diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index a220bea..aeb7e1b 100644
--- a/include/clang/Driver/Options.td
+++ b/include/clang/Driver/Options.td
@@ -389,6 +389,7 @@
   HelpText<"Enable the *frontend*'s 'fast-math' mode. This has no effect on "
            "optimizations, but provides a preprocessor macro __FAST_MATH__ the "
            "same as GCC's -ffast-math flag.">;
+def fno_fast_math : Flag<"-fno-fast-math">, Group<f_Group>;
 def fmath_errno : Flag<"-fmath-errno">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Require math functions to indicate errors by setting errno">;
 def fno_math_errno : Flag<"-fno-math-errno">, Group<f_Group>;
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 8619b98..f77d8ee 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1749,25 +1749,30 @@
   // flag disables them after the flag enabling them, enable the codegen
   // optimization. This is complicated by several "umbrella" flags.
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+                               options::OPT_fno_fast_math,
                                options::OPT_ffinite_math_only,
                                options::OPT_fno_finite_math_only,
                                options::OPT_fhonor_infinities,
                                options::OPT_fno_honor_infinities))
-    if (A->getOption().getID() != options::OPT_fno_finite_math_only &&
+    if (A->getOption().getID() != options::OPT_fno_fast_math &&
+        A->getOption().getID() != options::OPT_fno_finite_math_only &&
         A->getOption().getID() != options::OPT_fhonor_infinities)
       CmdArgs.push_back("-menable-no-infs");
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+                               options::OPT_fno_fast_math,
                                options::OPT_ffinite_math_only,
                                options::OPT_fno_finite_math_only,
                                options::OPT_fhonor_nans,
                                options::OPT_fno_honor_nans))
-    if (A->getOption().getID() != options::OPT_fno_finite_math_only &&
+    if (A->getOption().getID() != options::OPT_fno_fast_math &&
+        A->getOption().getID() != options::OPT_fno_finite_math_only &&
         A->getOption().getID() != options::OPT_fhonor_nans)
       CmdArgs.push_back("-menable-no-nans");
 
   // -fmath-errno is the default on some platforms, e.g. BSD-derived OSes.
   bool MathErrno = getToolChain().IsMathErrnoDefault();
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+                               options::OPT_fno_fast_math,
                                options::OPT_fmath_errno,
                                options::OPT_fno_math_errno))
     MathErrno = A->getOption().getID() == options::OPT_fmath_errno;
@@ -1780,38 +1785,46 @@
   // madness.
   bool AssociativeMath = false;
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+                               options::OPT_fno_fast_math,
                                options::OPT_funsafe_math_optimizations,
                                options::OPT_fno_unsafe_math_optimizations,
                                options::OPT_fassociative_math,
                                options::OPT_fno_associative_math))
-    if (A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
+    if (A->getOption().getID() != options::OPT_fno_fast_math &&
+        A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
         A->getOption().getID() != options::OPT_fno_associative_math)
       AssociativeMath = true;
   bool ReciprocalMath = false;
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+                               options::OPT_fno_fast_math,
                                options::OPT_funsafe_math_optimizations,
                                options::OPT_fno_unsafe_math_optimizations,
                                options::OPT_freciprocal_math,
                                options::OPT_fno_reciprocal_math))
-    if (A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
+    if (A->getOption().getID() != options::OPT_fno_fast_math &&
+        A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
         A->getOption().getID() != options::OPT_fno_reciprocal_math)
       ReciprocalMath = true;
   bool SignedZeros = true;
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+                               options::OPT_fno_fast_math,
                                options::OPT_funsafe_math_optimizations,
                                options::OPT_fno_unsafe_math_optimizations,
                                options::OPT_fsigned_zeros,
                                options::OPT_fno_signed_zeros))
-    if (A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
+    if (A->getOption().getID() != options::OPT_fno_fast_math &&
+        A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
         A->getOption().getID() != options::OPT_fsigned_zeros)
       SignedZeros = false;
   bool TrappingMath = true;
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+                               options::OPT_fno_fast_math,
                                options::OPT_funsafe_math_optimizations,
                                options::OPT_fno_unsafe_math_optimizations,
                                options::OPT_ftrapping_math,
                                options::OPT_fno_trapping_math))
-    if (A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
+    if (A->getOption().getID() != options::OPT_fno_fast_math &&
+        A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
         A->getOption().getID() != options::OPT_ftrapping_math)
       TrappingMath = false;
   if (!MathErrno && AssociativeMath && ReciprocalMath && !SignedZeros &&
@@ -1821,6 +1834,7 @@
 
   // Validate and pass through -fp-contract option. 
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
+                               options::OPT_fno_fast_math,
                                options::OPT_ffp_contract)) {
     if (A->getOption().getID() == options::OPT_ffp_contract) {
       StringRef Val = A->getValue(Args);
@@ -1830,7 +1844,7 @@
         D.Diag(diag::err_drv_unsupported_option_argument)
           << A->getOption().getName() << Val;
       }
-    } else { // A is OPT_ffast_math
+    } else if (A->getOption().getID() == options::OPT_ffast_math) {
       // If fast-math is set then set the fp-contract mode to fast.
       CmdArgs.push_back(Args.MakeArgString("-ffp-contract=fast"));
     }
@@ -1841,10 +1855,12 @@
   // preprocessor macros. This is distinct from enabling any optimizations as
   // these options induce language changes which must survive serialization
   // and deserialization, etc.
-  if (Args.hasArg(options::OPT_ffast_math))
-    CmdArgs.push_back("-ffast-math");
-  if (Args.hasArg(options::OPT_ffinite_math_only))
-    CmdArgs.push_back("-ffinite-math-only");
+  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, options::OPT_fno_fast_math))
+    if (A->getOption().matches(options::OPT_ffast_math))
+      CmdArgs.push_back("-ffast-math");
+  if (Arg *A = Args.getLastArg(options::OPT_ffinite_math_only, options::OPT_fno_fast_math))
+    if (A->getOption().matches(options::OPT_ffinite_math_only))
+      CmdArgs.push_back("-ffinite-math-only");
 
