Make some tablegen tests more flexible.

[wolfy1961]

Some organizations have added operators downstream, and the 3 tests in this PR tend to fail with off-by-n errors (with n being the number of added operators) periodically.
To alleviate this. the proposed change is taking advantage of the fact that the 2nd and 3rd element in a switch table represent the lower and upper bounds of the operator id, and that the offset of the first byte of the encoded operations is a function of these 2 bounds.
Additionally, we the default label offset is encoded in a FileCheck variable.

[Pierre-vh]

LGTM

Do they fail sporadically, or are they just annoying to update?
I'm wondering if we could write a small script to autogenerate the checks at some point, similar to update_test_checks

[wolfy1961]

LGTM

Do they fail sporadically, or are they just annoying to update? I'm wondering if we could write a small script to autogenerate the checks at some point, similar to update_test_checks

They're not flaky, just annoying to update. The output from tblgen seems to be deterministic. A script sounds like a good idea, but I'm wondering how much it would have to know about the inner workings of tblgen or at least the details of the table layout.

Thanks for the review.