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fix replacement logic in collapse_vars (#2475)

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This commit is contained in:
Alex Lam S.L
2017-11-13 07:37:42 +08:00
committed by GitHub
parent 2ac5086831
commit 49fbe9c5ac
2 changed files with 174 additions and 102 deletions
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216
lib/compress.js
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@@ -839,6 +839,113 @@ merge(Compressor.prototype, {
var args;
var candidates = [];
var stat_index = statements.length;
var scanner = new TreeTransformer(function(node, descend) {
if (abort) return node;
// Skip nodes before `candidate` as quickly as possible
if (!hit) {
if (node === candidate) {
hit = true;
return node;
}
return;
}
// Stop immediately if these node types are encountered
var parent = scanner.parent();
if (node instanceof AST_Assign && node.operator != "=" && lhs.equivalent_to(node.left)
|| node instanceof AST_Call && lhs instanceof AST_PropAccess && lhs.equivalent_to(node.expression)
|| node instanceof AST_Debugger
|| node instanceof AST_IterationStatement && !(node instanceof AST_For)
|| node instanceof AST_SymbolRef && !node.is_declared(compressor)
|| node instanceof AST_Try
|| node instanceof AST_With
|| parent instanceof AST_For && node !== parent.init) {
abort = true;
return node;
}
// Replace variable with assignment when found
if (can_replace
&& !(node instanceof AST_SymbolDeclaration)
&& lhs.equivalent_to(node)) {
if (is_lhs(node, parent)) {
if (candidate.multiple) replaced++;
return node;
}
CHANGED = abort = true;
replaced++;
compressor.info("Collapsing {name} [{file}:{line},{col}]", {
name: node.print_to_string(),
file: node.start.file,
line: node.start.line,
col: node.start.col
});
if (candidate instanceof AST_UnaryPostfix) {
return make_node(AST_UnaryPrefix, candidate, candidate);
}
if (candidate instanceof AST_VarDef) {
if (candidate.multiple) {
abort = false;
return node;
}
var def = candidate.name.definition();
if (def.references.length - def.replaced == 1 && !compressor.exposed(def)) {
def.replaced++;
return maintain_this_binding(parent, node, candidate.value);
}
return make_node(AST_Assign, candidate, {
operator: "=",
left: make_node(AST_SymbolRef, candidate.name, candidate.name),
right: candidate.value
});
}
candidate.write_only = false;
return candidate;
}
// These node types have child nodes that execute sequentially,
// but are otherwise not safe to scan into or beyond them.
var sym;
if (node instanceof AST_Call
|| node instanceof AST_Exit
|| node instanceof AST_PropAccess
&& (side_effects || node.expression.may_throw_on_access(compressor))
|| node instanceof AST_SymbolRef
&& (lvalues[node.name]
|| side_effects && !references_in_scope(node.definition()))
|| (sym = lhs_or_def(node))
&& (sym instanceof AST_PropAccess || sym.name in lvalues)
|| (side_effects || !replace_all)
&& (parent instanceof AST_Binary && lazy_op(parent.operator)
|| parent instanceof AST_Case
|| parent instanceof AST_Conditional
|| parent instanceof AST_If)) {
if (!(node instanceof AST_Scope)) descend(node, scanner);
abort = true;
return node;
}
// Skip (non-executed) functions and (leading) default case in switch statements
if (node instanceof AST_Default || node instanceof AST_Scope) return node;
});
var multi_replacer = new TreeTransformer(function(node) {
if (abort) return node;
// Skip nodes before `candidate` as quickly as possible
if (!hit) {
if (node === candidate) {
hit = true;
return node;
}
return;
}
// Replace variable when found
if (node instanceof AST_SymbolRef
&& node.name == def.name) {
if (!--replaced) abort = true;
if (is_lhs(node, multi_replacer.parent())) return node;
def.replaced++;
value_def.replaced--;
return candidate.value;
}
// Skip (non-executed) functions and (leading) default case in switch statements
if (node instanceof AST_Default || node instanceof AST_Scope) return node;
});
while (--stat_index >= 0) {
// Treat parameters as collapsible in IIFE, i.e.
