RFR: 8365911: AArch64: Fix encoding error in sve_cpy for negative floats [v2]

[erifan]

> The sve_cpy instruction is not correctly implemented for negative floating-point values. The issues include:
> 
> 1. When a negative floating-point number (e.g. `-1.0`) is passed, the `checked_cast<int8_t>(pack(d))` check fails. For example, assume `d = -1.0`:
> - `pack(-1.0)` returns an unsigned int with the 7th bit set, i.e., `0xf0`.
> - `checked_cast<int8_t>(0xf0)` casts `0xf0` to an int8_t value, which is `-16`.
> - Casting this int8_t `-16` back to unsigned int results in `0xfffffff0`.
> - The check compares `0xf0` to `0xfffffff0`, which obviously fails.
> 
> 2. Additionally, the encoding of the negative floating-point number is incorrect:
> - The imm8 field can fall outside the valid range of **[-128, 127]**.
> - Bit **13** should be encoded as **0** for floating-point numbers.
> 
> This PR fixes these issues and renames floating-point `sve_cpy` as `sve_fcpy`.
> 
> Some test cases are added to aarch64-asmtest.py, and all tests passed.

erifan 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 three additional commits since the last revision:

 - Don't rename sve_cpy as sve_fcpy
 - Merge branch 'master' into JDK-8365911
 - 8365911: AArch64: Fix encoding error in sve_cpy for negative floats
   
   The sve_cpy instruction is not correctly implemented for negative
   floating-point values. The issues include:
   
   1. When a negative floating-point number (e.g. `-1.0`) is passed, the
   `checked_cast<int8_t>(pack(d))` check fails. For example, assume `d = -1.0`:
   - `pack(-1.0)` returns an unsigned int with the 7th bit set, i.e., `0xf0`.
   - `checked_cast<int8_t>(0xf0)` casts `0xf0` to an int8_t value, which is `-16`.
   - Casting this int8_t `-16` back to unsigned int results in `0xfffffff0`.
   - The check compares `0xf0` to `0xfffffff0`, which obviously fails.
   
   2. Additionally, the encoding of the negative floating-point number is incorrect:
   - The imm8 field can fall outside the valid range of **[-128, 127]**.
   - Bit **13** should be encoded as **0** for floating-point numbers.
   
   This PR fixes these issues and renames floating-point `sve_cpy` as `sve_fcpy`.
   
   Some test cases are added to aarch64-asmtest.py, and all tests passed.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26951/files
  - new: https://git.openjdk.org/jdk/pull/26951/files/dad0e011..16a06948

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26951&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26951&range=00-01

  Stats: 16389 lines in 782 files changed: 11717 ins; 2213 del; 2459 mod
  Patch: https://git.openjdk.org/jdk/pull/26951.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26951/head:pull/26951

PR: https://git.openjdk.org/jdk/pull/26951