RFR: JDK-8302040: Port fdlibm sqrt to Java

[Joe Darcy]

On Thu, 23 Feb 2023 23:28:11 GMT, Joe Darcy <darcy at openjdk.org> wrote:

> The wheel of FDLIBM porting turns a notch and sqrt comes into play.
> 
> While the sqrt operation usually has a hardware implementation that is intrinsified, for completeness a software implementation should be available as well.

src/java.base/share/classes/java/lang/FdLibm.java line 689:

> 687:             ix0 += (m << 20);
> 688:             z = __HI(z, ix0);
> 689:             z = __LO(z, ix1);

I was tempted to rewrite these line as something like:
`return Double.longBitsToDouble((long)ix0 << 32 | (long)ix1);`
and may do so in a future refactoring.

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PR: https://git.openjdk.org/jdk/pull/12736