[14]: RFR(XXS): 8236944:The legVecZ operand should be limited to zmm0-zmm15 registers

[Viswanathan, Sandhya]

JBS: https://bugs.openjdk.java.net/browse/JDK-8236944
Webrev: http://cr.openjdk.java.net/~sviswanathan/8236944/webrev.00/

Currently legVecZ operand is defined as follows:
operand legVecZ() %{
  constraint(ALLOC_IN_RC(vectorz_reg_vl));
  match(VecZ);
  format %{ %}
  interface(REG_INTER);
%}
This allows legVecZ to be zmm0-zmm31 on platforms supporting AVX 512 vl.

The legVecZ should instead be defined as:
operand legVecZ() %{
  constraint(ALLOC_IN_RC(vectorz_reg_legacy));
  match(VecZ);
  format %{ %}
  interface(REG_INTER);
%}

Please consider this for JDK 14.

Best Regards,
Sandhya