org.graalvm.compiler.virtual.phases.ea

Class ReadEliminationPhase

java.lang.Object

org.graalvm.compiler.phases.BasePhase<CoreProvidersT>

org.graalvm.compiler.virtual.phases.ea.EffectsPhase<CoreProviders>

org.graalvm.compiler.virtual.phases.ea.ReadEliminationPhase

All Implemented Interfaces:

PhaseSizeContract

public class ReadEliminationPhase
extends EffectsPhase<CoreProviders>

This phase performs read and (simple) write elimination on a graph. It operates on multiple granularities, i.e., before and after high-tier lowering. The phase iterates the graph in a reverse-post-order fashion ReentrantBlockIterator and tracks the currently active value for a specific LocationIdentity, which allows the removal of subsequent reads if no writes happen in between, etc. if the value read from memory is in a virtual register (node). A trivial example for read elimination can be seen below:

 int i = object.fieldValue;
 // code not changing object.fieldValue but using i
 consume(object.fieldValue);
 

Read elimination will transform this piece of code to the code below and remove the second, unnecessary, memory read of the field:

 int i = object.fieldValue;
 // code not changing object.fieldValue but using i
 consume(i);
 

Nested Class Summary

Nested classes/interfaces inherited from class org.graalvm.compiler.virtual.phases.ea.EffectsPhase

EffectsPhase.Closure<T>

Nested classes/interfaces inherited from class org.graalvm.compiler.phases.BasePhase

BasePhase.ApplyScope, BasePhase.BasePhaseStatistics, BasePhase.PhaseOptions, BasePhase.SharedGlobalPhaseState

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	considerGuards

Fields inherited from class org.graalvm.compiler.virtual.phases.ea.EffectsPhase

canonicalizer

Constructor Summary

Constructors

Constructor and Description
ReadEliminationPhase(CanonicalizerPhase canonicalizer)
ReadEliminationPhase(CanonicalizerPhase canonicalizer, boolean considerGuards)

Method Summary

Modifier and Type	Method and Description
float	codeSizeIncrease() Returns a factor >=1 that determines what the final code size in terms of the sum of the node code sizes NodeSize of all nodes is.
protected EffectsPhase.Closure<?>	createEffectsClosure(CoreProviders context, StructuredGraph.ScheduleResult schedule, ControlFlowGraph cfg)
protected void	run(StructuredGraph graph, CoreProviders context)

Methods inherited from class org.graalvm.compiler.virtual.phases.ea.EffectsPhase

postIteration, runAnalysis

Methods inherited from class org.graalvm.compiler.phases.BasePhase

apply, apply, applyScope, contractorName, equals, getName, hashCode, shouldDumpAfterAtBasicLevel, shouldDumpBeforeAtBasicLevel

Methods inherited from class java.lang.Object

clone, getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.graalvm.compiler.phases.contract.PhaseSizeContract

checkContract

Field Detail

considerGuards

protected final boolean considerGuards

Constructor Detail

ReadEliminationPhase

public ReadEliminationPhase(CanonicalizerPhase canonicalizer)

ReadEliminationPhase

public ReadEliminationPhase(CanonicalizerPhase canonicalizer,
                            boolean considerGuards)

Method Detail

run

protected void run(StructuredGraph graph,
                   CoreProviders context)

Overrides:

run in class EffectsPhase<CoreProviders>

createEffectsClosure

protected EffectsPhase.Closure<?> createEffectsClosure(CoreProviders context,
                                                       StructuredGraph.ScheduleResult schedule,
                                                       ControlFlowGraph cfg)

Specified by:

createEffectsClosure in class EffectsPhase<CoreProviders>

codeSizeIncrease

public float codeSizeIncrease()

Description copied from interface: PhaseSizeContract

Returns a factor >=1 that determines what the final code size in terms of the sum of the node code sizes NodeSize of all nodes is.

Specified by:

codeSizeIncrease in interface PhaseSizeContract

Overrides:

codeSizeIncrease in class BasePhase<CoreProviders>

Returns:

a factor that determines how much the code size can be increased by this phase