// unnest any child blocks private static void UnnestBlocks(JsBlock node) { // walk the list of items backwards -- if we come // to any blocks, unnest the block recursively. // Remove any empty statements as well. // We walk backwards because we could be adding any number of statements // and we don't want to have to modify the counter. for (int ndx = node.Count - 1; ndx >= 0; --ndx) { var nestedBlock = node[ndx] as JsBlock; if (nestedBlock != null) { // unnest recursively UnnestBlocks(nestedBlock); // if the block has a block scope, then we can't really unnest it // without merging lexical scopes if (nestedBlock.BlockScope == null) { // remove the nested block node.RemoveAt(ndx); // then start adding the statements in the nested block to our own. // go backwards so we can just keep using the same index node.InsertRange(ndx, nestedBlock.Children); } } else if (node[ndx] is JsEmptyStatement) { // remove empty statements (lone semicolons) node.RemoveAt(ndx); } else if (ndx > 0) { // see if the previous node is a conditional-compilation comment, because // we will also combine adjacent those var previousComment = node[ndx - 1] as JsConditionalCompilationComment; if (previousComment != null) { JsConditionalCompilationComment thisComment = node[ndx] as JsConditionalCompilationComment; if (thisComment != null) { // two adjacent conditional comments -- combine them into the first. previousComment.Statements.Append(thisComment.Statements); // and remove the second one (which is now a duplicate) node.RemoveAt(ndx); } } } } }
public override void Visit(JsBlock node) { if (node != null) { // there really is no point in nesting blocks that don't have any special scopes // attached to them. Unnest any now, before we start combining var statements. UnnestBlocks(node); // if we get here, we are going to want to optimize the curly-braces to eliminate // unneeded ones in all blocks except try/catch/finally. So make sure we reset the // force-braces properties for all blocks whose parent isn't a try-statement. node.ForceBraces = node.Parent is JsTryNode; if (m_combineAdjacentVars) { // look at the statements in the block. // if there are multiple var statements adjacent to each other, combine them. // walk BACKWARDS down the list because we'll be removing items when we encounter // multiple vars, etc. // we also don't need to check the first one, since there is nothing before it. for (int ndx = node.Count - 1; ndx > 0; --ndx) { // if the previous node is not a Var, then we don't need to try and combine // it with the current node var previousVar = node[ndx - 1] as JsVar; if (previousVar != null && node[ndx] is JsVar) { // add the items in this VAR to the end of the previous previousVar.Append(node[ndx]); // delete this item from the block node.RemoveAt(ndx); } else { // do the same thing for lexical declarations var previousLex = node[ndx - 1] as JsLexicalDeclaration; var thisLex = node[ndx] as JsLexicalDeclaration; if (previousLex != null && thisLex != null) { // but we can only combine them if they are the same type (let or const) if (previousLex.StatementToken == thisLex.StatementToken) { previousLex.Append(node[ndx]); node.RemoveAt(ndx); } } else { // try doing the same for const-statements: combine adjacent ones var previousConst = node[ndx - 1] as JsConstStatement; if (previousConst != null && node[ndx] is JsConstStatement) { // they are both ConstStatements, so adding the current one to the // previous one will combine them, then delete the latter one. previousConst.Append(node[ndx]); node.RemoveAt(ndx); } } } } } // recurse down the tree after we've combined the adjacent var statements base.Visit(node); } }
private static int RelocateVar(JsBlock block, int insertAt, JsVar varStatement) { // if the var statement is at the next position to insert, then we don't need // to do anything. if (block[insertAt] != varStatement) { // check to see if the current position is a var and we are the NEXT statement. // if that's the case, we don't need to break out the initializer, just append all the // vardecls as-is to the current position. var existingVar = block[insertAt] as JsVar; if (existingVar != null && block[insertAt + 1] == varStatement) { // just append our vardecls to the insertion point, then delete our statement existingVar.Append(varStatement); block.RemoveAt(insertAt + 1); } else { // iterate through the decls and count how many have initializers var initializerCount = 0; for (var ndx = 0; ndx < varStatement.Count; ++ndx) { if (varStatement[ndx].Initializer != null) { ++initializerCount; } } // if there are more than two decls with initializers, then we won't actually // be gaining anything by moving the var to the top. We'll get rid of the four // bytes for the "var ", but we'll be adding two bytes for the name and comma // because name=init will still need to remain behind. if (initializerCount <= 2) { // first iterate through all the declarations in the var statement, // constructing an expression statement that is made up of assignment // operators for each of the declarations that have initializers (if any) // and removing all the initializers var assignments = new List <JsAstNode>(); for (var ndx = 0; ndx < varStatement.Count; ++ndx) { var varDecl = varStatement[ndx]; if (varDecl.Initializer != null) { if (varDecl.IsCCSpecialCase) { // create a vardecl with the same name and no initializer var copyDecl = new JsVariableDeclaration(varDecl.Context, varDecl.Parser) { Identifier = varDecl.Identifier, NameContext = varDecl.VariableField.OriginalContext, VariableField = varDecl.VariableField }; // replace the special vardecl with the copy varStatement[ndx] = copyDecl; // add the original vardecl to the list of "assignments" assignments.Add(varDecl); // add the new decl to the field's declaration list, and remove the old one // because we're going to change that to an assignment. varDecl.VariableField.Declarations.Add(copyDecl); varDecl.VariableField.Declarations.Remove(varDecl); } else { // hold on to the object so we don't lose it to the GC var initializer = varDecl.Initializer; // remove it from the vardecl varDecl.Initializer = null; // create an assignment operator for a lookup to the name // as the left, and the initializer as the right, and add it to the list var lookup = new JsLookup(varDecl.VariableField.OriginalContext, varDecl.Parser) { Name = varDecl.Identifier, VariableField = varDecl.VariableField, }; assignments.Add(new JsBinaryOperator(varDecl.Context, varDecl.Parser) { Operand1 = lookup, Operand2 = initializer, OperatorToken = JsToken.Assign, OperatorContext = varDecl.AssignContext }); // add the new lookup to the field's references varDecl.VariableField.References.Add(lookup); } } } // now if there were any initializers... if (assignments.Count > 0) { // we want to create one big expression from all the assignments and replace the // var statement with the assignment(s) expression. Start at position n=1 and create // a binary operator of n-1 as the left, n as the right, and using a comma operator. var expression = assignments[0]; for (var ndx = 1; ndx < assignments.Count; ++ndx) { expression = JsCommaOperator.CombineWithComma(null, expression.Parser, expression, assignments[ndx]); } // replace the var with the expression. // we still have a pointer to the var, so we can insert it back into the proper // place next. varStatement.Parent.ReplaceChild(varStatement, expression); } else { // no initializers. // if the parent is a for-in statement... var forInParent = varStatement.Parent as JsForIn; if (forInParent != null) { // we want to replace the var statement with a lookup for the var // there should be only one vardecl var varDecl = varStatement[0]; var lookup = new JsLookup(varDecl.VariableField.OriginalContext, varStatement.Parser) { Name = varDecl.Identifier, VariableField = varDecl.VariableField }; varStatement.Parent.ReplaceChild(varStatement, lookup); varDecl.VariableField.References.Add(lookup); } else { // just remove the var statement altogether varStatement.Parent.ReplaceChild(varStatement, null); } } // if the statement at the insertion point is a var-statement already, // then we just need to append our vardecls to it. Otherwise we'll insert our // var statement at the right point if (existingVar != null) { // append the varstatement we want to move to the existing var, which will // transfer all the vardecls to it. existingVar.Append(varStatement); } else { // move the var to the insert point, incrementing the position or next time block.Insert(insertAt, varStatement); } } } } return(insertAt); }
private static int RelocateVar(JsBlock block, int insertAt, JsVar varStatement) { // if the var statement is at the next position to insert, then we don't need // to do anything. if (block[insertAt] != varStatement) { // check to see if the current position is a var and we are the NEXT statement. // if that's the case, we don't need to break out the initializer, just append all the // vardecls as-is to the current position. var existingVar = block[insertAt] as JsVar; if (existingVar != null && block[insertAt + 1] == varStatement) { // just append our vardecls to the insertion point, then delete our statement existingVar.Append(varStatement); block.RemoveAt(insertAt + 1); } else { // iterate through the decls and count how many have initializers var initializerCount = 0; for (var ndx = 0; ndx < varStatement.Count; ++ndx) { if (varStatement[ndx].Initializer != null) { ++initializerCount; } } // if there are more than two decls with initializers, then we won't actually // be gaining anything by moving the var to the top. We'll get rid of the four // bytes for the "var ", but we'll be adding two bytes for the name and comma // because name=init will still need to remain behind. if (initializerCount <= 2) { // first iterate through all the declarations in the var statement, // constructing an expression statement that is made up of assignment // operators for each of the declarations that have initializers (if any) // and removing all the initializers var assignments = new List<JsAstNode>(); for (var ndx = 0; ndx < varStatement.Count; ++ndx) { var varDecl = varStatement[ndx]; if (varDecl.Initializer != null) { if (varDecl.IsCCSpecialCase) { // create a vardecl with the same name and no initializer var copyDecl = new JsVariableDeclaration(varDecl.Context, varDecl.Parser) { Identifier = varDecl.Identifier, NameContext = varDecl.VariableField.OriginalContext, VariableField = varDecl.VariableField }; // replace the special vardecl with the copy varStatement[ndx] = copyDecl; // add the original vardecl to the list of "assignments" assignments.Add(varDecl); // add the new decl to the field's declaration list, and remove the old one // because we're going to change that to an assignment. varDecl.VariableField.Declarations.Add(copyDecl); varDecl.VariableField.Declarations.Remove(varDecl); } else { // hold on to the object so we don't lose it to the GC var initializer = varDecl.Initializer; // remove it from the vardecl varDecl.Initializer = null; // create an assignment operator for a lookup to the name // as the left, and the initializer as the right, and add it to the list var lookup = new JsLookup(varDecl.VariableField.OriginalContext, varDecl.Parser) { Name = varDecl.Identifier, VariableField = varDecl.VariableField, }; assignments.Add(new JsBinaryOperator(varDecl.Context, varDecl.Parser) { Operand1 = lookup, Operand2 = initializer, OperatorToken = JsToken.Assign, OperatorContext = varDecl.AssignContext }); // add the new lookup to the field's references varDecl.VariableField.References.Add(lookup); } } } // now if there were any initializers... if (assignments.Count > 0) { // we want to create one big expression from all the assignments and replace the // var statement with the assignment(s) expression. Start at position n=1 and create // a binary operator of n-1 as the left, n as the right, and using a comma operator. var expression = assignments[0]; for (var ndx = 1; ndx < assignments.Count; ++ndx) { expression = JsCommaOperator.CombineWithComma(null, expression.Parser, expression, assignments[ndx]); } // replace the var with the expression. // we still have a pointer to the var, so we can insert it back into the proper // place next. varStatement.Parent.ReplaceChild(varStatement, expression); } else { // no initializers. // if the parent is a for-in statement... var forInParent = varStatement.Parent as JsForIn; if (forInParent != null) { // we want to replace the var statement with a lookup for the var // there should be only one vardecl var varDecl = varStatement[0]; var lookup = new JsLookup(varDecl.VariableField.OriginalContext, varStatement.Parser) { Name = varDecl.Identifier, VariableField = varDecl.VariableField }; varStatement.Parent.ReplaceChild(varStatement, lookup); varDecl.VariableField.References.Add(lookup); } else { // just remove the var statement altogether varStatement.Parent.ReplaceChild(varStatement, null); } } // if the statement at the insertion point is a var-statement already, // then we just need to append our vardecls to it. Otherwise we'll insert our // var statement at the right point if (existingVar != null) { // append the varstatement we want to move to the existing var, which will // transfer all the vardecls to it. existingVar.Append(varStatement); } else { // move the var to the insert point, incrementing the position or next time block.Insert(insertAt, varStatement); } } } } return insertAt; }
private void CombineWithPreviousExpression(JsBlock node, int ndx) { JsIfNode ifNode; JsForNode forNode; JsWhileNode whileNode; JsReturnNode returnNode; if (node[ndx].IsExpression) { CombineTwoExpressions(node, ndx); } else if ((returnNode = node[ndx] as JsReturnNode) != null) { CombineReturnWithExpression(node, ndx, returnNode); } else if ((forNode = node[ndx] as JsForNode) != null) { CombineForNodeWithExpression(node, ndx, forNode); } else if ((ifNode = node[ndx] as JsIfNode) != null) { // transform: expr;if(cond)... => if(expr,cond)... // combine the previous expression with the if-condition via comma, then delete // the previous statement. ifNode.Condition = JsCommaOperator.CombineWithComma(null, m_parser, node[ndx - 1], ifNode.Condition); node.RemoveAt(ndx - 1); } else if ((whileNode = node[ndx] as JsWhileNode) != null && m_parser.Settings.IsModificationAllowed(JsTreeModifications.ChangeWhileToFor)) { // transform: expr;while(cond)... => for(expr;cond;)... // zero-sum, and maybe a little worse for performance because of the nop iterator, // but combines two statements into one, which may have savings later on. var initializer = node[ndx - 1]; node[ndx] = new JsForNode(null, m_parser) { Initializer = initializer, Condition = whileNode.Condition, Body = whileNode.Body }; node.RemoveAt(ndx - 1); } }
private void CombineReturnWithExpression(JsBlock node, int ndx, JsReturnNode returnNode) { // see if the return node has an expression operand if (returnNode.Operand != null && returnNode.Operand.IsExpression) { // check for lookup[ASSIGN]expr2;return expr1. var beforeExpr = node[ndx - 1] as JsBinaryOperator; JsLookup lookup; if (beforeExpr != null && beforeExpr.IsAssign && (lookup = beforeExpr.Operand1 as JsLookup) != null) { if (returnNode.Operand.IsEquivalentTo(lookup)) { // we have lookup[ASSIGN]expr2;return lookup. // if lookup is a local variable in the current scope, we can replace with return expr2; // if lookup is an outer reference, we can replace with return lookup[ASSIGN]expr2 if (beforeExpr.OperatorToken == JsToken.Assign) { // check to see if lookup is in the current scope from which we are returning if (lookup.VariableField == null || lookup.VariableField.OuterField != null || lookup.VariableField.IsReferencedInnerScope) { // transform: lookup[ASSIGN]expr2;return lookup => return lookup[ASSIGN]expr2 // lookup points to outer field (or we don't know) // replace the operand on the return node with the previous expression and // delete the previous node. // first be sure to remove the lookup in the return operand from the references // to field. JsDetachReferences.Apply(returnNode.Operand); returnNode.Operand = beforeExpr; node[ndx - 1] = null; } else { // transform: lookup[ASSIGN]expr2;return lookup => return expr2 // lookup is a variable local to the current scope, so when we return, the // variable won't exists anymore anyway. // replace the operand on the return node oprand with the right-hand operand of the // previous expression and delete the previous node. // we're eliminating the two lookups altogether, so remove them both from the // field's reference table. var varField = lookup.VariableField; JsDetachReferences.Apply(lookup, returnNode.Operand); returnNode.Operand = beforeExpr.Operand2; node[ndx - 1] = null; // now that we've eliminated the two lookups, see if the local variable isn't // referenced anymore. If it isn't, we might be able to remove the variable, too. // (need to pick up those changes to keep track of a field's declarations, though) if (varField.RefCount == 0) { // it's not. if there's only one declaration and it either has no initializer or // is initialized to a constant, get rid of it. var nameDecl = varField.OnlyDeclaration; if (nameDecl != null) { // we only had one declaration. if (nameDecl.Initializer == null || nameDecl.Initializer.IsConstant) { // and it either had no initializer or it was initialized to a constant. // but it has no references, so let's whack it. Actually, only if it was // a var-decl (leave parameter and function decls alone). var varDecl = nameDecl as JsVariableDeclaration; if (varDecl != null) { // save the declaration parent (var, const, or let) and remove the // child vardecl from its list var declStatement = varDecl.Parent as JsDeclaration; declStatement.Remove(varDecl); varField.WasRemoved = true; // if the parent statement is now empty, remove it, too. this will // move everything up one index, but that'll just mean an extra