public void Visit(IfNode node)
{
if (node != null)
{
// if we have an else block, then the if statement
// requires a separator if the else block does.
// otherwise only if the true case requires one.
if (node.FalseBlock != null && node.FalseBlock.Count > 0)
{
node.FalseBlock.Accept(this);
}
else if (node.TrueBlock != null && node.TrueBlock.Count > 0)
{
node.TrueBlock.Accept(this);
}
else
{
DoesRequire = false;
}
}
}
public void Visit(IfNode node)
{
// starts with an 'if', so we don't care
}
internal Conditional CanBeReturnOperand(AstNode ultimateOperand, bool isFunctionLevel)
{
Conditional conditional = null;
try
{
if (TrueBlock != null && TrueBlock.Count == 1)
{
ReturnNode returnNode = TrueBlock[0] as ReturnNode;
if (returnNode != null)
{
AstNode expr1 = returnNode.Operand;
if (FalseBlock == null || FalseBlock.Count == 0)
{
// no false branch to speak of. Convert to conditional.
// if there is an ultimate expression, use it.
// if we are not at the function body level, we can't
// combine these. But if we are we can
// use a false expression of "void 0" (undefined)
if (ultimateOperand != null || isFunctionLevel)
{
conditional = new Conditional(
(Context == null ? null : Context.Clone()),
Parser,
Condition,
expr1 ?? CreateVoidNode(),
ultimateOperand ?? CreateVoidNode());
}
}
else if (FalseBlock.Count == 1)
{
// there is a false branch with only a single statement
// see if it is a return statement
returnNode = FalseBlock[0] as ReturnNode;
if (returnNode != null)
{
// it is. so we have if(cond)return expr1;else return expr2
// return cond?expr1:expr2
AstNode expr2 = returnNode.Operand;
conditional = new Conditional(
(Context == null ? null : Context.Clone()),
Parser,
Condition,
expr1 ?? CreateVoidNode(),
expr2 ?? CreateVoidNode());
}
else
{
// see if it's another if-statement
IfNode elseIf = FalseBlock[0] as IfNode;
if (elseIf != null)
{
// it's a nested if-statement. See if IT can be a return argument.
Conditional expr2 = elseIf.CanBeReturnOperand(ultimateOperand, isFunctionLevel);
if (expr2 != null)
{
// it can, so we can just nest the conditionals
conditional = new Conditional(
(Context == null ? null : Context.Clone()),
Parser,
Condition,
expr1,
expr2);
}
}
// else neither return- nor if-statement
}
}
// else false branch has more than one statement
}
// else the single statement is not a return-statement
}
// else no true branch, or not a single statement in the branch
}
catch (NotImplementedException)
{
// one of the clone calls probably failed.
// don't say this can be a return argument.
}
return(conditional);
}
internal override void AnalyzeNode()
{
// javascript doesn't have block scope, so there really is no point
// in nesting blocks. Unnest any now, before we start combining var statements
UnnestBlocks();
// if we want to remove debug statements...
if (Parser.Settings.StripDebugStatements && Parser.Settings.IsModificationAllowed(TreeModifications.StripDebugStatements))
{
// do it now before we try doing other things
StripDebugStatements();
}
// these variables are used to check for combining a particular type of
// for-statement with preceding var-statements.
ForNode targetForNode = null;
string targetName = null;
// check to see if we want to combine adjacent var statements
bool combineVarStatements = Parser.Settings.IsModificationAllowed(TreeModifications.CombineVarStatements);
// check to see if we want to combine a preceding var with a for-statement
bool moveVarIntoFor = Parser.Settings.IsModificationAllowed(TreeModifications.MoveVarIntoFor);
// 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.
