Method from

winch/codegen/src/abi/mod.rs:310–365

Creates [`ABIResults`] from a slice of `WasmType`. This function maps the given return types to their ABI specific representation. It does so, by iterating over them and applying the given `map` closure. The map closure takes a [WasmValType], maps its ABI representation, according to the calling convention. In the case of results, one result is stored in registers and the rest at particular offset

(
        returns: &[WasmValType],
        call_conv: &CallingConvention,
        mut map: F,
    )

    /// results, one result is stored in registers and the rest at particular
    /// offsets in the stack.
    pub fn from<F>(
        returns: &[WasmValType],
        call_conv: &CallingConvention,
        mut map: F,
    ) -> Result<Self>
    where
        F: FnMut(&WasmValType, u32) -> Result<(ABIOperand, u32)>,
    {
        if returns.len() == 0 {
            return Ok(Self::default());
        }

        type FoldTuple = (SmallVec<[ABIOperand; 6]>, HashSet<Reg>, u32);
        type FoldTupleResult = Result<FoldTuple>;

        let fold_impl =
            |(mut operands, mut regs, stack_bytes): FoldTuple, arg| -> FoldTupleResult {
                let (operand, bytes) = map(arg, stack_bytes)?;
                if operand.is_reg() {
                    regs.insert(operand.unwrap_reg());
                }
                operands.push(operand);
                Ok((operands, regs, bytes))
            };

        // When dealing with multiple results, Winch's calling convention stores the
        // last return value in a register rather than the first one. In that
        // sense, Winch's return values in the ABI signature are "reversed" in
        // terms of storage. This technique is particularly helpful to ensure that
        // the following invariants are maintained:
        // * Spilled memory values always precede register values
        // * Spilled values are stored from oldest to newest, matching their
        //   respective locations on the machine stack.
        let (mut operands, regs, bytes) = if call_conv.is_default() {
            returns
                .iter()
                .rev()
                .try_fold((SmallVec::new(), HashSet::with_capacity(1), 0), fold_impl)?
        } else {
            returns
                .iter()
                .try_fold((SmallVec::new(), HashSet::with_capacity(1), 0), fold_impl)?
        };

        // Similar to above, we reverse the result of the operands calculation
        // to ensure that they match the declared order.
        if call_conv.is_default() {
            operands.reverse();
        }

        Ok(Self::new(ABIOperands {
            inner: operands,
            regs,
            bytes,
        }))
    }

    /// Create a new [`ABIResults`] from [`ABIOperands`].