Investigate why `wasm-merge` + `wasm-opt` output is larger than the corresponding monolithic module processed with `wasm-opt`

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Quiet
Tech stack
kotlin, wasm
Domain
compilers, performance

Research direction

Start by reproducing the reported size comparison with wasm-merge, wasm-split, and wasm-opt using the Compose Multiplatform inputs described in KT-86859. Compare the optimized monolithic and merged binaries to identify the causes of the size difference; done means documenting the causes and proposing improvements for Binaryen or Kotlin.

Written by the indexing model from the issue text.

Description

Recently, we experimented with applying wasm-merge and wasm-split to a Compose Multiplatform application using different Kotlin compilation modes as input. More detailed results are available here.

The results most relevant to this issue are:

  • Original Opt × Monolith: 6,159,539 bytes
  • Merged Opt × Closed World: 6,589,864 bytes

As shown above, the second binary is larger. It would be useful to investigate the reasons for this difference and suggest possible improvements on both on Binaryen and Kotlin sides.

Dominant language
WebAssembly
Stars
8.6k
Forks
885
Avg merge
1d 20h
Merged PRs (30d)
64

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