45 SYSTEM PROPERTY: -Dnashorn.compiler.intarithmetic

    53 SYSTEM PROPERTY: -Dnashorn.serialize.compression=<x>

    46 

    54 

    47 (and integer arithmetic in general)

    55 This property sets the compression level used when deflating serialized

    48 

    56 AST structures of anonymous split functions. Valid values range from 0 to 9,

    49 <currently disabled - this is being refactored for update releases> 

    57 the default value is 4. Higher values will reduce memory size of serialized

    50 

    58 AST but increase CPU usage required for compression.

    51 Arithmetic operations in Nashorn (except bitwise ones) typically

    59 

    52 coerce the operands to doubles (as per the JavaScript spec). To switch

    60 

    53 this off and remain in integer mode, for example for "var x = a&b; var

    61 SYSTEM PROPERTY: -Dnashorn.codegen.debug.trace=<x>

    54 y = c&d; var z = x*y;", use this flag. This will force the

    55 multiplication of variables that are ints to be done with the IMUL

    56 bytecode and the result "z" to become an int.

    57 

    58 WARNING: Note that is is experimental only to ensure that type support

    59 exists for all primitive types. The generated code is unsound. This

    60 will be the case until we do optimizations based on it. There is a CR

    61 in Nashorn to do better range analysis, and ensure that this is only

    62 done where the operation can't overflow into a wider type. Currently

    63 no overflow checking is done, so at the moment, until range analysis

    64 has been completed, this option is turned off.

    65 

    66 We've experimented by using int arithmetic for everything and putting

    67 overflow checks afterwards, which would recompute the operation with

    68 the correct precision, but have yet to find a configuration where this

    69 is faster than just using doubles directly, even if the int operation

    70 does not overflow. Getting access to a JVM intrinsic that does branch

    71 on overflow would probably alleviate this.

    72 

    73 The future:

    74 

    75 We are transitioning to an optimistic type system that uses int

    76 arithmetic everywhere until proven wrong. The problem here is mostly

    77 catch an overflow exception and rolling back the state to a new method

    78 with less optimistic assumptions for an operation at a particular

    79 program point. This will most likely not be in the Java 8.0 release

    80 but likely end up in an update release

    81 

    82 For Java 8, several java.lang.Math methods like addExact, subExact and

    83 mulExact are available to help us. Experiments intrinsifying these

    84 show a lot of promise, and we have devised a system that basically

    85 does on stack replacement with exceptions in bytecode to revert

    86 erroneous assumptions. An explanation of how this works and what we

    87 are doing can be found here:

    88 http://www.slideshare.net/lagergren/lagergren-jvmls2013final

    89 

    90 Experiments with this show significant ~x2-3 performance increases on

    91 pretty much everything, provided that optimistic assumptions don't

    92 fail much. It will affect warmup time negatively, depending on how

    93 many erroneous too optimistic assumptions are placed in the code at

    94 compile time. We don't think this will be much of an issue.

    95 

    96 For example for a small benchmark that repeatedly executes this

    97 method taken from the Crypto Octane benchmark 

    98 

    99 function am3(i,x,w,j,c,n) {

   100   var this_array = this.array;

   101   var w_array    = w.array;

   102   var xl = x&0x3fff, xh = x>>14;

   103   while(--n >= 0) {

   104     var l = this_array[i]&0x3fff;

   105     var h = this_array[i++]>>14;

   106     var m = xh*l+h*xl;

   107     l = xl*l+((m&0x3fff)<<14)+w_array[j]+c;

   108     c = (l>>28)+(m>>14)+xh*h;

   109     w_array[j++] = l&0xfffffff;

   110   }

   111 

   112   return c;

   113 }

   114 

   115 The performance increase more than doubles. We are also working hard

   116 with the code generation team in the Java Virtual Machine to fix

   117 things that are lacking in invokedynamic performance, which is another

   118 area where a lot of ongoing performance work takes place

   119 

   120 "Pessimistic" bytecode for am3, guaranteed to be semantically correct:

   121 

   122 // access flags 0x9

   123   public static am3(Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;

