com.oracle.graal.lir.ssi

Class SSIUtil

java.lang.Object

com.oracle.graal.lir.ssi.SSIUtil

public final class SSIUtil
extends Object

Utilities for working with Static-Single-Information LIR form.

Representation of φ and σ

There are no explicit φ/σ LIRInstructions. Instead, they are implemented as parallel copy that spans across a control-flow edge. The variables introduced by φ/σ of a specific block are attached to the StandardOp.LabelOp of the block. The outgoing values from the predecessor are input to the StandardOp.BlockEndOp of the predecessor. When it does not matter whether we are talking about a φ or a σ we call the values that are defined by a label incoming and the values that are input to the StandardOp.BlockEndOp of the predecessor outgoing.

Implementation Details

For our purposes we want a maximal SSI form, which means that all values that are alive across basic block boundaries are gated with a φ/σ. In other words the outgoing and incoming values of the StandardOp.BlockEndOp and StandardOp.LabelOp are equivalent to the live-out and live-in set of the corresponding block. As a side effect variables are local to a block. We reuse the name of the predecessor if they represent the same value (i.e. not a real φ definition).

Examples

Merge (φ)

 B0 -> B1
   ...
   v0|i = ...
   JUMP ~[v0|i, int[0|0x0]] destination: B0 -> B1
 ________________________________________________

 B2 -> B1
   ...
   v1|i = ...
   v2|i = ...
   JUMP ~[v1|i, v2|i] destination: B2 -> B1
 ________________________________________________

 B1 <- B0,B2
   [v3|i, v4|i] = LABEL
   ...
 

Note: the outgoing values of a block can contain constants (see B0).

Split (σ)

 B0 -> B1,B2
   ...
   v0|i = ...
   v1|i = ...
   v2|i = ...
   TEST (x: v1|i, y: v1|i)
   BRANCH ~[v2|i, v0|j] condition: <, true: B1 false: B2
 ________________________________________________

 B1 <- B0
   [-, v0|j] = LABEL
   ...
 ________________________________________________

 B2 <- B0
   [v2|i, v0|j] = LABEL
   ...
 

Note: If a incoming value is not needed in a branch it is ignored (see B1).

Constructor Summary

Constructors

Constructor and Description
SSIUtil()

Method Summary

Modifier and Type	Method and Description
static void	forEachRegisterHint(LIR lir, AbstractBlockBase<?> block, StandardOp.LabelOp label, Value targetValue, LIRInstruction.OperandMode mode, ValueConsumer valueConsumer)
static void	forEachValuePair(LIR lir, AbstractBlockBase<?> toBlock, AbstractBlockBase<?> fromBlock, SSAUtil.PhiValueVisitor visitor) Visits each SIGMA/PHI value pair of an edge, i.e.
static StandardOp.LabelOp	incoming(LIR lir, AbstractBlockBase<?> block)
private static LIRInstruction	incomingInst(LIR lir, AbstractBlockBase<?> block)
private static int	indexOfValue(StandardOp.LabelOp label, Value value)
static StandardOp.BlockEndOp	outgoing(LIR lir, AbstractBlockBase<?> block)
static LIRInstruction	outgoingInst(LIR lir, AbstractBlockBase<?> block)
static void	removeIncoming(LIR lir, AbstractBlockBase<?> block)
static void	removeOutgoing(LIR lir, AbstractBlockBase<?> block)

Methods inherited from class java.lang.Object

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

Constructor Detail

SSIUtil

public SSIUtil()

Method Detail

outgoing

public static StandardOp.BlockEndOp outgoing(LIR lir,
                                             AbstractBlockBase<?> block)

outgoingInst

public static LIRInstruction outgoingInst(LIR lir,
                                          AbstractBlockBase<?> block)

incoming

public static StandardOp.LabelOp incoming(LIR lir,
                                          AbstractBlockBase<?> block)

incomingInst

private static LIRInstruction incomingInst(LIR lir,
                                           AbstractBlockBase<?> block)

removeIncoming

public static void removeIncoming(LIR lir,
                                  AbstractBlockBase<?> block)

removeOutgoing

public static void removeOutgoing(LIR lir,
                                  AbstractBlockBase<?> block)

forEachValuePair

public static void forEachValuePair(LIR lir,
                                    AbstractBlockBase<?> toBlock,
                                    AbstractBlockBase<?> fromBlock,
                                    SSAUtil.PhiValueVisitor visitor)

Visits each SIGMA/PHI value pair of an edge, i.e. the outgoing value from the predecessor and the incoming value to the merge block.

forEachRegisterHint

public static void forEachRegisterHint(LIR lir,
                                       AbstractBlockBase<?> block,
                                       StandardOp.LabelOp label,
                                       Value targetValue,
                                       LIRInstruction.OperandMode mode,
                                       ValueConsumer valueConsumer)

indexOfValue

private static int indexOfValue(StandardOp.LabelOp label,
                                Value value)