RFR: 8299308: Add Assembler::testw register + immediate function for x86

Fri Dec 23 10:35:48 UTC 2022

On Fri, 23 Dec 2022 10:00:28 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

> The testw register + immediate instruction is missing in the x86 assembler. It's used by generational ZGC. Let's add it.

Is it really needed, `testw r, i16` has the prefix 0x66 as a length changing prefix, which will bottle the predecoder. It is better to zero-extend to a 32-bit value and use `testl r, i32`.

Thanks.

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PR: https://git.openjdk.org/jdk/pull/11772