   124    L0

   125     LINENUMBER 12 L0

   126     ALOAD 0

   127     INVOKEDYNAMIC dyn:getProp|getElem|getMethod:array(Ljava/lang/Object;)Ljava/lang/Object; [

   128       // handle kind 0x6 : INVOKESTATIC

   129       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   130       // arguments:

   131       0

   132     ]

   133     ASTORE 8

   134    L1

   135     LINENUMBER 13 L1

   136     ALOAD 3

   137     INVOKEDYNAMIC dyn:getProp|getElem|getMethod:array(Ljava/lang/Object;)Ljava/lang/Object; [

   138       // handle kind 0x6 : INVOKESTATIC

   139       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   140       // arguments:

   141       0

   142     ]

   143     ASTORE 9

   144    L2

   145     LINENUMBER 14 L2

   146     ALOAD 2

   147     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toInt32 (Ljava/lang/Object;)I

   148     SIPUSH 16383

   149     IAND

   150     ISTORE 10

   151     ALOAD 2

   152     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toInt32 (Ljava/lang/Object;)I

   153     BIPUSH 14

   154     ISHR

   155     ISTORE 11

   156    L3

   157     LINENUMBER 15 L3

   158     GOTO L4

   159    L5

   160     LINENUMBER 16 L5

   161    FRAME FULL [java/lang/Object java/lang/Object java/lang/Object java/lang/Object java/lang/Object java/lang/Object java/lang/Double T java/lang/Object java/lang/Object I I] []

   162     ALOAD 8

   163     ALOAD 1

   164     INVOKEDYNAMIC dyn:getElem|getProp|getMethod(Ljava/lang/Object;Ljava/lang/Object;)I [

   165       // handle kind 0x6 : INVOKESTATIC

   166       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   167       // arguments:

   168       0

   169     ]

   170     SIPUSH 16383

   171     IAND

   172     INVOKESTATIC java/lang/Integer.valueOf (I)Ljava/lang/Integer;

   173     ASTORE 12

   174    L6

   175     LINENUMBER 17 L6

   176     ALOAD 8

   177     ALOAD 1

   178     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toNumber (Ljava/lang/Object;)D

   179     DUP2

   180     DCONST_1

   181     DADD

   182     INVOKESTATIC java/lang/Double.valueOf (D)Ljava/lang/Double;

   183     ASTORE 1

   184     INVOKEDYNAMIC dyn:getElem|getProp|getMethod(Ljava/lang/Object;D)I [

   185       // handle kind 0x6 : INVOKESTATIC

   186       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   187       // arguments:

   188       0

   189     ]

   190     BIPUSH 14

   191     ISHR

   192     ISTORE 13

   193    L7

   194     LINENUMBER 18 L7

   195     ILOAD 11

   196     I2D

   197     ALOAD 12

   198     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toNumber (Ljava/lang/Object;)D

   199     DMUL

   200     ILOAD 13

   201     I2D

   202     ILOAD 10

   203     I2D

   204     DMUL

   205     DADD

   206     DSTORE 14

   207    L8

   208     LINENUMBER 19 L8

   209     ILOAD 10

   210     I2D

   211     ALOAD 12

   212     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toNumber (Ljava/lang/Object;)D

   213     DMUL

   214     DLOAD 14

   215     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toInt32 (D)I

   216     SIPUSH 16383

   217     IAND

   218     BIPUSH 14

   219     ISHL

   220     I2D

   221     DADD

   222     ALOAD 9

   223     ALOAD 4

   224     INVOKEDYNAMIC dyn:getElem|getProp|getMethod(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object; [

   225       // handle kind 0x6 : INVOKESTATIC

   226       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   227       // arguments:

   228       0

   229     ]

   230     INVOKEDYNAMIC ADD:ODO_D(DLjava/lang/Object;)Ljava/lang/Object; [

   231       // handle kind 0x6 : INVOKESTATIC

   232       jdk/nashorn/internal/runtime/linker/Bootstrap.runtimeBootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;)

   233       // arguments: none

   234     ]

   235     ALOAD 5

   236     INVOKEDYNAMIC ADD:OOO_I(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object; [

   237       // handle kind 0x6 : INVOKESTATIC

   238       jdk/nashorn/internal/runtime/linker/Bootstrap.runtimeBootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;)

   239       // arguments: none

   240     ]

