v8編譯過程(parser.cc文件)

1.創建編譯環境MakeAST()

???????? 解析器AstBuildingParser parser->掃描器Scanner scanner_

?????????????????????????????????????????????????????????????????????????? ? 掃描器結構: (1)TokenDesc ?current_

?????????????????????????????????????????????????????????????????????????????????????????????????????? ?(2)TokenDesc ?next_

?????????????????????????????????????????????????????????????????????????????????????????????????????? ?(3)緩沖 source_

?

2.語法分析(包含詞法分析),創建抽象語法樹(AST)FunctionLiteral-----(語句,聲明,)

MakeAST()->ParseProgram()->ParseSourceElements():

???????? 進入while循環,每次解析一個JS語句

???????? While(peek()!=end_token)

???????? {

?????????????????? Statement* stat = ParseStatement(NULL, CHECK_OK);//解析一個語句

??? ???? if (stat == NULL || stat->IsEmpty()) continue;//函數聲明語句不放入FunctionLiteral

?? ????? ……

??? ???? processor->Add(stat);//放入最外層FunctionLiteral的ZoneList

???????? }

ParseStatement():解析一個語句

?(1)根據下一個Token判斷語句類型,并進入相應的語句解析函數

switch (peek()) //取下一個Token

{

???????? case Token::LBRACE:

????? ?? return ParseBlock(labels, ok);????????????????????????? //{}Block語句

??? case Token::CONST:?

??? case Token::VAR:

????? ?? stmt = ParseVariableStatement(ok);????????????????????? //變量聲明語句

????? ?? break;

??? case Token::SEMICOLON:

????? ?? Next();

???? ??? ?return factory()->EmptyStatement();??????????????????? //空語句

??? case Token::IF:

????? ?? stmt = ParseIfStatement(labels, ok);??????????????????? //If語句

????? ?? break;

??? case Token::DO:

????? ?? stmt = ParseDoWhileStatement(labels, ok);?????????????? //Do循環語句

????? ?? break;

??? case Token::WHILE:

????? ?? stmt = ParseWhileStatement(labels, ok);???????????????? //While循環語句

????? ?? break;

??? case Token::FOR:

????? ?? stmt = ParseForStatement(labels, ok);?????????????????? //For循環語句

????? ?? break;

??? case Token::CONTINUE:

????? ?? stmt = ParseContinueStatement(ok);????????????????????? //Continue語句

????? ?? break;

??? case Token::BREAK:

????? ?? stmt = ParseBreakStatement(labels, ok);???????????????? //Break語句

????? ?? break;

??? case Token::RETURN:

????? ?? stmt = ParseReturnStatement(ok);??????????????????????? //返回語句

????? ?? break;

??? case Token::WITH:

????? ?? stmt = ParseWithStatement(labels, ok);????????????????? //With語句??

????? ?? break;

??? case Token::SWITCH:

????? ?? stmt = ParseSwitchStatement(labels, ok);??????????????? //Switch語句

????? ?? break;

??? case Token::THROW:

????? ?? stmt = ParseThrowStatement(ok);???????????????????????? //Throw語句

????? ?? break;

case Token::TRY:

????? {……}????????????????????????????????????????????????? //Try語句

??? case Token::FUNCTION:

????? ?? return ParseFunctionDeclaration(ok);??????????????????? //函數聲明語句

??? case Token::NATIVE:

????? ?? return ParseNativeDeclaration(ok);

??? case Token::DEBUGGER:

????? ?? stmt = ParseDebuggerStatement(ok);????????????????????? //Debugger語句

????? ?? break;

default: stmt = ParseExpressionOrLabelledStatement(labels, ok);//其他語句(表達式/標號)

}

(2)解析語句

???????? 首先,調用掃描器Scanner(對JS源碼進行詞法分析):每次掃描Scan()得到當前Token和下一個Token,把Token描述信息分別放入TokenDesc current_和 TokenDesc next_中,把Token的值放入緩沖source_中.