loop. if (declStatement.Count == 0) { declStatement.Parent.ReplaceChild(declStatement, null); } } } } } } } else { // it's an assignment, but it's not =. That means it's one of the OP= operators. // we can't remove the field altogether. But we can move the assignment into the // return statement and get rid of the lone lookup. // transform: lookup OP= expr;return lookup => return lookup OP= expr; if (lookup.VariableField != null) { // we're getting rid of the lookup, so remove it from the field's list of references JsDetachReferences.Apply(returnNode.Operand); } // remove the expression from the block and put it in the operand of // the return statement. node.RemoveAt(ndx - 1); returnNode.Operand = beforeExpr; // is this field scoped only to this function? if (lookup.VariableField != null && lookup.VariableField.OuterField == null && !lookup.VariableField.IsReferencedInnerScope) { // in fact, the lookup is in the current scope, so assigning to it is a waste // because we're going to return (this is a return statement, after all). // we can get rid of the assignment part and just keep the operator: // transform: lookup OP= expr;return lookup => return lookup OP expr; beforeExpr.OperatorToken = JsScanner.StripAssignment(beforeExpr.OperatorToken); } } } else { // transform: expr1;return expr2 to return expr1,expr2 var binOp = JsCommaOperator.CombineWithComma(null, m_parser, node[ndx - 1], returnNode.Operand); // replace the operand on the return node with the new expression and // delete the previous node returnNode.Operand = binOp; node[ndx - 1] = null; } } else { // transform: expr1;return expr2 to return expr1,expr2 var binOp = JsCommaOperator.CombineWithComma(null, m_parser, node[ndx - 1], returnNode.Operand); // replace the operand on the return node with the new expression and // delete the previous node returnNode.Operand = binOp; node[ndx - 1] = null; } } }
private static void StripDebugStatements(JsBlock node) { // walk the list backwards for (int ndx = node.Count - 1; ndx >= 0; --ndx) { // if this item pops positive... if (node[ndx].IsDebuggerStatement) { // just remove it JsDetachReferences.Apply(node[ndx]); node.RemoveAt(ndx); } } }
public override void Visit(JsBlock node) { if (node != null) { // if this block has a block scope, then look at the lexically-declared names (if any) // and throw an error if any are defined as var's within this scope (ES6 rules). // if this is the body of a function object, use the function scope. JsActivationObject lexicalScope = node.BlockScope; if (lexicalScope == null) { var functionObject = node.Parent as JsFunctionObject; if (functionObject != null) { lexicalScope = functionObject.FunctionScope; } } if (lexicalScope != null) { foreach (var lexDecl in lexicalScope.LexicallyDeclaredNames) { var varDecl = lexicalScope.VarDeclaredName(lexDecl.Name); if (varDecl != null) { // collision. // if the lexical declaration is a let or const declaration (as opposed to a function declaration), // then force the warning to an error. This is so the function declaration will remain a warning if // it collides with a var. varDecl.NameContext.HandleError(JsError.DuplicateLexicalDeclaration, lexDecl is JsLexicalDeclaration); // mark them both a no-rename to preserve the collision in the output lexDecl.VariableField.IfNotNull(v => v.CanCrunch = false); varDecl.VariableField.IfNotNull(v => v.CanCrunch = false); } } } // we might things differently if these statements are the body collection for a function // because we can assume the implicit return statement at the end of it bool isFunctionLevel = (node.Parent is JsFunctionObject); // if we want to remove debug statements... if (m_parser.Settings.StripDebugStatements && m_parser.Settings.IsModificationAllowed(JsTreeModifications.StripDebugStatements)) { // do it now before we try doing other things StripDebugStatements(node); } // analyze all the statements in our block and recurse them if (node.BlockScope != null) { m_scopeStack.Push(node.BlockScope); } try { // don't call the base class to recurse -- let's walk the block // backwards in case any of the children opt to delete themselves. for (var ndx = node.Count - 1; ndx >= 0; --ndx) { node[ndx].Accept(this); } } finally { if (node.BlockScope != null) { m_scopeStack.Pop(); } } if (m_parser.Settings.RemoveUnneededCode) { // go forward, and check the count each iteration because we might be ADDING statements to the block. // let's look at all our if-statements. If a true-clause ends in a return, then we don't // need the else-clause; we can pull its statements out and stick them after the if-statement. // also, if we encounter a return-, break- or continue-statement, we can axe everything after it for (var ndx = 0; ndx < node.Count; ++ndx) { // see if it's an if-statement with both a true and a false block var ifNode = node[ndx] as JsIfNode; if (ifNode != null && ifNode.TrueBlock != null && ifNode.TrueBlock.Count > 0 && ifNode.FalseBlock != null) { // now check to see if the true block ends in a return statement if (ifNode.TrueBlock[ifNode.TrueBlock.Count - 1] is JsReturnNode) { // transform: if(cond){statements1;return}else{statements2} to if(cond){statements1;return}statements2 // it does. insert all the false-block statements after the if-statement node.InsertRange(ndx + 1, ifNode.FalseBlock.Children); // and then remove the false block altogether ifNode.FalseBlock = null; } } else if (node[ndx] is JsReturnNode || node[ndx] is JsBreak || node[ndx] is JsContinueNode || node[ndx] is JsThrowNode) { // we have an exit node -- no statments afterwards will be executed, so clear them out. // transform: {...;return;...} to {...;return} // transform: {...;break;...} to {...;break} // transform: {...;continue;...} to {...;continue} // transform: {...;throw;...