org.jikesrvm.compilers.opt.ssa

Class GCP

java.lang.Object

org.jikesrvm.compilers.opt.driver.OptimizationPlanElement

org.jikesrvm.compilers.opt.driver.OptimizationPlanCompositeElement

org.jikesrvm.compilers.opt.ssa.GCP

public final class GCP
extends OptimizationPlanCompositeElement

Global code placement comes in two flavours. The first is loop invariant code motion (LICM), the second is global common sub expression elimination (GCSE).

LICM is applied to HIR and LIR, GCSE only to LIR and before LICM.

Both algorithms run on SSA and use the dominator tree to determine positions for operations. That's why these operations are called code placement instead of code motion.

There is no code yet to deal with partial redundancies.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	GCP.GCPFinalization This class sets up the IR state prior to entering SSA for GCP
private static class	GCP.GCPPreparation This class sets up the IR state prior to entering SSA for GCP

Constructor Summary

Constructors

Constructor and Description
GCP() Makes sure we are in SSA and have global value numbers at hand.

Method Summary

Modifier and Type	Method and Description
boolean	shouldPerform(OptOptions options) Redefine shouldPerform so that none of the subphases will occur unless we pass through this test.
(package private) static boolean	tooBig(IR ir)
static boolean	usesOrDefsPhysicalRegisterOrAddressType(Instruction inst)

Methods inherited from class org.jikesrvm.compilers.opt.driver.OptimizationPlanCompositeElement

compose, elapsedTime, getName, initializeForMeasureCompilation, perform, printingEnabled, reportStats

Methods inherited from class org.jikesrvm.compilers.opt.driver.OptimizationPlanElement

prettyPrintTime

Methods inherited from class java.lang.Object

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

Constructor Detail

GCP

public GCP()

Makes sure we are in SSA and have global value numbers at hand. Then execute the transformations.

Method Detail

shouldPerform

public boolean shouldPerform(OptOptions options)

Redefine shouldPerform so that none of the subphases will occur unless we pass through this test.

Overrides:

shouldPerform in class OptimizationPlanCompositeElement

Parameters:

options - The Options object for the current compilation.

Returns:

true if the plan element should be performed.

tooBig

static boolean tooBig(IR ir)

usesOrDefsPhysicalRegisterOrAddressType

public static boolean usesOrDefsPhysicalRegisterOrAddressType(Instruction inst)