Integrated: 8281453: New optimization: convert ~x into -1-x when ~x is used in an arithmetic expression

[Zhiqiang Zang]

On Tue, 8 Feb 2022 05:51:37 GMT, Zhiqiang Zang <duke at openjdk.org> 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)`.
> 
> To generalize, I convert `~x` into `-1-x` when `~x` is used only in arithmetic expression. For example, `c-(~x)` will be converted into `c-(-1-x)` which will match other pattern and will be transformed again in next iteration and finally become `x+(c+1)`.
> 
> Also the conversion from `~x` into `-1-x` happens when `x` is an arithmetic expression itself. For example, `~(x+c)` will be transformed into `-1-(x+c)` and eventually `(-c-1)-x`.
> 
> The results of the microbenchmark are as follows:
> 
> Baseline:                                                               
> Benchmark                         Mode  Cnt  Score   Error  Units
> NotOpTransformation.baselineInt   avgt   60  0.440 ± 0.002  ns/op
> NotOpTransformation.baselineLong  avgt   60  0.440 ± 0.001  ns/op
> NotOpTransformation.testInt1      avgt   60  0.613 ± 0.006  ns/op
> NotOpTransformation.testInt2      avgt   60  0.868 ± 0.036  ns/op
> NotOpTransformation.testLong1     avgt   60  0.674 ± 0.008  ns/op
> NotOpTransformation.testLong2     avgt   60  0.698 ± 0.006  ns/op
> 
> Patch:
> Benchmark                         Mode  Cnt  Score    Error  Units
> NotOpTransformation.baselineInt   avgt   60  0.440 ±  0.001  ns/op
> NotOpTransformation.baselineLong  avgt   60  0.440 ±  0.001  ns/op
> NotOpTransformation.testInt1      avgt   60  0.329 ±  0.001  ns/op
> NotOpTransformation.testInt2      avgt   60  0.329 ±  0.001  ns/op
> NotOpTransformation.testLong1     avgt   60  0.329 ±  0.001  ns/op
> NotOpTransformation.testLong2     avgt   60  0.329 ±  0.001  ns/op

This pull request has now been integrated.

Changeset: 5dd851d8
Author:    Zhiqiang Zang <zhiqiang.zang at utexas.edu>
Committer: Vladimir Kozlov <kvn at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/5dd851d872c50ef33034c56007c58e6fa69ebd32
Stats:     957 lines in 7 files changed: 562 ins; 376 del; 19 mod

8281453: New optimization: convert ~x into -1-x when ~x is used in an arithmetic expression

Reviewed-by: kvn

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PR: https://git.openjdk.org/jdk/pull/7376