8162496: missing precedence edge for anti_dependence
Summary: fix Implicit Null Check optimization code.
Reviewed-by: roland, aph
--- a/hotspot/src/share/vm/opto/block.cpp Thu Aug 18 11:26:35 2016 +0300
+++ b/hotspot/src/share/vm/opto/block.cpp Thu Aug 18 14:31:02 2016 -0700
@@ -1212,6 +1212,9 @@
if (j >= 1 && n->is_Mach() && n->as_Mach()->ideal_Opcode() == Op_CreateEx) {
assert(j == 1 || block->get_node(j-1)->is_Phi(), "CreateEx must be first instruction in block");
}
+ if (n->needs_anti_dependence_check()) {
+ verify_anti_dependences(block, n);
+ }
for (uint k = 0; k < n->req(); k++) {
Node *def = n->in(k);
if (def && def != n) {
--- a/hotspot/src/share/vm/opto/block.hpp Thu Aug 18 11:26:35 2016 +0300
+++ b/hotspot/src/share/vm/opto/block.hpp Thu Aug 18 14:31:02 2016 -0700
@@ -186,14 +186,13 @@
Block* lone_fall_through(); // Return lone fall-through Block or null
Block* dom_lca(Block* that); // Compute LCA in dominator tree.
-#ifdef ASSERT
+
bool dominates(Block* that) {
int dom_diff = this->_dom_depth - that->_dom_depth;
if (dom_diff > 0) return false;
for (; dom_diff < 0; dom_diff++) that = that->_idom;
return this == that;
}
-#endif
// Report the alignment required by this block. Must be a power of 2.
// The previous block will insert nops to get this alignment.
@@ -481,9 +480,9 @@
MachNode* _goto;
Block* insert_anti_dependences(Block* LCA, Node* load, bool verify = false);
- void verify_anti_dependences(Block* LCA, Node* load) {
+ void verify_anti_dependences(Block* LCA, Node* load) const {
assert(LCA == get_block_for_node(load), "should already be scheduled");
- insert_anti_dependences(LCA, load, true);
+ const_cast<PhaseCFG*>(this)->insert_anti_dependences(LCA, load, true);
}
bool move_to_next(Block* bx, uint b_index);
--- a/hotspot/src/share/vm/opto/lcm.cpp Thu Aug 18 11:26:35 2016 +0300
+++ b/hotspot/src/share/vm/opto/lcm.cpp Thu Aug 18 14:31:02 2016 -0700
@@ -240,6 +240,14 @@
continue;
}
+ // Check that node's control edge is not-null block's head or dominates it,
+ // otherwise we can't hoist it because there are other control dependencies.
+ Node* ctrl = mach->in(0);
+ if (ctrl != NULL && !(ctrl == not_null_block->head() ||
+ get_block_for_node(ctrl)->dominates(not_null_block))) {
+ continue;
+ }
+
// check if the offset is not too high for implicit exception
{
intptr_t offset = 0;
@@ -379,9 +387,12 @@
block->add_inst(best);
map_node_to_block(best, block);
- // Move the control dependence
- if (best->in(0) && best->in(0) == old_block->head())
- best->set_req(0, block->head());
+ // Move the control dependence if it is pinned to not-null block.
+ // Don't change it in other cases: NULL or dominating control.
+ if (best->in(0) == not_null_block->head()) {
+ // Set it to control edge of null check.
+ best->set_req(0, proj->in(0)->in(0));
+ }
// Check for flag-killing projections that also need to be hoisted
// Should be DU safe because no edge updates.
@@ -437,6 +448,18 @@
latency_from_uses(nul_chk);
latency_from_uses(best);
+
+ // insert anti-dependences to defs in this block
+ if (! best->needs_anti_dependence_check()) {
+ for (uint k = 1; k < block->number_of_nodes(); k++) {
+ Node *n = block->get_node(k);
+ if (n->needs_anti_dependence_check() &&
+ n->in(LoadNode::Memory) == best->in(StoreNode::Memory)) {
+ // Found anti-dependent load
+ insert_anti_dependences(block, n);
+ }
+ }
+ }
}