RFR: 8311847: Fix -Wconversion for assembler.hpp emit_int8,16 callers

[Dean Long]

On Tue, 11 Jul 2023 02:52:52 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Please review changes to fix -Wconversion warnings that come from assembler_<cpu>.cpp by adding narrow_casts to the emit_int8,16,24, and 32 functions.  And some other fixups with checked_cast.
>> 
>> Ran tier1 on Oracle platforms, and tier1-4 on linux-x64-debug, linux-aarch64-debug, windows-x64-debug.
>
> src/hotspot/share/asm/assembler.hpp line 328:
> 
>> 326:                                                                                                  narrow_cast<uint8_t>(x2),
>> 327:                                                                                                  narrow_cast<uint8_t>(x3),
>> 328:                                                                                                  narrow_cast<uint8_t>(x4)); }
> 
> I'd rather add new alternative entry points for "int", so the existing callers using uint8_t don't need to perform unnecessary widening and narrowing.
> Instead of narrow_cast<uint8_t>(x), how about (uint8_t)checked_cast<int8_t>(x)?

How many callers are passing in negative values and actually need these convenience functions?

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PR Review Comment: https://git.openjdk.org/jdk/pull/14822#discussion_r1259116990