Index: cfe/trunk/include/clang/Basic/DiagnosticCommonKinds.td
===================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticCommonKinds.td
+++ cfe/trunk/include/clang/Basic/DiagnosticCommonKinds.td
@@ -199,6 +199,9 @@
 def err_target_unsupported_abi : Error<"ABI '%0' is not supported on CPU '%1'">;
 def err_target_unsupported_abi_for_triple : Error<
   "ABI '%0' is not supported for '%1'">;
+def err_unsupported_abi_for_opt : Error<"'%0' can only be used with the '%1' ABI">;
+def err_mips_fp64_req : Error<
+    "'%0' can only be used if the target supports the mfhc1 and mthc1 instructions">;
 def err_target_unknown_fpmath : Error<"unknown FP unit '%0'">;
 def err_target_unsupported_fpmath : Error<
     "the '%0' unit is not supported with this instruction set">;
Index: cfe/trunk/lib/Basic/Targets/Mips.h
===================================================================
--- cfe/trunk/lib/Basic/Targets/Mips.h
+++ cfe/trunk/lib/Basic/Targets/Mips.h
@@ -57,7 +57,7 @@
   bool UseIndirectJumpHazard;
 
 protected:
-  bool HasFP64;
+  enum FPModeEnum { FPXX, FP32, FP64 } FPMode;
   std::string ABI;
 
 public:
@@ -66,7 +66,7 @@
         IsNan2008(false), IsAbs2008(false), IsSingleFloat(false),
         IsNoABICalls(false), CanUseBSDABICalls(false), FloatABI(HardFloat),
         DspRev(NoDSP), HasMSA(false), DisableMadd4(false),
-        UseIndirectJumpHazard(false), HasFP64(false) {
+        UseIndirectJumpHazard(false), FPMode(FPXX) {
     TheCXXABI.set(TargetCXXABI::GenericMIPS);
 
     setABI(getTriple().isMIPS32() ? "o32" : "n64");
@@ -181,6 +181,8 @@
     return TargetInfo::initFeatureMap(Features, Diags, CPU, FeaturesVec);
   }
 
+  unsigned getISARev() const;
+
   void getTargetDefines(const LangOptions &Opts,
                         MacroBuilder &Builder) const override;
 
@@ -305,7 +307,7 @@
     IsSingleFloat = false;
     FloatABI = HardFloat;
     DspRev = NoDSP;
-    HasFP64 = isFP64Default();
+    FPMode = isFP64Default() ? FP64 : FPXX;
 
     for (const auto &Feature : Features) {
       if (Feature == "+single-float")
@@ -325,9 +327,11 @@
       else if (Feature == "+nomadd4")
         DisableMadd4 = true;
       else if (Feature == "+fp64")
-        HasFP64 = true;
+        FPMode = FP64;
       else if (Feature == "-fp64")
-        HasFP64 = false;
+        FPMode = FP32;
+      else if (Feature == "+fpxx")
+        FPMode = FPXX;
       else if (Feature == "+nan2008")
         IsNan2008 = true;
       else if (Feature == "-nan2008")
Index: cfe/trunk/lib/Basic/Targets/Mips.cpp
===================================================================
--- cfe/trunk/lib/Basic/Targets/Mips.cpp
+++ cfe/trunk/lib/Basic/Targets/Mips.cpp
@@ -59,6 +59,16 @@
   Values.append(std::begin(ValidCPUNames), std::end(ValidCPUNames));
 }
 
+unsigned MipsTargetInfo::getISARev() const {
+  return llvm::StringSwitch<unsigned>(getCPU())
+             .Cases("mips32", "mips64", 1)
+             .Cases("mips32r2", "mips64r2", 2)
+             .Cases("mips32r3", "mips64r3", 3)
+             .Cases("mips32r5", "mips64r5", 5)
+             .Cases("mips32r6", "mips64r6", 6)
+             .Default(0);
+}
+
 void MipsTargetInfo::getTargetDefines(const LangOptions &Opts,
                                       MacroBuilder &Builder) const {
   if (BigEndian) {
@@ -84,13 +94,8 @@
     Builder.defineMacro("_MIPS_ISA", "_MIPS_ISA_MIPS64");
   }
 
