Method ensure_stack_state

winch/codegen/src/codegen/control.rs:409–430

This function ensures that the state of the -- machine and value -- stack is the right one when reaching a control frame branch in which reachability is restored or when reaching the end of a function in an unreachable state. This function is intended to be called when handling an unreachable else or end. This function will truncate the value stack to the base length of the control frame and wil

(
        &mut self,
        masm: &mut M,
        context: &mut CodeGenContext<Emission>,
    )

    // NB: This method is assumed to be called *before* pushing any block
    // results to the value stack, so that any excess values are cleaned up.
    pub fn ensure_stack_state<M: MacroAssembler>(
        &mut self,
        masm: &mut M,
        context: &mut CodeGenContext<Emission>,
    ) -> Result<()> {
        let state = self.stack_state();
        // This assumes that at jump sites, the machine stack pointer will be
        // adjusted to match the expectations of the target branch (e.g.
        // `target_offset`); after performing the jump, the MacroAssembler
        // implementation will soft-reset the stack pointer offset to its
        // original offset, ensure that other parts of the program have access
        // to the right offset, this is especially important in conditional
        // branches.
        // When restoring reachability we ensure that the MacroAssembler offset
        // is set to match the expectations of the target branch, similar to how
        // the machine stack pointer was adjusted at jump sites.
        masm.reset_stack_pointer(state.target_offset)?;
        // We use the base length, because this function is assumed to be called
        // *before* pushing any results to the value stack. This way, any excess
        // values will be discarded.
        context.truncate_stack_to(state.base_len)
    }

    /// Return the type information of the block.
    pub fn sig(&self) -> &BlockSig {