com.oracle.svm.core.deopt

Class Deoptimizer

java.lang.Object

com.oracle.svm.core.deopt.Deoptimizer

public final class Deoptimizer
extends Object

Performs deoptimization. The method to deoptimize (= the source method) is either a specialized runtime compiled method or an image compiled test method with the Specialize annotation. The target method is always an image compiled method.

Deoptimization is not limited to a single method. It can be done for all deoptimizable methods in the call stack. A method is deoptimizable if deoptimization information is available.

Deoptimization is done in two steps:

1. A call to Deoptimizer.deoptimizeInRange(org.graalvm.nativeimage.c.function.CodePointer, org.graalvm.nativeimage.c.function.CodePointer, boolean) walks the stack and for each method to deoptimize it builds a DeoptimizedFrame. This handle contains all constants and materialized objects which are needed to build the deoptimization target frames. It is stored in the stack slot right above the return address. The return address (to the deoptimized method) is replaced by a pointer to Deoptimizer.deoptStub(com.oracle.svm.core.deopt.DeoptimizedFrame).

       :                                :
       |                                |
       |                                |
       +--------------------------------+   frame of the
       | outgoing stack parameters      |   deopmethod
       +--------------------------------+
       | pointer to DeoptimizedFrame    |
       +--------------------------------+---------
       | pointer to deoptStub           |   return address
       +--------------------------------+---------
       |                                |
       |                                |   frame of Deoptimizer.deoptimizeInRange(org.graalvm.nativeimage.c.function.CodePointer, org.graalvm.nativeimage.c.function.CodePointer, boolean) or
       |                                |   a method which called it
       :     ...                        :
    

   From now on, the frame of the deoptimized method is no longer valid and the GC will ignore it. Instead the GC will also visit the pointer to the DeoptimizedFrame. In other words: the frame of the deoptimized method is "replaced" by a single entry, a pointer to DeoptimizedFrame, which contains all objects which are needed by the deoptimization targets.

   There is one exception: outgoing parameters. Outgoing parameters of a deoptimized method may still be accessed by a called method, even after the first step of deoptimization is done. Therefore the calling convention must make sure that there is a free stack slot for the DeoptimizedFrame between the outgoing parameters and the return address slot.

   Exception from the exception: outgoing object parameters are always copied to registers at the beginning of the called method. Therefore we don't have to worry about GC these parameters.

2. Now when a called method will return to a deoptimized method, the Deoptimizer.deoptStub(com.oracle.svm.core.deopt.DeoptimizedFrame) will be called instead. It reads the DeoptimizedFrame handle and replaces the deoptimized method's frame with the frame(s) of the deopt target method(s). Note that the deopt stub is completely allocation free.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	Deoptimizer.DeoptStub
static class	Deoptimizer.Options
static class	Deoptimizer.StubType Custom method prologues and epilogues required for deoptimization.

Field Summary

Fields

Modifier and Type	Field and Description
protected static long	deoptStubFrameSize The size of frame for the deoptimization stub.
protected int	targetContentSize The size of the new stack content after all stack entries are built).
static boolean	testGCinDeoptimizer If true, the GC is called during deoptimization.

Constructor Summary

Constructors

Constructor and Description
Deoptimizer(org.graalvm.word.Pointer sourceSp, CodeInfoQueryResult sourceChunk)

