Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -2194,6 +2194,10 @@
    Allow Reciprocal - Allow optimizations to use the reciprocal of an
    argument rather than perform division.
 
+``contract``
+   Allow floating-point contraction (e.g. fusing a multiply followed by an
+   addition into a fused multiply-and-add).
+
 ``fast``
    Fast - Allow algebraically equivalent transformations that may
    dramatically change results in floating point (e.g. reassociate). This
Index: include/llvm/IR/Instruction.h
===================================================================
--- include/llvm/IR/Instruction.h
+++ include/llvm/IR/Instruction.h
@@ -333,6 +333,9 @@
   /// Determine whether the allow-reciprocal flag is set.
   bool hasAllowReciprocal() const;
 
+  /// Determine whether the allow-contract flag is set.
+  bool hasAllowContract() const;
+
   /// Convenience function for getting all the fast-math flags, which must be an
   /// operator which supports these flags. See LangRef.html for the meaning of
   /// these flags.
Index: include/llvm/IR/Operator.h
===================================================================
--- include/llvm/IR/Operator.h
+++ include/llvm/IR/Operator.h
@@ -174,12 +174,15 @@
   FastMathFlags(unsigned F) : Flags(F) { }
 
 public:
+  /// This is how the bits are used in Value::SubclassData so they should fit
+  /// there too.
   enum {
     UnsafeAlgebra   = (1 << 0),
     NoNaNs          = (1 << 1),
     NoInfs          = (1 << 2),
     NoSignedZeros   = (1 << 3),
-    AllowReciprocal = (1 << 4)
+    AllowReciprocal = (1 << 4),
+    AllowContract   = (1 << 5)
   };
 
   FastMathFlags() = default;
@@ -195,6 +198,7 @@
   bool noInfs() const          { return 0 != (Flags & NoInfs); }
   bool noSignedZeros() const   { return 0 != (Flags & NoSignedZeros); }
   bool allowReciprocal() const { return 0 != (Flags & AllowReciprocal); }
+  bool allowContract() const { return 0 != (Flags & AllowContract); }
   bool unsafeAlgebra() const   { return 0 != (Flags & UnsafeAlgebra); }
 
   /// Flag setters
@@ -202,12 +206,16 @@
   void setNoInfs()          { Flags |= NoInfs; }
   void setNoSignedZeros()   { Flags |= NoSignedZeros; }
   void setAllowReciprocal() { Flags |= AllowReciprocal; }
+  void setAllowContract(bool B) {
+    Flags = (Flags & ~AllowContract) | B * AllowContract;
+  }
   void setUnsafeAlgebra() {
     Flags |= UnsafeAlgebra;
     setNoNaNs();
     setNoInfs();
     setNoSignedZeros();
     setAllowReciprocal();
+    setAllowContract(true);
   }
 
   void operator&=(const FastMathFlags &OtherFlags) {
@@ -259,6 +267,12 @@
       (B * FastMathFlags::AllowReciprocal);
   }
 
+  void setHasAllowContract(bool B) {
+    SubclassOptionalData =
+        (SubclassOptionalData & ~FastMathFlags::AllowContract) |
+        (B * FastMathFlags::AllowContract);
+  }
+
   /// Convenience function for setting multiple fast-math flags.
   /// FMF is a mask of the bits to set.
   void setFastMathFlags(FastMathFlags FMF) {
@@ -302,6 +316,12 @@
     return (SubclassOptionalData & FastMathFlags::AllowReciprocal) != 0;
   }
 
