RFR: 8313882: Fix -Wconversion warnings in runtime code [v2]

[Dean Long]

On Tue, 8 Aug 2023 20:09:56 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Here are fixes to silence -Wconversion warnings in runtime code.  Use direct cast for 64 bit int to double, otherwise default to checked_cast<>.  I changed the declaration of _held_monitor_count and _jni_monitor count to intx to fix cascade of warnings coming from this.
>> 
>> src/hotspot/share/runtime/synchronizer.cpp:1802:41: warning: conversion from 'intx' {aka 'long int'} to 'int' may change value [-Wconversion]
>>  1802 |     _thread->dec_held_monitor_count(rec + 1);
>>       |                                     ~~~~^~~
>> 
>> Tested with tier1-4 on linux-x64-debug and windows-x64-debug and tier1 on Oracle supported platforms.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Make bytecode.hpp index() functions return u2 not long.

src/hotspot/share/runtime/arguments.cpp line 1667:

> 1665: 
> 1666:     if (InitialHeapSize == 0) {
> 1667:       julong reasonable_initial = (julong)((phys_mem * (julong)InitialRAMPercentage) / 100);

This and the two changes above loses the fractional part.
Suggestion:

      julong reasonable_initial = (julong)((double)phys_mem * InitialRAMPercentage / 100.0);

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PR Review Comment: https://git.openjdk.org/jdk/pull/15177#discussion_r1287692376