[InstCombine][test] add tests for icmp with constant and offset; NFC

Author: rotateright

llvm/test/Transforms/InstCombine/icmp-add.ll

@@ -747,3 +747,49 @@ define i1 @with_nuw_large_negative(i8 %x, i8 %y) {
   %tobool = icmp eq i8 %t2, %t1
   ret i1 %tobool
 }
+
+define i1 @ugt_offset(i8 %a) {
+; CHECK-LABEL: @ugt_offset(
+; CHECK-NEXT:    [[T:%.*]] = add i8 [[A:%.*]], 124
+; CHECK-NEXT:    [[OV:%.*]] = icmp ugt i8 [[T]], -5
+; CHECK-NEXT:    ret i1 [[OV]]
+;
+  %t = add i8 %a, 124
+  %ov = icmp ugt i8 %t, 251
+  ret i1 %ov
+}
+
+define i1 @ugt_offset_use(i32 %a) {
+; CHECK-LABEL: @ugt_offset_use(
+; CHECK-NEXT:    [[T:%.*]] = add i32 [[A:%.*]], 42
+; CHECK-NEXT:    call void @use(i32 [[T]])
+; CHECK-NEXT:    [[OV:%.*]] = icmp ugt i32 [[T]], -2147483607
+; CHECK-NEXT:    ret i1 [[OV]]
+;
+  %t = add i32 %a, 42
+  call void @use(i32 %t)
+  %ov = icmp ugt i32 %t, 2147483689
+  ret i1 %ov
+}
+
+define <2 x i1> @ugt_offset_splat(<2 x i5> %a) {
+; CHECK-LABEL: @ugt_offset_splat(
+; CHECK-NEXT:    [[T:%.*]] = add <2 x i5> [[A:%.*]], <i5 9, i5 9>
+; CHECK-NEXT:    [[OV:%.*]] = icmp ugt <2 x i5> [[T]], <i5 -8, i5 -8>
+; CHECK-NEXT:    ret <2 x i1> [[OV]]
+;
+  %t = add <2 x i5> %a, <i5 9, i5 9>
+  %ov = icmp ugt <2 x i5> %t, <i5 24, i5 24>
+  ret <2 x i1> %ov
+}
+
+define i1 @ugt_wrong_offset(i8 %a) {
+; CHECK-LABEL: @ugt_wrong_offset(
+; CHECK-NEXT:    [[T:%.*]] = add i8 [[A:%.*]], 123
+; CHECK-NEXT:    [[OV:%.*]] = icmp ugt i8 [[T]], -5
+; CHECK-NEXT:    ret i1 [[OV]]
+;
+  %t = add i8 %a, 123
+  %ov = icmp ugt i8 %t, 251
+  ret i1 %ov
+}