RFR: 8290917: x86: Memory-operand arithmetic instructions have too low costs

[Vladimir Kozlov]

On Sat, 6 Aug 2022 09:53:01 GMT, Quan Anh Mai <duke at openjdk.org> wrote:

> The pattern `AddI (LoadI mem) imm` should be matched by a load followed by an add with constant, instead, it is currently matched as a constant load followed by an add with memory. The reason is that the cost of `addI_rReg_mem` is too low, this patch fixes this by increasing the cost of this fused instruction.
> 
> Testing: Manually run the test case in the JBS and look at the compiled code.
> 
> I also do some small clean-ups in x86_64.ad:
> 
> - For some reasons, `incl(Address)` is less efficient than `addl(Address, int)` as the former results in 3 uops in the fused domain as opposed to 2 in cases of the latter (according to [uops.info](uops.info)). As a result, I propose to remove the corresponding rules.
> - The `mulHiL` rules have unnecessary constraints on the input registers, these can be removed. The `no_rax_RegL` operand as a consequence can also be removed.
> - The rules involving long division by a constant can be removed because it has been covered by the optimiser during idealisation.
> - The pattern `SubI src imm` and the likes never match because they are converted to `AddI src -imm` by the optimiser. As a result, these rules can be removed
> - The rules involving shifting the argument by 1 are covered by and exactly the same as the corresponding rules of shifting by an immediate. As a result, they can be removed.
> - Some rules involving and-ing with a bit mask have unnecessary constraints on the target register.
> 
> Please kindly review, thank you very much.

`instruct incI_mem(memory dst, immI_1 src, rFlagsReg cr)` should be one instruction, not 2 as you pointed in JBS, because it increments by 1. The same should be true for other instructions which has `immI_1`, `immL1`, `immI_M1`, `immL_M1`.

I agree with your removal of `Sub*` instructions.

Would be nice to have JMH micros for all these changes to verify that score stay the same or better.

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PR: https://git.openjdk.org/jdk/pull/9791