Index: lib/Driver/Tools.h
===================================================================
--- lib/Driver/Tools.h
+++ lib/Driver/Tools.h
@@ -126,6 +126,8 @@
       : Tool("clang::as", "clang integrated assembler", TC, RF_Full) {}
   void AddMIPSTargetArgs(const llvm::opt::ArgList &Args,
                          llvm::opt::ArgStringList &CmdArgs) const;
+  void AddX86TargetArgs(const llvm::opt::ArgList &Args,
+                        llvm::opt::ArgStringList &CmdArgs) const;
   bool hasGoodDiagnostics() const override { return true; }
   bool hasIntegratedAssembler() const override { return false; }
   bool hasIntegratedCPP() const override { return false; }
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -6375,6 +6375,20 @@
   CmdArgs.push_back(ABIName.data());
 }
 
+void ClangAs::AddX86TargetArgs(const ArgList &Args,
+                                ArgStringList &CmdArgs) const {
+  if (Arg *A = Args.getLastArg(options::OPT_masm_EQ)) {
+    StringRef Value = A->getValue();
+    if (Value == "intel" || Value == "att") {
+      CmdArgs.push_back("-mllvm");
+      CmdArgs.push_back(Args.MakeArgString("-x86-asm-syntax=" + Value));
+    } else {
+      getToolChain().getDriver().Diag(diag::err_drv_unsupported_option_argument)
+          << A->getOption().getName() << Value;
+    }
+  }
+}
+
 void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
                            const InputInfo &Output, const InputInfoList &Inputs,
                            const ArgList &Args,
@@ -6522,6 +6536,11 @@
   case llvm::Triple::mips64el:
     AddMIPSTargetArgs(Args, CmdArgs);
     break;
+    
+  case llvm::Triple::x86:
+  case llvm::Triple::x86_64:
+    AddX86TargetArgs(Args, CmdArgs);
+    break;
   }
 
   // Consume all the warning flags. Usually this would be handled more
Index: test/Driver/masm.s
===================================================================
--- test/Driver/masm.s
+++ test/Driver/masm.s
@@ -0,0 +1,11 @@
+// RUN: %clang -target i386-unknown-linux -masm=intel -c %s -### 2>&1 | FileCheck --check-prefix=CHECK-INTEL %s
+// RUN: %clang -target i386-unknown-linux -masm=att -c %s -### 2>&1 | FileCheck --check-prefix=CHECK-ATT %s
+// RUN: %clang -target i386-unknown-linux -c -masm=somerequired %s -### 2>&1 | FileCheck --check-prefix=CHECK-SOMEREQUIRED %s
+// RUN: %clang -target arm-unknown-eabi -c -masm=intel %s -### 2>&1 | FileCheck --check-prefix=CHECK-ARM %s
+
+// CHECK-INTEL: -x86-asm-syntax=intel
+// CHECK-ATT: -x86-asm-syntax=att
+// CHECK-SOMEREQUIRED: error: unsupported argument 'somerequired' to option 'masm='
+// CHECK-ARM: warning: argument unused during compilation: '-masm=intel'
+.text
+mov    al, 0