   241     ASTORE 12

   242    L9

   243     LINENUMBER 20 L9

   244     ALOAD 12

   245     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toInt32 (Ljava/lang/Object;)I

   246     BIPUSH 28

   247     ISHR

   248     I2D

   249     DLOAD 14

   250     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toInt32 (D)I

   251     BIPUSH 14

   252     ISHR

   253     I2D

   254     DADD

   255     ILOAD 11

   256     I2D

   257     ILOAD 13

   258     I2D

   259     DMUL

   260     DADD

   261     INVOKESTATIC java/lang/Double.valueOf (D)Ljava/lang/Double;

   262     ASTORE 5

   263    L10

   264     LINENUMBER 21 L10

   265     ALOAD 9

   266     ALOAD 4

   267     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toNumber (Ljava/lang/Object;)D

   268     DUP2

   269     DCONST_1

   270     DADD

   271     INVOKESTATIC java/lang/Double.valueOf (D)Ljava/lang/Double;

   272     ASTORE 4

   273     ALOAD 12

   274     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toInt32 (Ljava/lang/Object;)I

   275     LDC 268435455

   276     IAND

   277     INVOKEDYNAMIC dyn:setElem|setProp(Ljava/lang/Object;DI)V [

   278       // handle kind 0x6 : INVOKESTATIC

   279       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   280       // arguments:

   281       0

   282     ]

   283    L4

   284    FRAME FULL [java/lang/Object java/lang/Object java/lang/Object java/lang/Object java/lang/Object java/lang/Object java/lang/Object T java/lang/Object java/lang/Object I I] []

   285     ALOAD 6

   286     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.toNumber (Ljava/lang/Object;)D

   287     LDC -1.0

   288     DADD

   289     DUP2

   290     INVOKESTATIC java/lang/Double.valueOf (D)Ljava/lang/Double;

   291     ASTORE 6

   292     DCONST_0

   293     DCMPL

   294     IFGE L5

   295    L11

   296     LINENUMBER 24 L11

   297     ALOAD 5

   298     ARETURN

   299 

   300 "Optimistic" bytecode that requires invalidation on e.g overflow. Factor

   301 x2-3 speedup:

   302 

   303 public static am3(Ljava/lang/Object;IILjava/lang/Object;III)I

   304    L0

   305     LINENUMBER 12 L0

   306     ALOAD 0

   307     INVOKEDYNAMIC dyn:getProp|getElem|getMethod:array(Ljava/lang/Object;)Ljava/lang/Object; [

   308       // handle kind 0x6 : INVOKESTATIC

   309       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   310       // arguments:

   311       0

   312     ]

   313     ASTORE 8

   314    L1

   315     LINENUMBER 13 L1

   316     ALOAD 3

   317     INVOKEDYNAMIC dyn:getProp|getElem|getMethod:array(Ljava/lang/Object;)Ljava/lang/Object; [

   318       // handle kind 0x6 : INVOKESTATIC

   319       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   320       // arguments:

   321       0

   322     ]

   323     ASTORE 9

   324    L2

   325     LINENUMBER 14 L2

   326     ILOAD 2

   327     SIPUSH 16383

   328     IAND

   329     ISTORE 10

   330     ILOAD 2

   331     BIPUSH 14

   332     ISHR

   333     ISTORE 11

   334    L3

   335     LINENUMBER 15 L3

   336     GOTO L4

   337    L5

   338     LINENUMBER 16 L5

   339    FRAME FULL [java/lang/Object I I java/lang/Object I I I T java/lang/Object java/lang/Object I I] []

   340     ALOAD 8

   341     ILOAD 1

   342     INVOKEDYNAMIC dyn:getElem|getProp|getMethod(Ljava/lang/Object;I)I [

   343       // handle kind 0x6 : INVOKESTATIC

   344       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   345       // arguments:

   346       0

   347     ]

   348     SIPUSH 16383

   349     IAND

   350     ISTORE 12

   351    L6

   352     LINENUMBER 17 L6

   353     ALOAD 8

   354     ILOAD 1

   355     DUP

   356     ICONST_1

   357     IADD

   358     ISTORE 1

   359     INVOKEDYNAMIC dyn:getElem|getProp|getMethod(Ljava/lang/Object;I)I [

   360       // handle kind 0x6 : INVOKESTATIC

   361       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   362       // arguments:

