com.oracle.truffle.sl

Class SLLanguage

java.lang.Object

com.oracle.truffle.api.TruffleLanguage<SLContext>

com.oracle.truffle.sl.SLLanguage

public final class SLLanguage
extends com.oracle.truffle.api.TruffleLanguage<SLContext>

SL is a simple language to demonstrate and showcase features of Truffle. The implementation is as simple and clean as possible in order to help understanding the ideas and concepts of Truffle. The language has first class functions, and objects are key-value stores.

SL is dynamically typed, i.e., there are no type names specified by the programmer. SL is strongly typed, i.e., there is no automatic conversion between types. If an operation is not available for the types encountered at run time, a type error is reported and execution is stopped. For example, 4 - "2" results in a type error because subtraction is only defined for numbers.

Types:

• Number: arbitrary precision integer numbers. The implementation uses the Java primitive type long to represent numbers that fit into the 64 bit range, and SLBigNumber for numbers that exceed the range. Using a primitive type such as long is crucial for performance.
• Boolean: implemented as the Java primitive type boolean.
• String: implemented as the Java standard type String.
• Function: implementation type SLFunction.
• Object: efficient implementation using the object model provided by Truffle. The implementation type of objects is a subclass of DynamicObject.
• Null (with only one value null): implemented as the singleton SLNull.SINGLETON.

The class SLTypes lists these types for the Truffle DSL, i.e., for type-specialized operations that are specified using Truffle DSL annotations.

Language concepts:

• Literals for numbers , strings, and functions.
• Basic arithmetic, logical, and comparison operations: +, -, *, /, logical and, logical or, ==, !=, <, ≤, >, ≥.
• Local variables: local variables must be defined (via a write) before they can be used (by a read). Local variables are not visible outside of the block where they were first defined.
• Basic control flow statements: blocks, if, while with break and continue, return.
• Debugging control: debugger statement uses DebuggerTags#AlwaysHalt tag to halt the execution when run under the debugger.
• Function calls: invocations are efficiently implemented with polymorphic inline caches.
• Object access: SLReadPropertyNode and SLWritePropertyNode use a cached DynamicObjectLibrary as the polymorphic inline cache for property reads and writes, respectively.

Syntax and parsing:
The syntax is described as an attributed grammar. The SimpleLanguageParser and SimpleLanguageLexer are automatically generated by ANTLR 4. The grammar contains semantic actions that build the AST for a method. To keep these semantic actions short, they are mostly calls to the SLNodeFactory that performs the actual node creation. All functions found in the SL source are added to the SLFunctionRegistry, which is accessible from the SLContext.

Builtin functions:
Library functions that are available to every SL source without prior definition are called builtin functions. They are added to the SLFunctionRegistry when the SLContext is created. Some of the current builtin functions are

• readln: Read a String from the standard input.
• println: Write a value to the standard output.
• nanoTime: Returns the value of a high-resolution time, in nanoseconds.
• defineFunction: Parses the functions provided as a String argument and adds them to the function registry. Functions that are already defined are replaced with the new version.
• stckTrace: Print all function activations with all local variables.

Nested Class Summary

Nested classes/interfaces inherited from class com.oracle.truffle.api.TruffleLanguage

com.oracle.truffle.api.TruffleLanguage.ContextLocalFactory<C,T>, com.oracle.truffle.api.TruffleLanguage.ContextPolicy, com.oracle.truffle.api.TruffleLanguage.ContextReference<C>, com.oracle.truffle.api.TruffleLanguage.ContextThreadLocalFactory<C,T>, com.oracle.truffle.api.TruffleLanguage.Env, com.oracle.truffle.api.TruffleLanguage.ExitMode, com.oracle.truffle.api.TruffleLanguage.InlineParsingRequest, com.oracle.truffle.api.TruffleLanguage.LanguageReference<L extends com.oracle.truffle.api.TruffleLanguage>, com.oracle.truffle.api.TruffleLanguage.ParsingRequest, com.oracle.truffle.api.TruffleLanguage.Provider, com.oracle.truffle.api.TruffleLanguage.Registration

Field Summary

Fields

Modifier and Type	Field and Description
static int	counter
static String	ID
static String	MIME_TYPE
static com.oracle.truffle.api.strings.TruffleString.Encoding	STRING_ENCODING

Constructor Summary

Constructors

Constructor and Description
SLLanguage()

Method Summary

Modifier and Type	Method and Description
protected SLContext	createContext(com.oracle.truffle.api.TruffleLanguage.Env env)
SLObject	createObject(com.oracle.truffle.api.instrumentation.AllocationReporter reporter) Allocate an empty object.
protected void	exitContext(SLContext context, com.oracle.truffle.api.TruffleLanguage.ExitMode exitMode, int exitCode)
static SLLanguage	get(com.oracle.truffle.api.nodes.Node node)
protected Object	getLanguageView(SLContext context, Object value)
com.oracle.truffle.api.RootCallTarget	getOrCreateUndefinedFunction(com.oracle.truffle.api.strings.TruffleString name)
com.oracle.truffle.api.object.Shape	getRootShape()
protected Object	getScope(SLContext context)
protected void	initializeMultipleContexts() SLLanguage specifies the TruffleLanguage.ContextPolicy.SHARED in Registration#contextPolicy().
static void	installBuiltin(com.oracle.truffle.api.dsl.NodeFactory<? extends SLBuiltinNode> builtin)
boolean	isSingleContext()
protected boolean	isVisible(SLContext context, Object value)
com.oracle.truffle.api.RootCallTarget	lookupBuiltin(com.oracle.truffle.api.dsl.NodeFactory<? extends SLBuiltinNode> factory)
static com.oracle.truffle.api.nodes.NodeInfo	lookupNodeInfo(Class<?> clazz)
protected com.oracle.truffle.api.CallTarget	parse(com.oracle.truffle.api.TruffleLanguage.ParsingRequest request)
protected boolean	patchContext(SLContext context, com.oracle.truffle.api.TruffleLanguage.Env newEnv)

