RFR: 8349452: Fix performance regression for Arrays.fill() with AVX512 [v5]

[Srinivas Vamsi Parasa]

> The goal of this PR is to fix the performance regression in Arrays.fill() x86 stubs caused by masked AVX stores. The fix is to replace the masked AVX stores with store instructions without masks (i.e. unmasked stores). `fill32_masked()` and `fill64_masked()` stubs are replaced with `fill32_unmasked()` and `fill64_unmasked()` respectively.
> 
> To speedup unmasked stores, array fills for sizes < 64 bytes are broken down into sequences of 32B, 16B, 8B, 4B, 2B and 1B stores, depending on the size.
> 
> 
> ### **Performance comparison for byte array fills in a loop for 1 million times**
> 
> 
> UseAVX=3   ByteArray Size | +OptimizeFill    (Masked store   stub)     [secs] | -OptimizeFill   (No stub)   [secs] | --->This PR: +OptimizeFill   (Unmasked store   stub)   [secs]
> -- | -- | -- | --
> 1 | 0.46 | 0.14 | 0.263
> 2 | 0.46 | 0.16 | 0.264
> 5 | 0.46 | 0.29 | 0.299
> 10 | 0.46 | 0.58 | 0.303
> 15 | 0.46 | 0.42 | 0.271
> 16 | 0.46 | 0.46 | 0.32
> 17 | 0.21 | 0.5 | 0.299
> 20 | 0.21 | 0.37 | 0.299
> 25 | 0.21 | 0.59 | 0.282
> 31 | 0.21 | 0.53 | 0.273
> 32 | 0.21 | 0.58 | 0.199
> 35 | 0.5 | 0.77 | 0.259
> 40 | 0.5 | 0.61 | 0.33
> 45 | 0.5 | 0.52 | 0.281
> 48 | 0.5 | 0.66 | 0.32
> 49 | 0.22 | 0.69 | 0.3
> 50 | 0.22 | 0.78 | 0.3
> 55 | 0.22 | 0.67 | 0.292
> 60 | 0.22 | 0.67 | 0.3293
> 64 | 0.22 | 0.82 | 0.23
> 70 | 0.51 | 1.1 | 0.34
> 80 | 0.49 | 0.89 | 0.365
> 90 | 0.225 | 0.68 | 0.33
> 100 | 0.54 | 1.09 | 0.347
> 110 | 0.6 | 0.98 | 0.36
> 120 | 0.26 | 0.75 | 0.386
> 128 | 0.266 | 1.1 | 0.289

Srinivas Vamsi Parasa has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - Merge branch 'master' of https://git.openjdk.java.net/jdk into fill_array
 - undo jccb to jcc change as needed
 - refactor code to use fill32_tail at the end of the stub
 - undo size check for fill64_masked
 - 8349452: Fix performance regression for Arrays.fill() with AVX512

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28442/files
  - new: https://git.openjdk.org/jdk/pull/28442/files/57dc6c4a..fd8b6c21

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28442&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28442&range=03-04

  Stats: 6836 lines in 227 files changed: 4452 ins; 1415 del; 969 mod
  Patch: https://git.openjdk.org/jdk/pull/28442.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28442/head:pull/28442

PR: https://git.openjdk.org/jdk/pull/28442