UncommonTrapStub (Graal OpenJDK Project Documentation)

java.lang.Object
- com.oracle.graal.hotspot.stubs.Stub
- - com.oracle.graal.hotspot.stubs.SnippetStub
  - - com.oracle.graal.hotspot.stubs.UncommonTrapStub

All Implemented Interfaces:

Snippets

Direct Known Subclasses:

AMD64UncommonTrapStub, SPARCUncommonTrapStub
```
public class UncommonTrapStub
extends SnippetStub
```
Uncommon trap stub. This is the entry point for code which is returning to a de-optimized frame. The steps taken by this frame are as follows:
push a dummy "register_save" and save the return values (O0, O1, F0/F1, G1) and all potentially live registers (at a pollpoint many registers can be live).
call the C routine: Deoptimization::fetch_unroll_info (this function returns information about the number and size of interpreter frames which are equivalent to the frame which is being deoptimized)
deallocate the unpack frame, restoring only results values. Other volatile registers will now be captured in the vframeArray as needed.
deallocate the deoptimization frame
in a loop using the information returned in the previous step push new interpreter frames (take care to propagate the return values through each new frame pushed)
create a dummy "unpack_frame" and save the return values (O0, O1, F0)
call the C routine: Deoptimization::unpack_frames (this function lays out values on the interpreter frame which was just created)
deallocate the dummy unpack_frame
ensure that all the return values are correctly set and then do a return to the interpreter entry point
ATTENTION: We cannot do any complicated operations e.g. logging via printf in this snippet because we change the current stack layout and so the code is very sensitive to register allocation.

Field Summary

Fields
Modifier and Type Field and Description

static LocationIdentity STACK_BANG_LOCATION

private TargetDescription target
- Fields inherited from class com.oracle.graal.hotspot.stubs.SnippetStub
  method, SnippetGraphUnderConstruction
- Fields inherited from class com.oracle.graal.hotspot.stubs.Stub
  code, compResult, linkage, providers

Fields
Modifier and Type	Field and Description
`static LocationIdentity`	`STACK_BANG_LOCATION`
`private TargetDescription`	`target`

Constructor Summary

Constructors
Constructor and Description

UncommonTrapStub(HotSpotProviders providers, TargetDescription target, HotSpotForeignCallLinkage linkage)

Constructors
Constructor and Description
`UncommonTrapStub(HotSpotProviders providers, TargetDescription target, HotSpotForeignCallLinkage linkage)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`private static int`	`deoptimizationUnpackDeopt()`
`private static int`	`deoptimizationUnpackUncommonTrap()`
`private static int`	`deoptimizationUnrollBlockCallerAdjustmentOffset()`
`private static int`	`deoptimizationUnrollBlockFramePcsOffset()`
`private static int`	`deoptimizationUnrollBlockFrameSizesOffset()`
`private static int`	`deoptimizationUnrollBlockInitialInfoOffset()`
`private static int`	`deoptimizationUnrollBlockNumberOfFramesOffset()`
`private static int`	`deoptimizationUnrollBlockSizeOfDeoptimizedFrameOffset()`
`private static int`	`deoptimizationUnrollBlockTotalFrameSizesOffset()`
`protected Object`	`getConstantParameterValue(int index, String name)`
`boolean`	`preservesRegisters()` Determines if this stub preserves all registers apart from those it destroys.
`private static Word`	`readRegister(Register register)` Reads the value of the passed register as a Word.
`private static int`	`stackBias()` Deprecated. This method should go away as soon as JDK-8032410 hits the Graal repository.
`private static int`	`stackShadowPages()`
`private static void`	`uncommonTrapHandler(Register threadRegister, Register stackPointerRegister)` Uncommon trap handler.
`static int`	`unpackFrames(ForeignCallDescriptor unpackFrames, Word thread, int mode)`
`private static void`	`writeRegister(Register register, Word value)` Writes the value of the passed register.

Methods inherited from class com.oracle.graal.hotspot.stubs.SnippetStub
checkConstArg, debugScopeContext, getGraph, getInstalledCodeOwner, makeConstArgs, toString

Methods inherited from class com.oracle.graal.hotspot.stubs.Stub
getCode, getCompilationResult, getDestroyedRegisters, getLinkage, getRegisterConfig, getStubs, initDestroyedRegisters

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

STACK_BANG_LOCATION

public static final LocationIdentity STACK_BANG_LOCATION

target
```
private final TargetDescription target
```

Constructor Detail

UncommonTrapStub

public UncommonTrapStub(HotSpotProviders providers,
                        TargetDescription target,
                        HotSpotForeignCallLinkage linkage)

Method Detail
- preservesRegisters
```
public boolean preservesRegisters()
```
  Description copied from class: Stub
  
  Determines if this stub preserves all registers apart from those it destroys.
  