Method Summary

Modifier and Type	Method and Description
static DeoptimizedFrame	checkDeoptimized(org.graalvm.word.Pointer sourceSp) Checks if a physical stack frame (identified by the stack pointer) was deoptimized, and returns the DeoptimizedFrame in that case.
static int	decodeDebugId(jdk.vm.ci.meta.JavaConstant actionAndReason)
static int	decodeDebugId(long actionAndReason)
static jdk.vm.ci.meta.DeoptimizationAction	decodeDeoptAction(jdk.vm.ci.meta.JavaConstant actionAndReason)
static jdk.vm.ci.meta.DeoptimizationAction	decodeDeoptAction(long actionAndReason)
static jdk.vm.ci.meta.DeoptimizationReason	decodeDeoptReason(jdk.vm.ci.meta.JavaConstant actionAndReason)
static jdk.vm.ci.meta.DeoptimizationReason	decodeDeoptReason(long actionAndReason)
static void	deoptimizeAll() Deoptimizes all method(s) in all call stacks (= the calling methods).
static void	deoptimizeFrame(org.graalvm.word.Pointer sourceSp, boolean ignoreNonDeoptimizable, jdk.vm.ci.meta.SpeculationLog.SpeculationReason speculation) Deoptimizes the given frame.
static void	deoptimizeInRange(org.graalvm.nativeimage.c.function.CodePointer fromIp, org.graalvm.nativeimage.c.function.CodePointer toIp, boolean deoptAll) Deoptimize a specific method.
DeoptimizedFrame	deoptSourceFrame(org.graalvm.nativeimage.c.function.CodePointer pc, boolean ignoreNonDeoptimizable, org.graalvm.nativeimage.IsolateThread currentThread) Deoptimizes a source frame.
static void	deoptStub(DeoptimizedFrame frame) Performs the second step of deoptimization: the actual rewriting of a deoptimized method's frame.
static jdk.vm.ci.meta.JavaConstant	encodeDeoptActionAndReason(jdk.vm.ci.meta.DeoptimizationAction action, jdk.vm.ci.meta.DeoptimizationReason reason, int speculationId)
static long	encodeDeoptActionAndReasonToLong(jdk.vm.ci.meta.DeoptimizationAction action, jdk.vm.ci.meta.DeoptimizationReason reason, int speculationId)
static void	invalidateMethodOfFrame(org.graalvm.word.Pointer sourceSp, jdk.vm.ci.meta.SpeculationLog.SpeculationReason speculation) Invalidates the InstalledCode of the method of the given frame.
static void	logRecentDeoptimizationEvents(Log log)
jdk.vm.ci.meta.JavaConstant	readLocalVariable(int idx, FrameInfoQueryResult sourceFrame) Reads the value of a local variable in the given frame.

Methods inherited from class java.lang.Object

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

Field Detail

testGCinDeoptimizer

public static boolean testGCinDeoptimizer

If true, the GC is called during deoptimization. The deoptimizer allocates some objects (in the first step), so GC must work inside the deoptimizer.

targetContentSize

protected int targetContentSize

The size of the new stack content after all stack entries are built).

deoptStubFrameSize

protected static long deoptStubFrameSize

The size of frame for the deoptimization stub. Initialized to 0 in the native image and updated at first use at run time. Cached because it is a constant, expensive to compute, and computing it before I become uninterruptible saves making a lot of extraneous code uninterruptible.

Constructor Detail

Deoptimizer

public Deoptimizer(org.graalvm.word.Pointer sourceSp,
                   CodeInfoQueryResult sourceChunk)

Method Detail

encodeDeoptActionAndReasonToLong

public static long encodeDeoptActionAndReasonToLong(jdk.vm.ci.meta.DeoptimizationAction action,
                                                    jdk.vm.ci.meta.DeoptimizationReason reason,
                                                    int speculationId)

encodeDeoptActionAndReason

public static jdk.vm.ci.meta.JavaConstant encodeDeoptActionAndReason(jdk.vm.ci.meta.DeoptimizationAction action,
                                                                     jdk.vm.ci.meta.DeoptimizationReason reason,
                                                                     int speculationId)

decodeDeoptAction

public static jdk.vm.ci.meta.DeoptimizationAction decodeDeoptAction(long actionAndReason)

decodeDeoptReason

public static jdk.vm.ci.meta.DeoptimizationReason decodeDeoptReason(long actionAndReason)

decodeDebugId

public static int decodeDebugId(long actionAndReason)

decodeDeoptAction

public static jdk.vm.ci.meta.DeoptimizationAction decodeDeoptAction(jdk.vm.ci.meta.JavaConstant actionAndReason)

decodeDeoptReason

public static jdk.vm.ci.meta.DeoptimizationReason decodeDeoptReason(jdk.vm.ci.meta.JavaConstant actionAndReason)

decodeDebugId

public static int decodeDebugId(jdk.vm.ci.meta.JavaConstant actionAndReason)

checkDeoptimized

public static DeoptimizedFrame checkDeoptimized(org.graalvm.word.Pointer sourceSp)

