RFR: 8313249: Fix -Wconversion warnings in verifier code

[Coleen Phillimore]

On Fri, 28 Jul 2023 19:10:48 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> See bugid for comments.  Most of the verifier code deals with ints, so the u2 and other parameters weren't really needed and can be promoted to int. Mostly types are changed, but a few checked_cast<>s are added.
>> Tested with tier1-4, sanity Oracle platforms.
>
> src/hotspot/share/classfile/stackMapTableFormat.hpp line 481:
> 
>> 479: 
>> 480:   static u1 chops_to_frame_type(int chop) {
>> 481:     return (u1)(251 - chop);
> 
> This looks dangerous. If the range is alway within `u1`, it should use `checked_cast<u1>`, and you should also assert `chop <= 251`.

I agree, this one I should have used checked_cast<u1>.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15056#discussion_r1278097762