RFR: 8307513: C2: intrinsify Math.max(long,long) and Math.min(long,long) [v9]

[Emanuel Peter]

On Mon, 13 Jan 2025 17:12:31 GMT, Galder Zamarreño <galder at openjdk.org> wrote:

>> This patch intrinsifies `Math.max(long, long)` and `Math.min(long, long)` in order to help improve vectorization performance.
>> 
>> Currently vectorization does not kick in for loops containing either of these calls because of the following error:
>> 
>> 
>> VLoop::check_preconditions: failed: control flow in loop not allowed
>> 
>> 
>> The control flow is due to the java implementation for these methods, e.g.
>> 
>> 
>> public static long max(long a, long b) {
>>     return (a >= b) ? a : b;
>> }
>> 
>> 
>> This patch intrinsifies the calls to replace the CmpL + Bool nodes for MaxL/MinL nodes respectively.
>> By doing this, vectorization no longer finds the control flow and so it can carry out the vectorization.
>> E.g.
>> 
>> 
>> SuperWord::transform_loop:
>>     Loop: N518/N126  counted [int,int),+4 (1025 iters)  main has_sfpt strip_mined
>>  518  CountedLoop  === 518 246 126  [[ 513 517 518 242 521 522 422 210 ]] inner stride: 4 main of N518 strip mined !orig=[419],[247],[216],[193] !jvms: Test::test @ bci:14 (line 21)
>> 
>> 
>> Applying the same changes to `ReductionPerf` as in https://github.com/openjdk/jdk/pull/13056, we can compare the results before and after. Before the patch, on darwin/aarch64 (M1):
>> 
>> 
>> ==============================
>> Test summary
>> ==============================
>>    TEST                                              TOTAL  PASS  FAIL ERROR
>>    jtreg:test/hotspot/jtreg/compiler/loopopts/superword/ReductionPerf.java
>>                                                          1     1     0     0
>> ==============================
>> TEST SUCCESS
>> 
>> long min   1155
>> long max   1173
>> 
>> 
>> After the patch, on darwin/aarch64 (M1):
>> 
>> 
>> ==============================
>> Test summary
>> ==============================
>>    TEST                                              TOTAL  PASS  FAIL ERROR
>>    jtreg:test/hotspot/jtreg/compiler/loopopts/superword/ReductionPerf.java
>>                                                          1     1     0     0
>> ==============================
>> TEST SUCCESS
>> 
>> long min   1042
>> long max   1042
>> 
>> 
>> This patch does not add an platform-specific backend implementations for the MaxL/MinL nodes.
>> Therefore, it still relies on the macro expansion to transform those into CMoveL.
>> 
>> I've run tier1 and hotspot compiler tests on darwin/aarch64 and got these results:
>> 
>> 
>> ==============================
>> Test summary
>> ==============================
>>    TEST                                              TOTAL  PA...
>
> Galder Zamarreño has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Make sure it runs with cpus with either avx512 or asimd

test/hotspot/jtreg/compiler/loopopts/superword/MinMaxRed_Long.java line 2:

> 1: /*
> 2:  * Copyright (c) 2024, Red Hat, Inc. All rights reserved.

Should probably be 2025 by now, right? At least that is our policy for Oracle, not sure what you want to do at Red Hat

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PR Review Comment: https://git.openjdk.org/jdk/pull/20098#discussion_r1914414960