} to {...;throw} // we've found an exit statement, and it's not the last statement in the function. // walk the rest of the statements and delete anything that isn't a function declaration // or a var- or const-statement. for (var ndxRemove = node.Count - 1; ndxRemove > ndx; --ndxRemove) { var funcObject = node[ndxRemove] as JsFunctionObject; if (funcObject == null || funcObject.FunctionType != JsFunctionType.Declaration) { // if it's a const-statement, leave it. // we COULD check to see if the constant is referenced anywhere and delete // any that aren't. Maybe later. // we also don't want to do like the var-statements and remove the initializers. // Not sure if any browsers would fail a const WITHOUT an initializer. if (!(node[ndxRemove] is JsConstStatement)) { var varStatement = node[ndxRemove] as JsVar; if (varStatement != null) { // var statements can't be removed, but any initializers should // be deleted since they won't get executed. for (var ndxDecl = 0; ndxDecl < varStatement.Count; ++ndxDecl) { if (varStatement[ndxDecl].Initializer != null) { varStatement[ndxDecl].Initializer = null; } } } else { // not a function declaration, and not a var statement -- get rid of it JsDetachReferences.Apply(node[ndxRemove]); node.RemoveAt(ndxRemove); } } } } } } } // now check the last statement -- if it's an if-statement where the true-block is a single return // and there is no false block, convert this one statement to a conditional. We might back it out later // if we don't combine the conditional with other stuff. // but we can only do this if we're at the functional level because of the implied return at the end // of that block. if (isFunctionLevel && node.Count > 0 && m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfConditionReturnToCondition)) { JsReturnNode returnNode; var ifNode = FindLastStatement(node) as JsIfNode; if (ifNode != null && ifNode.FalseBlock == null && ifNode.TrueBlock.Count == 1 && (returnNode = ifNode.TrueBlock[0] as JsReturnNode) != null) { // if the return node doesn't have an operand, then we can just replace the if-statement with its conditional if (returnNode.Operand == null) { // if the condition is a constant, then eliminate it altogether if (ifNode.Condition.IsConstant) { // delete the node altogether. Because the condition is a constant, // there is no else-block, and the if-block only contains a return // with no expression, we don't have anything to detach. node.ReplaceChild(ifNode, null); } else { // transform: {...;if(cond)return;} to {...;cond;} node.ReplaceChild(ifNode, ifNode.Condition); } } else if (returnNode.Operand.IsExpression) { // this is a strategic replacement that might pay off later. And if // it doesn't, we'll eventually back it out after all the other stuff // if applied on top of it. // transform: if(cond)return expr;} to return cond?expr:void 0} var conditional = new JsConditional(null, m_parser) { Condition = ifNode.Condition, TrueExpression = returnNode.Operand, FalseExpression = CreateVoidNode() }; // replace the if-statement with the new return node node.ReplaceChild(ifNode, new JsReturnNode(ifNode.Context, m_parser) { Operand = conditional }); Optimize(conditional); } } } // now walk through and combine adjacent expression statements, and adjacent var-for statements // and adjecent expression-return statements if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.CombineAdjacentExpressionStatements)) { CombineExpressions(node); } // check to see if we want to combine a preceding var with a for-statement if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.MoveVarIntoFor)) { // look at the statements in the block. // walk BACKWARDS down the list because we'll be removing items when we encounter // var statements that can be moved inside a for statement's initializer // we also don't need to check the first one, since there is nothing before it. for (int ndx = node.Count - 1; ndx > 0; --ndx) { // see if the previous statement is a var statement // (we've already combined adjacent var-statements) JsForNode forNode; JsWhileNode whileNode; var previousVar = node[ndx - 1] as JsVar; if (previousVar != null && (forNode = node[ndx] as JsForNode) != null) { // BUT if the var statement has any initializers containing an in-operator, first check // to see if we haven't killed that move before we try moving it. Opera 11 seems to have // an issue with that syntax, even if properly parenthesized. if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.MoveInExpressionsIntoForStatement) || !previousVar.ContainsInOperator) { // and see if the forNode's initializer is empty if (forNode.Initializer != null) { // not empty -- see if it is a Var node JsVar varInitializer = forNode.Initializer as JsVar; if (varInitializer != null) { // transform: var decls1;for(var decls2;...) to for(var decls1,decls2;...) // we want to PREPEND the initializers in the previous var-statement // to our for-statement's initializer var-statement list varInitializer.InsertAt(0, previousVar); // then remove the previous var statement node.RemoveAt(ndx - 1); // this will bump the for node up one position in the list, so the next iteration // will be right back on this node in case there are other var statements we need // to combine } else { // we want to see if the initializer expression is a series of one or more // simple assignments to variables that are in the previous var statement. // if all the expressions are assignments to variables that are defined in the // previous var statement, then we can just move the var statement into the // for statement. var binaryOp = forNode.Initializer as JsBinaryOperator; if (binaryOp != null && AreAssignmentsInVar(binaryOp, previousVar)) { // transform: var decls;for(expr1;...) to for(var decls,expr1;...) // WHERE expr1 only consists of assignments to variables that are declared // in that previous var-statement. // TODO: we *could* also do it is the expr1 assignments are to lookups that are // defined in THIS scope (not any outer scopes), because it wouldn't hurt to have // then in a var statement again. // create a list and fill it with all the var-decls created from the assignment // operators in the expression var