001: /* Copyright (C) 2004 - 2007 db4objects Inc. http://www.db4o.com
002:
003: This file is part of the db4o open source object database.
004:
005: db4o is free software; you can redistribute it and/or modify it under
006: the terms of version 2 of the GNU General Public License as published
007: by the Free Software Foundation and as clarified by db4objects' GPL
008: interpretation policy, available at
009: http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
010: Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
011: Suite 350, San Mateo, CA 94403, USA.
012:
013: db4o is distributed in the hope that it will be useful, but WITHOUT ANY
014: WARRANTY; without even the implied warranty of MERCHANTABILITY or
015: FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
016: for more details.
017:
018: You should have received a copy of the GNU General Public License along
019: with this program; if not, write to the Free Software Foundation, Inc.,
020: 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
021: package EDU.purdue.cs.bloat.tree;
022:
023: import java.util.*;
024:
025: import EDU.purdue.cs.bloat.cfg.*;
026:
027: /**
028: * <tt>PhiJoinStmt</tt> represents a phi-function inserted into a control flow
029: * graph during conversion of variables to static single-assignment form. A
030: * <tt>PhiJoinStmt</tt> at a point of control flow convergence.
031: *
032: * @see EDU.purdue.cs.bloat.ssa.SSAConstructionInfo SSAConstructionInfo
033: */
034: public class PhiJoinStmt extends PhiStmt {
035: Map operands; // Operands to a PhiStmt (mapping between a Block
036:
037: // and a VarExpr occurring at that block)
038: Block block; // Basic block containing this PhiJoinStmt
039:
040: /**
041: * Constructor.
042: *
043: * @param target
044: * The target of this PhiStmt.
045: * @param block
046: * The basic Block in which this PhiJoinStmt resides.
047: */
048: public PhiJoinStmt(final VarExpr target, final Block block) {
049: super (target);
050:
051: this .block = block;
052: this .operands = new HashMap();
053:
054: final Iterator preds = block.graph().preds(block).iterator();
055:
056: while (preds.hasNext()) {
057: final Block pred = (Block) preds.next();
058: final VarExpr operand = (VarExpr) target.clone();
059: operands.put(pred, operand);
060: operand.setParent(this );
061: operand.setDef(null);
062: }
063: }
064:
065: /**
066: * Set the operand to this PhiJoinStmt for a given Block to a given
067: * expression.
068: *
069: * @param block
070: *
071: * @param expr
072: *
073: */
074: public void setOperandAt(final Block block, final Expr expr) {
075: final Expr operand = (Expr) operands.get(block);
076:
077: if (operand != null) {
078: operand.cleanup();
079: }
080:
081: if (expr != null) {
082: operands.put(block, expr);
083: expr.setParent(this );
084: } else {
085: operands.remove(block);
086: }
087: }
088:
089: /**
090: * Returns the occurrence of the variable with which this PhiJoinStmt is
091: * concerned (usually represented by a VarExpr) at a given block.
092: *
093: * @param block
094: * The block at which an occurrence of the variable occurs.
095: *
096: * @see VarExpr
097: */
098: public Expr operandAt(final Block block) {
099: return (Expr) operands.get(block);
100: }
101:
102: /**
103: * Returns the number of operands that this PhiJoinStmt has.
104: */
105: public int numOperands() {
106: return block.graph().preds(block).size();
107: }
108:
109: /**
110: * Returns the predacessor nodes (in the CFG not dominator graph) of the
111: * block in which this PhiJoinStmt occurs.
112: */
113: public Collection preds() {
114: return block.graph().preds(block);
115: }
116:
117: /**
118: * Returns the operands of this PhiJoinStmt. They are usually of type
119: * VarExpr.
120: *
121: * @see VarExpr
122: */
123: public Collection operands() {
124: if (operands != null) {
125: operands.keySet().retainAll(preds());
126: return operands.values();
127: }
128:
129: return new ArrayList();
130: }
131:
132: public void visitForceChildren(final TreeVisitor visitor) {
133: if (visitor.reverse()) {
134: target.visit(visitor);
135: }
136:
137: final Iterator e = operands().iterator();
138:
139: while (e.hasNext()) {
140: final Expr operand = (Expr) e.next();
141: operand.visit(visitor);
142: }
143:
144: if (!visitor.reverse()) {
145: target.visit(visitor);
146: }
147: }
148:
149: public void visit(final TreeVisitor visitor) {
150: visitor.visitPhiJoinStmt(this);
151: }
152: }
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