[Minification] Hoist static methods with alias

[SukkaW]

Describe the feature

Given the following code:

const a = {};
Object.assign(a, {});
const b = {};
Object.assign(b, {});
Object.assign(b, a);

Currently both terser and swc can only minified the code into

const a={};Object.assign(a,{});const b={};Object.assign(b,{}),Object.assign(b,a);

Here is my proposal, a new compress option unsafe_hoist_static_method_alias. In the compress phase, swc counts and replaces static built-in object methods with aliases:

const __ObjectAssign = Object.assign;

const a = {};
__ObjectAssign(a, {});
const b = {};
__ObjectAssign(b, {});
__ObjectAssign(b, a);

In the mangle phase, swc can mangle __ObjectAssign into a shorter name:

const s=Object.assign,c={};s(c,{});const n={};s(n,{}),s(n,c);

Note that this optimization should only applied to built-in objects' known static methods (Object.assign, Reflect.apply, etc.). Also since it is possible for user code to override built-in objects' static methods, this option should be prefixed with unsafe and should not be enabled by default.

Babel plugin or link to the feature description

No response

Additional context

No response

[kdy1]

I like the idea, although I'm not sure if how many users are using unsafe_ options.

This operation should be done by precompress pass at https://github.com/swc-project/swc/blob/d437fd8283e689101e6e783040cab7f4f277a324/crates/swc_ecma_minifier/src/pass/precompress.rs

[SukkaW]

We can hoist built-in objects as well:

const mapA = new Map();
const mapB = new Map();
const mapC = new Map();
const mapD = new Map();

console.log(mapA, mapB, mapC, mapD);

Currently this can only be minified into:

const n=new Map;console.log(n,new Map,new Map,new Map);

But if we alias Map to a variable:

const __Map = Map;

const mapA = new __Map();
const mapB = new __Map();
const mapC = new __Map();
const mapD = new __Map();

console.log(mapA, mapB, mapC, mapD);

Now the minified version:

const n=Map,e=new n;console.log(e,new n,new n,new n);