varDecls = new List<JsVariableDeclaration>(); ConvertAssignmentsToVarDecls(binaryOp, varDecls, m_parser); // then go through and append each one to the var statement before us foreach (var varDecl in varDecls) { previousVar.Append(varDecl); } // move the previous var-statement into our initializer forNode.Initializer = previousVar; // and remove the previous var-statement from the list. node.RemoveAt(ndx - 1); // this will bump the for node up one position in the list, so the next iteration // will be right back on this node, but the initializer will not be null } } } else { // transform: var decls;for(;...) to for(var decls;...) // if it's empty, then we're free to add the previous var statement // to this for statement's initializer. remove it from it's current // position and add it as the initializer node.RemoveAt(ndx - 1); forNode.Initializer = previousVar; // this will bump the for node up one position in the list, so the next iteration // will be right back on this node, but the initializer will not be null } } } else if (previousVar != null && (whileNode = node[ndx] as JsWhileNode) != null && m_parser.Settings.IsModificationAllowed(JsTreeModifications.ChangeWhileToFor)) { // transform: var ...;while(cond)... => for(var ...;cond;)... node[ndx] = new JsForNode(null, m_parser) { Initializer = previousVar, Condition = whileNode.Condition, Body = whileNode.Body }; node.RemoveAt(ndx - 1); } } } // see if the last statement is a return statement JsReturnNode lastReturn; if ((lastReturn = FindLastStatement(node) as JsReturnNode) != null) { // set this flag to true if we end up adding an expression to the block. // before exiting, we'll go through and combine adjacent expressions again if this // flag has been set to true. bool changedStatementToExpression = false; // get the index of the statement before the last return // (skip over function decls and importand comments) var indexPrevious = PreviousStatementIndex(node, lastReturn); // just out of curiosity, let's see if we fit a common pattern: // var name=expr;return name; // or // const name=expr;return name; // if so, we can cut out the var and simply return the expression JsLookup lookup; if ((lookup = lastReturn.Operand as JsLookup) != null && indexPrevious >= 0) { // use the base class for both the var- and const-statements so we will // pick them both up at the same time var varStatement = node[indexPrevious] as JsDeclaration; if (varStatement != null) { // if the last vardecl in the var statement matches the return lookup, and no // other references exist for this field (refcount == 1)... JsVariableDeclaration varDecl; if ((varDecl = varStatement[varStatement.Count - 1]).Initializer != null && varDecl.IsEquivalentTo(lookup) && varDecl.VariableField.RefCount == 1) { // clean up the field's references because we're removing both the lookup reference // in the return statement and the vardecl. varDecl.VariableField.References.Remove(lookup); varDecl.VariableField.Declarations.Remove(varDecl); if (varStatement.Count == 1) { // transform: ...;var name=expr;return name} to ...;return expr} // there's only one vardecl in the var, so get rid of the entire statement lastReturn.Operand = varDecl.Initializer; node.RemoveAt(indexPrevious); } else { // multiple vardecls are in the statement; we only need to get rid of the last one lastReturn.Operand = varDecl.Initializer; varStatement[varStatement.Count - 1] = null; } } } } // check to see if we can combine the return statement with a previous if-statement // into a simple return-conditional. The true statement needs to have no false block, // and only one statement in the true block. JsConditional conditional; JsIfNode previousIf; while (indexPrevious >= 0 && lastReturn != null && (previousIf = node[indexPrevious] as JsIfNode) != null && previousIf.TrueBlock != null && previousIf.TrueBlock.Count == 1 && previousIf.FalseBlock == null) { // assume no change is made for this loop bool somethingChanged = false; // and that one true-block statement needs to be a return statement var previousReturn = previousIf.TrueBlock[0] as JsReturnNode; if (previousReturn != null) { if (lastReturn.Operand == null) { if (previousReturn.Operand == null) { // IF we are at the function level, then the block ends in an implicit return (undefined) // and we can change this if to just the condition. If we aren't at the function level, // then we have to leave the return, but we can replace the if with just the condition. if (!isFunctionLevel) { // not at the function level, so the return must stay. if (previousIf.Condition.IsConstant) { // transform: if(cond)return;return} to return} node.RemoveAt(indexPrevious); somethingChanged = true; } else { // transform: if(cond)return;return} to cond;return} node[indexPrevious] = previousIf.Condition; } } else if (previousIf.Condition.IsConstant) { // transform: remove if(cond)return;return} because cond is a constant node.ReplaceChild(lastReturn, null); node.RemoveAt(indexPrevious); somethingChanged = true; } else { // transform: if(cond)return;return} to cond} // replace the final return with just the condition, then remove the previous if if (node.ReplaceChild(lastReturn, previousIf.Condition)) { node.RemoveAt(indexPrevious); somethingChanged = true; } } } else { // transform: if(cond)return expr;return} to return cond?expr:void 0 conditional = new JsConditional(null, m_parser) { Condition = previousIf.Condition, TrueExpression = previousReturn.Operand, FalseExpression = CreateVoidNode() }; // replace the final return with the new return, then delete the previous if-statement if (node.ReplaceChild(lastReturn, new JsReturnNode(null, m_parser) { Operand = conditional })) { node.RemoveAt(indexPrevious); Optimize(conditional); somethingChanged = true; } } } else { if (previousReturn.Operand == null) { // transform: if(cond)return;return expr} to return cond?void 0:expr conditional = new JsConditional(null, m_parser) { Condition = previousIf.Condition, TrueExpression = CreateVoidNode(), FalseExpression = lastReturn.Operand }; // replace the final return with the new return, then delete the previous if-statement if (node.ReplaceChild(lastReturn, new JsReturnNode(null, m_parser) { Operand = conditional })) { node.RemoveAt(indexPrevious); Optimize(conditional); somethingChanged = true; } } else if (previousReturn.Operand.IsEquivalentTo(lastReturn.Operand)) { if (previousIf.Condition.IsConstant) { // the condition is constant, and the returns return the same thing. // get rid of the if statement altogether. // transform: if(cond)return expr;return expr} to return expr} JsDetachReferences.Apply(previousReturn.Operand); node.RemoveAt(indexPrevious); somethingChanged = true; } else { // transform: if(cond)return expr;return expr} to return cond,expr} // create a new binary op with the condition and the final-return operand, // replace the operand on the final-return with the new binary operator, // and then delete the previous if-statement JsDetachReferences.Apply(previousReturn.Operand); lastReturn.Operand = JsCommaOperator.CombineWithComma(null, m_parser, previousIf.Condition, lastReturn.Operand); node.RemoveAt(indexPrevious); somethingChanged = true; } } else { // transform: if(cond)return expr1;return expr2} to return cond?expr1:expr2} // create a new conditional with the condition and the return operands, // replace the operand on the final-return with the new conditional operator, // and then delete the previous if-statement // transform: if(cond)return expr1;return expr2} to return cond?expr1:expr2} conditional = new JsConditional(null, m_parser) { Condition = previousIf.Condition, TrueExpression = previousReturn.Operand, FalseExpression = lastReturn.Operand }; // replace the operand on the final-return with the new conditional operator, // and then delete the previous if-statement lastReturn.Operand = conditional; node.RemoveAt(indexPrevious); Optimize(conditional); somethingChanged = true; } } } if (!somethingChanged) { // nothing changed -- break out of the loop break; } else { // set the flag that indicates something changed in at least one of these loops changedStatementToExpression = true; // and since we changed something, we need to bump the index down one // AFTER we grab the last return node (which has slipped into the same position // as the previous node) lastReturn = node[indexPrevious--] as JsReturnNode; } } // if we added any more expressions since we ran our expression-combination logic, // run it again. if (changedStatementToExpression && m_parser.Settings.IsModificationAllowed(JsTreeModifications.CombineAdjacentExpressionStatements)) { CombineExpressions(node); } // and FINALLY, we want to see if what we did previously didn't pan out and we end // in something like return cond?expr:void 0, in which case we want to change it // back to a simple if(condition)return expr; (saves four bytes). // see if the last statement is a return statement that returns a conditional if (lastReturn != null && (conditional = lastReturn.Operand as JsConditional) != null) { var unaryOperator = conditional.FalseExpression as JsUnaryOperator; if (unaryOperator != null && unaryOperator.OperatorToken == JsToken.Void && unaryOperator.Operand is JsConstantWrapper) { unaryOperator = conditional.TrueExpression as JsUnaryOperator; if (unaryOperator != null && unaryOperator.OperatorToken == JsToken.Void) { if (isFunctionLevel) { // transform: ...;return cond?void 0:void 0} to ...;cond} // function level ends in an implicit "return void 0" node.ReplaceChild(lastReturn, conditional.Condition); } else { // transform: ...;return cond?void 0:void 0} to ...;cond;return} // non-function level doesn't end in an implicit return, // so we need to break them out into two statements node.ReplaceChild(lastReturn, conditional.Condition); node.Append(new JsReturnNode(null, m_parser)); } } else if (isFunctionLevel) { // transform: ...;return cond?expr:void 0} to ...;if(cond)return expr} // (only works at the function-level because of the implicit return statement) var ifNode = new JsIfNode(lastReturn.Context, m_parser) { Condition = conditional.Condition, TrueBlock = JsAstNode.ForceToBlock(new JsReturnNode(null, m_parser) { Operand = conditional.TrueExpression }) }; node.ReplaceChild(lastReturn, ifNode); } } else if (isFunctionLevel) { unaryOperator = conditional.TrueExpression as JsUnaryOperator; if (unaryOperator != null && unaryOperator.OperatorToken == JsToken.Void && unaryOperator.Operand is JsConstantWrapper) { // transform: ...;return cond?void 0;expr} to ...;if(!cond)return expr} // (only works at the function level because of the implicit return) // get the logical-not of the conditional var logicalNot = new JsLogicalNot(conditional.Condition, m_parser); logicalNot.Apply(); // create a new if-node based on the condition, with the branches swapped // (true-expression goes to false-branch, false-expression goes to true-branch var ifNode = new JsIfNode(lastReturn.Context, m_parser) { Condition = conditional.Condition, TrueBlock = JsAstNode.ForceToBlock(new JsReturnNode(null, m_parser) { Operand = conditional.FalseExpression }) }; node.ReplaceChild(lastReturn, ifNode); } } } } if (m_parser.Settings.IsModificationAllowed(JsTreeModifications.CombineEquivalentIfReturns)) { // walk backwards looking for if(cond1)return expr1;if(cond2)return expr2; // (backwards, because we'll be combining those into one statement, reducing the number of statements. // don't go all the way to zero, because each loop will compare the statement to the PREVIOUS // statement, and the first statement (index==0) has no previous statement. for (var ndx = node.Count - 1; ndx > 0; --ndx) { // see if the current statement is an if-statement with no else block, and a true // block that contains a single return-statement WITH an expression. JsAstNode currentExpr = null; JsAstNode condition2; if (IsIfReturnExpr(node[ndx], out condition2, ref currentExpr) != null) { // see if the previous statement is