// we also don't need to check the first one, since there is nothing before it.
for (int ndx = m_list.Count - 1; ndx > 0; --ndx)
{
// if the previous node is not a Var, then we don't need to try and combine
// it withthe current node
Var previousVar = m_list[ndx - 1] as Var;
if (previousVar != null)
{
// see if THIS item is also a Var...
if (m_list[ndx] is Var && combineVarStatements)
{
// add the items in this VAR to the end of the previous
previousVar.Append(m_list[ndx]);
// delete this item from the block
m_list.RemoveAt(ndx);
// if we have a target for-node waiting for another comparison....
if (targetForNode != null)
{
// check to see if the variable we are looking for is in the new list
if (previousVar.Contains(targetName))
{
// IT DOES! we can combine the var statement with the initializer in the for-statement
// we already know it's a binaryop, or it wouldn't be a target for-statement
BinaryOperator binaryOp = targetForNode.Initializer as BinaryOperator;
// create a vardecl that matches our assignment initializer
// ignore duplicates because this scope will already have the variable defined.
VariableDeclaration varDecl = new VariableDeclaration(
binaryOp.Context.Clone(),
Parser,
targetName,
binaryOp.Operand1.Context.Clone(),
binaryOp.Operand2,
0,
true
);
// append it to the preceding var-statement
previousVar.Append(varDecl);
// move the previous vardecl to our initializer
targetForNode.ReplaceChild(targetForNode.Initializer, previousVar);
// and remove the previous var from the list.
m_list.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
// but now we no longer need the target mechanism -- the for-statement is
// not the current node again
targetForNode = null;
}
}
}
else if (moveVarIntoFor)
{
// see if this item is a ForNode
ForNode forNode = m_list[ndx] as ForNode;
if (forNode != null)
{
// and see if the forNode's initializer is empty
if (forNode.Initializer != null)
{
// not empty -- see if it is a Var node
Var varInitializer = forNode.Initializer as Var;
if (varInitializer != null)
{
// we want to PREPEND the initializers in the previous var statement
// to our for-statement's initializer list
varInitializer.InsertAt(0, previousVar);
// then remove the previous var statement
m_list.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
{
// see if the initializer is a simple assignment
BinaryOperator binaryOp = forNode.Initializer as BinaryOperator;
if (binaryOp != null && binaryOp.OperatorToken == JSToken.Assign)
{
// it is. See if it's a simple lookup
Lookup lookup = binaryOp.Operand1 as Lookup;
if (lookup != null)
{
// it is. see if that variable is in the previous var statement
if (previousVar.Contains(lookup.Name))
{
// create a vardecl that matches our assignment initializer
// ignore duplicates because this scope will already have the variable defined.
VariableDeclaration varDecl = new VariableDeclaration(
binaryOp.Context.Clone(),
Parser,
lookup.Name,
lookup.Context.Clone(),
binaryOp.Operand2,
0,
true
);
// append it to the var statement before us
previousVar.Append(varDecl);
// move the previous vardecl to our initializer
forNode.ReplaceChild(forNode.Initializer, previousVar);
// and remove the previous var from the list.
m_list.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
{
// it's not in the immediately preceding var-statement, but that doesn't mean it won't be in
// a var-statement immediately preceding that one -- in which case they'll get combined and
// then it WILL be in the immediately preceding var-statement. So hold on to this
// for statement and we'll check after we do a combine.
targetForNode = forNode;
targetName = lookup.Name;
}
}
}
}
}
else
{
// 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
m_list.RemoveAt(ndx - 1);
forNode.ReplaceChild(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
{
// not a var statement. make sure the target for-node is cleared.
targetForNode = null;
ConditionalCompilationComment previousComment = m_list[ndx - 1] as ConditionalCompilationComment;
if (previousComment != null)
{
ConditionalCompilationComment thisComment = m_list[ndx] as ConditionalCompilationComment;
if (thisComment != null)
{
// two adjacent conditional comments -- combine them into the first.
