RFR: 8281453: New optimization: convert "c-(~x)" into "x+(c+1)" and "~(c-x)" into "x+(-c-1)" [v6]

[Vladimir Kozlov]

On Sat, 26 Mar 2022 03:25:25 GMT, Zhiqiang Zang <duke at openjdk.java.net> wrote:

>> Similar to `(~x)+c` -> `(c-1)-x` and `~(x+c)` -> `(-c-1)-x` in #6858, we can also introduce similar optimizations for subtraction, `c-(~x)` -> `x+(c+1)` and `~(c-x)` -> `x+(-c-1)`.
>> 
>> The results of the microbenchmark are as follows:
>> 
>> Baseline:                                                                                                                                         
>> Benchmark                        Mode  Cnt  Score   Error  Units
>> SubIdealCMinusNotX.baselineInt   avgt   60  0.504 ± 0.011  ns/op
>> SubIdealCMinusNotX.baselineLong  avgt   60  0.484 ± 0.004  ns/op
>> SubIdealCMinusNotX.testInt1      avgt   60  0.779 ± 0.004  ns/op
>> SubIdealCMinusNotX.testInt2      avgt   60  0.896 ± 0.004  ns/op
>> SubIdealCMinusNotX.testLong1     avgt   60  0.722 ± 0.004  ns/op
>> SubIdealCMinusNotX.testLong2     avgt   60  0.720 ± 0.005  ns/op
>> 
>> Patch:
>> Benchmark                        Mode  Cnt  Score   Error  Units
>> SubIdealCMinusNotX.baselineInt   avgt   60  0.487 ± 0.009  ns/op
>> SubIdealCMinusNotX.baselineLong  avgt   60  0.486 ± 0.009  ns/op
>> SubIdealCMinusNotX.testInt1      avgt   60  0.372 ± 0.010  ns/op
>> SubIdealCMinusNotX.testInt2      avgt   60  0.365 ± 0.003  ns/op
>> SubIdealCMinusNotX.testLong1     avgt   60  0.369 ± 0.004  ns/op
>> SubIdealCMinusNotX.testLong2     avgt   60  0.399 ± 0.016  ns/op
>
> Zhiqiang Zang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   clean.

This change touches the same code as #7795
I suggest to update after that one is pushed.

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PR: https://git.openjdk.java.net/jdk/pull/7376