   363       0

   364     ]

   365     BIPUSH 14

   366     ISHR

   367     ISTORE 13

   368    L7

   369     LINENUMBER 18 L7

   370     ILOAD 11

   371     ILOAD 12

   372     BIPUSH 8

   373     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.mulExact (III)I

   374     ILOAD 13

   375     ILOAD 10

   376     BIPUSH 9

   377     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.mulExact (III)I

   378     IADD

   379     ISTORE 14

   380    L8

   381     LINENUMBER 19 L8

   382     ILOAD 10

   383     ILOAD 12

   384     BIPUSH 11

   385     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.mulExact (III)I

   386     ILOAD 14

   387     SIPUSH 16383

   388     IAND

   389     BIPUSH 14

   390     ISHL

   391     IADD

   392     ALOAD 9

   393     ILOAD 4

   394     INVOKEDYNAMIC dyn:getElem|getProp|getMethod(Ljava/lang/Object;I)I [

   395       // handle kind 0x6 : INVOKESTATIC

   396       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   397       // arguments:

   398       0

   399     ]

   400     IADD

   401     ILOAD 5

   402     IADD

   403     ISTORE 12

   404    L9

   405     LINENUMBER 20 L9

   406     ILOAD 12

   407     BIPUSH 28

   408     ISHR

   409     ILOAD 14

   410     BIPUSH 14

   411     ISHR

   412     IADD

   413     ILOAD 11

   414     ILOAD 13

   415     BIPUSH 21

   416     INVOKESTATIC jdk/nashorn/internal/runtime/JSType.mulExact (III)I

   417     IADD

   418     ISTORE 5

   419    L10

   420     LINENUMBER 21 L10

   421     ALOAD 9

   422     ILOAD 4

   423     DUP

   424     ICONST_1

   425     IADD

   426     ISTORE 4

   427     ILOAD 12

   428     LDC 268435455

   429     IAND

   430     INVOKEDYNAMIC dyn:setElem|setProp(Ljava/lang/Object;II)V [

   431       // handle kind 0x6 : INVOKESTATIC

   432       jdk/nashorn/internal/runtime/linker/Bootstrap.bootstrap((Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;I)Ljava/lang/invoke/CallSite;)

   433       // arguments:

   434       0

   435     ]

   436    L4

   437    FRAME SAME

   438     ILOAD 6

   439     ICONST_M1

   440     IADD

   441     DUP

   442     ISTORE 6

   443     ICONST_0

   444     IF_ICMPGE L5

   445    L11

   446     LINENUMBER 24 L11

   447     ILOAD 5

   448     IRETURN

   449 

   450 

   451 SYSTEM PROPERTY: -Dnashorn.codegen.debug, -Dnashorn.codegen.debug.trace=<x>

   456 SYSTEM_PROPERTY: -Dnashorn.fields.debug

    66 SYSTEM PROPERTY: -Dnashorn.fields.objects

   457 

    67 

   458 See the description on the fields logger below.

    68 When this property is true, Nashorn will only use object fields for

   459 

    69 AccessorProperties. This means that primitive values must be boxed

   460 

    70 when stored in a field, which is significantly slower than using

   461 SYSTEM PROPERTY: -Dnashorn.fields.dual

    71 primitive fields.

   462 

    72 

   463 When this property is true, Nashorn will attempt to use primitive

    73 By default, Nashorn uses dual object and long fields. Ints are

   464 fields for AccessorProperties (currently just AccessorProperties, not

    74 represented as the 32 low bits of the long fields. Doubles are

   465 spill properties). Memory footprint for script objects will increase,

    75 represented as the doubleToLongBits of their value. This way a

   466 as we need to maintain both a primitive field (a long) as well as an

    76 single field can be used for all primitive types. Packing and

   467 Object field for the property value. Ints are represented as the 32

    77 unpacking doubles to their bit representation is intrinsified by

   468 low bits of the long fields. Doubles are represented as the

    78 the JVM and extremely fast.

   469 doubleToLongBits of their value. This way a single field can be used

   470 for all primitive types. Packing and unpacking doubles to their bit

   471 representation is intrinsified by the JVM and extremely fast.