Methods inherited from class com.oracle.truffle.api.TruffleLanguage

areOptionsCompatible, createContextLocal, createContextThreadLocal, disposeContext, disposeThread, finalizeContext, getAsynchronousStackDepth, getLanguageHome, getOptionDescriptors, initializeContext, initializeMultiThreading, initializeThread, isThreadAccessAllowed, parse

Methods inherited from class java.lang.Object

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

Field Detail

counter

public static volatile int counter

ID

public static final String ID

See Also:

Constant Field Values

MIME_TYPE

public static final String MIME_TYPE

See Also:

Constant Field Values

STRING_ENCODING

public static final com.oracle.truffle.api.strings.TruffleString.Encoding STRING_ENCODING

Constructor Detail

SLLanguage

public SLLanguage()

Method Detail

createContext

protected SLContext createContext(com.oracle.truffle.api.TruffleLanguage.Env env)

Specified by:

createContext in class com.oracle.truffle.api.TruffleLanguage<SLContext>

patchContext

protected boolean patchContext(SLContext context,
                               com.oracle.truffle.api.TruffleLanguage.Env newEnv)

Overrides:

patchContext in class com.oracle.truffle.api.TruffleLanguage<SLContext>

getOrCreateUndefinedFunction

public com.oracle.truffle.api.RootCallTarget getOrCreateUndefinedFunction(com.oracle.truffle.api.strings.TruffleString name)

lookupBuiltin

public com.oracle.truffle.api.RootCallTarget lookupBuiltin(com.oracle.truffle.api.dsl.NodeFactory<? extends SLBuiltinNode> factory)

lookupNodeInfo

public static com.oracle.truffle.api.nodes.NodeInfo lookupNodeInfo(Class<?> clazz)

parse

protected com.oracle.truffle.api.CallTarget parse(com.oracle.truffle.api.TruffleLanguage.ParsingRequest request)
                                           throws Exception

Overrides:

parse in class com.oracle.truffle.api.TruffleLanguage<SLContext>

Throws:

Exception

initializeMultipleContexts

protected void initializeMultipleContexts()

SLLanguage specifies the TruffleLanguage.ContextPolicy.SHARED in Registration#contextPolicy(). This means that a single TruffleLanguage instance can be reused for multiple language contexts. Before this happens the Truffle framework notifies the language by invoking SLLanguage.initializeMultipleContexts(). This allows the language to invalidate certain assumptions taken for the single context case. One assumption SL takes for single context case is located in SLEvalRootNode. There functions are only tried to be registered once in the single context case, but produce a boundary call in the multi context case, as function registration is expected to happen more than once. Value identity caches should be avoided and invalidated for the multiple contexts case as no value will be the same. Instead, in multi context case, a language should only use types, shapes and code to speculate. For a new language it is recommended to start with TruffleLanguage.ContextPolicy.EXCLUSIVE and as the language gets more mature switch to TruffleLanguage.ContextPolicy.SHARED.

Overrides:

initializeMultipleContexts in class com.oracle.truffle.api.TruffleLanguage<SLContext>

isSingleContext

public boolean isSingleContext()

getLanguageView

protected Object getLanguageView(SLContext context,
                                 Object value)

Overrides:

getLanguageView in class com.oracle.truffle.api.TruffleLanguage<SLContext>

isVisible

protected boolean isVisible(SLContext context,
                            Object value)

Overrides:

isVisible in class com.oracle.truffle.api.TruffleLanguage<SLContext>

getScope

protected Object getScope(SLContext context)

Overrides:

getScope in class com.oracle.truffle.api.TruffleLanguage<SLContext>

getRootShape

public com.oracle.truffle.api.object.Shape getRootShape()

createObject

public SLObject createObject(com.oracle.truffle.api.instrumentation.AllocationReporter reporter)

Allocate an empty object. All new objects initially have no properties. Properties are added when they are first stored, i.e., the store triggers a shape change of the object.

get

public static SLLanguage get(com.oracle.truffle.api.nodes.Node node)

installBuiltin

public static void installBuiltin(com.oracle.truffle.api.dsl.NodeFactory<? extends SLBuiltinNode> builtin)

exitContext

protected void exitContext(SLContext context,
                           com.oracle.truffle.api.TruffleLanguage.ExitMode exitMode,
                           int exitCode)

Overrides:

exitContext in class com.oracle.truffle.api.TruffleLanguage<SLContext>