Skip to content

Commit

Permalink
enhance collapse_vars (#3613)
Browse files Browse the repository at this point in the history
  • Loading branch information
@alexlamsl
alexlamsl committed Nov 29, 2019
1 parent 5a88c30 commit 1b61a81
Show file tree
Hide file tree
Showing 2 changed files with 260 additions and 49 deletions.
129 changes: 90 additions & 39 deletions lib/compress.js
View file
Expand Up @@ -1116,7 +1116,7 @@ merge(Compressor.prototype, {
var args;
var candidates = [];
var stat_index = statements.length;
var scanner = new TreeTransformer(function(node) {
var scanner = new TreeTransformer(function(node, descend) {
if (abort) return node;
// Skip nodes before `candidate` as quickly as possible
if (!hit) {
Expand Down Expand Up @@ -1151,11 +1151,16 @@ merge(Compressor.prototype, {
return node;
}
if (is_lhs(node, parent)) {
if (value_def) replaced++;
if (value_def && !hit_rhs) {
assign_used = true;
replaced++;
}
return node;
} else if (value_def) {
if (!hit_rhs) replaced++;
return node;
} else {
replaced++;
if (value_def) return node;
}
CHANGED = abort = true;
AST_Node.info("Collapsing {name} [{file}:{line},{col}]", {
Expand Down Expand Up @@ -1188,6 +1193,14 @@ merge(Compressor.prototype, {
stop_after = node;
if (node instanceof AST_Scope) abort = true;
}
// Scan but don't replace inside getter/setter
if (node instanceof AST_Accessor) {
var replace = can_replace;
can_replace = false;
descend(node, scanner);
can_replace = replace;
return node;
}
return handle_custom_scan_order(node);
}, function(node) {
if (abort) return;
Expand All @@ -1200,9 +1213,28 @@ merge(Compressor.prototype, {
if (!hit) {
if (node !== hit_stack[hit_index]) return node;
hit_index++;
if (hit_index < hit_stack.length) return;
hit = true;
return node;
switch (hit_stack.length - hit_index) {
case 0:
hit = true;
if (assign_used) return node;
if (node instanceof AST_VarDef) return node;
def.replaced++;
var parent = multi_replacer.parent();
if (parent instanceof AST_Sequence && parent.tail_node() !== node) {
value_def.replaced++;
return MAP.skip;
}
return get_rvalue(candidate);
case 1:
if (!assign_used && node.body === candidate) {
hit = true;
def.replaced++;
value_def.replaced++;
return null;
}
default:
return;
}
}
// Replace variable when found
if (node instanceof AST_SymbolRef
Expand All @@ -1215,7 +1247,8 @@ merge(Compressor.prototype, {
}
// Skip (non-executed) functions and (leading) default case in switch statements
if (node instanceof AST_Default || node instanceof AST_Scope) return node;
});
}, patch_sequence);
var force_single;
while (--stat_index >= 0) {
// Treat parameters as collapsible in IIFE, i.e.
// function(a, b){ ... }(x());
Expand Down Expand Up @@ -1248,7 +1281,10 @@ merge(Compressor.prototype, {
} : side_effects_external : return_false;
var funarg = candidate.name instanceof AST_SymbolFunarg;
var hit = funarg;
var abort = false, replaced = 0, can_replace = !args || !hit;
var abort = false;
var replaced = 0;
var assign_used = false;
var can_replace = !args || !hit;
if (!can_replace) {
for (var j = compressor.self().argnames.lastIndexOf(candidate.name) + 1; !abort && j < args.length; j++) {
args[j].transform(scanner);
Expand All @@ -1260,20 +1296,22 @@ merge(Compressor.prototype, {
}
if (value_def) {
var def = lhs.definition();
if (abort) {
var referenced = def.references.length - def.replaced;
if (candidate instanceof AST_Assign) referenced--;
if (referenced > replaced) {
replaced = false;
} else {
abort = false;
}
var referenced = def.references.length - def.replaced;
if (candidate instanceof AST_Assign) referenced--;
if (replaced && referenced == replaced) {
abort = false;
} else if (candidate instanceof AST_Assign) {
candidates.push(hit_stack);
force_single = true;
continue;
} else {
replaced = false;
}
if (!abort) {
if (replaced) {
hit_index = 0;
hit = funarg;
for (var i = stat_index; !abort && i < statements.length; i++) {
statements[i].transform(multi_replacer);
if (!statements[i].transform(multi_replacer)) statements.splice(i--, 1);
}
value_def.single_use = false;
}
Expand Down Expand Up @@ -1502,17 +1540,22 @@ merge(Compressor.prototype, {

