RFR: 8327964: Simplify BigInteger.implMultiplyToLen intrinsic

[Dean Long]

On Tue, 12 Mar 2024 10:44:54 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.

src/hotspot/share/opto/library_call.cpp line 5934:

> 5932:     // 'y_start' points to y array + scaled ylen
> 5933: 
> 5934:     Node* zlen = _gvn.transform(new AddINode(xlen, ylen));

Would could generate one less instruction in the code cache if we did this `add` in the native runtime function.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18226#discussion_r1529102070