Checks if a physical stack frame (identified by the stack pointer) was deoptimized, and returns the DeoptimizedFrame in that case.

deoptimizeAll

public static void deoptimizeAll()

Deoptimizes all method(s) in all call stacks (= the calling methods). Only used for testing.

deoptimizeInRange

public static void deoptimizeInRange(org.graalvm.nativeimage.c.function.CodePointer fromIp,
                                     org.graalvm.nativeimage.c.function.CodePointer toIp,
                                     boolean deoptAll)

Deoptimize a specific method.

Parameters:

fromIp - The lower address (including) of the method's code.

toIp - The upper address (excluding) of the method's code.

deoptimizeFrame

public static void deoptimizeFrame(org.graalvm.word.Pointer sourceSp,
                                   boolean ignoreNonDeoptimizable,
                                   jdk.vm.ci.meta.SpeculationLog.SpeculationReason speculation)

Deoptimizes the given frame.

Parameters:

ignoreNonDeoptimizable - if set to true, a frame that cannot be deoptimized is ignored instead of raising an error (use for deoptimzation testing only).

invalidateMethodOfFrame

public static void invalidateMethodOfFrame(org.graalvm.word.Pointer sourceSp,
                                           jdk.vm.ci.meta.SpeculationLog.SpeculationReason speculation)

Invalidates the InstalledCode of the method of the given frame. The method must be a runtime compiled method, since there is not InstalledCode for native image methods.

deoptStub

public static void deoptStub(DeoptimizedFrame frame)

Performs the second step of deoptimization: the actual rewriting of a deoptimized method's frame.

The pointer to the deopt stub code was installed in the return address slot by Deoptimizer.deoptimizeInRange(org.graalvm.nativeimage.c.function.CodePointer, org.graalvm.nativeimage.c.function.CodePointer, boolean). Therefore the stub is "called" when a method wants to return to a deoptimized method.

When Deoptimizer.deoptStub(com.oracle.svm.core.deopt.DeoptimizedFrame) is "called", the stack looks like this:

    :                                :
    |                                |
    |                                |   frame of the
    +--------------------------------+   deoptimized method
    | pointer to DeoptimizedFrame    |
    +--------------------------------+--------- no return address between the frames!
    |                                |
    |                                |   frame of
    |                                |   Deoptimizer.deoptStub(com.oracle.svm.core.deopt.DeoptimizedFrame)
    :     ...                        :
 

Parameters:

frame - This is the handle which was created in Deoptimizer.deoptimizeInRange(org.graalvm.nativeimage.c.function.CodePointer, org.graalvm.nativeimage.c.function.CodePointer, boolean). It is fetched from the stack (the slot above the original return address) and passed as parameter. The instructions for fetching the frame handle must be generated in this method's prolog by a backend-specific FrameContext class. The prolog also stores the original return value registers in the frame.

readLocalVariable

public jdk.vm.ci.meta.JavaConstant readLocalVariable(int idx,
                                                     FrameInfoQueryResult sourceFrame)

Reads the value of a local variable in the given frame. If the local variable is a virtual object, the object (and all other objects reachable from it) are materialized.

Parameters:

idx - the number of the local variable.

sourceFrame - the frame to access, which must be an inlined frame of the physical frame that this deoptimizer has been created for.

deoptSourceFrame

public DeoptimizedFrame deoptSourceFrame(org.graalvm.nativeimage.c.function.CodePointer pc,
                                         boolean ignoreNonDeoptimizable,
                                         org.graalvm.nativeimage.IsolateThread currentThread)

Deoptimizes a source frame.

Parameters:

pc - A code address inside the source method (= the method to deoptimize)

logRecentDeoptimizationEvents

public static void logRecentDeoptimizationEvents(Log log)