RFR: 8290169: adlc: Improve child constraints for vector unary operations

[Hao Sun]

As demonstrated in [1], the child constrait generated for *predicated
vector unary operation* is the super set of that generated for the
*unpredicated* version. As a result, there exists a risk for predicated
vector unary operaions to match the unpredicated rules by accident.

In this patch, we resolve this issue by generating one extra check
"rChild == NULL" ONLY for vector unary operations. In this way, the
child constraints for predicated/unpredicated vector unary operations
are exclusive now.

Following the example in [1], the dfa state generated for AbsVI is shown
below.


void  State::_sub_Op_AbsVI(const Node *n){
  if( STATE__VALID_CHILD(_kids[0], VREG) && STATE__VALID_CHILD(_kids[1], PREGGOV) &&
      ( UseSVE > 0 ) )
  {
    unsigned int c = _kids[0]->_cost[VREG]+_kids[1]->_cost[PREGGOV] + SVE_COST;
      DFA_PRODUCTION(VREG, vabsI_masked_rule, c)
  }
  if( STATE__VALID_CHILD(_kids[0], VREG) && _kids[1] == NULL &&  <---- 1
      ( UseSVE > 0) )
  {
    unsigned int c = _kids[0]->_cost[VREG] + SVE_COST;
    if (STATE__NOT_YET_VALID(VREG) || _cost[VREG] > c) {
      DFA_PRODUCTION(VREG, vabsI_rule, c)
    }
  }
  ...


We can see that the constraint at line 1 cannot be matched for
predicated AbsVI node now.

The main updates are made in adlc/dfa part. Ideally, we should only
add the extra check for affected platforms, i.e. AVX-512 and SVE. But we
didn't do that because it would be better not to introduce any
architecture dependent implementation here.

Besides, workarounds in both aarch64_sve.ad and x86.ad are removed. 1)
Many "is_predicated_vector()" checks can be removed in aarch64_sve.ad
file. 2) Default instruction cost is used for involving rules in x86.ad
file.

[1]. https://github.com/shqking/jdk/commit/50ec9b19

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

Commit messages:
 - 8290169: adlc: Improve child constraints for vector unary operations

Changes: https://git.openjdk.org/jdk/pull/9534/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9534&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290169
  Stats: 192 lines in 5 files changed: 28 ins; 97 del; 67 mod
  Patch: https://git.openjdk.org/jdk/pull/9534.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9534/head:pull/9534

PR: https://git.openjdk.org/jdk/pull/9534