Index: lib/Driver/ToolChains/Arch/X86.cpp
===================================================================
--- lib/Driver/ToolChains/Arch/X86.cpp
+++ lib/Driver/ToolChains/Arch/X86.cpp
@@ -40,8 +40,8 @@
       return Args.MakeArgString(CPU);
   }
 
-  if (const Arg *A = Args.getLastArg(options::OPT__SLASH_arch)) {
-    // Mapping built by referring to X86TargetInfo::getDefaultFeatures().
+  if (const Arg *A = Args.getLastArgNoClaim(options::OPT__SLASH_arch)) {
+    // Mapping built by looking at lib/Basic's X86TargetInfo::initFeatureMap().
     StringRef Arch = A->getValue();
     const char *CPU;
     if (Triple.getArch() == llvm::Triple::x86) {
@@ -58,8 +58,10 @@
                 .Case("AVX2", "haswell")
                 .Default(nullptr);
     }
-    if (CPU)
+    if (CPU) {
+      A->claim();
       return CPU;
+    }
   }
 
   // Select the default CPU if none was given (or detection failed).
@@ -141,30 +143,6 @@
       Features.push_back("+ssse3");
   }
 
-  // Set features according to the -arch flag on MSVC.
-  if (Arg *A = Args.getLastArg(options::OPT__SLASH_arch)) {
-    StringRef Arch = A->getValue();
-    bool ArchUsed = false;
-    // First, look for flags that are shared in x86 and x86-64.
-    if (ArchType == llvm::Triple::x86_64 || ArchType == llvm::Triple::x86) {
-      if (Arch == "AVX" || Arch == "AVX2") {
-        ArchUsed = true;
-        Features.push_back(Args.MakeArgString("+" + Arch.lower()));
-      }
-    }
-    // Then, look for x86-specific flags.
-    if (ArchType == llvm::Triple::x86) {
-      if (Arch == "IA32") {
-        ArchUsed = true;
-      } else if (Arch == "SSE" || Arch == "SSE2") {
-        ArchUsed = true;
-        Features.push_back(Args.MakeArgString("+" + Arch.lower()));
-      }
-    }
-    if (!ArchUsed)
-      D.Diag(clang::diag::warn_drv_unused_argument) << A->getAsString(Args);
-  }
-
   // Now add any that the user explicitly requested on the command line,
   // which may override the defaults.
   handleTargetFeaturesGroup(Args, Features, options::OPT_m_x86_Features_Group);
Index: test/Driver/cl-x86-flags.c
===================================================================
--- test/Driver/cl-x86-flags.c
+++ test/Driver/cl-x86-flags.c
@@ -1,88 +1,92 @@
 // REQUIRES: x86-registered-target
 
+// expected-no-diagnostics
+
 // We support -m32 and -m64.  We support all x86 CPU feature flags in gcc's -m
 // flag space.
 // RUN: %clang_cl /Zs /WX -m32 -m64 -msse3 -msse4.1 -mavx -mno-avx \
 // RUN:     --target=i386-pc-win32 -### -- 2>&1 %s | FileCheck -check-prefix=MFLAGS %s
 // MFLAGS-NOT: argument unused during compilation
 
-// RUN: %clang_cl -m32 -arch:IA32 --target=i386 -### -- 2>&1 %s | FileCheck -check-prefix=IA32 %s
-// IA32: "-target-cpu" "i386"
-// IA32-NOT: -target-feature
-// IA32-NOT: argument unused during compilation
+// RUN: %clang_cl -m32 -arch:IA32 --target=i386-pc-windows /c -Xclang -verify -DTEST_32_ARCH_IA32 -- %s
+#if defined(TEST_32_ARCH_IA32)
+#if _M_IX86_FP || __AVX__ || __AVX2__ || __AVX512F__  || __AVX512BW__
+#error fail
+#endif
+#endif
 
-// RUN: %clang_cl -m32 -arch:ia32 --target=i386 -### -- 2>&1 %s | FileCheck -check-prefix=ia32 %s
+// arch: args are case-sensitive.
+// RUN: %clang_cl -m32 -arch:ia32 --target=i386-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=ia32 %s
 // ia32: argument unused during compilation
-// ia32-NOT: -target-feature
 
-// RUN: %clang_cl -m64 -arch:IA32 --target=x86_64 -### -- 2>&1 %s | FileCheck -check-prefix=IA3264 %s
+// RUN: %clang_cl -m64 -arch:IA32 --target=x86_64-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=IA3264 %s
 // IA3264: argument unused during compilation
-// IA3264-NOT: -target-feature
 
-// RUN: %clang_cl -m32 -arch:SSE --target=i386 -### -- 2>&1 %s | FileCheck -check-prefix=SSE %s
-// SSE: "-target-cpu" "pentium3"
-// SSE: -target-feature
-// SSE: +sse
-// SSE-NOT: argument unused during compilation
+// RUN: %clang_cl -m32 -arch:SSE --target=i386-pc-windows /c -Xclang -verify -DTEST_32_ARCH_SSE -- %s
+#if defined(TEST_32_ARCH_SSE)
+#if _M_IX86_FP != 1 || __AVX__ || __AVX2__ || __AVX512F__  || __AVX512BW__
+#error fail
+#endif
+#endif
 
-// RUN: %clang_cl -m32 -arch:sse --target=i386 -### -- 2>&1 %s | FileCheck -check-prefix=sse %s
+// RUN: %clang_cl -m32 -arch:sse --target=i386-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=sse %s
 // sse: argument unused during compilation
-// sse-NOT: -target-feature
 