// function(a, b){ ... }(x());
@@ -862,121 +969,24 @@ merge(Compressor.prototype, {
var side_effects = value_has_side_effects(candidate);
var hit = candidate.name instanceof AST_SymbolFunarg;
var abort = false, replaced = 0, can_replace = !args || !hit;
var tt = new TreeTransformer(function(node, descend) {
if (abort) return node;
// Skip nodes before `candidate` as quickly as possible
if (!hit) {
if (node === candidate) {
hit = true;
return node;
}
return;
}
// Stop immediately if these node types are encountered
var parent = tt.parent();
if (node instanceof AST_Assign && node.operator != "=" && lhs.equivalent_to(node.left)
|| node instanceof AST_Call && lhs instanceof AST_PropAccess && lhs.equivalent_to(node.expression)
|| node instanceof AST_Debugger
|| node instanceof AST_IterationStatement && !(node instanceof AST_For)
|| node instanceof AST_SymbolRef && !node.is_declared(compressor)
|| node instanceof AST_Try
|| node instanceof AST_With
|| parent instanceof AST_For && node !== parent.init) {
abort = true;
return node;
}
// Replace variable with assignment when found
if (can_replace
&& !(node instanceof AST_SymbolDeclaration)
&& !is_lhs(node, parent)
&& lhs.equivalent_to(node)) {
CHANGED = abort = true;
replaced++;
compressor.info("Collapsing {name} [{file}:{line},{col}]", {
name: node.print_to_string(),
file: node.start.file,
line: node.start.line,
col: node.start.col
});
if (candidate instanceof AST_UnaryPostfix) {
return make_node(AST_UnaryPrefix, candidate, candidate);
}
if (candidate instanceof AST_VarDef) {
if (candidate.multiple) {
abort = false;
return node;
}
var def = candidate.name.definition();
if (def.references.length - def.replaced == 1 && !compressor.exposed(def)) {
def.replaced++;
return maintain_this_binding(parent, node, candidate.value);
}
return make_node(AST_Assign, candidate, {
operator: "=",
left: make_node(AST_SymbolRef, candidate.name, candidate.name),
right: candidate.value
});
}
candidate.write_only = false;
return candidate;
}
// These node types have child nodes that execute sequentially,
// but are otherwise not safe to scan into or beyond them.
var sym;
if (node instanceof AST_Call
|| node instanceof AST_Exit
|| node instanceof AST_PropAccess
&& (side_effects || node.expression.may_throw_on_access(compressor))
|| node instanceof AST_SymbolRef
&& (lvalues[node.name]
|| side_effects && !references_in_scope(node.definition()))
|| (sym = lhs_or_def(node))
&& (sym instanceof AST_PropAccess || sym.name in lvalues)
|| (side_effects || !replace_all)
&& (parent instanceof AST_Binary && lazy_op(parent.operator)
|| parent instanceof AST_Case
|| parent instanceof AST_Conditional
|| parent instanceof AST_If)) {
if (!(node instanceof AST_Scope)) descend(node, tt);
abort = true;
return node;
}
// Skip (non-executed) functions and (leading) default case in switch statements
if (node instanceof AST_Default || node instanceof AST_Scope) return node;
});
if (!can_replace) {
for (var j = compressor.self().argnames.lastIndexOf(candidate.name) + 1; !abort && j < args.length; j++) {
args[j].transform(tt);
args[j].transform(scanner);
}
can_replace = true;
}
for (var i = stat_index; !abort && i < statements.length; i++) {
statements[i].transform(tt);
statements[i].transform(scanner);
}
if (candidate.multiple) {
var def = candidate.name.definition();
if (abort && def.references.length > replaced) replaced = false;
if (abort && def.references.length - def.replaced > replaced) replaced = false;
else {
abort = false;
hit = candidate.name instanceof AST_SymbolFunarg;
var value_def = candidate.value.definition();
for (var i = stat_index; !abort && i < statements.length; i++) {
statements[i].transform(new TreeTransformer(function(node) {
if (abort) return node;
if (!hit) {
if (node === candidate) {
hit = true;
return node;
}
return;
}
if (node instanceof AST_SymbolRef && node.name == def.name) {
def.replaced++;
value_def.replaced--;
if (!--replaced) abort = true;
return candidate.value;
}
}));
statements[i].transform(multi_replacer);
}
}
}
@@ -2549,12 +2559,14 @@ merge(Compressor.prototype, {
var def = tail.pop();
compressor.warn("Converting duplicated definition of variable {name} to assignment [{file}:{line},{col}]", template(def.name));
remove(var_defs, def);
drop_decl(def.name.definition());
side_effects.unshift(make_node(AST_Assign, def, {
operator: "=",
left: make_node(AST_SymbolRef, def.name, def.name),
right: def.value
}));
def = def.name.definition();
drop_decl(def);
def.replaced--;
}
}
if (head.length > 0 || tail.length > 0) {