Index: include/clang/Driver/CLCompatOptions.td
===================================================================
--- include/clang/Driver/CLCompatOptions.td
+++ include/clang/Driver/CLCompatOptions.td
@@ -138,6 +138,9 @@
 
 // Non-aliases:
 
+def _SLASH_arch : CLCompileJoined<"arch:">,
+  HelpText<"Set architecture for code generation">;
+
 def _SLASH_M_Group : OptionGroup<"</M group>">, Group<cl_compile_Group>;
 
 def _SLASH_EH : CLJoined<"EH">, HelpText<"Exception handling model">;
@@ -207,7 +210,6 @@
 // Unsupported:
 
 def _SLASH_AI : CLJoined<"AI">;
-def _SLASH_arch : CLJoined<"arch:">;
 def _SLASH_bigobj : CLFlag<"bigobj">;
 def _SLASH_clr : CLJoined<"clr">;
 def _SLASH_d2Zi_PLUS : CLFlag<"d2Zi+">;
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -1446,6 +1446,25 @@
       Features.push_back("+ssse3");
   }
 
+  // Set features according to the -arch flag on MSVC
+  if (Triple.isKnownWindowsMSVCEnvironment()) {
+    if (Arg *A = Args.getLastArg(options::OPT__SLASH_arch)) {
+      std::string Arch = A->getValue();
+      std::transform(Arch.begin(), Arch.end(), Arch.begin(), std::tolower);
+      // First, look for flags that are shared in x86 and x86-64.
+      if (Triple.getArch() == llvm::Triple::x86_64 ||
+          Triple.getArch() == llvm::Triple::x86) {
+        if (Arch == "avx" || Arch == "avx2")
+          Features.push_back(Args.MakeArgString("+" + Arch));
+      }
+      // Then, look for x86-specific flags.
+      if (Triple.getArch() == llvm::Triple::x86) {
+        if (Arch == "sse" || Arch == "sse2")
+          Features.push_back(Args.MakeArgString("+" + Arch));
+      }
+    }
+  }
+
   // Now add any that the user explicitly requested on the command line,
   // which may override the defaults.
   for (arg_iterator it = Args.filtered_begin(options::OPT_m_x86_Features_Group),
Index: test/Driver/cl-options.c
===================================================================
--- test/Driver/cl-options.c
+++ test/Driver/cl-options.c
@@ -198,7 +198,6 @@
 // (/Zs is for syntax-only)
 // RUN: %clang_cl /Zs \
 // RUN:     /AIfoo \
-// RUN:     /arch:sse2 \
 // RUN:     /clr:pure \
 // RUN:     /docname \
 // RUN:     /d2Zi+ \
Index: test/Driver/cl-x86-flags.c
===================================================================
--- test/Driver/cl-x86-flags.c
+++ test/Driver/cl-x86-flags.c
@@ -8,5 +8,39 @@
 // RUN:     -### -- 2>&1 %s | FileCheck -check-prefix=MFLAGS %s
 // MFLAGS-NOT: argument unused during compilation
 
+// -arch:IA32 is no-op.
+// RUN: %clang_cl -m32 -arch:IA32 -### -- 2>&1 %s | FileCheck -check-prefix=IA32 %s
+// IA32-NOT: -target-feature
+
+// RUN: %clang_cl -m32 -arch:SSE -### -- 2>&1 %s | FileCheck -check-prefix=SSE %s
+// SSE: -target-feature
+// SSE: +sse
+
+// RUN: %clang_cl -m32 -arch:SSE2 -### -- 2>&1 %s | FileCheck -check-prefix=SSE2 %s
+// SSE2: -target-feature
+// SSE2: +sse2
+
+// RUN: %clang_cl -m64 -arch:SSE -### -- 2>&1 %s | FileCheck -check-prefix=SSE64 %s
+// SSE64-NOT: -target-feature
+
+// RUN: %clang_cl -m64 -arch:SSE2 -### -- 2>&1 %s | FileCheck -check-prefix=SSE264 %s
+// SSE264-NOT: -target-feature
+
+// RUN: %clang_cl -m32 -arch:AVX -### -- 2>&1 %s | FileCheck -check-prefix=AVX %s
+// AVX: -target-feature
+// AVX: +avx
+
+// RUN: %clang_cl -m32 -arch:AVX2 -### -- 2>&1 %s | FileCheck -check-prefix=AVX2 %s
+// AVX2: -target-feature
+// AVX2: +avx2
+
+// RUN: %clang_cl -m64 -arch:AVX -### -- 2>&1 %s | FileCheck -check-prefix=AVX64 %s
+// AVX64: -target-feature
+// AVX64: +avx
+
+// RUN: %clang_cl -m64 -arch:AVX2 -### -- 2>&1 %s | FileCheck -check-prefix=AVX264 %s
+// AVX264: -target-feature
+// AVX264: +avx2
+
 void f() {
 }