Index: lib/Transforms/InstCombine/InstCombineSelect.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -54,6 +54,31 @@
   return Builder.CreateSelect(Builder.CreateICmp(Pred, A, B), A, B);
 }
 
+/// Fold
+///   %A = icmp eq i8 %x, 0
+///   %B = op i8 %x, %z
+///   %C = select i1 %A, i8 %B, i8 %y
+/// To
+///   %C = select i1 %A, i8 %z, i8 %y
+/// OP: binop with an identity constant
+/// TODO: support for non-commutative and FP opcodes
+static Value *foldSelectInstWithBinaryOp(SelectInst &Sel,
+                                         InstCombiner::BuilderTy &Builder) {
+  Value *Cond = Sel.getCondition();
+  Value *TrueVal = Sel.getTrueValue();
+  Value *FalseVal = Sel.getFalseValue();
+
+  Value *X, *Z, *C;
+  CmpInst::Predicate Pred;
+  if (match(Cond, m_ICmp(Pred, m_Value(X), m_Value(C))) &&
+      Pred == ICmpInst::ICMP_EQ)
+    if (match(TrueVal, m_c_BinOp(m_Specific(X), m_Value(Z))) &&
+        ConstantExpr::getBinOpIdentity(cast<Instruction>(TrueVal)->getOpcode(),
+                                       X->getType()) == C)
+      return Builder.CreateSelect(Cond, Z, FalseVal);
+  return nullptr;
+}
+
 /// This folds:
 ///  select (icmp eq (and X, C1)), TC, FC
 ///    iff C1 is a power 2 and the difference between TC and FC is a power-of-2.
@@ -1961,5 +1986,8 @@
   if (Instruction *Select = foldSelectCmpXchg(SI))
     return Select;
 
+  if (Value *V = foldSelectInstWithBinaryOp(SI, Builder))
+    return replaceInstUsesWith(SI, V);
+
   return nullptr;
-}
+}
Index: test/Transforms/InstCombine/select-binop-icmp.ll
===================================================================
--- test/Transforms/InstCombine/select-binop-icmp.ll
+++ test/Transforms/InstCombine/select-binop-icmp.ll
@@ -4,9 +4,8 @@
 define i32 @select_xor_icmp(i32 %x, i32 %y, i32 %z) {
 ; CHECK-LABEL: @select_xor_icmp(
 ; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], 0
-; CHECK-NEXT:    [[B:%.*]] = xor i32 [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[C:%.*]] = select i1 [[A]], i32 [[B]], i32 [[Y:%.*]]
-; CHECK-NEXT:    ret i32 [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %A = icmp eq i32 %x, 0
   %B = xor i32 %x, %z
@@ -17,9 +16,8 @@
 define i32 @select_mul_icmp(i32 %x, i32 %y, i32 %z) {
 ; CHECK-LABEL: @select_mul_icmp(
 ; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], 1
-; CHECK-NEXT:    [[B:%.*]] = mul i32 [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[C:%.*]] = select i1 [[A]], i32 [[B]], i32 [[Y:%.*]]
-; CHECK-NEXT:    ret i32 [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %A = icmp eq i32 %x, 1
   %B = mul i32 %x, %z
@@ -30,9 +28,8 @@
 define i32 @select_add_icmp(i32 %x, i32 %y, i32 %z) {
 ; CHECK-LABEL: @select_add_icmp(
 ; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], 0
-; CHECK-NEXT:    [[B:%.*]] = add i32 [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[C:%.*]] = select i1 [[A]], i32 [[B]], i32 [[Y:%.*]]
-; CHECK-NEXT:    ret i32 [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %A = icmp eq i32 %x, 0
   %B = add i32 %x, %z
@@ -43,9 +40,8 @@
 define i32 @select_or_icmp(i32 %x, i32 %y, i32 %z) {
 ; CHECK-LABEL: @select_or_icmp(
 ; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], 0
-; CHECK-NEXT:    [[B:%.*]] = or i32 [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[C:%.*]] = select i1 [[A]], i32 [[B]], i32 [[Y:%.*]]
-; CHECK-NEXT:    ret i32 [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %A = icmp eq i32 %x, 0
   %B = or i32 %x, %z
@@ -56,9 +52,8 @@
 define i32 @select_and_icmp(i32 %x, i32 %y, i32 %z) {
 ; CHECK-LABEL: @select_and_icmp(
 ; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], -1
-; CHECK-NEXT:    [[B:%.*]] = and i32 [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[C:%.*]] = select i1 [[A]], i32 [[B]], i32 [[Y:%.*]]
-; CHECK-NEXT:    ret i32 [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %A = icmp eq i32 %x, -1
   %B = and i32 %x, %z
@@ -69,9 +64,8 @@
 define <2 x i8> @select_xor_icmp_vec(<2 x i8> %x, <2 x i8> %y, <2 x i8> %z) {
 ; CHECK-LABEL: @select_xor_icmp_vec(
 ; CHECK-NEXT:    [[A:%.*]] = icmp eq <2 x i8> [[X:%.*]], zeroinitializer
-; CHECK-NEXT:    [[B:%.*]] = xor <2 x i8> [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[C:%.*]] = select <2 x i1> [[A]], <2 x i8> [[B]], <2 x i8> [[Y:%.*]]
-; CHECK-NEXT:    ret <2 x i8> [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = select <2 x i1> [[A]], <2 x i8> [[Z:%.*]], <2 x i8> [[Y:%.*]]
+; CHECK-NEXT:    ret <2 x i8> [[TMP1]]
 ;
   %A = icmp eq <2 x i8>  %x, <i8 0, i8 0>
   %B = xor <2 x i8>  %x, %z
@@ -79,25 +73,11 @@
   ret <2 x i8>  %C
 }
 
