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

[Dean Long]

On Tue, 11 Jul 2023 01:26:44 GMT, Coleen Phillimore <coleenp 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 297:

> 295:   constexpr T narrow_cast(int x) const {
> 296:    if (x < 0) {
> 297:     assert(x > -(std::numeric_limits<T>::max() - 1), "too negative");

Suggestion:

    assert(x >= -std::numeric_limits<T>::max(), "too negative"); // >= -256 for 8 bits

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PR Review Comment: https://git.openjdk.org/jdk/pull/14822#discussion_r1259405009