// this will actually make the second block a nested block within the first block,
// but they'll be flattened when the comment's block gets recursed.
previousComment.Statements.Append(thisComment.Statements);
// and remove the second one (which is now a duplicate)
m_list.RemoveAt(ndx);
}
}
}
}
if (m_blockScope != null)
{
ScopeStack.Push(m_blockScope);
}
try
{
// call the base class to recurse
base.AnalyzeNode();
}
finally
{
if (m_blockScope != null)
{
ScopeStack.Pop();
}
}
// NOW that we've recursively analyzed all the child nodes in this block, let's see
// if we can further reduce the statements by checking for a couple good opportunities
if (Parser.Settings.RemoveUnneededCode)
{
// Transform: {var foo=expression;return foo;} to: {return expression;}
if (m_list.Count == 2 && Parser.Settings.IsModificationAllowed(TreeModifications.VarInitializeReturnToReturnInitializer))
{
Var varStatement = m_list[0] as Var;
ReturnNode returnStatement = m_list[1] as ReturnNode;
// see if we have two statements in our block: a var with a single declaration, and a return
if (returnStatement != null && varStatement != null &&
varStatement.Count == 1 && varStatement[0].Initializer != null)
{
// now see if the return is returning a lookup for the same var we are declaring in the
// previous statement
Lookup lookup = returnStatement.Operand as Lookup;
if (lookup != null &&
string.Compare(lookup.Name, varStatement[0].Identifier, StringComparison.Ordinal) == 0)
{
// it's a match!
// create a combined context starting with the var and adding in the return
Context context = varStatement.Context.Clone();
context.UpdateWith(returnStatement.Context);
// create a new return statement
ReturnNode newReturn = new ReturnNode(context, Parser, varStatement[0].Initializer);
// clear out the existing statements
m_list.Clear();
// and add our new one
Append(newReturn);
}
}
}
// we do things differently if these statements are the last in a function
// because we can assume the implicit return
bool isFunctionLevel = (Parent is FunctionObject);
// see if we want to change if-statement that forces a return to a return conditional
if (Parser.Settings.IsModificationAllowed(TreeModifications.IfElseReturnToReturnConditional))
{
// transform: {...; if(cond1)return;} to {...;cond;}
// transform: {...; if(cond1)return exp1;else return exp2;} to {...;return cond1?exp1:exp2;}
if (m_list.Count >= 1)
{
// see if the last statement is an if-statement with a true-block containing only one statement
IfNode ifStatement = m_list[m_list.Count - 1] as IfNode;
if (ifStatement != null &&
ifStatement.TrueBlock != null)
{
// see if this if-statement is structured such that we can convert it to a
// Conditional node that is the operand of a return statement
Conditional returnOperand = ifStatement.CanBeReturnOperand(null, isFunctionLevel);
if (returnOperand != null)
{
// it can! change it.
ReturnNode returnNode = new ReturnNode(
(Context == null ? null : Context.Clone()),
Parser,
returnOperand);
// replace the if-statement with the return statement
ReplaceChild(ifStatement, returnNode);
}
}
// else last statement is not an if-statement, or true block is not a single statement
}
// transform: {...; if(cond1)return exp1;return exp2;} to {...; return cond1?exp1:exp2;}
// my cascade! changing the two statements to a return may cause us to run this again if the
// third statement up becomes the penultimate and is an if-statement
while (m_list.Count > 1)
{
int lastIndex = m_list.Count - 1;
// end in a return statement?
ReturnNode finalReturn = m_list[lastIndex] as ReturnNode;
if (finalReturn != null)
{
// it does -- see if the penultimate statement is an if-block
IfNode ifNode = m_list[lastIndex - 1] as IfNode;
if (ifNode != null)
{
// if followed by return. See if the if statement can be changed to a
// return of a conditional, using the operand of the following return
// as the ultimate expression
Conditional returnConditional = ifNode.CanBeReturnOperand(finalReturn.Operand, isFunctionLevel);
if (returnConditional != null)
{
// it can! so create the new return statement.
