extend escape analysis on constant expression properties

[alexlamsl]

fixes #2508

[kzc]

Any idea about this one?

$ echo 'var o = { f: function(x){console.log(x)} }; console.log(o.f);' | bin/uglifyjs --toplevel -mc hoist_props,passes=9
var o={f:function(o){console.log(o)}};console.log(o.f);

[alexlamsl]

Any idea about this one?

console in console.log(x) breaking the is_constant_expression() assumption - I can put in the scope paramter to make it pass.

[kzc]

Okay, how about this?

$ echo 'var o = { f: function(x){console.log(x)} }; o.f(o.f);' | bin/uglifyjs --toplevel -mc hoist_props,passes=9
var f={f:function(f){console.log(f)}};f.f(f.f);

[alexlamsl]

Okay, how about this?

Exact same cause.

[alexlamsl]

#2509 (comment) & #2509 (comment) addressed in 9ddb75c

[kzc]

Good to see you like a challenge.

This PR should bake in the fuzzer for a little bit longer than normal I think.

[alexlamsl]

I'll get this to 100kFuzz, merge, then leave the whole master soaking as soon as the weekend starts.

[alexlamsl]

node test/benchmark.js gives identical results between master and #2509 for -mc and --toplevel -mc keep_fargs=0,unsafe,pure_getters,passes=10000

[kzc]

So no optimization opportunities in the benchmark code. This PR will be useful in scope hoisting bundler code.

[alexlamsl]

Do you have a representative example that is publicly available on the web?

We can expand test/benchmark.js a bit.

[kzc]

Not really, just Rollup test cases - and Rollup itself - it's self-hosted. Mind you uglify-es would have to be used because it's ES6. Once converted to ES5 it complicates the code preventing some optimizations. I'll keep a look out for such code to add to the benchmark.

[kzc]

Here's a Rollup source file with exports that ought to benefit once imported, scope hoisted and bundled now that arrows will work with hoist_props:

https://github.com/rollup/rollup/blob/v0.51.8/src/ast/values.js

Once this PR is merged into harmony I can test that hypothesis on the Rollup ES6 distro bundle.

[kzc]

Unfortunately upon examining the Rollup source code those particular exports are not used in a manner that will benefit from this optimization.