   472 

   473 While dual fields in theory runs significantly faster than Object

   474 fields due to reduction of boxing and memory allocation overhead,

   475 there is still work to be done to make this a general purpose

   476 solution. Research is ongoing.

   651 

   167 "getContext" - return the current Nashorn context.

   652 SYSTEM PROPERTY: -Dnashorn.methodhandles.debug,

   168 

   653 -Dnashorn.methodhandles.debug=create

   169 "equalWithoutType" - Returns true if if the two objects are both

   654 

   170 property maps, and they have identical properties in the same order,

   655 If this property is enabled, each MethodHandle related call that uses

   171 but allows the properties to differ in their types.

   656 the java.lang.invoke package gets its MethodHandle intercepted and an

   172 

   657 instrumentation printout of arguments and return value appended to

   173 "diffPropertyMaps" Returns a diagnostic string representing the difference

   658 it. This shows exactly which method handles are executed and from

   174 of two property maps.

   659 where. (Also MethodTypes and SwitchPoints). This can be augmented with

   175 

   660 more information, for example, instance count, by subclassing or

   176 "getClass" - Returns the Java class of an object, or undefined if null.

   661 further extending the TraceMethodHandleFactory implementation in

   177 

   662 MethodHandleFactory.java.

   178 "toJavaString" - Returns the Java toString representation of an object.

   663 

   179 

   664 If the property is specialized with "=create" as its option,

   180 "toIdentString" - Returns a string representation of an object consisting

   665 instrumentation will be shown for method handles upon creation time

   181 of its java class name and hash code.

   666 rather than at runtime usage.

   182 

   183 "getListenerCount" - Return the number of property listeners for a

   184 script object.

   185 

   186 "getEventQueueCapacity" - Get the capacity of the event queue.

   187 

   188 "setEventQueueCapacity" - Set the event queue capacity.

   189 

   190 "addRuntimeEvent" - Add a runtime event to the runtime event queue.

   191 The queue has a fixed size (see -Dnashorn.runtime.event.queue.size)

   192 and the oldest entry will be thrown out of the queue is about to overflow.

   193 

   194 "expandEventQueueCapacity" - Expands the event queue capacity,

   195 or truncates if capacity is lower than current capacity. Then only

   196 the newest entries are kept.

   197 

   198 "clearRuntimeEvents" - Clear the runtime event queue.

   199 

   200 "removeRuntimeEvent" - Remove a specific runtime event from the event queue.

   201 

   202 "getRuntimeEvents" - Return all runtime events in the queue as an array.

   203 

   204 "getLastRuntimeEvent" - Return the last runtime event in the queue.

   671 This does the same as nashorn.methodhandles.debug, but when enabled

   209 This enhances methodhandles logging (see below) to also dump the

   672 also dumps the stack trace for every instrumented method handle

   210 stack trace for every instrumented method handle operation.

   673 operation. Warning: This is enormously verbose, but provides a pretty

   211 Warning: This is enormously verbose, but provides a pretty

   676 See the description of the codegen logger below for a more verbose

   214 

   677 description of this option

   215 SYSTEM PROPERTY: -Dnashorn.cce

   678 

   216 

   679 

   217 Setting this system property causes the Nashorn linker to rely on

   680 SYSTEM PROPERTY: -Dnashorn.scriptfunction.specialization.disable

   218 ClassCastExceptions for triggering a callsite relink. If not set, the linker

   681 

   219 will add an explicit instanceof guard.

   682 There are several "fast path" implementations of constructors and

   220 

   683 functions in the NativeObject classes that, in their original form,

   221 

   684 take a variable amount of arguments. Said functions are also declared

   222 SYSTEM PROPERTY: -Dnashorn.spill.threshold=<x>

   685 to take Object parameters in their original form, as this is what the

   223 

   686 JavaScript specification mandates.

   224 This property sets the number of fields in an object from which to use

   687 However, we often know quite a lot more at a callsite of one of these

   225 generic array based spill storage instead of Java fields. The default value

   688 functions. For example, Math.min is called with a fixed number (2) of

   226 is 256.