// the context of this new return statement should start with a clone of
// the if-statement and updated with the return statement
Context context = ifNode.Context.Clone();
context.UpdateWith(finalReturn.Context);
// create the new return node
ReturnNode newReturn = new ReturnNode(
context,
Parser,
returnConditional);
// remove the last node (the old return)
m_list.RemoveAt(lastIndex--);
// and replace the if-statement with the new return
m_list[lastIndex] = newReturn;
newReturn.Parent = this;
// we collapsed the last two statements, and we KNOW the last one is a
// return -- go back up to the top of the loop to see if we can keep going.
continue;
}
}
}
// if we get here, then something went wrong, we didn't collapse the last
// two statements, so break out of the loop
break;
}
// now we may have converted the last functional statement
// from if(cond)return expr to return cond?expr:void 0, which is four
// extra bytes. So let's check to see if the last statement in the function
// now fits this pattern, and if so, change it back.
// We didn't just NOT change it in the first place because changing it could've
// enabled even more changes that would save a lot more space. But apparently
// those subsequent changes didn't pan out.
if (m_list.Count >= 1)
{
int lastIndex = m_list.Count - 1;
ReturnNode returnNode = m_list[lastIndex] as ReturnNode;
if (returnNode != null)
{
Conditional conditional = returnNode.Operand as Conditional;
if (conditional != null)
{
VoidNode falseVoid = conditional.FalseExpression as VoidNode;
if (falseVoid != null && falseVoid.Operand is ConstantWrapper)
{
// we have the required pattern: "return cond?expr:void 0"
// (well, the object of the void is a constant, at least).
// undo it back to "if(cond)return expr" because that takes fewer bytes.
// by default, the operand of the return operator will be the
// true branch of the conditional
AstNode returnOperand = conditional.TrueExpression;
VoidNode trueVoid = conditional.TrueExpression as VoidNode;
if (trueVoid != null && trueVoid.Operand is ConstantWrapper)
{
// the true branch of the conditional is a void operator acting
// on a constant! So really, there is no operand to the return statement
returnOperand = null;
if (Parser.Settings.IsModificationAllowed(TreeModifications.IfConditionReturnToCondition))
{
// actually, we have return cond?void 0:void 0,
// which would get changed back to function{...;if(cond)return}
// BUT we can just shorten it to function{...;cond}
m_list[lastIndex] = conditional.Condition;
conditional.Condition.Parent = this;
return;
}
}
IfNode ifNode = new IfNode(
returnNode.Context.Clone(),
Parser,
conditional.Condition,
new ReturnNode(returnNode.Context.Clone(), Parser, returnOperand),
null);
m_list[lastIndex] = ifNode;
ifNode.Parent = this;
}
}
}
}
}
}
}
public void Visit(IfNode node)
{
DebugEx.Fail("shouldn't get here");
}
public override void Visit(Block node)
{
if (node != null)
{
// 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 FunctionObject);
// if we want to remove debug statements...
if (m_parser.Settings.StripDebugStatements && m_parser.Settings.IsModificationAllowed(TreeModifications.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)
{
ScopeStack.Push(node.BlockScope);
}
try
{
// call the base class to recurse
base.Visit(node);
}
finally
{
if (node.BlockScope != null)
{
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 IfNode;
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 ReturnNode)
{
// 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.ReplaceChild(ifNode.FalseBlock, null);
}
}
else if (node[ndx] is ReturnNode
|| node[ndx] is Break
|| node[ndx] is ContinueNode)
{
// we have a return node -- no statments afterwards will be executed, so clear them out.
// transform: {...;return;...} to {...;return}
// transform: {...;break;...} to {...;break}
// transform: {...;continue;...} to {...;continue}
// we've found a return 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 statement.
