examples/Mini/ASTIfExpr.java

/* Generated By:JJTree: Do not edit this line. ASTIfExpr.java */
/* JJT: 0.3pre1 */

package Mini;
import org.apache.bcel.classfile.*;
import org.apache.bcel.generic.*;

/**
 *
 * @version $Id$
 * @author  <A HREF="http://www.berlin.de/~markus.dahm/">M. Dahm</A>
 */
public class ASTIfExpr extends ASTExpr implements org.apache.bcel.Constants {
  private ASTExpr if_expr, then_expr, else_expr;

  // Generated methods
  ASTIfExpr(int id) {
    super(id);
  }

  ASTIfExpr(MiniParser p, int id) {
    super(p, id);
  }

  public static Node jjtCreate(MiniParser p, int id) {
    return new ASTIfExpr(p, id);
  }

  /**
   * Overrides ASTExpr.closeNode()
   * Cast children nodes Node[] to appropiate type ASTExpr[]
   */
  public void closeNode() {
    if_expr = (ASTExpr)children[0];
    then_expr = (ASTExpr)children[1];

    if(children.length == 3) // has else branch
      else_expr = (ASTExpr)children[2];
    else
      MiniC.addError(if_expr.getLine(), if_expr.getColumn(),
		     "IF expression has no ELSE branch");

    children=null; // Throw away
  }

  /**
   * Overrides ASTExpr.traverse()
   */
  public ASTExpr traverse(Environment env) { 
    this.env = env;

    if_expr   = if_expr.traverse(env);
    then_expr = then_expr.traverse(env);

    if(else_expr != null)
      else_expr = else_expr.traverse(env);

    return this;
  }

  /**
   * Second pass
   * Overrides AstExpr.eval()
   * @return type of expression
   * @param expected type
   */
  public int eval(int expected) {
    int then_type, else_type, if_type;

    if((if_type=if_expr.eval(T_BOOLEAN)) != T_BOOLEAN)
      MiniC.addError(if_expr.getLine(), if_expr.getColumn(),
		     "IF expression is not of type boolean, but " + 
		     TYPE_NAMES[if_type] + ".");

    then_type=then_expr.eval(expected);

    if((expected != T_UNKNOWN) && (then_type != expected))
      MiniC.addError(then_expr.getLine(), then_expr.getColumn(),
		     "THEN expression is not of expected type " +
		     TYPE_NAMES[expected] + " but " + TYPE_NAMES[then_type] + ".");

    if(else_expr != null) {
      else_type = else_expr.eval(expected);

      if((expected != T_UNKNOWN) && (else_type != expected))
	MiniC.addError(else_expr.getLine(), else_expr.getColumn(),
		       "ELSE expression is not of expected type " +
		       TYPE_NAMES[expected] + " but " + TYPE_NAMES[else_type] + ".");
      else if(then_type == T_UNKNOWN) {
	then_type = else_type;
	then_expr.setType(else_type);
      }
    }
    else {
      else_type = then_type;
      else_expr = then_expr;
    }

    if(then_type != else_type)
      MiniC.addError(line, column,
		     "Type mismatch in THEN-ELSE: " +
		     TYPE_NAMES[then_type] + " vs. " + TYPE_NAMES[else_type] + ".");

    type = then_type;

    is_simple = if_expr.isSimple() && then_expr.isSimple() && else_expr.isSimple();

    return type;
  }

  /**
   * Fourth pass, produce Java code.
   */
  public void code(StringBuffer buf) {
    if_expr.code(buf);

    buf.append("    if(" + ASTFunDecl.pop() + " == 1) {\n");
    int size = ASTFunDecl.size;
    then_expr.code(buf);
    ASTFunDecl.size = size; // reset stack
    buf.append("    } else {\n");
    else_expr.code(buf);
    buf.append("    }\n");
  }

  /**
   * Fifth pass, produce Java byte code.
   */
  public void byte_code(InstructionList il, MethodGen method, ConstantPoolGen cp) {
    if_expr.byte_code(il, method, cp);

    InstructionList then_code = new InstructionList();
    InstructionList else_code = new InstructionList();

    then_expr.byte_code(then_code, method, cp);
    else_expr.byte_code(else_code, method, cp);

    BranchHandle i, g;

    i = il.append(new IFEQ(null)); // If POP() == FALSE(i.e. 0) then branch to ELSE
    ASTFunDecl.pop();
    il.append(then_code);
    g = il.append(new GOTO(null));
    i.setTarget(il.append(else_code));
    g.setTarget(il.append(InstructionConstants.NOP)); // May be optimized away later
  }

  public void dump(String prefix) {
    System.out.println(toString(prefix));

    if_expr.dump(prefix + " ");
    then_expr.dump(prefix + " ");
    if(else_expr != null)
      else_expr.dump(prefix + " ");
  }
}