[InstCombine] Add check of i1 types in select-to-zext/sext transformation

When doing select-to-zext/sext transformations, we should
not handle TrueVal and FalseVal of i1 type otherwise it
would result in zext/sext i1 to i1.

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D93272

Author: CongzheUalberta

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -2606,7 +2606,10 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
   // select i1 %c, <2 x i8> <1, 1>, <2 x i8> <0, 0>
   // because that may need 3 instructions to splat the condition value:
   // extend, insertelement, shufflevector.
-  if (SelType->isIntOrIntVectorTy() &&
+  //
+  // Do not handle i1 TrueVal and FalseVal otherwise would result in
+  // zext/sext i1 to i1.
+  if (SelType->isIntOrIntVectorTy() && !SelType->isIntOrIntVectorTy(1) &&
       CondVal->getType()->isVectorTy() == SelType->isVectorTy()) {
     // select C, 1, 0 -> zext C to int
     if (match(TrueVal, m_One()) && match(FalseVal, m_Zero()))