diff --git a/include/llvm/IR/Operator.h b/include/llvm/IR/Operator.h
index 119156a50e0..a30a84685d8 100644
--- a/include/llvm/IR/Operator.h
+++ b/include/llvm/IR/Operator.h
@@ -210,6 +210,10 @@ public:
     setNoSignedZeros();
     setAllowReciprocal();
   }
+
+  void operator&=(const FastMathFlags &OtherFlags) {
+    Flags &= OtherFlags.Flags;
+  }
 };
 
 
diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 71990a27ac0..29ab6c0623e 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1232,7 +1232,10 @@ Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
             LHSOrig = Builder->CreateFPExt(LHSOrig, CI.getType());
           if (RHSOrig->getType() != CI.getType())
             RHSOrig = Builder->CreateFPExt(RHSOrig, CI.getType());
-          return BinaryOperator::Create(OpI->getOpcode(), LHSOrig, RHSOrig);
+          Instruction *RI =
+            BinaryOperator::Create(OpI->getOpcode(), LHSOrig, RHSOrig);
+          RI->copyFastMathFlags(OpI);
+          return RI;
         }
         break;
       case Instruction::FMul:
@@ -1246,7 +1249,10 @@ Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
             LHSOrig = Builder->CreateFPExt(LHSOrig, CI.getType());
           if (RHSOrig->getType() != CI.getType())
             RHSOrig = Builder->CreateFPExt(RHSOrig, CI.getType());
-          return BinaryOperator::CreateFMul(LHSOrig, RHSOrig);
+          Instruction *RI =
+            BinaryOperator::CreateFMul(LHSOrig, RHSOrig);
+          RI->copyFastMathFlags(OpI);
+          return RI;
         }
         break;
       case Instruction::FDiv:
@@ -1261,7 +1267,10 @@ Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
             LHSOrig = Builder->CreateFPExt(LHSOrig, CI.getType());
           if (RHSOrig->getType() != CI.getType())
             RHSOrig = Builder->CreateFPExt(RHSOrig, CI.getType());
-          return BinaryOperator::CreateFDiv(LHSOrig, RHSOrig);
+          Instruction *RI =
+            BinaryOperator::CreateFDiv(LHSOrig, RHSOrig);
+          RI->copyFastMathFlags(OpI);
+          return RI;
         }
         break;
       case Instruction::FRem:
@@ -1274,6 +1283,8 @@ Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
         else if (RHSWidth <= SrcWidth)
           RHSOrig = Builder->CreateFPExt(RHSOrig, LHSOrig->getType());
         Value *ExactResult = Builder->CreateFRem(LHSOrig, RHSOrig);
+        if (Instruction *RI = dyn_cast<Instruction>(ExactResult))
+          RI->copyFastMathFlags(OpI);
         return CastInst::CreateFPCast(ExactResult, CI.getType());
     }
 
@@ -1281,7 +1292,9 @@ Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
     if (BinaryOperator::isFNeg(OpI)) {
       Value *InnerTrunc = Builder->CreateFPTrunc(OpI->getOperand(1),
                                                  CI.getType());
-      return BinaryOperator::CreateFNeg(InnerTrunc);
+      Instruction *RI = BinaryOperator::CreateFNeg(InnerTrunc);
+      RI->copyFastMathFlags(OpI);
+      return RI;
     }
   }
 
diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 283bec2881f..555ffc77523 100644
--- a/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -901,6 +901,11 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
             Value *NegVal;  // Compute -Z
             if (SI.getType()->isFPOrFPVectorTy()) {
               NegVal = Builder->CreateFNeg(SubOp->getOperand(1));
+              if (Instruction *NegInst = dyn_cast<Instruction>(NegVal)) {
+                FastMathFlags Flags = AddOp->getFastMathFlags();
+                Flags &= SubOp->getFastMathFlags();
+                NegInst->setFastMathFlags(Flags);
+              }
             } else {
               NegVal = Builder->CreateNeg(SubOp->getOperand(1));
             }
@@ -913,9 +918,15 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
               Builder->CreateSelect(CondVal, NewTrueOp,
                                     NewFalseOp, SI.getName() + ".p");
 
-            if (SI.getType()->isFPOrFPVectorTy())
-              return BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel);
-            else
+            if (SI.getType()->isFPOrFPVectorTy()) {
+              Instruction *RI =
+                BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel);
+
+              FastMathFlags Flags = AddOp->getFastMathFlags();
+              Flags &= SubOp->getFastMathFlags();
+              RI->setFastMathFlags(Flags);
+              return RI;
+            } else
               return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
           }
         }
diff --git a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index c0b9b2fc3e5..178be61b43e 100644
--- a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -638,6 +638,8 @@ static Value *BuildNew(Instruction *I, ArrayRef<Value*> NewOps) {
       if (isa<PossiblyExactOperator>(BO)) {
         New->setIsExact(BO->isExact());
       }
+      if (isa<FPMathOperator>(BO))
+        New->copyFastMathFlags(I);
       return New;
     }
     case Instruction::ICmp:
diff --git a/test/Transforms/InstCombine/fast-math.ll b/test/Transforms/InstCombine/fast-math.ll
index 0371488dfd8..de51c494685 100644
--- a/test/Transforms/InstCombine/fast-math.ll
+++ b/test/Transforms/InstCombine/fast-math.ll
@@ -160,6 +160,22 @@ define float @fold15(float %x, float %y) {
 ; CHECK: ret
 }
 
+; (select X+Y, X-Y) => X + (select Y, -Y)
+define float @fold16(float %x, float %y) {
+  %cmp = fcmp ogt float %x, %y
+  %plus = fadd fast float %x, %y
+  %minus = fsub fast float %x, %y
+  %r = select i1 %cmp, float %plus, float %minus
+  ret float %r
+; CHECK: fold16
+; CHECK: fsub fast float
+; CHECK: select
+; CHECK: fadd fast float
+; CHECK: ret
+}
+
+
+
 ; =========================================================================
 ;
 ;   Testing-cases about fmul begin
diff --git a/test/Transforms/InstCombine/fpcast.ll b/test/Transforms/InstCombine/fpcast.ll
index 05d1b48d599..9be66fd42c6 100644
--- a/test/Transforms/InstCombine/fpcast.ll
+++ b/test/Transforms/InstCombine/fpcast.ll
@@ -31,6 +31,15 @@ define half @test4(float %a) {
   ret half %c
 }
 
+; CHECK: test4-fast
+define half @test4-fast(float %a) {
+; CHECK: fptrunc
+; CHECK: fsub fast
+  %b = fsub fast float -0.0, %a
+  %c = fptrunc float %b to half
+  ret half %c
+}
+
 ; CHECK: test5
 define half @test5(float %a, float %b, float %c) {
 ; CHECK: fcmp ogt