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

[Galder Zamarreño]

On Tue, 9 Jul 2024 12:07:37 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  PASS  FAIL ERROR
>    jtreg:test/hotspot/jtreg:tier1                     2500  2500     0     0
>>> jtreg:test/jdk:tier1                     ...

Working on it

-------------

PR Comment: https://git.openjdk.org/jdk/pull/20098#issuecomment-2313102213