RFR: 8281453: New optimization: convert `~x` into `-1-x` when `~x` is used in an arithmetic expression [v9]
Zhiqiang Zang
duke at openjdk.org
Thu Sep 15 16:53:44 UTC 2022
> 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:
include microbenchmark.
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/7376/files
- new: https://git.openjdk.org/jdk/pull/7376/files/f7345fd9..1c238b8d
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=7376&range=08
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=7376&range=07-08
Stats: 98 lines in 1 file changed: 98 ins; 0 del; 0 mod
Patch: https://git.openjdk.org/jdk/pull/7376.diff
Fetch: git fetch https://git.openjdk.org/jdk pull/7376/head:pull/7376
PR: https://git.openjdk.org/jdk/pull/7376
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