RFR: JDK-8287349: Merge LDR instructions to improve C1 OSR performance

[kristylee88]

On Sat, 28 May 2022 06:28:57 GMT, Zhuojun Miao <zmiao at openjdk.org> wrote:

> Since MacroAssembler added merge_ldst, we can use different
> destination registers for contiguous-memory LDR instructions to improve performance.

Marked as reviewed by kristylee88 at github.com (no known OpenJDK username).

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PR: https://git.openjdk.java.net/jdk/pull/8933