  Overrides:
  
  preservesRegisters in class Stub
- getConstantParameterValue
```
protected Object getConstantParameterValue(int index,
                                           String name)
```
  Overrides:
  
  getConstantParameterValue in class SnippetStub
- uncommonTrapHandler
```
private static void uncommonTrapHandler(Register threadRegister,
                                        Register stackPointerRegister)
```
  Uncommon trap handler. We save the argument return registers. We call the first C routine, fetch_unroll_info(). This routine captures the return values and returns a structure which describes the current frame size and the sizes of all replacement frames. The current frame is compiled code and may contain many inlined functions, each with their own JVM state. We pop the current frame, then push all the new frames. Then we call the C routine unpack_frames() to populate these frames. Finally unpack_frames() returns us the new target address. Notice that callee-save registers are BLOWN here; they have already been captured in the vframeArray at the time the return PC was patched.
- readRegister
```
private static Word readRegister(Register register)
```
  Reads the value of the passed register as a Word.
- writeRegister
```
private static void writeRegister(Register register,
                                  Word value)
```
  Writes the value of the passed register.
  
  Parameters:
  
  value - value the register should be set to
- stackShadowPages
```
private static int stackShadowPages()
```
- stackBias
```
@Deprecated
private static int stackBias()
```
  Deprecated. This method should go away as soon as JDK-8032410 hits the Graal repository.
  
  Returns the stack bias for the host architecture.
  
  Returns:
  
  stack bias
- deoptimizationUnrollBlockSizeOfDeoptimizedFrameOffset
```
private static int deoptimizationUnrollBlockSizeOfDeoptimizedFrameOffset()
```
- deoptimizationUnrollBlockCallerAdjustmentOffset
```
private static int deoptimizationUnrollBlockCallerAdjustmentOffset()
```
- deoptimizationUnrollBlockNumberOfFramesOffset
```
private static int deoptimizationUnrollBlockNumberOfFramesOffset()
```
- deoptimizationUnrollBlockTotalFrameSizesOffset
```
private static int deoptimizationUnrollBlockTotalFrameSizesOffset()
```
- deoptimizationUnrollBlockFrameSizesOffset
```
private static int deoptimizationUnrollBlockFrameSizesOffset()
```
- deoptimizationUnrollBlockFramePcsOffset
```
private static int deoptimizationUnrollBlockFramePcsOffset()
```
- deoptimizationUnrollBlockInitialInfoOffset
```
private static int deoptimizationUnrollBlockInitialInfoOffset()
```
- deoptimizationUnpackDeopt
```
private static int deoptimizationUnpackDeopt()
```
- deoptimizationUnpackUncommonTrap
```
private static int deoptimizationUnpackUncommonTrap()
```
- unpackFrames
```
public static int unpackFrames(ForeignCallDescriptor unpackFrames,
                               Word thread,
                               int mode)
```

Class UncommonTrapStub

Field Summary

Fields inherited from class com.oracle.graal.hotspot.stubs.SnippetStub

Fields inherited from class com.oracle.graal.hotspot.stubs.Stub

Constructor Summary

Method Summary

Methods inherited from class com.oracle.graal.hotspot.stubs.SnippetStub

Methods inherited from class com.oracle.graal.hotspot.stubs.Stub

Methods inherited from class java.lang.Object

Field Detail

STACK_BANG_LOCATION

target

Constructor Detail

UncommonTrapStub

Method Detail

preservesRegisters

getConstantParameterValue

uncommonTrapHandler

readRegister

writeRegister

stackShadowPages

stackBias

deoptimizationUnrollBlockSizeOfDeoptimizedFrameOffset

deoptimizationUnrollBlockCallerAdjustmentOffset

deoptimizationUnrollBlockNumberOfFramesOffset

deoptimizationUnrollBlockTotalFrameSizesOffset

deoptimizationUnrollBlockFrameSizesOffset

deoptimizationUnrollBlockFramePcsOffset

deoptimizationUnrollBlockInitialInfoOffset

deoptimizationUnpackDeopt

deoptimizationUnpackUncommonTrap

unpackFrames