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enhance collapse_vars (#4885)
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@alexlamsl
alexlamsl committed May 1, 2021
1 parent 8bbfaac commit 16411dc
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Showing 3 changed files with 41 additions and 33 deletions.
69 changes: 38 additions & 31 deletions lib/compress.js
View file
Expand Up @@ -1902,6 +1902,7 @@ merge(Compressor.prototype, {
hit_stack = candidates.pop();
var hit_index = 0;
var candidate = hit_stack[hit_stack.length - 1];
var remaining;
var value_def = null;
var stop_after = null;
var stop_if_hit = null;
Expand Down Expand Up @@ -1944,25 +1945,22 @@ merge(Compressor.prototype, {
statements[i].transform(scanner);
}
if (value_def) {
var def = lhs.definition();
var referenced = def.references.length - def.replaced;
if (candidate instanceof AST_Assign) referenced--;
if (!replaced || referenced > replaced) {
if (!replaced || remaining > replaced) {
candidates.push(hit_stack);
force_single = true;
continue;
}
var def = lhs.definition();
abort = false;
hit_index = 0;
hit = funarg;
for (var i = stat_index; !abort && i < statements.length; i++) {
if (!statements[i].transform(multi_replacer)) statements.splice(i--, 1);
}
if (candidate !== hit_stack[hit_stack.length - 1]) {
replaced = false;
} else if (candidate instanceof AST_VarDef) {
replaced = !compressor.exposed(def) && def.references.length == def.replaced;
}
replaced = candidate instanceof AST_VarDef
&& candidate === hit_stack[hit_stack.length - 1]
&& def.references.length == def.replaced
&& !compressor.exposed(def);
value_def.last_ref = false;
value_def.single_use = false;
}
Expand Down Expand Up @@ -2252,7 +2250,7 @@ merge(Compressor.prototype, {
if (!arg) continue;
var candidate = make_node(AST_VarDef, sym, {
name: sym,
value: arg
value: arg,
});
candidate.name_index = i;
candidate.arg_index = value ? len + i : i;
Expand All @@ -2268,12 +2266,11 @@ merge(Compressor.prototype, {
extract_candidates(node, unused);
});
} else if (expr instanceof AST_Assign) {
if (!(expr.left instanceof AST_Destructured)) candidates.push(hit_stack.slice());
extract_candidates(expr.left);
var lhs = expr.left;
if (!(lhs instanceof AST_Destructured)) candidates.push(hit_stack.slice());
extract_candidates(lhs);
extract_candidates(expr.right);
if (expr.left instanceof AST_SymbolRef) {
assignments[expr.left.name] = (assignments[expr.left.name] || 0) + 1;
}
if (lhs instanceof AST_SymbolRef) assignments[lhs.name] = (assignments[lhs.name] || 0) + 1;
} else if (expr instanceof AST_Await) {
extract_candidates(expr.expression, unused);
} else if (expr instanceof AST_Binary) {
Expand Down Expand Up @@ -2555,6 +2552,7 @@ merge(Compressor.prototype, {
force_single = false;
return;
}
if (remaining < 1) return;
var value = rhs instanceof AST_Assign && rhs.operator == "=" ? rhs.left : rhs;
if (!(value instanceof AST_SymbolRef)) return;
var def = value.definition();
Expand All @@ -2577,32 +2575,41 @@ merge(Compressor.prototype, {

function get_lhs(expr) {
if (expr instanceof AST_Assign) {
var def, lhs = expr.left;
if (expr.operator == "="
&& lhs instanceof AST_SymbolRef
&& (def = lhs.definition()).references[0] === lhs
&& !(scope.uses_arguments && is_funarg(def))
&& !compressor.exposed(def)) {
var referenced = def.references.length - def.replaced;
if (referenced > 1) mangleable_var(expr.right);
}
var lhs = expr.left;
if (expr.operator != "=") return lhs;
if (!(lhs instanceof AST_SymbolRef)) return lhs;
var def = lhs.definition();
if (scope.uses_arguments && is_funarg(def)) return lhs;
if (compressor.exposed(def)) return lhs;
remaining = def.references.length - def.replaced - (assignments[def.name] || 0);
if (def.fixed && lhs.fixed) remaining = Math.min(remaining, def.references.filter(function(ref) {
return ref.fixed === lhs.fixed;
}).length - 1);
mangleable_var(expr.right);
return lhs;
}
if (expr instanceof AST_Binary) return expr.right.left;
if (expr instanceof AST_Unary) return expr.expression;
if (expr instanceof AST_VarDef) {
var def = expr.name.definition();
var lhs = expr.name;
var def = lhs.definition();
if (def.const_redefs) return;
if (!member(expr.name, def.orig)) return;
if (!member(lhs, def.orig)) return;
if (scope.uses_arguments && is_funarg(def)) return;
var declared = def.orig.length - def.eliminated - (declare_only[def.name] || 0);
var referenced = def.references.length - def.replaced - (assignments[def.name] || 0);
if (declared > 1 && !(expr.name instanceof AST_SymbolFunarg)) {
remaining = def.references.length - def.replaced - (assignments[def.name] || 0);
if (def.fixed) remaining = Math.min(remaining, def.references.filter(function(ref) {
if (!ref.fixed) return true;
if (!ref.fixed.assigns) return true;
var assign = ref.fixed.assigns[0];
return assign === lhs || get_rvalue(assign) === expr.value;
}).length);
if (declared > 1 && !(lhs instanceof AST_SymbolFunarg)) {
mangleable_var(expr.value);
return make_node(AST_SymbolRef, expr.name, expr.name);
return make_node(AST_SymbolRef, lhs, lhs);
}
if (mangleable_var(expr.value) || referenced == 1 && !compressor.exposed(def)) {
return make_node(AST_SymbolRef, expr.name, expr.name);
if (mangleable_var(expr.value) || remaining == 1 && !compressor.exposed(def)) {
return make_node(AST_SymbolRef, lhs, lhs);
}
return;
}
Expand Down
2 changes: 1 addition & 1 deletion test/compress/collapse_vars.js
View file
Expand Up @@ -4724,7 +4724,7 @@ cascade_statement: {
}
function f3(a, b) {
for (; a < b; a++)
if ((c = a) && b)
if (c = a, a && b)
var c = c = b(a);
}
}
Expand Down
3 changes: 2 additions & 1 deletion test/compress/hoist_vars.js
View file
Expand Up @@ -232,8 +232,9 @@ issue_4736: {
expect: {
(function() {
(function() {
var b = 1 << 30;
0,
console.log(1073741824);
console.log(b);
})();
})();
}
Expand Down

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