-// RUN: %clang_cl -m32 -arch:SSE2 --target=i386 -### -- 2>&1 %s | FileCheck -check-prefix=SSE2 %s
-// SSE2: "-target-cpu" "pentium4"
-// SSE2: -target-feature
-// SSE2: +sse2
-// SSE2-NOT: argument unused during compilation
+// RUN: %clang_cl -m32 -arch:SSE2 --target=i386-pc-windows /c -Xclang -verify -DTEST_32_ARCH_SSE2 -- %s
+#if defined(TEST_32_ARCH_SSE2)
+#if _M_IX86_FP != 2 || __AVX__ || __AVX2__ || __AVX512F__  || __AVX512BW__
+#error fail
+#endif
+#endif
 
-// RUN: %clang_cl -m32 -arch:sse2 --target=i386 -### -- 2>&1 %s | FileCheck -check-prefix=sse %s
+// RUN: %clang_cl -m32 -arch:sse2 --target=i386-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=sse %s
 // sse2: argument unused during compilation
-// sse2-NOT: -target-feature
 
-// RUN: %clang_cl -m64 -arch:SSE --target=x86_64 -### -- 2>&1 %s | FileCheck -check-prefix=SSE64 %s
+// RUN: %clang_cl -m64 -arch:SSE --target=x86_64-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=SSE64 %s
 // SSE64: argument unused during compilation
-// SSE64-NOT: -target-feature
-// SSE64-NOT: pentium3
 
-// RUN: %clang_cl -m64 -arch:SSE2 --target=x86_64 -### -- 2>&1 %s | FileCheck -check-prefix=SSE264 %s
+// RUN: %clang_cl -m64 -arch:SSE2 --target=x86_64-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=SSE264 %s
 // SSE264: argument unused during compilation
-// SSE264-NOT: -target-feature
 
-// RUN: %clang_cl -m32 -arch:AVX --target=i386 -### -- 2>&1 %s | FileCheck -check-prefix=AVX %s
-// AVX: "-target-cpu" "sandybridge"
-// AVX: -target-feature
-// AVX: +avx
+// RUN: %clang_cl -m32 -arch:AVX --target=i386-pc-windows /c -Xclang -verify -DTEST_32_ARCH_AVX -- %s
+#if defined(TEST_32_ARCH_AVX)
+#if _M_IX86_FP != 2 || !__AVX__ || __AVX2__ || __AVX512F__  || __AVX512BW__
+#error fail
+#endif
+#endif
 
-// RUN: %clang_cl -m32 -arch:avx --target=i386 -### -- 2>&1 %s | FileCheck -check-prefix=avx %s
+// RUN: %clang_cl -m32 -arch:avx --target=i386-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=avx %s
 // avx: argument unused during compilation
-// avx-NOT: -target-feature
 
-// RUN: %clang_cl -m32 -arch:AVX2 --target=i386 -### -- 2>&1 %s | FileCheck -check-prefix=AVX2 %s
-// AVX2: "-target-cpu" "haswell"
-// AVX2: -target-feature
-// AVX2: +avx2
+// RUN: %clang_cl -m32 -arch:AVX2 --target=i386-pc-windows /c -Xclang -verify -DTEST_32_ARCH_AVX2 -- %s
+#if defined(TEST_32_ARCH_AVX2)
+#if _M_IX86_FP != 2 || !__AVX__ || !__AVX2__ || __AVX512F__  || __AVX512BW__
+#error fail
+#endif
+#endif
 
-// RUN: %clang_cl -m32 -arch:avx2 --target=i386 -### -- 2>&1 %s | FileCheck -check-prefix=avx2 %s
+// RUN: %clang_cl -m32 -arch:avx2 --target=i386-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=avx2 %s
 // avx2: argument unused during compilation
-// avx2-NOT: -target-feature
 
-// RUN: %clang_cl -m64 -arch:AVX --target=x86_64 -### -- 2>&1 %s | FileCheck -check-prefix=AVX64 %s
-// AVX64: "-target-cpu" "sandybridge"
-// AVX64: -target-feature
-// AVX64: +avx
+// RUN: %clang_cl -m64 -arch:AVX --target=x86_64-pc-windows /c -Xclang -verify -DTEST_64_ARCH_AVX -- %s
+#if defined(TEST_64_ARCH_AVX)
+#if _M_IX86_FP || !__AVX__ || __AVX2__ || __AVX512F__  || __AVX512BW__
+#error fail
+#endif
+#endif
 
-// RUN: %clang_cl -m64 -arch:avx --target=x86_64 -### -- 2>&1 %s | FileCheck -check-prefix=avx64 %s
+// RUN: %clang_cl -m64 -arch:avx --target=x86_64-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=avx64 %s
 // avx64: argument unused during compilation
-// avx64-NOT: -target-feature
 
-// RUN: %clang_cl -m64 -arch:AVX2 --target=x86_64 -### -- 2>&1 %s | FileCheck -check-prefix=AVX264 %s
-// AVX264: "-target-cpu" "haswell"
-// AVX264: -target-feature
-// AVX264: +avx2
+// RUN: %clang_cl -m64 -arch:AVX2 --target=x86_64-pc-windows /c -Xclang -verify -DTEST_64_ARCH_AVX2 -- %s
+#if defined(TEST_64_ARCH_AVX2)
+#if _M_IX86_FP || !__AVX__ || !__AVX2__ || __AVX512F__  || __AVX512BW__
+#error fail
+#endif
+#endif
 
-// RUN: %clang_cl -m64 -arch:avx2 --target=x86_64 -### -- 2>&1 %s | FileCheck -check-prefix=avx264 %s
+// RUN: %clang_cl -m64 -arch:avx2 --target=x86_64-pc-windows -### -- 2>&1 %s | FileCheck -check-prefix=avx264 %s
 // avx264: argument unused during compilation
-// avx264-NOT: -target-feature
 
 void f() {
 }