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

[Eric Liu]

> 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

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

Changes:
  - all: https://git.openjdk.java.net/jdk18/pull/49/files
  - new: https://git.openjdk.java.net/jdk18/pull/49/files/109d8838..24fb4fc9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk18&pr=49&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk18&pr=49&range=00-01

  Stats: 24 lines in 2 files changed: 18 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk18/pull/49.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18 pull/49/head:pull/49

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