1616
1617
1618 //------------------------------Ideal------------------------------------------
1619 // Return a node which is more "ideal" than the current node. Must preserve
1620 // the CFG, but we can still strip out dead paths.
1621 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1622 // The next should never happen after 6297035 fix.
1623 if( is_copy() ) // Already degraded to a Copy ?
1624 return NULL; // No change
1625
1626 Node *r = in(0); // RegionNode
1627 assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1628
1629 // Note: During parsing, phis are often transformed before their regions.
1630 // This means we have to use type_or_null to defend against untyped regions.
1631 if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1632 return NULL; // No change
1633
1634 // If all inputs are value types, push the value type node down through the
1635 // phi because value type nodes should be merged through their input values.
1636 bool all_vt = true;
1637 for (uint i = 1; i < req() && all_vt; ++i) {
1638 all_vt = in(i) && in(i)->is_ValueType();
1639 }
1640 if (req() > 2 && all_vt) {
1641 ValueTypeNode* vt = in(1)->as_ValueType()->clone_with_phis(phase, in(0));
1642 for (uint i = 2; i < req(); ++i) {
1643 vt->merge_with(phase, in(i)->as_ValueType(), i, i == (req()-1));
1644 }
1645 return vt;
1646 }
1647
1648 Node *top = phase->C->top();
1649 bool new_phi = (outcnt() == 0); // transforming new Phi
1650 // No change for igvn if new phi is not hooked
1651 if (new_phi && can_reshape)
1652 return NULL;
1653
1654 // The are 2 situations when only one valid phi's input is left
1655 // (in addition to Region input).
1656 // One: region is not loop - replace phi with this input.
1657 // Two: region is loop - replace phi with top since this data path is dead
1658 // and we need to break the dead data loop.
1659 Node* progress = NULL; // Record if any progress made
1660 for( uint j = 1; j < req(); ++j ){ // For all paths in
1661 // Check unreachable control paths
1662 Node* rc = r->in(j);
1663 Node* n = in(j); // Get the input
1664 if (rc == NULL || phase->type(rc) == Type::TOP) {
1665 if (n != top) { // Not already top?
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1616
1617
1618 //------------------------------Ideal------------------------------------------
1619 // Return a node which is more "ideal" than the current node. Must preserve
1620 // the CFG, but we can still strip out dead paths.
1621 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1622 // The next should never happen after 6297035 fix.
1623 if( is_copy() ) // Already degraded to a Copy ?
1624 return NULL; // No change
1625
1626 Node *r = in(0); // RegionNode
1627 assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1628
1629 // Note: During parsing, phis are often transformed before their regions.
1630 // This means we have to use type_or_null to defend against untyped regions.
1631 if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1632 return NULL; // No change
1633
1634 // If all inputs are value types, push the value type node down through the
1635 // phi because value type nodes should be merged through their input values.
1636 if (req() > 2 && in(1) && in(1)->is_ValueTypeBase()) {
1637 int opcode = in(1)->Opcode();
1638 uint i = 2;
1639 for (; i < req() && in(i) && in(i)->is_ValueTypeBase(); i++) {
1640 assert(in(i)->Opcode() == opcode, "mixing pointers and values?");
1641 }
1642 if (i == req()) {
1643 ValueTypeBaseNode* vt = in(1)->as_ValueTypeBase()->clone_with_phis(phase, in(0));
1644 for (uint i = 2; i < req(); ++i) {
1645 vt->merge_with(phase, in(i)->as_ValueType(), i, i == (req()-1));
1646 }
1647 return vt;
1648 }
1649 }
1650
1651 Node *top = phase->C->top();
1652 bool new_phi = (outcnt() == 0); // transforming new Phi
1653 // No change for igvn if new phi is not hooked
1654 if (new_phi && can_reshape)
1655 return NULL;
1656
1657 // The are 2 situations when only one valid phi's input is left
1658 // (in addition to Region input).
1659 // One: region is not loop - replace phi with this input.
1660 // Two: region is loop - replace phi with top since this data path is dead
1661 // and we need to break the dead data loop.
1662 Node* progress = NULL; // Record if any progress made
1663 for( uint j = 1; j < req(); ++j ){ // For all paths in
1664 // Check unreachable control paths
1665 Node* rc = r->in(j);
1666 Node* n = in(j); // Get the input
1667 if (rc == NULL || phase->type(rc) == Type::TOP) {
1668 if (n != top) { // Not already top?
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