Function compact_stack_frame

src/lower2/stackmaps.rs:317–387

(
    previous_locals: &[VerificationType],
    locals: &[VerificationType],
    stack: Vec<VerificationType>,
    instruction_delta: u16,
    byte_delta: u16,
)

            stack,
        ));
        previous_locals = locals;
        previous_instruction_offset = Some(target);
    }

    if frames.is_empty() {
        Ok(Vec::new())
    } else {
        Ok(vec![Attribute::StackMapTable { name_index, frames }])
    }
}

fn compact_stack_frame(
    offset_delta: u16,
    previous_locals: &[VerificationType],
    locals: &[VerificationType],
    stack: Vec<VerificationType>,
) -> StackFrame {
    if locals == previous_locals {
        return match stack.len() {
            0 => StackFrame::SameFrameExtended {
                frame_type: 251,
                offset_delta,
            },
            1 => StackFrame::SameLocals1StackItemFrameExtended {
                frame_type: 247,
                offset_delta,
                stack,
            },
            _ => StackFrame::FullFrame {
                frame_type: 255,
                offset_delta,
                locals: locals.to_vec(),
                stack,
            },
        };
    }

    if stack.is_empty() && locals.starts_with(previous_locals) {
        let appended = &locals[previous_locals.len()..];
        if (1..=3).contains(&appended.len()) {
            return StackFrame::AppendFrame {
                frame_type: 251 + appended.len() as u8,
                offset_delta,
                locals: appended.to_vec(),
            };
        }
    }
    if stack.is_empty() && previous_locals.starts_with(locals) {
        let removed = previous_locals.len() - locals.len();
        if (1..=3).contains(&removed) {
            return StackFrame::ChopFrame {
                frame_type: 251 - removed as u8,
                offset_delta,
            };
        }
    }

    StackFrame::FullFrame {