   // Decide whether to use verbose asm. Verbose assembly is the default on
   // toolchains which have the integrated assembler on by default.
diff --git a/test/Driver/fast-math.c b/test/Driver/fast-math.c
index 8426f09..17bf6ed 100644
--- a/test/Driver/fast-math.c
+++ b/test/Driver/fast-math.c
@@ -12,16 +12,46 @@
 // CHECK-NO-INFS: "-cc1"
 // CHECK-NO-INFS: "-menable-no-infs"
 //
+// RUN: %clang -### -fno-fast-math -fno-honor-infinities -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH-NO-INFS %s
+// CHECK-NO-FAST-MATH-NO-INFS: "-cc1"
+// CHECK-NO-FAST-MATH-NO-INFS: "-menable-no-infs"
+//
+// RUN: %clang -### -fno-honor-infinities -fno-fast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-INFS-NO-FAST-MATH %s
+// CHECK-NO-INFS-NO-FAST-MATH: "-cc1"
+// CHECK-NO-INFS-NO-FAST-MATH-NOT: "-menable-no-infs"
+//
 // RUN: %clang -### -fno-honor-nans -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-NANS %s
 // CHECK-NO-NANS: "-cc1"
 // CHECK-NO-NANS: "-menable-no-nans"
 //
+// RUN: %clang -### -fno-fast-math -fno-honor-nans -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH-NO-NANS %s
+// CHECK-NO-FAST-MATH-NO-NANS: "-cc1"
+// CHECK-NO-FAST-MATH-NO-NANS: "-menable-no-nans"
+//
+// RUN: %clang -### -fno-honor-nans -fno-fast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-NANS-NO-FAST-MATH %s
+// CHECK-NO-NANS-NO-FAST-MATH: "-cc1"
+// CHECK-NO-NANS-NO-FAST-MATH-NOT: "-menable-no-nans"
+//
 // RUN: %clang -### -fmath-errno -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-MATH-ERRNO %s
 // CHECK-MATH-ERRNO: "-cc1"
 // CHECK-MATH-ERRNO: "-fmath-errno"
 //
+// RUN: %clang -### -fno-fast-math -fmath-errno -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH-MATH-ERRNO %s
+// CHECK-NO-FAST-MATH-MATH-ERRNO: "-cc1"
+// CHECK-NO-FAST-MATH-MATH-ERRNO: "-fmath-errno"
+//
+// RUN: %clang -### -fmath-errno -fno-fast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MATH-ERRNO-NO-FAST-MATH %s
+// CHECK-MATH-ERRNO-NO-FAST-MATH: "-cc1"
+// CHECK-MATH-ERRNO-NO-FAST-MATH-NOT: "-fmath-errno"
+//
 // RUN: %clang -### -fmath-errno -fno-math-errno -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
 // RUN: %clang -### -target i686-apple-darwin -c %s 2>&1 \
@@ -43,6 +73,18 @@
 // CHECK-UNSAFE-MATH: "-cc1"
 // CHECK-UNSAFE-MATH: "-menable-unsafe-fp-math"
 //
+// RUN: %clang -### -fno-fast-math -fno-math-errno -fassociative-math -freciprocal-math \
+// RUN:     -fno-signed-zeros -fno-trapping-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH-UNSAFE-MATH %s
+// CHECK-NO-FAST-MATH-UNSAFE-MATH: "-cc1"
+// CHECK-NO-FAST-MATH-UNSAFE-MATH: "-menable-unsafe-fp-math"
+//
+// RUN: %clang -### -fno-fast-math -fno-math-errno -fassociative-math -freciprocal-math \
+// RUN:     -fno-fast-math -fno-signed-zeros -fno-trapping-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-UNSAFE-MATH-NO-FAST-MATH %s
+// CHECK-UNSAFE-MATH-NO-FAST-MATH: "-cc1"
+// CHECK-UNSAFE-MATH-NO-FAST-MATH-NOT: "-menable-unsafe-fp-math"
+//
 // Check that various umbrella flags also enable these frontend options.
 // RUN: %clang -### -ffast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-INFS %s
@@ -63,12 +105,19 @@
 // impact remains even if every optimization is disabled.
 // RUN: %clang -### -ffast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
+// RUN: %clang -### -fno-fast-math -ffast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
 // RUN: %clang -### -ffast-math -fno-finite-math-only \
 // RUN:     -fno-unsafe-math-optimizations -fmath-errno -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
 // CHECK-FAST-MATH: "-cc1"
 // CHECK-FAST-MATH: "-ffast-math"
 //
+// RUN: %clang -### -ffast-math -fno-fast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH %s
+// CHECK-NO-FAST-MATH: "-cc1"
+// CHECK-NO-FAST-MATH-NOT: "-ffast-math"
+//
 // Check various means of disabling these flags, including disabling them after
 // they've been enabled via an umbrella flag.
 // RUN: %clang -### -fno-honor-infinities -fhonor-infinities -c %s 2>&1 \