Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -520,14 +520,27 @@
 // Get Arch/CPU from args.
 static void getARMArchCPUFromArgs(const ArgList &Args,
                                   llvm::StringRef &Arch,
-                                  llvm::StringRef &CPU) {
+                                  llvm::StringRef &CPU,
+                                  bool FromAs=false) {
   if (const Arg *A = Args.getLastArg(options::OPT_mcpu_EQ))
     CPU = A->getValue();
   if (const Arg *A = Args.getLastArg(options::OPT_march_EQ))
     Arch = A->getValue();
+  if (!FromAs)
+    return;
+
+  for (const Arg *A : Args.filtered(options::OPT_Wa_COMMA,
+                                    options::OPT_Xassembler)) {
+    StringRef Value = A->getValue();
+    if (Value.startswith("-mcpu="))
+        CPU = Value.substr(6);
+    if (Value.startswith("-march="))
+        Arch = Value.substr(7);
+  }
 }
 
 // Handle -mhwdiv=.
+// FIXME: Use ARMTargetParser.
 static void getARMHWDivFeatures(const Driver &D, const Arg *A,
                                 const ArgList &Args,
                                 StringRef HWDiv,
@@ -558,7 +571,9 @@
     D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
 }
 
-// Check -march=.
+// Check if -march is valid by checking if it can be canonicalised and parsed.
+// getARMArch is used here instead of just checking the -march value in order
+// to handle -march=native correctly.
 static void checkARMArchName(const Driver &D, const Arg *A,
                              const ArgList &Args,
                              llvm::StringRef ArchName,
@@ -568,7 +583,7 @@
     D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
 }
 
-// Check -mcpu=.
+// Check -mcpu=. Needs ArchName to handle -mcpu=generic.
 static void checkARMCPUName(const Driver &D, const Arg *A,
                             const ArgList &Args,
                             llvm::StringRef CPUName,
@@ -677,6 +692,9 @@
   bool KernelOrKext =
       Args.hasArg(options::OPT_mkernel, options::OPT_fapple_kext);
   StringRef FloatABI = tools::arm::getARMFloatABI(D, Args, Triple);
+  const Arg *WaCPU = nullptr, *WaFPU = nullptr;
+  const Arg *WaHdiv = nullptr, *WaArch = nullptr;
+
   if (!ForAS) {
     // FIXME: Note, this is a hack, the LLVM backend doesn't actually use these
     // yet (it uses the -mfloat-abi and -msoft-float options), and it is
@@ -697,29 +715,53 @@
     // Use software floating point argument passing?
     if (FloatABI != "hard")
       Features.push_back("+soft-float-abi");
+  } else {
+    // Here, we make sure that -Wa,-mfpu/cpu/arch/hwdiv will be passed down
+    // to the assembler correctly.
+    for (const Arg *A : Args.filtered(options::OPT_Wa_COMMA,
+                                      options::OPT_Xassembler)) {
+      StringRef Value = A->getValue();
+      if (Value.startswith("-mfpu=")) {
+        WaFPU = A;
+      } else if (Value.startswith("-mcpu=")) {
+        WaCPU = A;
+      } else if (Value.startswith("-mhwdiv=")) {
+        WaHdiv = A;
+      } else if (Value.startswith("-march=")) {
+        WaArch = A;
+      }
+    }
   }
 
-  // Honor -mfpu=.
-  if (const Arg *A = Args.getLastArg(options::OPT_mfpu_EQ))
+  // Honor -mfpu=. ClangAs gives preference to -Wa,-mfpu=.
+  if (WaFPU)
+    getARMFPUFeatures(D, WaFPU, Args, StringRef(WaFPU->getValue()).substr(6), Features);
+  else if (const Arg *A = Args.getLastArg(options::OPT_mfpu_EQ))
     getARMFPUFeatures(D, A, Args, A->getValue(), Features);
-  // Honor -mhwdiv=
-  if (const Arg *A = Args.getLastArg(options::OPT_mhwdiv_EQ))
+  // Honor -mhwdiv=. ClangAs gives preference to -Wa,-mhwdiv=.
+  if (WaHdiv)
+    getARMHWDivFeatures(D, WaHdiv, Args, StringRef(WaHdiv->getValue()).substr(8), Features);
+  else if (const Arg *A = Args.getLastArg(options::OPT_mhwdiv_EQ))
     getARMHWDivFeatures(D, A, Args, A->getValue(), Features);
 
-  // Check if -march is valid by checking if it can be canonicalised and parsed.
-  // getARMArch is used here instead of just checking the -march value in order
-  // to handle -march=native correctly.
+  // Check -march. ClangAs gives preference to -Wa,-march=.
   StringRef ArchName;
-  if (const Arg *A = Args.getLastArg(options::OPT_march_EQ)) {
+  if (WaArch) {
+    ArchName = StringRef(WaArch->getValue()).substr(7);
+    checkARMArchName(D, WaArch, Args, ArchName, Triple);
+    // FIXME: Set Arch.
+  } else if (const Arg *A = Args.getLastArg(options::OPT_march_EQ)) {
     ArchName = A->getValue();
     checkARMArchName(D, A, Args, ArchName, Triple);
   }
 
