net.covers1624.coffeegrinder.bytecode.flow

Class ControlFlowGraph

java.lang.Object

net.covers1624.coffeegrinder.bytecode.flow.ControlFlowGraph

public class ControlFlowGraph
extends java.lang.Object

Holds the control flow graph. A separate graph is computed for each BlockContainer at the start of block transforms (before loop detection)

Created by covers1624 on 19/4/21.

Field Summary

Fields

Modifier and Type	Field and Description
ControlFlowNode[]	cfg Nodes array, indexed by original block index.
BlockContainer	container The container for which the ControlFlowGraph was created.
java.util.BitSet	directExits directExits.get(i) == true if cfg[i] directly contains a branch/leave instruction leaving container.
java.util.Map<Block,ControlFlowNode>	nodes A map of Block to ControlFlowNode.
java.util.BitSet	reachableExits reachableExits.get(i) == true if there is a path from cfg[i] to a node not dominated by cfg[i], or if there is a path from cfg[i] to a branch/leave instruction leaving the container.

Constructor Summary

Constructors

Constructor and Description
ControlFlowGraph(BlockContainer container) Constructs a control flow graph for the blocks in the given block container.

Method Summary

Modifier and Type	Method and Description
ControlFlowNode	getNode(Block block) Gets the control flow node for the block.
boolean	hasDirectExit(ControlFlowNode node) Gets whether the control flow node directly contains a branch/leave instruction exiting the container.
boolean	hasReachableExit(ControlFlowNode node) Returns true if there is a control flow path from node to one of the following: - Branch or leave instruction leaving this.container.
void	resetVisited() Resets all ControlFlowNode.visited flags for all nodes in this graph.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

container

public final BlockContainer container

The container for which the ControlFlowGraph was created.

This may differ from the container currently holding a block, because a transform could have moved the block since the CFG was created.

cfg

public final ControlFlowNode[] cfg

Nodes array, indexed by original block index.

Originally cfg[i].block == container.blocks.get(i) but may have since been moved/reordered by transforms.

nodes

public final java.util.Map<Block,ControlFlowNode> nodes

A map of Block to ControlFlowNode.

Unlike the cfg array, this can be used to discover control flow nodes even after blocks were moved/reordered by transforms.

directExits

public final java.util.BitSet directExits

directExits.get(i) == true if cfg[i] directly contains a branch/leave instruction leaving container.

reachableExits

public final java.util.BitSet reachableExits

reachableExits.get(i) == true if there is a path from cfg[i] to a node not dominated by cfg[i], or if there is a path from cfg[i] to a branch/leave instruction leaving the container.

Constructor Detail

ControlFlowGraph

public ControlFlowGraph(BlockContainer container)

Constructs a control flow graph for the blocks in the given block container.

Return statements, exceptions, or branches leaving the block container are not modeled by the control flow graph.

Parameters:

container - The container.

Method Detail

getNode

public ControlFlowNode getNode(Block block)

Gets the control flow node for the block.

Precondition: the block belonged to the container at the start of the block transforms (where the control flow graph was created).

Parameters:

block - The block to get the ControlFlowNode for.

Returns:

The ControlFlowNode.

hasReachableExit

public boolean hasReachableExit(ControlFlowNode node)

Returns true if there is a control flow path from node to one of the following: - Branch or leave instruction leaving this.container. - Branch instruction within this container to another node that is not dominated by node.

If this function returns false, the only way control flow can leave the set of nodes dominated by node is by executing a return; or throw; instruction.

Parameters:

node - The node to check.

Returns:

If the node has a reachable exit.

hasDirectExit

public boolean hasDirectExit(ControlFlowNode node)

Gets whether the control flow node directly contains a branch/leave instruction exiting the container.

Parameters:

node - The node to check.

Returns:

If the node has a direct exit.

resetVisited

public void resetVisited()

Resets all ControlFlowNode.visited flags for all nodes in this graph.