RFR: 8273239: Standardize Ticks APIs return type [v2]

[Paul Hohensee]

On Tue, 7 Sep 2021 17:27:00 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Simple change on return types of Ticks API.
>> 
>> The call of `milliseconds()` in `spinYield.cpp` seems a bug to me, because the unit in the message is `usecs`. Therefore, I changed it to `microseconds()`.
>> 
>> Test: tier1
>
> Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   template

Here's a [webrev](https://cr.openjdk.java.net/~phh/8273239/webrev.00/) that uses is_integral() to compute seconds/millis/micros/nanos at full width for both integral and floating point target types. Passes hotspot tier1 and gtest, running jdk tier1. Generated code looks correct.

There are quite a few places where seconds() * 1000.0, etc. could be replaced by uses of milliseconds<double>(), etc.

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PR: https://git.openjdk.java.net/jdk/pull/5332