RFR: 8261137: Optimization of Box nodes in uncommon_trap [v11]
Wang Huang
whuang at openjdk.java.net
Wed Mar 24 07:12:07 UTC 2021
> JDK-8075052 has removed useless autobox. However, in some cases, the box is still saved. For instance:
> @Benchmark
> public void testMethod(Blackhole bh) {
> int sum = 0;
> for (int i = 0; i < data.length; i++) {
> Integer ii = Integer.valueOf(data[i]);
> if (i < data.length) {
> sum += ii.intValue();
> }
> }
> bh.consume(sum);
> }
> Although the variable ii is only used at ii.intValue(), it cannot be eliminated as a result of being used by a hidden uncommon_trap.
> The uncommon_trap is generated by the optimized "if", because its condition is always true.
>
> We can postpone box in uncommon_trap in this situation. We treat box as a scalarized object by adding a SafePointScalarObjectNode in the uncommon_trap node,
> and deleting the use of box:
>
> There is no additional fail/error(s) of jtreg after this patch.
>
> I adjust my codes and add a new benchmark
>
> public class MyBenchmark {
>
> static int[] data = new int[10000];
>
> static {
> for(int i = 0; i < data.length; ++i) {
> data[i] = i * 1337 % 7331;
> }
> }
>
> @Benchmark
> public void testMethod(Blackhole bh) {
> int sum = 0;
> for (int i = 0; i < data.length; i++) {
> Integer ii = Integer.valueOf(data[i]);
> black();
> if (i < 100000) {
> sum += ii.intValue();
> }
> }
> bh.consume(sum);
> }
>
> public void black(){}
> }
>
>
> aarch64:
> base line:
> Benchmark Mode Samples Score Score error Units
> o.s.MyBenchmark.testMethod avgt 30 88.513 1.111 us/op
>
> opt:
> Benchmark Mode Samples Score Score error Units
> o.s.MyBenchmark.testMethod avgt 30 52.776 0.096 us/op
>
> x86:
> base line:
> Benchmark Mode Samples Score Score error Units
> o.s.MyBenchmark.testMethod avgt 30 81.066 3.156 us/op
>
> opt:
> Benchmark Mode Samples Score Score error Units
> o.s.MyBenchmark.testMethod avgt 30 55.596 0.775 us/op
Wang Huang has updated the pull request incrementally with one additional commit since the last revision:
refact SafePointScalarObjectNode constructor
-------------
Changes:
- all: https://git.openjdk.java.net/jdk/pull/2401/files
- new: https://git.openjdk.java.net/jdk/pull/2401/files/2f0276cd..fee961bb
Webrevs:
- full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2401&range=10
- incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2401&range=09-10
Stats: 11 lines in 5 files changed: 5 ins; 0 del; 6 mod
Patch: https://git.openjdk.java.net/jdk/pull/2401.diff
Fetch: git fetch https://git.openjdk.java.net/jdk pull/2401/head:pull/2401
PR: https://git.openjdk.java.net/jdk/pull/2401
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