RFR: 8282204: Use lea instructions for arithmetic operations on x86_64 [v10]

[Sandhya Viswanathan]

On Fri, 4 Mar 2022 08:29:40 GMT, Quan Anh Mai <duke at openjdk.java.net> wrote:

>> Hi,
>> 
>> This patch adds several matching rules for x86_64 backend to use `lea` instructions for several fused arithmetic operations. Also, `lea`s don't kill flags and allow different `dst` and `src`, so it is preferred over `sll` if possible, too. 
>> 
>> Thank you very much.
>
> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove unreached rules

src/hotspot/cpu/x86/vm_version_x86.hpp line 1062:

> 1060:   static bool supports_fast_3op_lea() {
> 1061:     return supports_fast_2op_lea() &&
> 1062:            ((is_intel() && supports_clwb()) || // Icelake and above

supports_clwb() is true on the previous Cascade Lake architecture as well so it will be good to pick some other new Icelake feature to differentiate.

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PR: https://git.openjdk.java.net/jdk/pull/7560