Index: lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1388,6 +1388,8 @@
   }
 
   // select C, 0, B + select C, A, 0 -> select C, A, B
+  // select C, A1, B1 + select C, A2, B2 -> select C, (A1+A2), (B1+B2) 
+  //   iff {A1,A2,B1,B2} are all constants 
   {
     Value *A1, *B1, *C1, *A2, *B2, *C2;
     if (match(LHS, m_Select(m_Value(C1), m_Value(A1), m_Value(B1))) &&
@@ -1401,6 +1403,17 @@
         } else if (match(B1, m_AnyZero()) && match(A2, m_AnyZero())) {
             Z1 = dyn_cast<Constant>(B1); B = B2;
             Z2 = dyn_cast<Constant>(A2); A = A1;
+        } else if (isa<Constant>(A1) && isa<Constant>(A2) &&
+                   isa<Constant>(B1) && isa<Constant>(B2)) {
+            Value *V0 = Builder.CreateFAdd(A1, A2);
+            Value *V1 = Builder.CreateFAdd(B1, B2);
+            if (Instruction *I0 = dyn_cast<Instruction>(V0))
+              I0->setFastMathFlags(I.getFastMathFlags());
+
+            if (Instruction *I1 = dyn_cast<Instruction>(V1))
+              I1->setFastMathFlags(I.getFastMathFlags());
+
+            return SelectInst::Create(C, V0, V1);
         }
 
         if (Z1 && Z2 &&
@@ -1760,6 +1773,29 @@
     }
   }
 
+  // select C, A1, B1 * select C, A2, B2 -> select C, (A1*A2), (B1*B2) 
+  //   iff {A1,A2,B1,B2} are all constants 
+  {
+    Value *A1, *B1, *C1, *A2, *B2, *C2;
+    if (match(Op0, m_Select(m_Value(C1), m_Value(A1), m_Value(B1))) &&
+        match(Op1, m_Select(m_Value(C2), m_Value(A2), m_Value(B2)))) {
+      if (C1 == C2) {
+        if (isa<Constant>(A1) && isa<Constant>(A2) &&
+            isa<Constant>(B1) && isa<Constant>(B2)) {
+          Value *V0 = Builder.CreateFSub(A1, A2);
+          Value *V1 = Builder.CreateFSub(B1, B2);
+          if (Instruction *I0 = dyn_cast<Instruction>(V0))
+            I0->setFastMathFlags(I.getFastMathFlags());
+
+          if (Instruction *I1 = dyn_cast<Instruction>(V1))
+            I1->setFastMathFlags(I.getFastMathFlags());
+
+          return SelectInst::Create(C1, V0, V1);
+        }
+      }
+    }
+  }
+
   if (I.hasUnsafeAlgebra()) {
     if (Value *V = FAddCombine(Builder).simplify(&I))
       return replaceInstUsesWith(I, V);
Index: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -736,6 +736,29 @@
       }
     }
 
+    // select C, A1, B1 * select C, A2, B2 -> select C, (A1*A2), (B1*B2) 
+    //   iff {A1,A2,B1,B2} are all constants 
+    {
+      Value *A1, *B1, *C1, *A2, *B2, *C2;
+      if (match(Op0, m_Select(m_Value(C1), m_Value(A1), m_Value(B1))) &&
+          match(Op1, m_Select(m_Value(C2), m_Value(A2), m_Value(B2)))) {
+        if (C1 == C2) {
+          if (isa<Constant>(A1) && isa<Constant>(A2) &&
+              isa<Constant>(B1) && isa<Constant>(B2)) {
+            Value *V0 = Builder.CreateFMul(A1, A2);
+            Value *V1 = Builder.CreateFMul(B1, B2);
+            if (Instruction *I0 = dyn_cast<Instruction>(V0))
+              I0->setFastMathFlags(I.getFastMathFlags());
+
+            if (Instruction *I1 = dyn_cast<Instruction>(V1))
+              I1->setFastMathFlags(I.getFastMathFlags());
+
+            return SelectInst::Create(C1, V0, V1);
+          }
+        }
+      }
+    }
+
     // (X*Y) * X => (X*X) * Y where Y != X
     //  The purpose is two-fold:
     //   1) to form a power expression (of X).
Index: test/Transforms/InstCombine/select_arithmetic.ll
===================================================================
--- /dev/null
+++ test/Transforms/InstCombine/select_arithmetic.ll
@@ -0,0 +1,44 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define float @test1(i1 zeroext) #0 {
+  %2 = select i1 %0, float 5.000000e+00, float 6.000000e+00
+  %3 = select i1 %0, float 1.000000e+00, float 9.000000e+00
+  %4 = fadd float %2, %3
+  ret float %4
+; CHECK-LABEL: @test1(
+; CHECK: %2 = select i1 %0, float 6.000000e+00, float 1.500000e+01
+; CHECK-NOT: fadd
+; CHECK: ret float %2
+}
+
+define float @test2(i1 zeroext) #0 {
+  %2 = select i1 %0, float 5.000000e+00, float 6.000000e+00
+  %3 = select i1 %0, float 1.000000e+00, float 9.000000e+00
+  %4 = fsub float %2, %3
+  ret float %4
+; CHECK-LABEL: @test2(
+; CHECK: %2 = select i1 %0, float 4.000000e+00, float -3.000000e+00
+; CHECK-NOT: fsub
+; CHECK: ret float %2
+}
+
+define float @test3(i1 zeroext) #0 {
+  %2 = select i1 %0, float 5.000000e+00, float 6.000000e+00
+  %3 = select i1 %0, float 1.000000e+00, float 9.000000e+00
+  %4 = fmul float %2, %3
+  ret float %4
+; CHECK-LABEL: @test3(
+; CHECK: %2 = select i1 %0, float 5.000000e+00, float 5.400000e+01
+; CHECK-NOT: fmul
+; CHECK: ret float %2
+}
+
+attributes #0 = { noinline nounwind ssp uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cx16,+fxsr,+mmx,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.module.flags = !{!0}
+!llvm.ident = !{!1}
+
+!0 = !{i32 1, !"PIC Level", i32 2}
+!1 = !{!"Apple LLVM version 9.0.0 (clang-900.0.32)"}