Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -2760,8 +2760,10 @@
   if (MathErrno)
     CmdArgs.push_back("-fmath-errno");
 
+  // If -ffp-contract=off has been specified on the command line, then we must
+  // suppress the emission of -ffast-math and -menable-unsafe-fp-math to cc1.
   if (!MathErrno && AssociativeMath && ReciprocalMath && !SignedZeros &&
-      !TrappingMath)
+      !TrappingMath && !(FPContract.equals("off") || FPContract.equals("on")))
     CmdArgs.push_back("-menable-unsafe-fp-math");
 
   if (!SignedZeros)
@@ -2804,7 +2806,8 @@
   // that's consistent with gcc's behaviour.
   if (!HonorINFs && !HonorNaNs && !MathErrno && AssociativeMath &&
       ReciprocalMath && !SignedZeros && !TrappingMath && !RoundingFPMath) {
-    CmdArgs.push_back("-ffast-math");
+    if (!(FPContract.equals("off") || FPContract.equals("on")))
+      CmdArgs.push_back("-ffast-math");
     if (FPModel.equals("fast")) {
       if (FPContract.equals("fast"))
         // All set, do nothing.
Index: clang/test/Driver/fast-math.c
===================================================================
--- clang/test/Driver/fast-math.c
+++ clang/test/Driver/fast-math.c
@@ -180,6 +180,21 @@
 // CHECK-FAST-MATH: "-ffast-math"
 // CHECK-FAST-MATH: "-ffinite-math-only"
 //
+// -ffp-contract=off and -ffp-contract=on must disable the fast-math umbrella,
+// and the unsafe-fp-math umbrella (-ffp-conteact=fast leaves them enabled).
+// RUN: %clang -### -ffast-math -ffp-contract=off -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH %s
+// RUN: %clang -### -ffast-math -ffp-contract=off -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-UNSAFE-MATH %s
+// RUN: %clang -### -ffast-math -ffp-contract=on -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH %s
+// RUN: %clang -### -ffast-math -ffp-contract=on -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-UNSAFE-MATH %s
+// RUN: %clang -### -ffast-math -ffp-contract=fast -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
+// RUN: %clang -### -ffast-math -ffp-contract=fast -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-UNSAFE-MATH %s
+//
 // RUN: %clang -### -ffast-math -fno-fast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH %s
 // RUN: %clang -### -ffast-math -fno-finite-math-only -c %s 2>&1 \