-define <2 x i8> @select_xor_icmp_vec2(<2 x i8> %x, <2 x i8> %y, <2 x i8> %z) {
-; CHECK-LABEL: @select_xor_icmp_vec2(
-; CHECK-NEXT:    [[A:%.*]] = icmp eq <2 x i8> [[X:%.*]], <i8 0, i8 undef>
-; CHECK-NEXT:    [[B:%.*]] = xor <2 x i8> [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[C:%.*]] = select <2 x i1> [[A]], <2 x i8> [[B]], <2 x i8> [[Y:%.*]]
-; CHECK-NEXT:    ret <2 x i8> [[C]]
-;
-  %A = icmp eq <2 x i8>  %x, <i8 0, i8 undef>
-  %B = xor <2 x i8>  %x, %z
-  %C = select <2 x i1>  %A, <2 x i8>  %B, <2 x i8>  %y
-  ret <2 x i8>  %C
-}
-
 define i32 @select_xor_inv_icmp(i32 %x, i32 %y, i32 %z) {
 ; CHECK-LABEL: @select_xor_inv_icmp(
 ; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], 0
-; CHECK-NEXT:    [[B:%.*]] = xor i32 [[Z:%.*]], [[X]]
-; CHECK-NEXT:    [[C:%.*]] = select i1 [[A]], i32 [[B]], i32 [[Y:%.*]]
-; CHECK-NEXT:    ret i32 [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %A = icmp eq i32 %x, 0
   %B = xor i32 %z, %x
@@ -184,6 +164,19 @@
   ret <2 x i8>  %C
 }
 
+define <2 x i8> @select_xor_icmp_vec_bad_2(<2 x i8> %x, <2 x i8> %y, <2 x i8> %z) {
+; CHECK-LABEL: @select_xor_icmp_vec_bad_2(
+; CHECK-NEXT:    [[A:%.*]] = icmp eq <2 x i8> [[X:%.*]], <i8 0, i8 undef>
+; CHECK-NEXT:    [[B:%.*]] = xor <2 x i8> [[X]], [[Z:%.*]]
+; CHECK-NEXT:    [[C:%.*]] = select <2 x i1> [[A]], <2 x i8> [[B]], <2 x i8> [[Y:%.*]]
+; CHECK-NEXT:    ret <2 x i8> [[C]]
+;
+  %A = icmp eq <2 x i8>  %x, <i8 0, i8 undef>
+  %B = xor <2 x i8>  %x, %z
+  %C = select <2 x i1>  %A, <2 x i8>  %B, <2 x i8>  %y
+  ret <2 x i8>  %C
+}
+
 define i32 @select_mul_icmp_bad(i32 %x, i32 %y, i32 %z, i32 %k) {
 ; CHECK-LABEL: @select_mul_icmp_bad(
 ; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], 3