-  // We do a similar thing with -mcpu, but here things are complicated because
-  // the only function we have to check if a cpu is valid is
-  // getLLVMArchSuffixForARM which also needs an architecture.
+  // Check -mcpu. ClangAs gives preference to -Wa,-mcpu=.
   StringRef CPUName;
-  if (const Arg *A = Args.getLastArg(options::OPT_mcpu_EQ)) {
+  if (WaCPU) {
+    CPUName = StringRef(WaCPU->getValue()).substr(6);
+    checkARMCPUName(D, WaCPU, Args, CPUName, ArchName, Triple);
+    // FIXME: Set CPU.
+  } else if (const Arg *A = Args.getLastArg(options::OPT_mcpu_EQ)) {
     CPUName = A->getValue();
     checkARMCPUName(D, A, Args, CPUName, ArchName, Triple);
   }
@@ -1500,7 +1542,9 @@
   }
 }
 
-static std::string getCPUName(const ArgList &Args, const llvm::Triple &T) {
+static std::string getCPUName(const ArgList &Args,
+                              const llvm::Triple &T,
+                              bool FromAs=false) {
   switch (T.getArch()) {
   default:
     return "";
@@ -1514,7 +1558,7 @@
   case llvm::Triple::thumb:
   case llvm::Triple::thumbeb: {
     StringRef MArch, MCPU;
-    getARMArchCPUFromArgs(Args, MArch, MCPU);
+    getARMArchCPUFromArgs(Args, MArch, MCPU, FromAs);
     return arm::getARMTargetCPU(MCPU, MArch, T);
   }
   case llvm::Triple::mips:
@@ -2260,6 +2304,11 @@
           TakeNextArg = true;
       } else if (Value.startswith("-gdwarf-")) {
         CmdArgs.push_back(Value.data());
+      } else if (Value.startswith("-mcpu") ||
+                 Value.startswith("-mfpu") ||
+                 Value.startswith("-mhwdiv") ||
+                 Value.startswith("-march")) {
+        // Do nothing, we'll validate it later.
       } else {
         D.Diag(diag::err_drv_unsupported_option_argument)
             << A->getOption().getName() << Value;
@@ -3461,7 +3510,7 @@
   }
 
   // Add the target cpu
-  std::string CPU = getCPUName(Args, Triple);
+  std::string CPU = getCPUName(Args, Triple, /*FromAs*/ false);
   if (!CPU.empty()) {
     CmdArgs.push_back("-target-cpu");
     CmdArgs.push_back(Args.MakeArgString(CPU));
@@ -5283,7 +5332,7 @@
 
   // Add the target cpu
   const llvm::Triple Triple(TripleStr);
-  std::string CPU = getCPUName(Args, Triple);
+  std::string CPU = getCPUName(Args, Triple, /*FromAs*/ true);
   if (!CPU.empty()) {
     CmdArgs.push_back("-target-cpu");
     CmdArgs.push_back(Args.MakeArgString(CPU));
@@ -7347,7 +7396,7 @@
   case llvm::Triple::thumb:
   case llvm::Triple::thumbeb: {
     StringRef MArch, MCPU;
-    getARMArchCPUFromArgs(Args, MArch, MCPU);
+    getARMArchCPUFromArgs(Args, MArch, MCPU, /*FromAs*/ true);
     std::string Arch = arm::getARMTargetCPU(MCPU, MArch, getToolChain().getTriple());
     CmdArgs.push_back(Args.MakeArgString("-mcpu=" + Arch));
     break;
Index: test/Driver/arm-ias-Wa.s
===================================================================
--- /dev/null
+++ test/Driver/arm-ias-Wa.s
@@ -0,0 +1,44 @@
+// Test that different values of -Wa,-mcpu/mfpu/march/mhwdiv pick correct ARM target-feature(s).
+// Complete tests about -mcpu/mfpu/march/mhwdiv on other files.
+
+// CHECK: "cc1as"
+// ================================================================= CPU
+// RUN: %clang -target arm-linux-gnueabi -Wa,-mcpu=cortex-a15 -### -c %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-CPU %s
+// CHECK-CPU: "-target-cpu" "cortex-a15"
+
+// RUN: %clang -target arm -Wa,-mcpu=bogus -### -c %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-BOGUS-CPU %s
+// CHECK-BOGUS-CPU: error: {{.*}} does not support '-Wa,-mcpu=bogus'
+
+// ================================================================= FPU
+// RUN: %clang -target arm-linux-eabi -Wa,-mfpu=neon %s -### -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NEON %s
+// CHECK-NEON: "-target-feature" "+neon"
+
+// RUN: %clang -target arm-linux-eabi -Wa,-mfpu=bogus %s -### -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-BOGUS-FPU %s
+// CHECK-BOGUS-FPU: error: {{.*}} does not support '-Wa,-mfpu=bogus'
+
+// ================================================================= Arch
+// Arch validation only for now, in case we're passing to an external asm
+
+// RUN: %clang -target arm -Wa,-march=armbogusv6 -### -c %s 2>&1 \
+// RUN:   | FileCheck -check-prefix=CHECK-BOGUS %s
+// CHECK-BOGUS: error: {{.*}} does not support '-Wa,-march=armbogusv6'
+
+// ================================================================= HD Div
+// RUN: %clang -### -target arm %s -Wa,-mhwdiv=arm -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-ARM %s
+// CHECK-ARM: "-target-feature" "+hwdiv-arm"
+// CHECK-ARM: "-target-feature" "-hwdiv"
+
+// RUN: %clang -### -target arm %s -Wa,-mhwdiv=thumb -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-THUMB %s
+// CHECK-THUMB: "-target-feature" "-hwdiv-arm"
+// CHECK-THUMB: "-target-feature" "+hwdiv"
+
+// RUN: %clang -### -target arm %s -Wa,-mhwdiv=bogus -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-BOGUS-HDIV %s
+// CHECK-BOGUS-HDIV: error: {{.*}} does not support '-Wa,-mhwdiv=bogus'
+