-  const std::string ISARev = llvm::StringSwitch<std::string>(getCPU())
-                                 .Cases("mips32", "mips64", "1")
-                                 .Cases("mips32r2", "mips64r2", "2")
-                                 .Cases("mips32r3", "mips64r3", "3")
-                                 .Cases("mips32r5", "mips64r5", "5")
-                                 .Cases("mips32r6", "mips64r6", "6")
-                                 .Default("");
+  const std::string ISARev = std::to_string(getISARev());
+
   if (!ISARev.empty())
     Builder.defineMacro("__mips_isa_rev", ISARev);
 
@@ -129,9 +134,22 @@
   if (IsSingleFloat)
     Builder.defineMacro("__mips_single_float", Twine(1));
 
-  Builder.defineMacro("__mips_fpr", HasFP64 ? Twine(64) : Twine(32));
-  Builder.defineMacro("_MIPS_FPSET",
-                      Twine(32 / (HasFP64 || IsSingleFloat ? 1 : 2)));
+  switch (FPMode) {
+  case FPXX:
+    Builder.defineMacro("__mips_fpr", Twine(0));
+    break;
+  case FP32:
+    Builder.defineMacro("__mips_fpr", Twine(32));
+    break;
+  case FP64:
+    Builder.defineMacro("__mips_fpr", Twine(64));
+    break;
+}
+
+  if (FPMode == FP64 || IsSingleFloat)
+    Builder.defineMacro("_MIPS_FPSET", Twine(32));
+  else
+    Builder.defineMacro("_MIPS_FPSET", Twine(16));
 
   if (IsMips16)
     Builder.defineMacro("__mips16", Twine(1));
@@ -189,7 +207,7 @@
 bool MipsTargetInfo::hasFeature(StringRef Feature) const {
   return llvm::StringSwitch<bool>(Feature)
       .Case("mips", true)
-      .Case("fp64", HasFP64)
+      .Case("fp64", FPMode == FP64)
       .Default(false);
 }
 
