Meeting Summary: CS 315-02 Lecture/Lab (Fall 2025)¶

Quick Recap¶

The instructor (Greg) emphasized learning through hands-on problem solving, especially around function calls and register management.
The class reviewed stack allocation, saving/restoring registers, and the role of caller- and callee-saved registers in function calls.
Examples covered how the return address (RA) changes during calls, when and how to save registers, and how to write simple functions that don’t need stack frames.
The session introduced recursion, its role across languages, and how to translate recursive logic into assembly and iterative C.
Upcoming topics include more complex conditional logic in assembly and support for accessing Zoom recordings.

Instructor:
Share last fall’s midterm as a reference.
Provide practice problems by the end of the week.
Demonstrate a version of the “Add for F” program using S registers.
Explore using ChatGPT in study mode with Project 2 to support concept learning.
Students:
Complete the practice problems by next week.
Practice problem-solving skills to prepare for the exam.
Ensure understanding of assembly concepts used in the projects.
Follow RISC‑V calling conventions, especially around caller‑saved and callee‑saved registers.

The instructor emphasized that durable learning comes from struggle and hands-on practice rather than copying answers from AI tools.
Students were encouraged to invest time in understanding concepts deeply, ask for help when needed, and trust that projects are designed to prepare them for exams and real-world work.
The evolving role of developers in the age of AI was discussed, highlighting the value of expertise and problem-solving.

RA (return address) is treated as caller-saved: if the caller needs RA preserved across a call, it must save it.
The distinction between register classes was reviewed:
Caller-saved (volatile): typically argument registers (a0–a7), temporaries (t0–t6), and ra.
Callee-saved (non-volatile): s0–s11 (saved registers) and other non-volatile state. If a callee uses these, it must save/restore them.
Guidance:
Avoid redundant save/restore inside loops.
Simple leaf functions (no stack usage and no calls to other functions) do not require stack setup/teardown.

Function calls change the RA; saving RA and any needed registers is necessary to return correctly.
All addresses on the target architecture are 64-bit (8 bytes).
Stack frames must be aligned to a multiple of 16 bytes.
Example scenarios showed allocating 32 bytes to save multiple registers and maintain alignment.

The add4f function was demonstrated using:
Caller-saved registers.
S (saved) registers with proper callee-saved handling.
Students were advised to follow the original C logic closely when writing assembly.
Even if incorrect register choices “work,” they can reduce code quality and violate convention.

Recursion was discussed in the context of:
Traversing trees and graphs.
Functional programming languages where recursion replaces loops.
Two C-style patterns were compared:
Direct recursive returns.
Using intermediate variables to store return values, which often simplifies translation to assembly.
Single return points can be easier to debug, though multiple returns are common in practice.

A factorial example illustrated how to convert recursion to iteration:
Understand the recursive logic first.
Identify where values must persist across calls.
Use intermediate variables to hold return values.
Determine which registers to save, set up arguments, and preserve needed values after calls.
This example required only one additional stack slot beyond the usual frame.

Recursion was compared across Java and Python, then grounded in assembly translation.
The class examined building complex conditions in assembly using multiple branches to achieve high-level logic.
An exercise was assigned, with reminders about office hours and upcoming deadlines; students were encouraged to start early and ask questions via Campuswire.

A student requested an exam accommodation due to a family event and travel; the instructor is considering options.
For Zoom recordings, students should use the SSO login button to authenticate properly.