BlockGraph (Soot API)

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soot.toolkits.graph
Class BlockGraph

java.lang.Object
  soot.toolkits.graph.BlockGraph

All Implemented Interfaces:: Iterable<Block>, DirectedGraph<Block>

Direct Known Subclasses:: ArrayRefBlockGraph, BriefBlockGraph, ClassicCompleteBlockGraph, EnhancedBlockGraph, ExceptionalBlockGraph, ZonedBlockGraph

public abstract class BlockGraph
extends Object
implements DirectedGraph<Block>
extends Object
implements DirectedGraph<Block>

Represents the control flow graph of a Body at the basic block level. Each node of the graph is a Block while the edges represent the flow of control from one basic block to the next.

This is an abstract base class for different variants of BlockGraph, where the variants differ in how they analyze the control flow between individual units (represented by passing different variants of UnitGraph to the BlockGraph constructor) and in how they identify block leaders (represented by overriding BlockGraph's definition of computeLeaders().

Field Summary
`protected List<Block>`	`mBlocks`
`protected Body`	`mBody`
`protected List<Block>`	`mHeads`
`protected List<Block>`	`mTails`
`protected Chain<Unit>`	`mUnits`

Constructor Summary
`protected`	`BlockGraph(UnitGraph unitGraph)` Create a `BlockGraph` representing at the basic block level the control flow specified, at the `Unit` level, by a given `UnitGraph`.

Method Summary
`protected Map<Unit,Block>`	`buildBlocks(Set<Unit> leaders, UnitGraph unitGraph)` A utility method that does most of the work of constructing basic blocks, once the set of block leaders has been determined, and which designates the heads and tails of the graph.
`protected Set<Unit>`	`computeLeaders(UnitGraph unitGraph)` Utility method for computing the basic block leaders for a `Body`, given its `UnitGraph` (i.e., the instructions which begin new basic blocks).
`List<Block>`	`getBlocks()` Returns a list of the Blocks composing this graph.
`Body`	`getBody()` Returns the `Body` this `BlockGraph` is derived from.
`List<Block>`	`getHeads()` Returns a list of entry points for this graph.
`List<Block>`	`getPredsOf(Block b)` Returns a list of predecessors for the given node in the graph.
`List<Block>`	`getSuccsOf(Block b)` Returns a list of successors for the given node in the graph.
`List<Block>`	`getTails()` Returns a list of exit points for this graph.
`Iterator<Block>`	`iterator()` Returns an iterator for the nodes in this graph.
`int`	`size()` Returns the node count for this graph.
`String`	`toString()`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

mBody

protected Body mBody

mUnits

protected Chain<Unit> mUnits

mBlocks

protected List<Block> mBlocks

mHeads

protected List<Block> mHeads

mTails

protected List<Block> mTails

Constructor Detail

BlockGraph

protected BlockGraph(UnitGraph unitGraph)

Create a BlockGraph representing at the basic block level the control flow specified, at the Unit level, by a given UnitGraph.

Parameters:: unitGraph - A representation of the control flow at the level of individual Units.

Method Detail

computeLeaders

protected Set<Unit> computeLeaders(UnitGraph unitGraph)

Utility method for computing the basic block leaders for a Body, given its UnitGraph (i.e., the instructions which begin new basic blocks).

This implementation designates as basic block leaders :

Any Unit which has zero predecessors (e.g. the Unit following a return or unconditional branch) or more than one predecessor (e.g. a merge point).
Units which are the target of any branch (even if they have no other predecessors and the branch has no other successors, which is possible for the targets of unconditional branches or degenerate conditional branches which both branch and fall through to the same Unit).
All successors of any Unit which has more than one successor (this includes the successors of Units which may throw an exception that gets caught within the Body, as well the successors of conditional branches).
The first Unit in any Trap handler. (Strictly speaking, if unitGraph were a ExceptionalUnitGraph that included only a single unexceptional predecessor for some handler—because no trapped unit could possibly throw the exception that the handler catches, while the code preceding the handler fell through to the handler's code—then you could merge the handler into the predecessor's basic block; but such situations occur only in carefully contrived bytecode.)

Parameters:: unitGraph - is the Unit-level CFG which is to be split into basic blocks.
Returns:: the Set of Units in unitGraph which are block leaders.

buildBlocks

protected Map<Unit,Block> buildBlocks(Set<Unit> leaders,
                                      UnitGraph unitGraph)

A utility method that does most of the work of constructing basic blocks, once the set of block leaders has been determined, and which designates the heads and tails of the graph.

BlockGraph provides an implementation of buildBlocks() which splits the Units in unitGraph so that each Unit in the passed set of block leaders is the first unit in a block. It defines as heads the blocks which begin with Units which are heads in unitGraph, and defines as tails the blocks which end with Units which are tails in unitGraph. Subclasses might override this behavior.

Parameters:: leaders - Contains Units which are to be block leaders.; unitGraph - Provides information about the predecessors and successors of each Unit in the Body, for determining the predecessors and successors of each created Block.
Returns:: a Map from Units which begin or end a block to the block which contains them.

getBody

public Body getBody()

Returns the Body this BlockGraph is derived from.

Returns:: The Body this BlockGraph is derived from.

getBlocks

public List<Block> getBlocks()

Returns a list of the Blocks composing this graph.

Returns:: A list of the blocks composing this graph in the same order as they partition underlying Body instance's unit chain.
See Also:: Block

toString

public String toString()

Overrides:: toString in class Object