for (var ndxRemove = node.Count - 1; ndxRemove > ndx; --ndxRemove)
{
var funcObject = node[ndxRemove] as FunctionObject;
if (funcObject == null || funcObject.FunctionType != FunctionType.Declaration)
{
var varStatement = node[ndxRemove] as Var;
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].ReplaceChild(varStatement[ndxDecl].Initializer, null);
}
}
}
else
{
// not a function declaration, and not a var statement -- get rid of it
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(TreeModifications.IfConditionReturnToCondition))
{
ReturnNode returnNode;
var ifNode = FindLastStatement(node) as IfNode;
if (ifNode != null && ifNode.FalseBlock == null
&& ifNode.TrueBlock.Count == 1
&& (returnNode = ifNode.TrueBlock[0] as ReturnNode) != 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)
{
// transform: if(cond)return;} to cond}
// TODO: if the condition is a constant, then eliminate it altogether
node.ReplaceChild(ifNode, ifNode.Condition);
}
else if (returnNode.Operand.IsExpression)
{
// transform: if(cond)return expr;} to return cond?expr:void 0}
var conditional = new Conditional(
null, m_parser, ifNode.Condition,
returnNode.Operand,
CreateVoidNode());
// replace the if-statement with the new return node
node.ReplaceChild(ifNode, new ReturnNode(ifNode.Context, m_parser, 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(TreeModifications.CombineAdjacentExpressionStatements))
{
CombineExpressions(node);
}
// check to see if we want to combine a preceding var with a for-statement
if (m_parser.Settings.IsModificationAllowed(TreeModifications.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)
ForNode forNode;
var previousVar = node[ndx - 1] as Var;
if (previousVar != null && (forNode = node[ndx] as ForNode) != null)
{
// and see if the forNode's initializer is empty
if (forNode.Initializer != null)
{
// not empty -- see if it is a Var node
Var varInitializer = forNode.Initializer as Var;
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.
BinaryOperator binaryOp = forNode.Initializer as BinaryOperator;
if (binaryOp != null && AreAssignmentsInVar(binaryOp, previousVar))
{
// transform: var decls;for(expr1;...) to for(var decls,expr1;...)
// create a list and fill it with all the var-decls created from the assignment
// operators in the expression
var varDecls = new List<VariableDeclaration>();
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.ReplaceChild(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.SetInitializer(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
}
}
}
}
// see if the last statement is a return statement
ReturnNode lastReturn;
if ((lastReturn = FindLastStatement(node) as ReturnNode) != 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;
// if so, we can cut out the var and simply return the expression
Lookup lookup;
if ((lookup = lastReturn.Operand as Lookup) != null && indexPrevious >= 0)
{
var varStatement = node[indexPrevious] as Var;
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)...
VariableDeclaration varDecl;
if ((varDecl = varStatement[varStatement.Count - 1]).Initializer != null
&& varDecl.IsEquivalentTo(lookup)
&& varDecl.Field.RefCount == 1)
{
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.ReplaceChild(lookup, varDecl.Initializer);
node.RemoveAt(indexPrevious);
}
else
{
// multiple vardecls are in the statement; we only need to get rid of the last one
lastReturn.ReplaceChild(lookup, varDecl.Initializer);
varStatement.ReplaceChild(varDecl, 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.
Conditional conditional;
IfNode previousIf;
while (indexPrevious >= 0
&& lastReturn != null
&& (previousIf = node[indexPrevious] as IfNode) != 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 ReturnNode;
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)
{
// transform: if(cond)return;return} to cond;return}
node.ReplaceChild(previousIf, previousIf.Condition);
}
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 Conditional(null, m_parser,
previousIf.Condition,
previousReturn.Operand,
CreateVoidNode());
// replace the final return with the new return, then delete the previous if-statement
if (node.ReplaceChild(lastReturn, new ReturnNode(null, m_parser, 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 Conditional(null, m_parser,
previousIf.Condition,
CreateVoidNode(),
lastReturn.Operand);
// replace the final return with the new return, then delete the previous if-statement
if (node.ReplaceChild(lastReturn, new ReturnNode(null, m_parser, conditional)))
{
node.RemoveAt(indexPrevious);
Optimize(conditional);
somethingChanged = true;
}
}
else if (previousReturn.Operand.IsEquivalentTo(lastReturn.Operand))
{
// 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
if (lastReturn.ReplaceChild(lastReturn.Operand,
new BinaryOperator(null, m_parser, previousIf.Condition, lastReturn.Operand, JSToken.Comma)))
{
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 Conditional(null, m_parser,
previousIf.Condition, previousReturn.Operand, lastReturn.Operand);
// replace the operand on the final-return with the new conditional operator,
// and then delete the previous if-statement
if (lastReturn.ReplaceChild(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 ReturnNode;
}
}
// if we added any more expressions since we ran our expression-combination logic,
// run it again.
