[InstCombine] Add additional test for invert of lshr (NFC)

Author: nikic

llvm/test/Transforms/InstCombine/free-inversion.ll

@@ -524,3 +524,15 @@ define i8 @lshr_not_nneg(i8 %x, i8 %y) {
   %shr.not = xor i8 %shr, -1
   ret i8 %shr.not
 }
+
+define i8 @lshr_not_nneg2(i8 %x) {
+; CHECK-LABEL: @lshr_not_nneg2(
+; CHECK-NEXT:    [[SHR:%.*]] = lshr i8 [[X:%.*]], 1
+; CHECK-NEXT:    [[SHR_NOT1:%.*]] = or i8 [[SHR]], -128
+; CHECK-NEXT:    ret i8 [[SHR_NOT1]]
+;
+  %x.not = xor i8 %x, -1
+  %shr = lshr i8 %x.not, 1
+  %shr.not = xor i8 %shr, -1
+  ret i8 %shr.not
+}