[vectorIntrinsics] RFR: 8266286: Add LoadVectorGather and StoreVectorScatter's partial version

[Xiaohong Gong]

On Fri, 28 May 2021 09:37:28 GMT, Wang Huang <whuang at openjdk.org> wrote:

> * Add LoadVectorGather and StoreVectorScatter's partial version
> * use `sve_whilelo`

src/hotspot/cpu/aarch64/aarch64_sve.ad line 4173:

> 4171: instruct gatherI_partial(vReg dst, indirect mem, vReg idx, pRegGov pTmp, rFlagsReg cr) %{
> 4172:   predicate(UseSVE > 0 &&
> 4173:             n->as_LoadVectorGather()->memory_size() >= 16 &&

Since there is the min vector size (size in byte >= 16) limitation in `op_sve_supported`, is this needed here?

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PR: https://git.openjdk.java.net/panama-vector/pull/87