Chapter 4 — Generating Assembly Programs

Machine language is the set of binary-encoded instructions a processor can execute. Assembly language is the human-readable textual form of machine language. Using mnemonics, programmers can write machine instructions without memorizing encodings and can control hardware directly.

For this lab manual, you do not need to become an expert at handwriting large assembly programs. Before continuing with later processor labs, you should be able to:

• Understand the basics of the RISC-V ISA (especially the unprivileged RV32I subset): registers, common instruction categories, and naming.
• Read simple RISC-V assembly and recognize how common control-flow constructs (if, for, while) appear after compilation.

The table below lists RV32I general-purpose registers and their common ABI names.

Register	ABI name	Saved by	Notes
x0	zero	—	Always 0; writes are ignored
x1	ra	Caller	Return address
x2	sp	Callee	Stack pointer
x3	gp	—	Global pointer
x4	tp	—	Thread pointer
x5–x7	t0–t2	Caller	Temporaries
x8	s0/fp	Callee	Saved register / frame pointer
x9	s1	Callee	Saved register
x10–x11	a0–a1	Caller	Args / return values
x12–x17	a2–a7	Caller	Function arguments
x18–x27	s2–s11	Callee	Saved registers
x28–x31	t3–t6	Caller	Temporaries

Table 4.1: RV32I general-purpose registers and ABI names.

This chapter focuses on generating assembly programs using existing toolchains: turning familiar high-level code (e.g., C) into bare-metal RISC-V assembly (no standard library, no OS calls) for use in later labs.