RFR: 8282204: Use lea instructions for arithmetic operations on x86_64 [v9]

[Jie Fu]

On Fri, 4 Mar 2022 06:59:02 GMT, Quan Anh Mai <duke at openjdk.java.net> wrote:

> I would refrain from doing that, carelessly changing `add`s to `lea`s may bring negative results in real-world situations since the latter is a little larger in size and lower in throughput. IMO the best solution would be emitting `lea` after the coalescing of an `add` or `shl` and its input fails (e.g when the `dst` operand is needed for other operations), resulting in a sequence `mov r1, r2; add r1, r3/imm` become `lea r1, [r2 + r3/imm]`. This happens after the register allocation phase and well after the matching phase. I perceive the peephole rules are more appropriate for this transformation but I'm still exploring this idea.

Sounds reasonable.
Shall we also remove `leaP_rReg_imm `?

-------------

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