10000 Intern unscoped global field name strings by gzm0 · Pull Request #4910 · scala-js/scala-js · GitHub
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Intern unscoped global field name strings #4910

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Intern unscoped global field name strings #4910

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Intern unscoped global field name strings 
Memory profile analysis shows ~120k duplicates of the string "$n"
amounting to ~6MB waste (on the test suite).

Further digging revealed that this happens through the "$n"
call-helper (null check) via:
- SJSGen#genCallHelper
- VarGen#globalVar
- VarGen#globalVarIdent
- VarGen#genericIdent

A more invasive (but efficient) alternative would be to move the
prefix to the call sites. As a result, no runtime interning would have
to be performed as the strings would end up being part ot the static
constant pool.

Discovered while working on #4906.
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@gzm0
gzm0 committed Oct 8, 2023
commit 21d00d9317388e28b562e966906bde4e2a594972
2 changes: 1 addition & 1 deletion linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/VarGen.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -262,7 +262,7 @@ private[emitter] final class VarGen(jsGen: JSGen, nameGen: NameGen,
origName: OriginalName = NoOriginalName)(
implicit pos: Position): Ident = {
val name =
if (subField == "") "$" + field
if (subField == "") ("$" + field).intern()
else "$" + field + "_" + subField

Ident(avoidClashWithGlobalRef(name), origName)
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