@@ -235,5 +253,30 @@
     return false;
   }
 
+  // -fpxx is valid only for the o32 ABI
+  if (FPMode == FPXX && (ABI == "n32" || ABI == "n64")) {
+    Diags.Report(diag::err_unsupported_abi_for_opt) << "-mfpxx" << "o32";
+    return false;
+  }
+
+  // -mfp32 and n32/n64 ABIs are incompatible
+  if (FPMode != FP64 && FPMode != FPXX && !IsSingleFloat &&
+      (ABI == "n32" || ABI == "n64")) {
+    Diags.Report(diag::err_opt_not_valid_with_opt) << "-mfpxx" << CPU;
+    return false;
+  }
+  // Mips revision 6 and -mfp32 are incompatible
+  if (FPMode != FP64 && FPMode != FPXX && (CPU == "mips32r6" ||
+      CPU == "mips64r6")) {
+    Diags.Report(diag::err_opt_not_valid_with_opt) << "-mfp32" << CPU;
+    return false;
+  }
+  // Option -mfp64 permitted on Mips32 iff revision 2 or higher is present
+  if (FPMode == FP64 && (CPU == "mips1" || CPU == "mips2" ||
+      getISARev() < 2) && ABI == "o32") {
+    Diags.Report(diag::err_mips_fp64_req) << "-mfp64";
+    return false;
+  }
+
   return true;
 }
Index: cfe/trunk/test/Preprocessor/init.c
===================================================================
--- cfe/trunk/test/Preprocessor/init.c
+++ cfe/trunk/test/Preprocessor/init.c
@@ -3442,7 +3442,7 @@
 // MIPS32BE:#define __mips 32
 // MIPS32BE:#define __mips__ 1
 // MIPS32BE:#define __mips_abicalls 1
-// MIPS32BE:#define __mips_fpr 32
+// MIPS32BE:#define __mips_fpr 0
 // MIPS32BE:#define __mips_hard_float 1
 // MIPS32BE:#define __mips_o32 1
 // MIPS32BE:#define _mips 1
@@ -3649,7 +3649,7 @@
 // MIPS32EL:#define __mips 32
 // MIPS32EL:#define __mips__ 1
 // MIPS32EL:#define __mips_abicalls 1
-// MIPS32EL:#define __mips_fpr 32
+// MIPS32EL:#define __mips_fpr 0
 // MIPS32EL:#define __mips_hard_float 1
 // MIPS32EL:#define __mips_o32 1
 // MIPS32EL:#define _mips 1
@@ -4900,6 +4900,41 @@
 // RUN:   | FileCheck -match-full-lines -check-prefix NOMIPS-ABS2008 %s
 // NOMIPS-ABS2008-NOT:#define __mips_abs2008 1
 //
+// RUN: %clang_cc1  \
+// RUN:   -E -dM -triple=mips-none-none < /dev/null \
+// RUN:   | FileCheck -match-full-lines -check-prefix MIPS32-NOFP %s
+// MIPS32-NOFP:#define __mips_fpr 0
+//
+// RUN: %clang_cc1 -target-feature +fpxx \
+// RUN:   -E -dM -triple=mips-none-none < /dev/null \
+// RUN:   | FileCheck -match-full-lines -check-prefix MIPS32-MFPXX %s
+// MIPS32-MFPXX:#define __mips_fpr 0
+//
+// RUN: %clang_cc1 -target-cpu mips32r6 -target-feature +fpxx \
+// RUN:   -E -dM -triple=mips-none-none < /dev/null \
+// RUN:   | FileCheck -match-full-lines -check-prefix MIPS32R6-MFPXX %s
+// MIPS32R6-MFPXX:#define __mips_fpr 0
+//
+// RUN: %clang_cc1  \
+// RUN:   -E -dM -triple=mips64-none-none < /dev/null \
+// RUN:   | FileCheck -match-full-lines -check-prefix MIPS64-NOFP %s
+// MIPS64-NOFP:#define __mips_fpr 64
+//
+// RUN: not %clang_cc1 -target-feature -fp64 \
+// RUN:   -E -dM -triple=mips64-none-none < /dev/null 2>&1 \
+// RUN:   | FileCheck -match-full-lines -check-prefix MIPS64-MFP32 %s
+// MIPS64-MFP32:error: option '-mfpxx' cannot be specified with 'mips64r2'
+//
+// RUN: not %clang_cc1 -target-feature +fpxx \
+// RUN:   -E -dM -triple=mips64-none-none < /dev/null 2>&1 \
+// RUN:   | FileCheck -match-full-lines -check-prefix MIPS64-MFPXX %s
+// MIPS64-MFPXX:error: '-mfpxx' can only be used with the 'o32' ABI
+//
+// RUN: not %clang_cc1 -target-cpu mips64r6 -target-feature +fpxx \
+// RUN:   -E -dM -triple=mips64-none-none < /dev/null 2>&1 \
+// RUN:   | FileCheck -match-full-lines -check-prefix MIPS64R6-MFPXX %s
+// MIPS64R6-MFPXX:error: '-mfpxx' can only be used with the 'o32' ABI
+//
 // RUN: %clang_cc1 -target-feature -fp64 \
 // RUN:   -E -dM -triple=mips-none-none < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefix MIPS32-MFP32 %s
@@ -4916,7 +4951,7 @@
 // RUN:   -E -dM -triple=mips-none-none < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefix MIPS32-MFP32SF %s
 // MIPS32-MFP32SF:#define _MIPS_FPSET 32
-// MIPS32-MFP32SF:#define __mips_fpr 32
+// MIPS32-MFP32SF:#define __mips_fpr 0
 //
 // RUN: %clang_cc1 -target-feature +fp64 \
 // RUN:   -E -dM -triple=mips64-none-none < /dev/null \