RFR: 8327964: Simplify BigInteger.implMultiplyToLen intrinsic [v5]

[Dean Long]

On Wed, 17 Apr 2024 12:35:54 GMT, Yudi Zheng <yzheng at openjdk.org> wrote:

>> Moving array construction within BigInteger.implMultiplyToLen intrinsic candidate to its caller simplifies the intrinsic implementation in JIT compiler.
>
> Yudi Zheng has updated the pull request incrementally with one additional commit since the last revision:
> 
>   address comment.

I think you'll want to ask port maintainers for aarch64/arm/ppc/riscv/s390 to review and test those changes.
There may be some opportunities for minor improvements, but those could be done later.  For example, we are computing `zlen` for the squareToLen stub even though the value is unused.  And both x86 and aarch64 seem to have unneeded save/restore code, even though I think all these registers are killed when called by a C2 runtime stub.

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PR Comment: https://git.openjdk.org/jdk/pull/18226#issuecomment-2062138149