RFR: 8282414: x86: Enhance the assembler to generate more compact instructions [v4]

[Sandhya Viswanathan]

On Sat, 26 Feb 2022 07:44:28 GMT, Quan Anh Mai <duke at openjdk.java.net> wrote:

>> Hi, this patch enhances the x86 assembler to emit more compact code for some popular instructions.
>> 
>> For common arithmetic instructions against immediates, if the immediate requires more than 1 byte to encode, we can still shave off 1 byte if the register operand is rax.
>> 
>> For test instruction, since the operation does not write the result, we can downgrade a long to an int and an int to a byte instruction if the immediate is positive and encodable using a smaller amount of bytes.
>> 
>> Thank you very much.
>
> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   comment

Looks good to me.

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Marked as reviewed by sviswanathan (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/7628