org.graalvm.compiler.truffle.runtime

Class BytecodeOSRMetadata

java.lang.Object

org.graalvm.compiler.truffle.runtime.BytecodeOSRMetadata

public final class BytecodeOSRMetadata
extends Object

Represents the metadata required to perform OSR compilation on Graal. An instance of this class is stored in the metadata field of a BytecodeOSRNode.

Performance note: We do not require the metadata field to be volatile. As long as the field is initialized under double-checked locking (as is done in GraalRuntimeSupport.pollBytecodeOSRBackEdge(com.oracle.truffle.api.nodes.BytecodeOSRNode), all threads will observe the same metadata instance. The JMM guarantees that the instance's final fields will be safely initialized before it is published; the non-final + non-volatile fields (e.g., the back edge counter) may not be, but we tolerate this inaccuracy in order to avoid volatile accesses in the hot path.

Field Summary

Fields

Modifier and Type	Field and Description
static BytecodeOSRMetadata	DISABLED
static int	OSR_POLL_INTERVAL

Method Summary

Modifier and Type	Method and Description
int	getBackEdgeCount()
Map<Integer,OptimizedCallTarget>	getOSRCompilations()
boolean	incrementAndPoll() Increment back edge count and return whether compilation should be polled.
void	restoreFrame(com.oracle.truffle.api.impl.FrameWithoutBoxing source, com.oracle.truffle.api.impl.FrameWithoutBoxing target) Transfer state from source to target.
void	transferFrame(com.oracle.truffle.api.impl.FrameWithoutBoxing source, com.oracle.truffle.api.impl.FrameWithoutBoxing target, int bytecodeTarget, Object targetMetadata) Transfer state from source to target.

Methods inherited from class java.lang.Object

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

Field Detail

DISABLED

public static final BytecodeOSRMetadata DISABLED

OSR_POLL_INTERVAL

public static final int OSR_POLL_INTERVAL

See Also:

Constant Field Values

Method Detail

incrementAndPoll

public boolean incrementAndPoll()

Increment back edge count and return whether compilation should be polled.

When the OSR threshold is reached, this method will return true after every OSR_POLL_INTERVAL back-edges. This method is thread-safe, but could under-count.

transferFrame

public void transferFrame(com.oracle.truffle.api.impl.FrameWithoutBoxing source,
                          com.oracle.truffle.api.impl.FrameWithoutBoxing target,
                          int bytecodeTarget,
                          Object targetMetadata)

Transfer state from source to target. Can be used to transfer state into an OSR frame.

restoreFrame

public void restoreFrame(com.oracle.truffle.api.impl.FrameWithoutBoxing source,
                         com.oracle.truffle.api.impl.FrameWithoutBoxing target)

Transfer state from source to target. Can be used to transfer state from an OSR frame to a parent frame. Overall less efficient than its counterpart, mainly due to not being able to speculate on the source tags: While entering bytecode OSR is done through specific entry points (likely back edges), returning could be done from anywhere within a method body (through regular returns, or exception thrown). While we could theoretically have the same mechanism as on entries (caching encountered return state), we could not efficiently be able to retrieve from the cache (as we do not get the equivalent of the int osrBytecodeTarget for returns), even ignoring the potential memory cost of such a cache. Therefore, we are doing a best-effort of copying over source to target, reading from the actual frames rather than a cache: If the tag cannot be constant-folded at this point, we get a switch in compiled code. Since we are at a boundary back to interpreted code, this cost should not be too high.

getOSRCompilations

public Map<Integer,OptimizedCallTarget> getOSRCompilations()

getBackEdgeCount

public int getBackEdgeCount()