Index: cfe/trunk/include/clang/Driver/Options.td
===================================================================
--- cfe/trunk/include/clang/Driver/Options.td
+++ cfe/trunk/include/clang/Driver/Options.td
@@ -1023,6 +1023,7 @@
 def m3dnowa : Flag<["-"], "m3dnowa">, Group<m_x86_Features_Group>;
 def m3dnow : Flag<["-"], "m3dnow">, Group<m_x86_Features_Group>;
 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 march_EQ : Joined<["-"], "march=">, Group<m_Group>;
 def masm_EQ : Joined<["-"], "masm=">, Group<m_Group>, Flags<[DriverOption]>;
Index: cfe/trunk/lib/Driver/Driver.cpp
===================================================================
--- cfe/trunk/lib/Driver/Driver.cpp
+++ cfe/trunk/lib/Driver/Driver.cpp
@@ -1913,14 +1913,18 @@
       Target.getOS() == llvm::Triple::Minix)
     return Target;
 
-  // Handle pseudo-target flags '-m64', '-m32' and '-m16'.
-  if (Arg *A = Args.getLastArg(options::OPT_m64, options::OPT_m32,
-                               options::OPT_m16)) {
+  // 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)) {
     llvm::Triple::ArchType AT = llvm::Triple::UnknownArch;
 
     if (A->getOption().matches(options::OPT_m64))
       AT = Target.get64BitArchVariant().getArch();
-    else if (A->getOption().matches(options::OPT_m32))
+    else if (A->getOption().matches(options::OPT_mx32) &&
+             Target.get64BitArchVariant().getArch() == llvm::Triple::x86_64) {
+      AT = llvm::Triple::x86_64;
+      Target.setEnvironment(llvm::Triple::GNUX32);
+    } else if (A->getOption().matches(options::OPT_m32))
       AT = Target.get32BitArchVariant().getArch();
     else if (A->getOption().matches(options::OPT_m16) &&
              Target.get32BitArchVariant().getArch() == llvm::Triple::x86) {
Index: cfe/trunk/test/Driver/linux-ld.c
===================================================================
--- cfe/trunk/test/Driver/linux-ld.c
+++ cfe/trunk/test/Driver/linux-ld.c
@@ -216,6 +216,40 @@
 // CHECK-X32: "-L[[SYSROOT]]/usr/lib"
 //
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+// RUN:     --target=x86_64-unknown-linux -mx32 \
+// RUN:     --sysroot=%S/Inputs/multilib_64bit_linux_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-64-TO-X32 %s
+// CHECK-64-TO-X32: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
+// CHECK-64-TO-X32: "{{.*}}/usr/lib/gcc/x86_64-unknown-linux/4.6.0/x32{{/|\\\\}}crtbegin.o"
+// CHECK-64-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/x32"
+// CHECK-64-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../../../x86_64-unknown-linux/lib/../libx32"
+// CHECK-64-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../../../libx32"
+// CHECK-64-TO-X32: "-L[[SYSROOT]]/lib/../libx32"
+// CHECK-64-TO-X32: "-L[[SYSROOT]]/usr/lib/../libx32"
+// CHECK-64-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0"
+// CHECK-64-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../../../x86_64-unknown-linux/lib"
+// CHECK-64-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../.."
+// CHECK-64-TO-X32: "-L[[SYSROOT]]/lib"
+// CHECK-64-TO-X32: "-L[[SYSROOT]]/usr/lib"
+//
+// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+// RUN:     --target=i386-unknown-linux -mx32 \
+// RUN:     --sysroot=%S/Inputs/multilib_64bit_linux_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-32-TO-X32 %s
+// CHECK-32-TO-X32: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
+// CHECK-32-TO-X32: "{{.*}}/usr/lib/gcc/x86_64-unknown-linux/4.6.0/x32{{/|\\\\}}crtbegin.o"
+// CHECK-32-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/x32"
+// CHECK-32-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../../../x86_64-unknown-linux/lib/../libx32"
+// CHECK-32-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../../../libx32"
+// CHECK-32-TO-X32: "-L[[SYSROOT]]/lib/../libx32"
+// CHECK-32-TO-X32: "-L[[SYSROOT]]/usr/lib/../libx32"
+// CHECK-32-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0"
+// CHECK-32-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../../../x86_64-unknown-linux/lib"
+// CHECK-32-TO-X32: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../.."
+// CHECK-32-TO-X32: "-L[[SYSROOT]]/lib"
+// CHECK-32-TO-X32: "-L[[SYSROOT]]/usr/lib"
+//
+// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=x86_64-unknown-linux -m32 \
 // RUN:     --gcc-toolchain=%S/Inputs/multilib_64bit_linux_tree/usr \
 // RUN:     --sysroot=%S/Inputs/multilib_32bit_linux_tree \