[jdk18] RFR: 8278889: AArch64: [vectorapi] VectorMaskLoadStoreTest.testMaskCast() test fail [v2]

[Eric Liu]

On Tue, 21 Dec 2021 13:14:59 GMT, Eric Liu <eliu at openjdk.org> wrote:

>> This bug appears intermittently and it's caused by vmaskAll_immI[1]
>> when the vector mask size is smaller than max predicate size of running
>> machine. It generates an all-true predicate without considering those
>> inactive bits. That may result in the wrong result of VectorMask.toLong.
>> The problematic code is as below:
>> 
>> 
>>         ShortVector.SPECIES_64.MaskAll(true).toLong()
>> 
>> assembly:
>> 
>>         ptrue   p0.h          <= MaskAll(true)
>>         mov     z16.h, p0/z, #1
>>         mov     z17.h, #0
>>         uzp1    z16.b, z16.b, z17.b
>>         fmov    x10, d16
>>         orr     x10, x10, x10, lsr #7
>>         orr     x10, x10, x10, lsr #14
>>         orr     x10, x10, x10, lsr #28
>>         and     x10, x10, #0xff
>> 
>> (gdb) p/x $p0 # on an SVE machine with vector length as 64 in bytes
>> $1 = {0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55}
>> 
>> Expected:
>> (gdb) p/x $p0
>> $1 = {0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}
>> 
>> 
>> 
>> Considering MaskAll is used in VectorMask.fromLong() only for a special
>> case and relies on the mechanism of inline and intrinsification, even it
>> could be optimized out, this patch also adds test cases for MaskAll to
>> reproduce this issue stably.
>> 
>> Also fix a small issue on register utilization for
>> sve_reduce_[max|min][D|F].
>> 
>> [1] https://github.com/openjdk/jdk18/blob/master/src/hotspot/cpu/aarch64/aarch64_sve.ad#L416
>> 
>> hotspot/compiler/vectorapi, jdk/incubator/vector passed on SVE enabled
>> system.
>> 
>> Change-Id: I9631f26f9232ffe7a28b74f14062d945c32fa1fb
>
> Eric Liu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   small fix
>   
>   Change-Id: Id71ebe5161fac08a689ee3ec538b485f6c172186

Thanks for all reviewers:P

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

PR: https://git.openjdk.java.net/jdk18/pull/49