[wasm-split] Not splitting correctly after wasm-opt

[biggs0125]

I'm trying to use wasm-split after having run wasm-opt on a module. The tool runs to completion and creates the modules as requested. However, when I try to load the modules I get an error:
Uncaught RuntimeError: null function or function signature mismatch

This comes from a call_indirect instruction:
call_indirect (param (ref $type337)) (result (ref $type144)) $.H

Pausing at that instruction and checking the $.H table, I see that table is empty. I believe this is a table generated by wasm-split.

If I do the same splits but without running wasm-opt on my module, everything loads as expected.

[tlively]

Can you provide a reproducer so we can investigate further?

[biggs0125]

The reproduction I have uses internal code so I don't think I can share it here. I've tried making a smaller reproduction and haven't been able to yet. I'll follow up to see if I can share through a different channel.

[aheejin]

I was able to experiment with the internal code reproducer. The reason turned out to be the loading order and duplicate-function-elimination pass.

@biggs0125's workflow is, start with 300 modules, wasm-merge them into a monolithic module, optimize it with wasm-opt, and split them back into 300 modules via a manifest file. He doesn't use placeholders and the module loading order is managed in a custom way.

A function in module140 calls another function in the same module in the original split files. But after running duplicate-function-elimination pass, the callee gets removed replaced with another function with the same contents in module1. So this becomes a call_indirect. So module1 has to be loaded before module1, but apparently that was not the case for his workflow.

As a temporary workaround, you can use --skip-pass=duplicate-function-elimination in the command line to skip running the pass. Will close this issue.