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Optimize object literals #974
Description
function o(x,y,z){ return {x,y,z} }Produces bytecode that sets the fields 1-by-1:
;; function o(x, y, z) { return {x, y, z} }
object
get_arg0 0 ; x
define_field x
get_arg1 1 ; y
define_field y
get_arg2 2 ; z
define_field z
return
It should be more efficient to use an "object template" that describes what properties the object has:
;; function o(x, y, z) { return {x, y, z} }
get_arg0 0 ; x
get_arg1 1 ; y
get_arg2 2 ; z
define_object <id> ; ( x y z -- o )
return
Benefits:
- reduces bytecode size
- object layout is known upfront, don't have to update JSShape repeatedly
Reacted by pastdue, Ammar Ahmed, Haruma and Lucas
Activity
bnoordhuis commentedon Sep 8, 2026
I experimented with this:
storing the object template out of band (like on
JSFunctionBytecode) makes it hard-to-impossible to (de)serialize function objects withJS_WriteObjectstoring it in the bytecode stream itself turns
define_objectinto a variable-length opcode (the only one we have) and dealing with that gets finicky. Not impossible but definitely finicky.There's no big difference in performance in my limited testing, although I don't pre-allocate the final
JSShapeyet. It definitely shrinks the bytecode for large object literals though, but how common are those?