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drop unused: toplevel, assign-only #1450

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10 changes: 9 additions & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -361,7 +361,15 @@ to set `true`; it's effectively a shortcut for `foo=true`).
- `loops` -- optimizations for `do`, `while` and `for` loops when we can
statically determine the condition

- `unused` -- drop unreferenced functions and variables
- `unused` -- drop unreferenced functions and variables (simple direct variable
assignments do not count as references unless set to `"keep_assign"`)

- `toplevel` -- drop unreferenced functions (`"funcs"`) and/or variables (`"vars"`)
in the toplevel scope (`false` by default, `true` to drop both unreferenced
functions and variables)

- `top_retain` -- prevent specific toplevel functions and variables from `unused`
removal (can be array, comma-separated, RegExp or function. Implies `toplevel`)

- `hoist_funs` -- hoist function declarations

Expand Down
72 changes: 67 additions & 5 deletions lib/compress.js
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,8 @@ function Compressor(options, false_by_default) {
booleans : !false_by_default,
loops : !false_by_default,
unused : !false_by_default,
toplevel : !!options["top_retain"],
top_retain : null,
hoist_funs : !false_by_default,
keep_fargs : true,
keep_fnames : false,
Expand All @@ -80,6 +82,21 @@ function Compressor(options, false_by_default) {
global_defs : {},
passes : 1,
}, true);
var top_retain = this.options["top_retain"];
if (top_retain instanceof RegExp) {
this.top_retain = function(def) {
return top_retain.test(def.name);
};
} else if (typeof top_retain === "function") {
this.top_retain = top_retain;
} else if (top_retain) {
if (typeof top_retain === "string") {
top_retain = top_retain.split(/,/);
}
this.top_retain = function(def) {
return top_retain.indexOf(def.name) >= 0;
};
}
var sequences = this.options["sequences"];
this.sequences_limit = sequences == 1 ? 200 : sequences | 0;
this.warnings_produced = {};
Expand Down Expand Up @@ -1407,25 +1424,53 @@ merge(Compressor.prototype, {
AST_Scope.DEFMETHOD("drop_unused", function(compressor){
var self = this;
if (compressor.has_directive("use asm")) return self;
var toplevel = compressor.option("toplevel");
if (compressor.option("unused")
&& !(self instanceof AST_Toplevel)
&& (!(self instanceof AST_Toplevel) || toplevel)
&& !self.uses_eval
&& !self.uses_with
) {
&& !self.uses_with) {
var assign_as_unused = !/keep_assign/.test(compressor.option("unused"));
var drop_funcs = /funcs/.test(toplevel);
var drop_vars = /vars/.test(toplevel);
if (!(self instanceof AST_Toplevel) || toplevel == true) {
drop_funcs = drop_vars = true;
}
var in_use = [];
var in_use_ids = {}; // avoid expensive linear scans of in_use
if (self instanceof AST_Toplevel && compressor.top_retain) {
self.variables.each(function(def) {
if (compressor.top_retain(def) && !(def.id in in_use_ids)) {
in_use_ids[def.id] = true;
in_use.push(def);
}
});
}
var initializations = new Dictionary();
// pass 1: find out which symbols are directly used in
// this scope (not in nested scopes).
var scope = this;
var tw = new TreeWalker(function(node, descend){
if (node !== self) {
if (node instanceof AST_Defun) {
if (!drop_funcs && scope === self) {
var node_def = node.name.definition();
if (!(node_def.id in in_use_ids)) {
in_use_ids[node_def.id] = true;
in_use.push(node_def);
}
}
initializations.add(node.name.name, node);
return true; // don't go in nested scopes
}
if (node instanceof AST_Definitions && scope === self) {
node.definitions.forEach(function(def){
if (!drop_vars) {
var node_def = def.name.definition();
if (!(node_def.id in in_use_ids)) {
in_use_ids[node_def.id] = true;
in_use.push(node_def);
}
}
if (def.value) {
initializations.add(def.name.name, def.value);
if (def.value.has_side_effects(compressor)) {
Expand All @@ -1435,6 +1480,14 @@ merge(Compressor.prototype, {
});
return true;
}
if (assign_as_unused
&& node instanceof AST_Assign
&& node.operator == "="
&& node.left instanceof AST_SymbolRef
&& scope === self) {
node.right.walk(tw);
return true;
}
if (node instanceof AST_SymbolRef) {
var node_def = node.definition();
if (!(node_def.id in in_use_ids)) {
Expand Down Expand Up @@ -1494,7 +1547,7 @@ merge(Compressor.prototype, {
}
}
}
if (node instanceof AST_Defun && node !== self) {
if (drop_funcs && node instanceof AST_Defun && node !== self) {
if (!(node.name.definition().id in in_use_ids)) {
compressor.warn("Dropping unused function {name} [{file}:{line},{col}]", {
name : node.name.name,
Expand All @@ -1506,7 +1559,7 @@ merge(Compressor.prototype, {
}
return node;
}
if (node instanceof AST_Definitions && !(tt.parent() instanceof AST_ForIn)) {
if (drop_vars && node instanceof AST_Definitions && !(tt.parent() instanceof AST_ForIn)) {
var def = node.definitions.filter(function(def){
if (def.name.definition().id in in_use_ids) return true;
var w = {
Expand Down Expand Up @@ -1569,6 +1622,15 @@ merge(Compressor.prototype, {
}
return node;
}
if (drop_vars && assign_as_unused
&& node instanceof AST_Assign
&& node.operator == "="
&& node.left instanceof AST_SymbolRef) {
var def = node.left.definition();
if (!(def.id in in_use_ids) && self.variables.get(def.name) === def) {
return node.right;
}
}
if (node instanceof AST_For) {
descend(node, this);

