[ConstraintElim] Add samesign test. NFC

Author: citymarina

llvm/test/Transforms/ConstraintElimination/transfer-samesign-facts.ll

@@ -303,3 +303,24 @@ define i1 @ugt_assumed_positive_values(i8 %a, i8 %b) {
 
   ret i1 %result
 }
+
+define i1 @samesign_flipped_signedness(i8 %a)  {
+; CHECK-LABEL: @samesign_flipped_signedness(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt i8 [[A:%.*]], 0
+; CHECK-NEXT:    br i1 [[TMP1]], label [[GREATER:%.*]], label [[EXIT:%.*]]
+; CHECK:       greater:
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp samesign sgt i8 [[A]], 0
+; CHECK-NEXT:    ret i1 [[TMP2]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret i1 false
+;
+  %1 = icmp ugt i8 %a, 0
+  br i1 %1, label %greater, label %exit
+
+greater:
+  %2 = icmp samesign sgt i8 %a, 0
+  ret i1 %2
+
+exit:
+  ret i1 false
+}