Hi Everyone, Please could some reviewers volunteer their time to have a look at this patch?
It was marked as a starter bug so I don't expect it will consume a lot of time. Thanks, Jason -----Original Message----- From: hotspot-dev <hotspot-dev-r...@openjdk.java.net> On Behalf Of Jason Tatton Sent: 11 September 2020 11:24 To: core-libs-dev@openjdk.java.net; hotspot-...@openjdk.java.net Subject: RFR: 8173585: Intrinsify StringLatin1.indexOf(char) This is an implementation of the indexOf(char) intrinsic for StringLatin1 (1 byte encoded Strings). It is provided for x86 and ARM64. The implementation is greatly inspired by the indexOf(char) intrinsic for StringUTF16. To incorporate it I had to make a small change to StringLatin1.java (refactor of functionality to intrisified private method) as well as code for C2. Submitted to: hotspot-compiler-dev and core-libs-dev as this patch contains a change to hotspot and java/lang/StringLatin1.java https://bugs.openjdk.java.net/browse/JDK-8173585 Details of testing: ============ I have created a jtreg test “compiler/intrinsics/string/TestStringLatin1IndexOfChar” to cover this new intrinsic. Note that, particularly for the x86 implementation of the intrinsic, the code path taken is dependent upon the length of the input String. Hence the test has been designed to cover all these cases. In summary they are: - A “short” string of < 16 characters. - A SIMD String of 16 – 31 characters. - A AVX2 SIMD String of 32 characters+. Hardware used for testing: ----------------------------- - Intel Xeon CPU E5-2680 (JVM did not recognize this as having AVX2 support) • Intel i7 processor (with AVX2 support). - AWS Graviton 2 (ARM 64 processor). I also ran; ‘run-test-tier1’ and ‘run-test-tier2’ for: x86_64 and aarch64. Possible future enhancements: ==================== For the x86 implementation there may be two further improvements we can make in order to improve performance of both the StringUTF16 and StringLatin1 indexOf(char) intrinsics: 1. Make use of AVX-512 instructions. 2. For “short” Strings (see below), I think it may be possible to modify the existing algorithm to still use SSE SIMD instructions instead of a loop. Benchmark results: ============ **Without** the new StringLatin1 indexOf(char) intrinsic: | Benchmark | Mode | Cnt | Score | Error | Units | | ------------- | ------------- |------------- |------------- | |------------- |------------- | IndexOfBenchmark.latin1_mixed_char | | avgt | 5 | **26,389.129** | ± 182.581 | ns/op | | IndexOfBenchmark.utf16_mixed_char | avgt | 5 | 17,885.383 | ± 435.933 | | ns/op | **With** the new StringLatin1 indexOf(char) intrinsic: | Benchmark | Mode | Cnt | Score | Error | Units | | ------------- | ------------- |------------- |------------- | |------------- |------------- | IndexOfBenchmark.latin1_mixed_char | | avgt | 5 | **17,875.185** | ± 407.716 | ns/op | | IndexOfBenchmark.utf16_mixed_char | avgt | 5 | 18,292.802 | ± 167.306 | | ns/op | The objective of the patch is to bring the performance of StringLatin1 indexOf(char) in line with StringUTF16 indexOf(char) for x86 and ARM64. We can see above that this has been achieved. Similar results were obtained when running on ARM. ------------- Commit messages: - 8173585: further whitespace changes required by jcheck - JDK-8173585 - whitespace changes required by jcheck - JDK-8173585 Changes: https://git.openjdk.java.net/jdk/pull/71/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=71&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8173585 Stats: 522 lines in 15 files changed: 506 ins; 0 del; 16 mod Patch: https://git.openjdk.java.net/jdk/pull/71.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/71/head:pull/71 PR: https://git.openjdk.java.net/jdk/pull/71