Expand Down
114 changes: 110 additions & 4 deletions test/compress/collapse_vars.js
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Original file line number Diff line number Diff line change
Expand Up @@ -338,8 +338,9 @@ collapse_vars_while: {
collapse_vars_do_while: {
options = {
collapse_vars:true, sequences:true, properties:true, dead_code:true, conditionals:true,
comparisons:true, evaluate:true, booleans:false, loops:false, unused:true, hoist_funs:true,
keep_fargs:true, if_return:true, join_vars:true, cascade:true, side_effects:true
comparisons:true, evaluate:true, booleans:false, loops:false, unused:"keep_assign",
hoist_funs:true, keep_fargs:true, if_return:true, join_vars:true, cascade:true,
side_effects:true
}
input: {
function f1(y) {
Expand Down Expand Up @@ -409,6 +410,79 @@ collapse_vars_do_while: {
}
}

collapse_vars_do_while_drop_assign: {
options = {
collapse_vars:true, sequences:true, properties:true, dead_code:true, conditionals:true,
comparisons:true, evaluate:true, booleans:false, loops:false, unused:true, hoist_funs:true,
keep_fargs:true, if_return:true, join_vars:true, cascade:true, side_effects:true
}
input: {
function f1(y) {
// The constant do-while condition `c` will be replaced.
var c = 9;
do { } while (c === 77);
}
function f2(y) {
// The non-constant do-while condition `c` will not be replaced.
var c = 5 - y;
do { } while (c);
}
function f3(y) {
// The constant `x` will be replaced in the do loop body.
function fn(n) { console.log(n); }
var a = 2, x = 7;
do {
fn(a = x);
break;
} while (y);
}
function f4(y) {
// The non-constant `a` will not be replaced in the do loop body.
var a = y / 4;
do {
return a;
} while (y);
}
function f5(y) {
function p(x) { console.log(x); }
do {
// The non-constant `a` will be replaced in p(a)
// because it is declared in same block.
var a = y - 3;
p(a);
} while (--y);
}
}
expect: {
function f1(y) {
do ; while (false);
}
function f2(y) {
var c = 5 - y;
do ; while (c);
}
function f3(y) {
function fn(n) { console.log(n); }
do {
fn(7);

@kzc kzc Jan 29, 2017

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Can you please set unused: 2 in the collapse_vars tests with different results?

break;
} while (y);
}
function f4(y) {
var a = y / 4;
do
return a;
while (y);
}
function f5(y) {
function p(x) { console.log(x); }
do {
p(y - 3);
} while (--y);
}
}
}

collapse_vars_seq: {
options = {
collapse_vars:true, sequences:true, properties:true, dead_code:true, conditionals:true,
Expand Down Expand Up @@ -567,8 +641,9 @@ collapse_vars_assignment: {
collapse_vars_lvalues: {
options = {
collapse_vars:true, sequences:true, properties:true, dead_code:true, conditionals:true,
comparisons:true, evaluate:true, booleans:true, loops:true, unused:true, hoist_funs:true,
keep_fargs:true, if_return:true, join_vars:true, cascade:true, side_effects:true
comparisons:true, evaluate:true, booleans:true, loops:true, unused:"keep_assign",
hoist_funs:true, keep_fargs:true, if_return:true, join_vars:true, cascade:true,
side_effects:true
}
input: {
function f0(x) { var i = ++x; return x += i; }
Expand All @@ -593,7 +668,38 @@ collapse_vars_lvalues: {
function f7(x) { var w = e1(), v = e2(), c = v - x; return (w = x) - c; }
function f8(x) { var w = e1(), v = e2(); return (w = x) - (v - x); }
function f9(x) { var w = e1(); return e2() - x - (w = x); }
}
}

collapse_vars_lvalues_drop_assign: {
options = {
collapse_vars:true, sequences:true, properties:true, dead_code:true, conditionals:true,
comparisons:true, evaluate:true, booleans:true, loops:true, unused:true, hoist_funs:true,
keep_fargs:true, if_return:true, join_vars:true, cascade:true, side_effects:true
}
input: {
function f0(x) { var i = ++x; return x += i; }
function f1(x) { var a = (x -= 3); return x += a; }
function f2(x) { var z = x, a = ++z; return z += a; }
function f3(x) { var a = (x -= 3), b = x + a; return b; }
function f4(x) { var a = (x -= 3); return x + a; }
function f5(x) { var w = e1(), v = e2(), c = v = --x, b = w = x; return b - c; }
function f6(x) { var w = e1(), v = e2(), c = v = --x, b = w = x; return c - b; }
function f7(x) { var w = e1(), v = e2(), c = v - x, b = w = x; return b - c; }
function f8(x) { var w = e1(), v = e2(), b = w = x, c = v - x; return b - c; }
function f9(x) { var w = e1(), v = e2(), b = w = x, c = v - x; return c - b; }
}
expect: {
function f0(x) { var i = ++x; return x += i; }
function f1(x) { var a = (x -= 3); return x += a; }
function f2(x) { var z = x, a = ++z; return z += a; }
function f3(x) { var a = (x -= 3); return x + a; }
function f4(x) { var a = (x -= 3); return x + a; }
function f5(x) { var v = (e1(), e2()), c = v = --x; return x - c; }
function f6(x) { e1(), e2(); return --x - x; }
function f7(x) { var v = (e1(), e2()), c = v - x; return x - c; }
function f8(x) { var v = (e1(), e2()); return x - (v - x); }
function f9(x) { e1(); return e2() - x - x; }
}
}

Expand Down
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