if (changedStatementToExpression
&& m_parser.Settings.IsModificationAllowed(TreeModifications.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 Conditional) != null)
{
VoidNode voidOperator = conditional.FalseExpression as VoidNode;
if (voidOperator != null && voidOperator.Operand is ConstantWrapper)
{
voidOperator = conditional.TrueExpression as VoidNode;
if (voidOperator != null)
{
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 ReturnNode(null, m_parser, null));
}
}
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 IfNode(lastReturn.Context,
m_parser,
conditional.Condition,
new ReturnNode(null, m_parser, conditional.TrueExpression),
null);
node.ReplaceChild(lastReturn, ifNode);
}
}
else if (isFunctionLevel)
{
voidOperator = conditional.TrueExpression as VoidNode;
if (voidOperator != null && voidOperator.Operand is ConstantWrapper)
{
// 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 LogicalNot(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 IfNode(lastReturn.Context,
m_parser,
conditional.Condition,
new ReturnNode(null, m_parser, conditional.FalseExpression),
null);
node.ReplaceChild(lastReturn, ifNode);
}
}
}
}
}
}
public override void Visit(IfNode node)
{
if (node != null)
{
if (m_parser.Settings.StripDebugStatements
&& m_parser.Settings.IsModificationAllowed(TreeModifications.StripDebugStatements))
{
if (node.TrueBlock != null && node.TrueBlock.IsDebuggerStatement)
{
node.ReplaceChild(node.TrueBlock, null);
}
if (node.FalseBlock != null && node.FalseBlock.IsDebuggerStatement)
{
node.ReplaceChild(node.FalseBlock, null);
}
}
// recurse....
base.Visit(node);
// now check to see if the two branches are now empty.
// if they are, null them out.
if (node.TrueBlock != null && node.TrueBlock.Count == 0)
{
node.ReplaceChild(node.TrueBlock, null);
}
if (node.FalseBlock != null && node.FalseBlock.Count == 0)
{
node.ReplaceChild(node.FalseBlock, null);
}
// if there is no true branch but a false branch, then
// put a not on the condition and move the false branch to the true branch.
if (node.TrueBlock == null && node.FalseBlock != null
&& m_parser.Settings.IsModificationAllowed(TreeModifications.IfConditionFalseToIfNotConditionTrue))
{
// logical-not the condition
var logicalNot = new LogicalNot(node.Condition, m_parser);
logicalNot.Apply();
// and swap the branches
node.SwapBranches();
}
else if (node.TrueBlock != null && node.FalseBlock != null)
{
// see if logical-notting the condition produces something smaller
var logicalNot = new LogicalNot(node.Condition, m_parser);
if (logicalNot.Measure() < 0)
{
// it does -- not the condition and swap the branches
logicalNot.Apply();
node.SwapBranches();
}
// see if the true- and false-branches each contain only a single statement
if (node.TrueBlock.Count == 1 && node.FalseBlock.Count == 1)
{
// they do -- see if the true-branch's statement is a return-statement
var trueReturn = node.TrueBlock[0] as ReturnNode;
if (trueReturn != null && trueReturn.Operand != null)
{
// it is -- see if the false-branch is also a return statement
var falseReturn = node.FalseBlock[0] as ReturnNode;
if (falseReturn != null && falseReturn.Operand != null)
{
// transform: if(cond)return expr1;else return expr2 to return cond?expr1:expr2
var conditional = new Conditional(null, m_parser,
node.Condition,
trueReturn.Operand,
falseReturn.Operand);
// create a new return node from the conditional and replace
// our if-node with it
var returnNode = new ReturnNode(
node.Context,
m_parser,
conditional);
node.Parent.ReplaceChild(
node,
returnNode);
Optimize(conditional);
}
}
}
}
else if (node.TrueBlock == null && node.FalseBlock == null
&& m_parser.Settings.IsModificationAllowed(TreeModifications.IfEmptyToExpression))
{
// NEITHER branches have anything now!
