RFR: 8274179: AArch64: Support SVE operations with encodable immediates [v3]

[Fei Gao]

> for(int i = 0; i < LENGTH; i++) {
>       c[i] = a[i] + 2;
>     }
> 
> For the case showed above, after superword optimization with SVE,
> without the patch, the vector add operation always has 2 z-reg inputs,
> like:
> mov     z16.s, #2
> add	z17.s, z17.s, z16.s
> 
> Considering sve has supported basic binary operations with immediate,
> this pattern could be further optimized to:
> add     z16.s, z16.s, #2
> 
> To implement it, we added some new match rules and assembler rules in
> the aarch64 backend. We also made some extensions on immediate types
> and functions to keep backward compatible.
> 
> With the patch, only these binary integer vector operations, +(add),
> -(sub), &(and), |(orr), and ^(eor) with immediate are supported for
> the optimization. Other vector operations are not supported currently.
> 
> Tested tier1 and test/hotspot/jtreg/compiler on SVE featured AArch64
> CPU, no new failure.
> 
> There is no obvious performance uplift but it can help remove one
> redundant mov instruction.

Fei Gao has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains two new commits since the last revision:

 - Split the original patch and leave the existing logic in Assembler entirely untouched
   
   Change-Id: If8ddcef07b15615d7dd0c3063c44d2b705fac6f7
 - Merge branch 'master' of github.com:fg1417/jdk into fg1417-20211026
   
   Change-Id: I52aa66d200b74ac312c5d40283b94854bc1142e6

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6115/files
  - new: https://git.openjdk.java.net/jdk/pull/6115/files/5ffd5cb1..a7a915af

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6115&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6115&range=01-02

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6115.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6115/head:pull/6115

PR: https://git.openjdk.java.net/jdk/pull/6115