RFR: 8313249: Fix -Wconversion warnings in verifier code [v2]

[David Holmes]

On Sat, 29 Jul 2023 19:19:49 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> I've struggled with the raw cast versus checked_cast usage in this PR - I could not determine what was guiding the usage of each type of cast. Shouldn't it always be a checked cast? Or does the preceding range check validate the use of a raw cast (so we don't range check twice)?
>
> To me, the two lines serves two purposes:
> 
> 
> assert(appends > 0 && appends < 4, "Invalid append amount");
> 
> This is the input expected by this function.
> 
> 
>     return static_cast<u1>(251 + appends);
> 
> 
> This is a mechanical check that the code is actually correctly written (i.e., you didn't mess up and wrote (253 + appends). That way the reader doesn't have do the math in order to trust this code.

True - the assert is checking a precondition; the checked_cast would be checking a postcondition.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/15056#discussion_r1278556176