function find_stop(node, level) {
var parent = scanner.parent(level);
if (parent instanceof AST_Array) return node;
if (parent instanceof AST_Array) return value_def ? find_stop(parent, level + 1) : node;
if (parent instanceof AST_Assign) return node;
if (parent instanceof AST_Binary) return node;
if (parent instanceof AST_Binary) {
if (!value_def || parent.left !== node) return node;
return find_stop(parent, level + 1);
}
if (parent instanceof AST_Call) return node;
if (parent instanceof AST_Case) return node;
if (parent instanceof AST_Conditional) return node;
if (parent instanceof AST_Definitions) return find_stop_unused(parent, level + 1);
if (parent instanceof AST_Exit) return node;
if (parent instanceof AST_If) return node;
if (parent instanceof AST_IterationStatement) return node;
if (parent instanceof AST_ObjectKeyVal) return node;
if (parent instanceof AST_ObjectKeyVal) {
return value_def ? find_stop(scanner.parent(level + 1), level + 2) : node;
}
if (parent instanceof AST_PropAccess) return node;
if (parent instanceof AST_Sequence) {
return (parent.tail_node() === node ? find_stop : find_stop_unused)(parent, level + 1);
Expand Down Expand Up @@ -1557,8 +1600,11 @@ merge(Compressor.prototype, {
return null;
}

function mangleable_var(var_def) {
var value = var_def.value;
function mangleable_var(value) {
if (force_single) {
force_single = false;
return;
}
if (!(value instanceof AST_SymbolRef)) return;
var def = value.definition();
if (def.undeclared) return;
Expand All @@ -1573,11 +1619,21 @@ merge(Compressor.prototype, {
var referenced = def.references.length - def.replaced;
var declared = def.orig.length - def.eliminated;
if (declared > 1 && !(expr.name instanceof AST_SymbolFunarg)
|| (referenced > 1 ? mangleable_var(expr) : !compressor.exposed(def))) {
|| (referenced > 1 ? mangleable_var(expr.value) : !compressor.exposed(def))) {
return make_node(AST_SymbolRef, expr.name, expr.name);
}
} else if (expr instanceof AST_Assign) {
var lhs = expr.left;
if (expr.operator == "=" && lhs instanceof AST_SymbolRef) {
var def = lhs.definition();
if (def.references[0] === lhs) {
var referenced = def.references.length - def.replaced;
if (referenced > 1) mangleable_var(expr.right);
}
}
return lhs;
} else {
return expr[expr instanceof AST_Assign ? "left" : "expression"];
return expr.expression;
}
}

Expand Down Expand Up @@ -1689,20 +1745,15 @@ merge(Compressor.prototype, {
node.value = null;
return node;
}
var parent = this.parent();
if (!parent) return in_list ? MAP.skip : null;
if (parent instanceof AST_Sequence) return MAP.skip;
var value = expr;
do {
value = get_rvalue(value);
} while (value instanceof AST_Assign);
return value;
}, function(node) {
if (node instanceof AST_Sequence) switch (node.expressions.length) {
case 0: return null;
case 1: return node.expressions[0];
}
}));
return in_list ? MAP.skip : null;
}, patch_sequence));
}

function patch_sequence(node) {
if (node instanceof AST_Sequence) switch (node.expressions.length) {
case 0: return null;
case 1: return node.expressions[0];
}
}

function is_lhs_local(lhs) {
Expand Down

0 comments on commit 1b61a81

Please sign in to comment.