// something we can do in the future: as long as the condition doesn't
// contain calls or assignments, we should be able to completely delete
// the statement altogether rather than changing it to an expression
// statement on the condition.
// I'm just not doing it yet because I don't
// know what the effect will be on the iteration of block statements.
// if we're on item, 5, for instance, and we delete it, will the next
// item be item 6, or will it return the NEW item 5 (since the old item
// 5 was deleted and everything shifted up)?
// We don't know what it is and what the side-effects may be, so
// just change this statement into an expression statement by replacing us with
// the expression
node.Parent.ReplaceChild(node, node.Condition);
// no need to analyze -- we already recursed
}
// if the true block is not empty, but it's an expression, there are a couple more
// optimizations we can make
if (node.TrueBlock != null && node.TrueBlock.IsExpression
&& m_parser.Settings.IsModificationAllowed(TreeModifications.IfExpressionsToExpression))
{
if (node.FalseBlock != null && node.FalseBlock.IsExpression)
{
// if this statement has both true and false blocks, and they are both expressions,
// then we can simplify this to a conditional expression.
// because the blocks are expressions, we know they only have ONE statement in them,
// so we can just dereference them directly.
Conditional conditional;
var logicalNot = new LogicalNot(node.Condition, m_parser);
if (logicalNot.Measure() < 0)
{
// applying a logical-not makes the condition smaller -- reverse the branches
logicalNot.Apply();
conditional = new Conditional(
node.Context,
m_parser,
node.Condition,
node.FalseBlock[0],
node.TrueBlock[0]);
}
else
{
// regular order
conditional = new Conditional(
node.Context,
m_parser,
node.Condition,
node.TrueBlock[0],
node.FalseBlock[0]);
}
node.Parent.ReplaceChild(
node,
conditional);
Optimize(conditional);
}
else if (node.FalseBlock == null
&& m_parser.Settings.IsModificationAllowed(TreeModifications.IfConditionCallToConditionAndCall))
{
// but first -- which operator to use? if(a)b --> a&&b, and if(!a)b --> a||b
// so determine which one is smaller: a or !a
// assume we'll use the logical-and, since that doesn't require changing the condition
var newOperator = JSToken.LogicalAnd;
var logicalNot = new LogicalNot(node.Condition, m_parser);
if (logicalNot.Measure() < 0)
{
// !a is smaller, so apply it and use the logical-or operator
logicalNot.Apply();
newOperator = JSToken.LogicalOr;
}
// because the true block is an expression, we know it must only have
// ONE statement in it, so we can just dereference it directly.
var binaryOp = new BinaryOperator(
node.Context,
m_parser,
node.Condition,
node.TrueBlock[0],
newOperator
);
// we don't need to analyse this new node because we've already analyzed
// the pieces parts as part of the if. And this visitor's method for the BinaryOperator
// doesn't really do anything else. Just replace our current node with this
// new node
node.Parent.ReplaceChild(node, binaryOp);
}
}
}
}
public void Visit(IfNode node)
{
ReportError(node);
}
public void Visit(IfNode node)
{
// invalid! ignore
IsValid = false;
}
public override void Visit(IfNode node)
{
if (node != null)
{
// depth-first
base.Visit(node);
if (m_parser.Settings.IsModificationAllowed(TreeModifications.EvaluateNumericExpressions))
{
// if the if-condition is a constant, we can eliminate one of the two branches
ConstantWrapper constantCondition = node.Condition as ConstantWrapper;
if (constantCondition != null)
{
// instead, replace the condition with a 1 if it's always true or a 0 if it's always false
if (constantCondition.IsNotOneOrPositiveZero)
{
try
{
node.ReplaceChild(node.Condition,
new ConstantWrapper(constantCondition.ToBoolean() ? 1 : 0, PrimitiveType.Number, node.Condition.Context, m_parser));
}
catch (InvalidCastException)
{
// ignore any invalid cast exceptions
}
}
}
}
}
}
