RFR: 8354471: Assertion failure with -XX:-EnableX86ECoreOpts [v2]

[Volodymyr Paprotski]

> The check to choose between AVX2 and AVX512 implementation was relying on `EnableX86ECoreOpts`. It should be relying on `supports_avxifma` and mirror the `UseIntPolyIntrinsics` check in `vm_version_x86.cpp`.
> 
> Note, in `stubGenerator_x86_64.cpp`, entry to the patched function is protected already:
> 
>   if (UseIntPolyIntrinsics) {
>     StubRoutines::_intpoly_montgomeryMult_P256 = generate_intpoly_montgomeryMult_P256();
>     StubRoutines::_intpoly_assign = generate_intpoly_assign();
>   }

Volodymyr Paprotski has updated the pull request incrementally with one additional commit since the last revision:

  flip the direction of if to prefer AVX512

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24644/files
  - new: https://git.openjdk.org/jdk/pull/24644/files/0ad246c6..ee1b099f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24644&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24644&range=00-01

  Stats: 19 lines in 1 file changed: 9 ins; 9 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/24644.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24644/head:pull/24644

PR: https://git.openjdk.org/jdk/pull/24644