com.oracle.graal.phases.graph

Class FixedNodeProbabilityCache

java.lang.Object

com.oracle.graal.phases.graph.FixedNodeProbabilityCache

All Implemented Interfaces:

ToDoubleFunction<FixedNode>

public class FixedNodeProbabilityCache
extends Object
implements ToDoubleFunction<FixedNode>

Compute probabilities for fixed nodes on the fly and cache them at AbstractBeginNodes.

Field Summary

Fields

Modifier and Type	Field and Description
private Map<FixedNode,Double>	cache
private static DebugMetric	metricComputeNodeProbability

Constructor Summary

Constructors

Constructor and Description
FixedNodeProbabilityCache()

Method Summary

Modifier and Type	Method and Description
double	applyAsDouble(FixedNode node) Given a FixedNode this method finds the most immediate AbstractBeginNode preceding it that either: has no predecessor (ie, the begin-node is a merge, in particular a loop-begin, or the start-node) has a control-split predecessor
private static FixedNode	findBegin(FixedNode node)
private double	handleMerge(FixedNode current, double probability)

Methods inherited from class java.lang.Object

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

Field Detail

metricComputeNodeProbability

private static final DebugMetric metricComputeNodeProbability

cache

private final Map<FixedNode,Double> cache

Constructor Detail

FixedNodeProbabilityCache

public FixedNodeProbabilityCache()

Method Detail

applyAsDouble

public double applyAsDouble(FixedNode node)

Given a FixedNode this method finds the most immediate AbstractBeginNode preceding it that either:

• has no predecessor (ie, the begin-node is a merge, in particular a loop-begin, or the start-node)
• has a control-split predecessor

The thus found AbstractBeginNode is equi-probable with the FixedNode it was obtained from. When computed for the first time (afterwards a cache lookup returns it) that probability is computed as follows, again depending on the begin-node's predecessor:

• No predecessor. In this case the begin-node is either:
• a merge-node, whose probability adds up those of its forward-ends
• a loop-begin, with probability as above multiplied by the loop-frequency
• Control-split predecessor: probability of the branch times that of the control-split

As an exception to all the above, a probability of 1 is assumed for a FixedNode that appears to be dead-code (ie, lacks a predecessor).

Specified by:

applyAsDouble in interface ToDoubleFunction<FixedNode>

handleMerge

private double handleMerge(FixedNode current,
                           double probability)

findBegin

private static FixedNode findBegin(FixedNode node)