diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -3996,6 +3996,15 @@
       return FalseVal;
   }
 
+  // select i1 Cond, i1 true, i1 false --> i1 Cond
+  assert(Cond->getType()->isIntOrIntVectorTy(1) &&
+         "Select must have bool or bool vector condition");
+  assert(TrueVal->getType() == FalseVal->getType() &&
+         "Select must have same types for true/false ops");
+  if (Cond->getType() == TrueVal->getType() &&
+      match(TrueVal, m_One()) && match(FalseVal, m_ZeroInt()))
+    return Cond;
+
   // select ?, X, X -> X
   if (TrueVal == FalseVal)
     return TrueVal;
diff --git a/llvm/test/Transforms/InstSimplify/select.ll b/llvm/test/Transforms/InstSimplify/select.ll
--- a/llvm/test/Transforms/InstSimplify/select.ll
+++ b/llvm/test/Transforms/InstSimplify/select.ll
@@ -3,8 +3,7 @@
 
 define i1 @bool_true_or_false(i1 %cond) {
 ; CHECK-LABEL: @bool_true_or_false(
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[COND:%.*]], i1 true, i1 false
-; CHECK-NEXT:    ret i1 [[S]]
+; CHECK-NEXT:    ret i1 [[COND:%.*]]
 ;
   %s = select i1 %cond, i1 true, i1 false
   ret i1 %s
@@ -12,8 +11,7 @@
 
 define <2 x i1> @bool_true_or_false_vec(<2 x i1> %cond) {
 ; CHECK-LABEL: @bool_true_or_false_vec(
-; CHECK-NEXT:    [[S:%.*]] = select <2 x i1> [[COND:%.*]], <2 x i1> <i1 true, i1 true>, <2 x i1> zeroinitializer
-; CHECK-NEXT:    ret <2 x i1> [[S]]
+; CHECK-NEXT:    ret <2 x i1> [[COND:%.*]]
 ;
   %s = select <2 x i1> %cond, <2 x i1> <i1 true, i1 true>, <2 x i1> zeroinitializer
   ret <2 x i1> %s
@@ -21,8 +19,7 @@
 
 define <2 x i1> @bool_true_or_false_vec_undef(<2 x i1> %cond) {
 ; CHECK-LABEL: @bool_true_or_false_vec_undef(
-; CHECK-NEXT:    [[S:%.*]] = select <2 x i1> [[COND:%.*]], <2 x i1> <i1 undef, i1 true>, <2 x i1> <i1 false, i1 undef>
-; CHECK-NEXT:    ret <2 x i1> [[S]]
+; CHECK-NEXT:    ret <2 x i1> [[COND:%.*]]
 ;
   %s = select <2 x i1> %cond, <2 x i1> <i1 undef, i1 true>, <2 x i1> <i1 false, i1 undef>
   ret <2 x i1> %s