/**
* Create the edges in the control flow graph with the basic blocks.
*
* @param insts the instructions
* @param numBlocks an array containing the number of basic block for each instruction.
* @param bbs the basic blocks
*/
private void findCFGEdges(Instruction[] insts, short[] numBlocks, BasicBlock[] bbs) {
for (int i = 0; i < bbs.length; ++i) {
BasicBlock bb = bbs[i];
Instruction lastInst = insts[bb.getEnd()];
if (lastInst.canComplete() && i != bbs.length - 1) {
// the next block is accessible
bb.addDefaultNextBlock(bbs[i + 1]);
}
if (lastInst instanceof JumpInstruction) {
// goto, jsr are distincts than other jump instructions.
Edge edge;
JumpInstruction jumpInst = (JumpInstruction) lastInst;
if (lastInst.getOpcode() == ClassfileConstants2.opc_goto) {
edge =
bb.addDefaultNextBlock(
bbs[numBlocks[getInstructionLine(insts, jumpInst.getTarget())]]);
jumpInst.setTarget(new EdgeLabel(edge));
} else if (lastInst.getOpcode() == ClassfileConstants2.opc_jsr) {
// do nothing here
// see method findSubRoutines
} else {
edge =
bb.addConditionNextBlock(
bbs[numBlocks[getInstructionLine(insts, jumpInst.getTarget())]]);
jumpInst.setTarget(new EdgeLabel(edge));
}
}
if (lastInst instanceof SwitchInstruction) {
SwitchInstruction si = (SwitchInstruction) lastInst;
for (int k = -1; k < si.getSwitchCount(); k++) {
Edge edge =
bb.addSwitchNextBlock(bbs[numBlocks[getInstructionLine(insts, si.getTarget(k))]]);
si.setTarget(k, new EdgeLabel(edge));
}
}
}
}
/**
* Find subroutines in the method. Create an object SubRoutine for each one. Add the edges.
*
* @param numBlocks an array containing the number of basic block for each instruction.
* @param insts the instructions
* @param bbs the basic blocks
*/
public void findSubRoutines(short[] numBlocks, final Instruction[] insts, BasicBlock[] bbs) {
for (int i = 0; i < bbs.length; ++i) {
Instruction lastInst = insts[bbs[i].getEnd()];
if (lastInst.getOpcode() == ClassfileConstants2.opc_jsr) {
JumpInstruction jumpInst = (JumpInstruction) lastInst;
BasicBlock subroutineCall = bbs[i];
BasicBlock subroutineReturn = bbs[i + 1];
final BasicBlock startSubroutine =
bbs[numBlocks[getInstructionLine(insts, jumpInst.getTarget())]];
SubRoutine sub = (SubRoutine) subroutines.get(startSubroutine);
if (sub == null) {
startSubroutine.setFirstBlockSubroutine(true);
// we have to create the SubRoutine object
// so we research the end block of the subroutine
// we follow a path from start block until we find the ret
final Map subs = subroutines;
final BasicBlock currentBB = startSubroutine;
// the search will not enter into nested subroutine
// because there is an edge after a block with
// a jsr and its next block.
graph.visitGraphFromNode(
currentBB,
new NodeVisitor() {
public boolean visit(Node n) {
BasicBlock bb = (BasicBlock) n;
Instruction last = insts[bb.getEnd()];
if (last.getOpcode() == ClassfileConstants2.opc_ret) {
// we found the end of the subroutine
SubRoutine s = new SubRoutine(startSubroutine, currentBB);
subs.put(startSubroutine, s);
return false;
}
return true;
}
});
if ((sub = (SubRoutine) subroutines.get(startSubroutine)) == null) {
// error
throw new RuntimeException("NO RETURN TO SUBROUTINE");
}
}
// add edges
Edge edgeCall = subroutineCall.addSubRoutineCallNextBlock(startSubroutine);
jumpInst.setTarget(new EdgeLabel(edgeCall));
Edge edgeReturn = sub.getEnd().addSubRoutineReturnNextBlock(subroutineReturn);
sub.addCall(edgeCall, edgeReturn);
}
}
// remove all edges from basic blocks which end by jsr with
// its next block.
for (int i = 0; i < bbs.length; ++i) {
Instruction lastInst = insts[bbs[i].getEnd()];
if (lastInst.getOpcode() == ClassfileConstants2.opc_jsr) {
BasicBlock subroutineCall = bbs[i];
BasicBlock subroutineReturn = bbs[i + 1];
subroutineCall.removeSuccessor(subroutineReturn);
}
}
}