1.1 --- a/src/share/vm/opto/cfgnode.cpp Fri Dec 21 10:27:49 2012 -0800
1.2 +++ b/src/share/vm/opto/cfgnode.cpp Sun Dec 23 17:08:22 2012 +0100
1.3 @@ -363,6 +363,49 @@
1.4 return true; // The Region node is unreachable - it is dead.
1.5 }
1.6
1.7 +bool RegionNode::try_clean_mem_phi(PhaseGVN *phase) {
1.8 + // Incremental inlining + PhaseStringOpts sometimes produce:
1.9 + //
1.10 + // cmpP with 1 top input
1.11 + // |
1.12 + // If
1.13 + // / \
1.14 + // IfFalse IfTrue /- Some Node
1.15 + // \ / / /
1.16 + // Region / /-MergeMem
1.17 + // \---Phi
1.18 + //
1.19 + //
1.20 + // It's expected by PhaseStringOpts that the Region goes away and is
1.21 + // replaced by If's control input but because there's still a Phi,
1.22 + // the Region stays in the graph. The top input from the cmpP is
1.23 + // propagated forward and a subgraph that is useful goes away. The
1.24 + // code below replaces the Phi with the MergeMem so that the Region
1.25 + // is simplified.
1.26 +
1.27 + PhiNode* phi = has_unique_phi();
1.28 + if (phi && phi->type() == Type::MEMORY && req() == 3 && phi->is_diamond_phi(true)) {
1.29 + MergeMemNode* m = NULL;
1.30 + assert(phi->req() == 3, "same as region");
1.31 + for (uint i = 1; i < 3; ++i) {
1.32 + Node *mem = phi->in(i);
1.33 + if (mem && mem->is_MergeMem() && in(i)->outcnt() == 1) {
1.34 + // Nothing is control-dependent on path #i except the region itself.
1.35 + m = mem->as_MergeMem();
1.36 + uint j = 3 - i;
1.37 + Node* other = phi->in(j);
1.38 + if (other && other == m->base_memory()) {
1.39 + // m is a successor memory to other, and is not pinned inside the diamond, so push it out.
1.40 + // This will allow the diamond to collapse completely.
1.41 + phase->is_IterGVN()->replace_node(phi, m);
1.42 + return true;
1.43 + }
1.44 + }
1.45 + }
1.46 + }
1.47 + return false;
1.48 +}
1.49 +
1.50 //------------------------------Ideal------------------------------------------
1.51 // Return a node which is more "ideal" than the current node. Must preserve
1.52 // the CFG, but we can still strip out dead paths.
1.53 @@ -375,6 +418,10 @@
1.54 bool has_phis = false;
1.55 if (can_reshape) { // Need DU info to check for Phi users
1.56 has_phis = (has_phi() != NULL); // Cache result
1.57 + if (has_phis && try_clean_mem_phi(phase)) {
1.58 + has_phis = false;
1.59 + }
1.60 +
1.61 if (!has_phis) { // No Phi users? Nothing merging?
1.62 for (uint i = 1; i < req()-1; i++) {
1.63 Node *if1 = in(i);
1.64 @@ -1005,7 +1052,9 @@
1.65 //------------------------------is_diamond_phi---------------------------------
1.66 // Does this Phi represent a simple well-shaped diamond merge? Return the
1.67 // index of the true path or 0 otherwise.
1.68 -int PhiNode::is_diamond_phi() const {
1.69 +// If check_control_only is true, do not inspect the If node at the
1.70 +// top, and return -1 (not an edge number) on success.
1.71 +int PhiNode::is_diamond_phi(bool check_control_only) const {
1.72 // Check for a 2-path merge
1.73 Node *region = in(0);
1.74 if( !region ) return 0;
1.75 @@ -1018,6 +1067,7 @@
1.76 Node *iff = ifp1->in(0);
1.77 if( !iff || !iff->is_If() ) return 0;
1.78 if( iff != ifp2->in(0) ) return 0;
1.79 + if (check_control_only) return -1;
1.80 // Check for a proper bool/cmp
1.81 const Node *b = iff->in(1);
1.82 if( !b->is_Bool() ) return 0;
