RFR(XS) 8026939: assert(Reachblock != NULL) failed: Reachblock must be non-NULL

[Niclas Adlertz]

Hi all,

Now that more nodes can be rematerialized due to fix JDK-8022783, a rematerialized node can have a spilled live range as input even when rematerializing input for phi nodes (in the Phi Node Splitting pass).
Prior to the JDK-8013830 and JDK-8005956 fixes, the Reachblock pointer could be wrong (hence the warning in JDK-8013830). Now, we pass in the correct block-reaches, i.e. the reaches for the 'pred' block.

Kind Regards,
Niclas Adlertz

JBS:    https://bugs.openjdk.java.net/browse/JDK-8026939
WEBREV: cr.openjdk.net is down so I'm pasting the diff here:

diff -r 52575a17a36c src/share/vm/opto/reg_split.cpp
--- a/src/share/vm/opto/reg_split.cpp	Mon Oct 21 09:21:41 2013 +0400
+++ b/src/share/vm/opto/reg_split.cpp	Mon Oct 21 15:34:42 2013 +0200
@@ -365,7 +365,6 @@
        }
  
        if (lidx < _lrg_map.max_lrg_id() && lrgs(lidx).reg() >= LRG::SPILL_REG) {
-        assert(Reachblock != NULL, "Reachblock must be non-NULL");
          Node *rdef = Reachblock[lrg2reach[lidx]];
          if (rdef) {
            spill->set_req(i, rdef);
@@ -476,7 +475,6 @@
  
    uint                 bidx, pidx, slidx, insidx, inpidx, twoidx;
    uint                 non_phi = 1, spill_cnt = 0;
-  Node               **Reachblock;
    Node                *n1, *n2, *n3;
    Node_List           *defs,*phis;
    bool                *UPblock;
@@ -559,7 +557,7 @@
  
      b  = _cfg.get_block(bidx);
      // Reaches & UP arrays for this block
-    Reachblock = Reaches[b->_pre_order];
+    Node** Reachblock = Reaches[b->_pre_order];
      UPblock    = UP[b->_pre_order];
      // Reset counter of start of non-Phi nodes in block
      non_phi = 1;
@@ -1315,6 +1313,7 @@
        pidx = pred->_pre_order;
        // Grab reaching def
        Node *def = Reaches[pidx][slidx];
+      Node** Reachblock = Reaches[pidx];
        assert( def, "must have reaching def" );
        // If input up/down sense and reg-pressure DISagree
        if (def->rematerialize()) {
@@ -1327,8 +1326,7 @@
                 _lrg_map.find(pred->get_node(insert - 1)) >= lrgs_before_phi_split) {
            insert--;
          }
-        // since the def cannot contain any live range input, we can pass in NULL as Reachlock parameter
-        def = split_Rematerialize(def, pred, insert, maxlrg, splits, slidx, lrg2reach, NULL, false);
+        def = split_Rematerialize(def, pred, insert, maxlrg, splits, slidx, lrg2reach, Reachblock, false);
          if (!def) {
            return 0;    // Bail out
          }