## MLton 20241230+git20251029+dfsg-5

# Flatten

Flatten is an optimization pass for the SSA IntermediateLanguage, invoked from SSASimplify.

## Description

This pass flattens arguments to SSA constructors, blocks, and functions.

If a tuple is explicitly available at all uses of a function (resp. block), then:

- The formals and call sites are changed so that the components of the tuple are passed.

- The tuple is reconstructed at the beginning of the body of the function (resp. block).

Similarly, if a tuple is explicitly available at all uses of a constructor, then:

- The constructor argument datatype is changed to flatten the tuple type.

- The tuple is passed flat at each `ConApp`.

- The tuple is reconstructed at each `Case` transfer target.

## Implementation

- `flatten.fun`

## Details and Notes