Index: lib/Transforms/InstCombine/InstCombineSelect.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -54,6 +54,43 @@
   return Builder.CreateSelect(Builder.CreateICmp(Pred, A, B), A, B);
 }
 
+/// Fold
+///   %A = icmp eq/ne 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 Instruction *
+foldSelectInstWithBinaryOp(SelectInst &Sel, InstCombiner::BuilderTy &Builder) {
+  Value *Cond = Sel.getCondition();
+  Value *TrueVal = Sel.getTrueValue();
+  Value *FalseVal = Sel.getFalseValue();
+
+  Value *X, *Z;
+  Constant *C;
+  CmpInst::Predicate Pred;
+  if (match(Cond, m_ICmp(Pred, m_Value(X), m_Constant(C)))) {
+    if (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) {
+        Sel.setTrueValue(Z);
+        return &Sel;
+      }
+    } else if (Pred == ICmpInst::ICMP_NE) {
+      if (match(FalseVal, m_c_BinOp(m_Specific(X), m_Value(Z))) &&
+          ConstantExpr::getBinOpIdentity(
+              cast<Instruction>(FalseVal)->getOpcode(), X->getType()) == C) {
+        Sel.setFalseValue(Z);
+        return &Sel;
+      }
+    }
+  }
+  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 +1998,8 @@
   if (Instruction *Select = foldSelectCmpXchg(SI))
     return Select;
 
+  if (Instruction *Select = foldSelectInstWithBinaryOp(SI, Builder))
+    return Select;
+
   return nullptr;
-}
+}
Index: test/Transforms/InstCombine/select-binop-icmp.ll
===================================================================
--- test/Transforms/InstCombine/select-binop-icmp.ll
+++ test/Transforms/InstCombine/select-binop-icmp.ll
@@ -4,8 +4,7 @@
 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:    [[C:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[C]]
 ;
   %A = icmp eq i32 %x, 0
@@ -14,11 +13,34 @@
   ret i32 %C
 }
 
+define i32 @select_xor_icmp2(i32 %x, i32 %y, i32 %z) {
+; CHECK-LABEL: @select_xor_icmp2(
+; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], 0
+; CHECK-NEXT:    [[C:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[C]]
+;
+  %A = icmp ne i32 %x, 0
+  %B = xor i32 %x, %z
+  %C = select i1 %A, i32 %y, i32 %B
+  ret i32 %C
+}
+
+define i32 @select_xor_icmp_meta(i32 %x, i32 %y, i32 %z) {
+; CHECK-LABEL: @select_xor_icmp_meta(
+; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], 0
+; CHECK-NEXT:    [[C:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]], !prof !0
+; CHECK-NEXT:    ret i32 [[C]]
+;
+  %A = icmp eq i32 %x, 0
+  %B = xor i32 %x, %z
+  %C = select i1 %A, i32 %B, i32 %y, !prof !0
+  ret i32 %C
+}
+
 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:    [[C:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[C]]
 ;
   %A = icmp eq i32 %x, 1
@@ -30,8 +52,7 @@
 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:    [[C:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[C]]
 ;
   %A = icmp eq i32 %x, 0
@@ -43,8 +64,7 @@
 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:    [[C:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[C]]
 ;
   %A = icmp eq i32 %x, 0
@@ -56,8 +76,7 @@
 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:    [[C:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[C]]
 ;
   %A = icmp eq i32 %x, -1
@@ -69,8 +88,7 @@
 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:    [[C:%.*]] = select <2 x i1> [[A]], <2 x i8> [[Z:%.*]], <2 x i8> [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i8> [[C]]
 ;
   %A = icmp eq <2 x i8>  %x, <i8 0, i8 0>
@@ -81,22 +99,20 @@
 
 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:    [[A:%.*]] = icmp eq <2 x i8> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    [[C:%.*]] = select <2 x i1> [[A]], <2 x i8> [[Z:%.*]], <2 x i8> [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i8> [[C]]
 ;
-  %A = icmp eq <2 x i8>  %x, <i8 0, i8 undef>
+  %A = icmp ne <2 x i8>  %x, <i8 0, i8 0>
   %B = xor <2 x i8>  %x, %z
-  %C = select <2 x i1>  %A, <2 x i8>  %B, <2 x i8>  %y
+  %C = select <2 x i1>  %A, <2 x i8>  %y, <2 x i8>  %B
   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:    [[C:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[C]]
 ;
   %A = icmp eq i32 %x, 0
@@ -105,6 +121,18 @@
   ret i32 %C
 }
 
+define i32 @select_xor_inv_icmp2(i32 %x, i32 %y, i32 %z) {
+; CHECK-LABEL: @select_xor_inv_icmp2(
+; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], 0
+; CHECK-NEXT:    [[C:%.*]] = select i1 [[A]], i32 [[Z:%.*]], i32 [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[C]]
+;
+  %A = icmp ne i32 %x, 0
+  %B = xor i32 %x, %z
+  %C = select i1 %A, i32 %y, i32 %B
+  ret i32 %C
+}
+
 ; Negative tests
 define i32 @select_xor_icmp_bad_1(i32 %x, i32 %y, i32 %z, i32 %k) {
 ; CHECK-LABEL: @select_xor_icmp_bad_1(
@@ -171,6 +199,19 @@
   ret i32 %C
 }
 
+define i32 @select_xor_icmp_bad_6(i32 %x, i32 %y, i32 %z) {
+; CHECK-LABEL: @select_xor_icmp_bad_6(
+; CHECK-NEXT:    [[A:%.*]] = icmp eq i32 [[X:%.*]], 1
+; CHECK-NEXT:    [[B:%.*]] = xor i32 [[X]], [[Z:%.*]]
+; CHECK-NEXT:    [[C:%.*]] = select i1 [[A]], i32 [[B]], i32 [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[C]]
+;
+  %A = icmp ne i32 %x, 1
+  %B = xor i32 %x, %z
+  %C = select i1 %A, i32 %y, i32 %B
+  ret i32 %C
+}
+
 define <2 x i8> @select_xor_icmp_vec_bad(<2 x i8> %x, <2 x i8> %y, <2 x i8> %z) {
 ; CHECK-LABEL: @select_xor_icmp_vec_bad(
 ; CHECK-NEXT:    [[A:%.*]] = icmp eq <2 x i8> [[X:%.*]], <i8 5, i8 3>
@@ -184,6 +225,19 @@
   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
@@ -328,3 +382,5 @@
   %C = select i1 %A, float %B, float %y
   ret float %C
 }
+
+!0 = !{!"branch_weights", i32 2, i32 10}