Keep long bigint literals in hexadecimal format

[KimlikDAO-bot]

Long bigint literals written in hexadecimal format (such as 0x123456789ABDEFn) should be kept as is. Currently GCC expands them to decimal bigint literals, which increases the compiled size significantly (up to ~20%).

Example:

const P = 0x2fadbe2852044d028597455bc2abbd1bc873af205dfabb8a304600f3e09eeba8n;
console.log(P);

is transformed to

console.log(21565680844461314807147611702860246336805372493508489110556896454939225549736n)

Many crypto libraries (hashing, verifiable computation, etc) include long list of large constants. Keeping such constants in hexadecimal form makes a big difference.

Writing the literals as BigInt("0xabc") is a workaround but is not ideal due to increased compiled size and runtime cost.

This incurs up to 20% blow up in compiled code size.

[rishipal]

Repro - https://closure-compiler.appspot.com/home#code%3D%252F%252F%2520%253D%253DClosureCompiler%253D%253D%250A%252F%252F%2520%2540compilation_level%2520ADVANCED_OPTIMIZATIONS%250A%252F%252F%2520%2540output_file_name%2520default.js%250A%252F%252F%2520%253D%253D%252FClosureCompiler%253D%253D%250A%250A%252F%252F%2520ADD%2520YOUR%2520CODE%2520HERE%250Aconst%2520P%2520%253D%25200x2fadbe2852044d028597455bc2abbd1bc873af205dfabb8a304600f3e09eeba8n%253B%250Aconsole.log(P)%253B%250A%250A

[KimlikDAO-bot]

Actually, in the advanced more, both numbers and bigints can be emitted in hexadecimal if it makes the output shorter (literals larger than a certain threshold which can be calculated)

If true is transformed to !0, this optimization can also be considered, which may be equally effective.

[rishipal]

This is a fair optimization request. We may not be able to prioritize this but we'd be happy to receive a PR of this change.

[KimlikDAO-bot]

Could you point me to the file where literals are emitted?

[brad4d]

I think you'd modify the code approximately here.

closure-compiler/src/com/google/javascript/jscomp/CodeGenerator.java

Line 421 in 15c5a2d

cc.add(node.getBigInt() + "n");

[KimlikDAO-bot]

@brad4d Thank you. Where would the tests for this go?

[lauraharker]

(Responding since Bradford is out) tests should go in https://github.com/google/closure-compiler/blob/master/test/com/google/javascript/jscomp/parsing/ParserTest.java. (correction - https://github.com/google/closure-compiler/blob/master/test/com/google/javascript/jscomp/CodePrinterTest.java) Thanks for the PR!

[lauraharker]

(Correction to my previous comment - I should have said https://github.com/google/closure-compiler/blob/master/test/com/google/javascript/jscomp/CodePrinterTest.java, sorry)

[KimlikDAO-bot]

Thank you. Added some tests. Let me know if there other testing surfaces