'
+
+// CHECK: "-cc1"
+// CHECK: "-triple" "i586-intel-elfiamcu"
+// CHECK: "-static-define"
+// CHECK: "-mfloat-abi" "soft"
+// CHECK: "-mstack-alignment=4"
+
+// CHECK: bin/gcc
+// CHECK: "-static"