rootnode.cpp revision 1472:c18cbe5936b8 
1/*
2 * Copyright (c) 1997, 2005, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
24
25#include "incls/_precompiled.incl"
26#include "incls/_rootnode.cpp.incl"
27
28//------------------------------Ideal------------------------------------------
29// Remove dead inputs
30Node *RootNode::Ideal(PhaseGVN *phase, bool can_reshape) {
31  for( uint i = 1; i < req(); i++ ) { // For all inputs
32    // Check for and remove dead inputs
33    if( phase->type(in(i)) == Type::TOP ) {
34      del_req(i--);             // Delete TOP inputs
35    }
36  }
37
38  // I used to do tail-splitting in the Ideal graph here, but it does not
39  // work.  The tail-splitting forces values live into the Return to be
40  // ready at a point which dominates the split returns.  This forces Stores
41  // to be hoisted high.  The "proper" fix would be to split Stores down
42  // each path, but this makes the split unprofitable.  If we want to do this
43  // optimization, it needs to be done after allocation so we can count all
44  // the instructions needing to be cloned in the cost metric.
45
46  // There used to be a spoof here for caffeine marks which completely
47  // eliminated very simple self-recursion recursions, but it's not worth it.
48  // Deep inlining of self-calls gets nearly all of the same benefits.
49  // If we want to get the rest of the win later, we should pattern match
50  // simple recursive call trees to closed-form solutions.
51
52  return NULL;                  // No further opportunities exposed
53}
54
55//=============================================================================
56HaltNode::HaltNode( Node *ctrl, Node *frameptr ) : Node(TypeFunc::Parms) {
57  Node* top = Compile::current()->top();
58  init_req(TypeFunc::Control,  ctrl        );
59  init_req(TypeFunc::I_O,      top);
60  init_req(TypeFunc::Memory,   top);
61  init_req(TypeFunc::FramePtr, frameptr    );
62  init_req(TypeFunc::ReturnAdr,top);
63}
64
65const Type *HaltNode::bottom_type() const { return Type::BOTTOM; }
66
67//------------------------------Ideal------------------------------------------
68Node *HaltNode::Ideal(PhaseGVN *phase, bool can_reshape) {
69  return remove_dead_region(phase, can_reshape) ? this : NULL;
70}
71
72//------------------------------Value------------------------------------------
73const Type *HaltNode::Value( PhaseTransform *phase ) const {
74  return ( phase->type(in(TypeFunc::Control)) == Type::TOP)
75    ? Type::TOP
76    : Type::BOTTOM;
77}
78
79const RegMask &HaltNode::out_RegMask() const {
80  return RegMask::Empty;
81}
82