+  /// Test whether this operation is permitted to
+  /// be floating-point contracted, aka the 'C' fast-math property.
+  bool hasAllowContract() const {
+    return (SubclassOptionalData & FastMathFlags::AllowContract) != 0;
+  }
+
   /// Convenience function for getting all the fast-math flags
   FastMathFlags getFastMathFlags() const {
     return FastMathFlags(SubclassOptionalData);
Index: lib/AsmParser/LLLexer.cpp
===================================================================
--- lib/AsmParser/LLLexer.cpp
+++ lib/AsmParser/LLLexer.cpp
@@ -548,6 +548,7 @@
   KEYWORD(ninf);
   KEYWORD(nsz);
   KEYWORD(arcp);
+  KEYWORD(contract);
   KEYWORD(fast);
   KEYWORD(nuw);
   KEYWORD(nsw);
Index: lib/AsmParser/LLParser.h
===================================================================
--- lib/AsmParser/LLParser.h
+++ lib/AsmParser/LLParser.h
@@ -193,6 +193,10 @@
         case lltok::kw_ninf: FMF.setNoInfs();          Lex.Lex(); continue;
         case lltok::kw_nsz:  FMF.setNoSignedZeros();   Lex.Lex(); continue;
         case lltok::kw_arcp: FMF.setAllowReciprocal(); Lex.Lex(); continue;
+        case lltok::kw_contract:
+          FMF.setAllowContract(true);
+          Lex.Lex();
+          continue;
         default: return FMF;
         }
       return FMF;
Index: lib/AsmParser/LLToken.h
===================================================================
--- lib/AsmParser/LLToken.h
+++ lib/AsmParser/LLToken.h
@@ -98,6 +98,7 @@
   kw_ninf,
   kw_nsz,
   kw_arcp,
+  kw_contract,
   kw_fast,
   kw_nuw,
   kw_nsw,
Index: lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- lib/Bitcode/Reader/BitcodeReader.cpp
+++ lib/Bitcode/Reader/BitcodeReader.cpp
@@ -971,6 +971,8 @@
     FMF.setNoSignedZeros();
   if (0 != (Val & FastMathFlags::AllowReciprocal))
     FMF.setAllowReciprocal();
+  if (0 != (Val & FastMathFlags::AllowContract))
+    FMF.setAllowContract(true);
   return FMF;
 }
 
Index: lib/IR/AsmWriter.cpp
===================================================================
--- lib/IR/AsmWriter.cpp
+++ lib/IR/AsmWriter.cpp
@@ -1073,6 +1073,8 @@
         Out << " nsz";
       if (FPO->hasAllowReciprocal())
         Out << " arcp";
+      if (FPO->hasAllowContract())
+        Out << " contract";
     }
   }
 
Index: lib/IR/Instruction.cpp
===================================================================
--- lib/IR/Instruction.cpp
+++ lib/IR/Instruction.cpp
@@ -209,6 +209,11 @@
   return cast<FPMathOperator>(this)->hasAllowReciprocal();
 }
 
+bool Instruction::hasAllowContract() const {
+  assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
+  return cast<FPMathOperator>(this)->hasAllowContract();
+}
+
 FastMathFlags Instruction::getFastMathFlags() const {
   assert(isa<FPMathOperator>(this) && "getting fast-math flag on invalid op");
   return cast<FPMathOperator>(this)->getFastMathFlags();
Index: unittests/IR/IRBuilderTest.cpp
===================================================================
--- unittests/IR/IRBuilderTest.cpp
+++ unittests/IR/IRBuilderTest.cpp
@@ -207,7 +207,26 @@
   EXPECT_TRUE(FCmp->hasAllowReciprocal());
 
   Builder.clearFastMathFlags();
- 
+
+  // Test FP-contract
+  FC = Builder.CreateFAdd(F, F);
+  ASSERT_TRUE(isa<Instruction>(FC));
+  FAdd = cast<Instruction>(FC);
+  EXPECT_FALSE(FAdd->hasAllowContract());
+
+  FMF.clear();
+  FMF.setAllowContract(true);
+  Builder.setFastMathFlags(FMF);
+
+  FC = Builder.CreateFAdd(F, F);
+  EXPECT_TRUE(Builder.getFastMathFlags().any());
+  EXPECT_TRUE(Builder.getFastMathFlags().AllowContract);
+  ASSERT_TRUE(isa<Instruction>(FC));
+  FAdd = cast<Instruction>(FC);
+  EXPECT_TRUE(FAdd->hasAllowContract());
+
+  Builder.clearFastMathFlags();
+
   // Test a call with FMF.
   auto CalleeTy = FunctionType::get(Type::getFloatTy(Ctx),
                                     /*isVarArg=*/false);