[vector] unsigned operations

[Paul Sandoz]

Hi

Here is an initial attempt to add unsigned operations:

  https://github.com/openjdk/panama-vector/compare/vectorIntrinsics...PaulSandoz:unsigned-comparison-operators?expand=1

An extra control bit is added, that when set, signifies unsigned comparison.

At the moment the compare intrinsic bails out if this bit is set:

I need some guidance on next steps to further update HotSpot:

- Do we need to enhance arch_supports_vector to check if it supports unsigned comparisons? It might make it easier initially to add support separately for different CPU architectures.

- I suspect I will need to push the unsigned bit into VectorMaskCmpNode and then, at least on x86, update the matching vector compare instruction methods to pass the signed bit to the instruction macros, which are updated accordingly.

Paul.