[InstCombine] Add additional test for icmp of two ranges (NFC)

Author: nikic

llvm/test/Transforms/InstCombine/or.ll

@@ -813,6 +813,24 @@ define <2 x i1> @test46_undef(<2 x i8> %c)  {
   ret <2 x i1> %or
 }
 
+; This is the variant of the above pattern where one of the ranges is
+; represented with an add.
+define i1 @two_ranges_to_mask_and_range_degenerate(i16 %x) {
+; CHECK-LABEL: @two_ranges_to_mask_and_range_degenerate(
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ult i16 [[X:%.*]], 12
+; CHECK-NEXT:    [[TMP1:%.*]] = add i16 [[X]], -16
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp ult i16 [[TMP1]], 12
+; CHECK-NEXT:    [[OR:%.*]] = or i1 [[CMP1]], [[TMP2]]
+; CHECK-NEXT:    ret i1 [[OR]]
+;
+  %cmp1 = icmp ult i16 %x, 12
+  %cmp2 = icmp uge i16 %x, 16
+  %cmp3 = icmp ult i16 %x, 28
+  %and = and i1 %cmp2, %cmp3
+  %or = or i1 %cmp1, %and
+  ret i1 %or
+}
+
 define i1 @test47(i8 signext %c)  {
 ; CHECK-LABEL: @test47(
 ; CHECK-NEXT:    [[TMP1:%.*]] = and i8 [[C:%.*]], -33