   689 integer arguments. The overhead of boxing these ints to Objects and

   690 folding them into an Object array for the generic varargs Math.min

   691 function is an order of magnitude slower than calling a specialized

   692 implementation of Math.min that takes two integers. Specialized

   693 functions and constructors are identified by the tag

   694 @SpecializedFunction and @SpecializedConstructor in the Nashorn

   695 code. The linker will link in the most appropriate (narrowest types,

   696 right number of types and least number of arguments) specialization if

   697 specializations are available.

   698 

   699 Every ScriptFunction may carry specializations that the linker can

   700 choose from. This framework will likely be extended for user defined

   701 functions. The compiler can often infer enough parameter type info

   702 from callsites for in order to generate simpler versions with less

   703 generic Object types. This feature depends on future lazy jitting, as

   704 there tend to be many calls to user defined functions, some where the

   705 callsite can be specialized, some where we mostly see object

   706 parameters even at the callsite.

   707 

   708 If this system property is set to true, the linker will not attempt to

   709 use any specialized function or constructor for native objects, but

   710 just call the generic one.

   722 

   238 SYSTEM PROPERTY: -Dnashorn.persistent.code.cache

   723 SYSTEM_PROPERTY: -Dnashorn.profilefile=<filename>

   239 

   240 This property can be used to set the directory where Nashorn stores

   241 serialized script classes generated with the -pcc/--persistent-code-cache

   242 option. The default directory name is "nashorn_code_cache".

   243 

   244 

   245 SYSTEM PROPERTY: -Dnashorn.typeInfo.maxFiles

   246 

   247 Maximum number of files to store in the type info cache. The type info cache

   248 is used to cache type data of JavaScript functions when running with

   249 optimistic types (-ot/--optimistic-types). There is one file per JavaScript

   250 function in the cache.

   251 

   252 The default value is 0 which means the feature is disabled. Setting this

   253 to something like 20000 is probably good enough for most applications and

   254 will usually cap the cache directory to about 80MB presuming a 4kB

   255 filesystem allocation unit. Set this to "unlimited" to run without limit.

   256 

   257 If the value is not 0 or "unlimited", Nashorn will spawn a cleanup thread

   258 that makes sure the number of files in the cache does not exceed the given

   259 value by deleting the least recently modified files.

   260 

   261 

   262 SYSTEM PROPERTY: -Dnashorn.typeInfo.cacheDir

   263 

   264 This property can be used to set the directory where Nashorn stores the

   265 type info cache when -Dnashorn.typeInfo.maxFiles is set to a nonzero

   266 value. The default location is platform specific. On Windows, it is

   267 "${java.io.tmpdir}\com.oracle.java.NashornTypeInfo". On Linux and

   268 Solaris it is "~/.cache/com.oracle.java.NashornTypeInfo". On Mac OS X,

   269 it is "~/Library/Caches/com.oracle.java.NashornTypeInfo".

   270 

   271 

   272 SYSTEM PROPERTY: -Dnashorn.typeInfo.cleanupDelaySeconds=<value>

   273 

   274 This sets the delay between cleanups of the typeInfo cache, in seconds.

   275 The default delay is 20 seconds.

   276 

   277 

   278 SYSTEM PROPERTY: -Dnashorn.profilefile=<filename>

   770 The subsystems that currently support logging are:

   330 The following is an incomplete list of subsystems that currently

   331 support logging. Look for classes implementing

   332 jdk.nashorn.internal.runtime.logging.Loggable for more loggers.

   839 

   409 * symbols

   840 * attr

   410 

   841 

   411 The symbols logger tracks the assignment os symbols to identifiers.

   842 The lowering annotates a FunctionNode with symbols for each identifier

   412 

   843 and transforms high level constructs into lower level ones, that the

   413 * scopedepths

   844 CodeGenerator consumes.

   414 

   845 

   415 This logs the calculation of scope depths for non-local symbols.

   846 Lower logging typically outputs things like post pass actions,

   847 insertions of casts because symbol types have been changed and type

   848 specialization information. Currently very little info is generated by

   849 this logger. This will probably change.

   850 

   851 

   852 * finalize

   853 

   854 This --log=finalize log option outputs information for type finalization,

   855 the third tier of the compiler. This means things like placement of 

   856 specialized scope nodes or explicit conversions. 

   857