/** -*- tab-width: 4 -*-
* This file is part of Erjang - A JVM-based Erlang VM
*
* Copyright (c) 2010 by Trifork
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
**/
package erjang.beam.loader;
import erjang.beam.BeamOpcode;
import erjang.beam.repr.Insn;
import erjang.beam.repr.Operands.Label;
import erjang.beam.repr.FunctionInfo;
import erjang.EAtom;
import java.util.List;
import java.util.ListIterator;
public class Rewriter {
public void rewriteFunctionBody(List<Insn> body, FunctionInfo sig) {
ListIterator<Insn> it = body.listIterator();
while (it.hasNext()) {
final Insn insn = it.next();
switch (insn.opcode()) {
case call_fun: {
int save_pos = savePos(it);
boolean trigger = (it.hasNext() &&
it.next().opcode() == BeamOpcode.deallocate &&
it.hasNext() &&
it.next().opcode() == BeamOpcode.K_return);
restorePos(it, save_pos);
if (trigger) {
Insn.I old = (Insn.I)insn;
it.set(new Insn.I(BeamOpcode.i_call_fun_last, old.i1)); // We don't care about deallocating.
it.next();
it.remove();
it.next();
it.remove();
}
}//switch
}
}
}
private int savePos(ListIterator<Insn> it) {return it.nextIndex() - 1;}
private void restorePos(ListIterator<Insn> it, int save_pos) {
// Only works for restoring backwards.
int i=0;
while (it.previousIndex() >= save_pos) {
int pi = it.previousIndex();
Insn insn = it.previous(); i++;
}
if (it.nextIndex() <= save_pos) it.next(); // Turn iterator.
}
private Insn nop() {return new Insn.I(BeamOpcode.label, -1);}
}