also the same pattern, but with // the equivalent expression as its return operand JsAstNode condition1; var matchedExpression = currentExpr; var ifNode = IsIfReturnExpr(node[ndx - 1], out condition1, ref matchedExpression); if (ifNode != null) { // it is a match! // let's combine them -- we'll add the current condition to the // previous condition with a logical-or and delete the current statement. // transform: if(cond1)return expr;if(cond2)return expr; to if(cond1||cond2)return expr; ifNode.Condition = new JsBinaryOperator(null, m_parser) { Operand1 = condition1, Operand2 = condition2, OperatorToken = JsToken.LogicalOr, TerminatingContext = ifNode.TerminatingContext ?? node.TerminatingContext }; JsDetachReferences.Apply(currentExpr); node.RemoveAt(ndx); } } } } if (isFunctionLevel && m_parser.Settings.IsModificationAllowed(JsTreeModifications.InvertIfReturn)) { // walk backwards looking for if (cond) return; whenever we encounter that statement, // we can change it to if (!cond) and put all subsequent statements in the block inside the // if's true-block. for (var ndx = node.Count - 1; ndx >= 0; --ndx) { var ifNode = node[ndx] as JsIfNode; if (ifNode != null && ifNode.FalseBlock == null && ifNode.TrueBlock != null && ifNode.TrueBlock.Count == 1) { var returnNode = ifNode.TrueBlock[0] as JsReturnNode; if (returnNode != null && returnNode.Operand == null) { // we have if(cond)return; // logical-not the condition, remove the return statement, // and move all subsequent sibling statements inside the if-statement. JsLogicalNot.Apply(ifNode.Condition, m_parser); ifNode.TrueBlock.Clear(); var ndxMove = ndx + 1; if (node.Count == ndxMove + 1) { // there's only one statement after our if-node. // see if it's ALSO an if-node with no else block. var secondIfNode = node[ndxMove] as JsIfNode; if (secondIfNode != null && (secondIfNode.FalseBlock == null || secondIfNode.FalseBlock.Count == 0)) { // it is! // transform: if(cond1)return;if(cond2){...} => if(!cond1&&cond2){...} // (the cond1 is already inverted at this point) // combine cond2 with cond1 via a logical-and, // move all secondIf statements inside the if-node, // remove the secondIf node. node.RemoveAt(ndxMove); ifNode.Condition = new JsBinaryOperator(null, m_parser) { Operand1 = ifNode.Condition, Operand2 = secondIfNode.Condition, OperatorToken = JsToken.LogicalAnd }; ifNode.TrueBlock = secondIfNode.TrueBlock; } else if (node[ndxMove].IsExpression && m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfConditionCallToConditionAndCall)) { // now we have if(cond)expr; optimize that! var expression = node[ndxMove]; node.RemoveAt(ndxMove); IfConditionExpressionToExpression(ifNode, expression); } } // just move all the following statements inside the if-statement while (node.Count > ndxMove) { var movedNode = node[ndxMove]; node.RemoveAt(ndxMove); ifNode.TrueBlock.Append(movedNode); } } } } } else { var isIteratorBlock = node.Parent is JsForNode || node.Parent is JsForIn || node.Parent is JsWhileNode || node.Parent is JsDoWhile; if (isIteratorBlock && m_parser.Settings.IsModificationAllowed(JsTreeModifications.InvertIfContinue)) { // walk backwards looking for if (cond) continue; whenever we encounter that statement, // we can change it to if (!cond) and put all subsequent statements in the block inside the // if's true-block. for (var ndx = node.Count - 1; ndx >= 0; --ndx) { var ifNode = node[ndx] as JsIfNode; if (ifNode != null && ifNode.FalseBlock == null && ifNode.TrueBlock != null && ifNode.TrueBlock.Count == 1) { var continueNode = ifNode.TrueBlock[0] as JsContinueNode; // if there's no label, then we're good. Otherwise we can only make this optimization // if the label refers to the parent iterator node. if (continueNode != null && (string.IsNullOrEmpty(continueNode.Label) || (LabelMatchesParent(continueNode.Label, node.Parent)))) { // if this is the last statement, then we don't really need the if at all // and can just replace it with its condition if (ndx < node.Count - 1) { // we have if(cond)continue;st1;...stn; // logical-not the condition, remove the continue statement, // and move all subsequent sibling statements inside the if-statement. JsLogicalNot.Apply(ifNode.Condition, m_parser); ifNode.TrueBlock.Clear(); // TODO: if we removed a labeled continue, do we need to fix up some label references? var ndxMove = ndx + 1; if (node.Count == ndxMove + 1) { // there's only one statement after our if-node. // see if it's ALSO an if-node with no else block. var secondIfNode = node[ndxMove] as JsIfNode; if (secondIfNode != null && (secondIfNode.FalseBlock == null || secondIfNode.FalseBlock.Count == 0)) { // it is! // transform: if(cond1)continue;if(cond2){...} => if(!cond1&&cond2){...} // (the cond1 is already inverted at this point) // combine cond2 with cond1 via a logical-and, // move all secondIf statements inside the if-node, // remove the secondIf node. ifNode.Condition = new JsBinaryOperator(null, m_parser) { Operand1 = ifNode.Condition, Operand2 = secondIfNode.Condition, OperatorToken = JsToken.LogicalAnd }; ifNode.TrueBlock = secondIfNode.TrueBlock; node.RemoveAt(ndxMove); } else if (node[ndxMove].IsExpression && m_parser.Settings.IsModificationAllowed(JsTreeModifications.IfConditionCallToConditionAndCall)) { // now we have if(cond)expr; optimize that! var expression = node[ndxMove]; node.RemoveAt(ndxMove); IfConditionExpressionToExpression(ifNode, expression); } } // just move all the following statements inside the if-statement while (node.Count > ndxMove) { var movedNode = node[ndxMove]; node.RemoveAt(ndxMove); ifNode.TrueBlock.Append(movedNode); } } else { // we have if(cond)continue} -- nothing after the if. // the loop is going to continue anyway, so replace the if-statement // with the condition and be done if (ifNode.Condition.IsConstant) { // consition is constant -- get rid of the if-statement altogether node.RemoveAt(ndx); } else { // condition isn't constant node[ndx] = ifNode.Condition; } } } } } } } } }