[tlively]

When DAE2 removes unused values, replacing an expression (such as a drop of a concrete block containing an unreachable child) with its kept children can change the expression's type from none to unreachable. Track when a replacement in Optimizer becomes unreachable and run ReFinalize in parallel on affected functions at the end of DAE2::optimize() after global type rewriting.

[gemini-code-assist]

Code Review

This pull request introduces a refinalization step in the Dead Argument Elimination (DAE2) pass to handle cases where removing unused expression results introduces new unreachability, requiring enclosing expressions to be refinalized. It adds a refinalize flag to FunctionInfo and runs a custom Refinalizer pass after global type rewriting to ensure correct type propagation for instructions like call_ref and ref.func. Test cases have been added to verify this behavior. There are no review comments, so I have no additional feedback to provide.

[aheejin]

LGTM % comments

[aheejin]

We seem to do results analysis now?

[tlively]

Yes, since #8903. I'll update the comment.

[aheejin]

It would be nice to elaborate what "scratch type" here is and why it is necessary. (Grepping the codebase with "scratch type" doesn't yield anything.
(Gemini told me it was this

binaryen/src/passes/DeadArgumentElimination2.cpp

Lines 1085 to 1090 in f1f3a48

	// Replace the function's type with a new type using only the kept
	// parameters and result. This ensures that newly added locals get the
	// right indices. Preserve sharedness in case this becomes the permanent
	// new type (when GC is disabled, see below).
	Signature sig(Type(keptParams),
	funcInfo->resultUsage ? func->getResults() : Type::none);

But it would have been nice if could be read without Gemini's help when you don't have a detailed knowledge about the pass)

Also it would be nice if the comment describes what goes wrong if refinalizing doesn't happen at the end in this test.

[tlively]

Updated the comment with a pointer to the code that creates this temporary type. (Explaining all the rationale for that would be too much for the test, I think). Also added an explanation of what would go wrong if we didn't refinalize at the right time.