Index: include/llvm/IR/Operator.h
===================================================================
--- include/llvm/IR/Operator.h
+++ include/llvm/IR/Operator.h
@@ -207,17 +207,24 @@
   bool isFast() const          { return all(); }
 
   /// Flag setters
-  void setAllowReassoc()    { Flags |= AllowReassoc; }
-  void setNoNaNs()          { Flags |= NoNaNs; }
-  void setNoInfs()          { Flags |= NoInfs; }
-  void setNoSignedZeros()   { Flags |= NoSignedZeros; }
-  void setAllowReciprocal() { Flags |= AllowReciprocal; }
-  // TODO: Change the other set* functions to take a parameter?
-  void setAllowContract(bool B) {
+  void setAllowReassoc(bool B = true) {
+    Flags = (Flags & ~AllowReassoc) | B * AllowReassoc;
+  }
+  void setNoNaNs(bool B = true) { Flags = (Flags & ~NoNaNs) | B * NoNaNs; }
+  void setNoInfs(bool B = true) { Flags = (Flags & ~NoInfs) | B * NoInfs; }
+  void setNoSignedZeros(bool B = true) {
+    Flags = (Flags & ~NoSignedZeros) | B * NoSignedZeros;
+  }
+  void setAllowReciprocal(bool B = true) {
+    Flags = (Flags & ~AllowReciprocal) | B * AllowReciprocal;
+  }
+  void setAllowContract(bool B = true) {
     Flags = (Flags & ~AllowContract) | B * AllowContract;
   }
-  void setApproxFunc()      { Flags |= ApproxFunc; }
-  void setFast()            { set(); }
+  void setApproxFunc(bool B = true) {
+    Flags = (Flags & ~ApproxFunc) | B * ApproxFunc;
+  }
+  void setFast(bool B = true) { B ? set() : clear(); }
 
   void operator&=(const FastMathFlags &OtherFlags) {
     Flags &= OtherFlags.Flags;