Is it possible to mark function as pure to optimize it out ignoring any side effects?

[GulgDev]

Hello! Currently, Binaryen is unable to optimize calls to malloc and other memory managment functions. Can I mark a function as pure to make Binaryen ignore any side effects of it? Thanks!

[kripken]

We do have an intrinsic for that, call.without.effects, that can mark a call (not a function, but you can mark all calls to a target) as having no effects. This is experimental and may change. Here is the test that shows its usage:

binaryen/test/lit/passes/vacuum-intrinsics.wast

Lines 35 to 40 in 85fc8bb

	(func $unused
	;; The result is unused, so we can remove the call.
	(drop
	(call $call.without.effects (ref.func $i))
	)
	)

More docs:

https://github.com/WebAssembly/binaryen?tab=readme-ov-file#intrinsics

[GulgDev]

Thank you! I don't know how I didn't see this, I've searched for this everywhere.

[kripken]

(about ref.func see BinaryenRefFunc)