???????? 其次,根據JS的語法語義進行相應(編譯時)處理

???????? 最后,

-1-一般(非聲明)語句:創建Statement對象,放入FunctionLiteral對象中ZoneList<Statement*>.

-2-變量聲明語句:創建Declaration對象放入當前抽象語法樹FunctionLiteral的Scope的decls_,

???????? ?????????????????? ?? 再由CallRuntime語句創建ExpressionStatement對象,放入body_ (JS語句???????????????????????????????????????????? ?????????????????? ??????????????????????????????????????????????????????????????????????????????????????????????????????????????? 數組)

-3-函數聲明語句:根據函數體創建新的抽象語法樹FunctionLiteral,放入新創建的

???????? ??????????????????????????? Declaration對象,再放入當前抽象語法樹FunctionLiteral的Scope的???????????????????????????????????????????? decls_.

?

解析完所有語句后,得到抽象語法樹FunctionLiteral。

????????

?

?

?

附:

抽象語法樹4種結點:Statement(語句),Expression(表達式),Declaration(聲明)和TargetCollector

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抽象語法樹FunctionLiteral結構

1.ZoneList<Statement*> body_????? JS語句數組

2.Scope* scope_?????

???????? (1)ZoneList<Declaration*> decls_ 變量、函數聲明數組(Declaration對象數組)

???????? (2)……….

3.……

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抽象語法樹FunctionLiteral結點的繼承層次

ZoneObject?????

|?????? AstNode

|?????? |?????? Statement

|?????? |?????? |?????? BreakableStatement

|?????? |?????? |?????? |?????? Block

|?????? |?????? |?????? |?????? IterationStatement

|?????? |?????? |?????? |?????? |?????? DoWhileStatement

|?????? |?????? |?????? |?????? |?????? WhileStatement

|?????? |?????? |?????? |?????? |?????? ForStatement

|?????? |?????? |?????? |?????? |?????? ForInstatement

|?????? |?????? |?????? |?????? SwitchStatement

|?????? |?????? |?????? ExpressionStatement

|?????? |?????? |?????? ContinueStatement

|?????? |?????? |?????? BreakStatement

|?????? |?????? |?????? ReturnStatement

|?????? |?????? |?????? WithEnterStatement

|?????? |?????? |?????? WithExitStatement

|?????? |?????? |?????? IfStatement

|?????? |?????? |?????? TryStatement

|?????? |?????? |?????? |?????? TryCatchStatement

|?????? |?????? |?????? |?????? TryFinallyStatement

|?????? |?????? |?????? DebuggerStatement

|?????? |?????? |?????? EmptyStatement

|?????? |?????? Expression (會被轉化為ExpressionStatement)

|?????? |?????? |?????? ValidLeftHandSideSentinel

|?????? |?????? |?????? Literal

|?????? |?????? |?????? MaterializedLiteral

|?????? |?????? |?????? |?????? ObjectLiteral

|?????? |?????? |?????? |?????? RegExpLiteral

|?????? |?????? |?????? |?????? ArrayLiteral

|?????? |?????? |?????? CatchExtensionObject

|?????? |?????? |?????? VariableProxy

|?????? |?????? |?????? |?????? VariableProxySentinel

|?????? |?????? |?????? Slot

|?????? |?????? |?????? Property

|?????? |?????? |?????? Call

|?????? |?????? |?????? CallNew

|?????? |?????? |?????? CallRuntime

|?????? |?????? |?????? UnaryOperation

|?????? |?????? |?????? BinaryOperation

|?????? |?????? |?????? CountOperation

|?????? |?????? |?????? CompareOperation

|?????? |?????? |?????? Conditional

|?????? |?????? |?????? Assignment

|?????? |?????? |?????? Throw

|?????? |?????? |?????? FunctionLiteral

|?????? |?????? |?????? ShareFunctionInfoLiteral

|?????? |?????? |?????? ThisFunction

|?????? |?????? Declaration

|?????? |?????? TargetCollector

|?????? CaseClause

總結

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