CMPT 295

• Unit - Machine-Level Programming
• Lecture 11 – Assembly language basics: Practice and DEMO -> leaq and arithmetic & logical instructions and memory addressing modes

Why did the programmer quit their job?

A never got arrays!

Summary

• leaq - load effective address instruction
• Using data as operand to an instruction:
  • Immediate (constant integral value)
  • Register (16 registers)
  • Memory (various memory addressing modes)
    • General Syntax: $\text{Imm}(r_{b}, r_{i}, s)$
• Arithmetic & logical operations
  • Arithmetic instructions: add*, sub*, imul* inc*, dec*, neg*, not*
  • Logical instructions: and*, or*, xor*
  • Shift instructions: sal*, sar*, shr*

Today’s Menu

• Introduction
  • C program -> assembly code -> machine level code
• Assembly language basics: data, move operation
  • (selected) Memory addressing modes
• (selected) Operation leaq and Arithmetic & logical operations (Annotation: practice and DEMO!)
• Conditional Statement – Condition Code + cmov*
• Loops
• Function call – Stack
• Array
• Buffer Overflow
• Floating-point operations

Demo

1. gcc uses leaq for addition -> sum_store.c
2. Writing our own assembly code (arith.s) using arithmetic instructions of x86-64 assembly language
3. makefile
   • when we compile our own *.s files with *.c files
   • when we compile only *.c files
4. How would gcc compile our arith.c into arith.s?

Summary

• Demo
  • Observation: C compiler will figure out different instruction combinations to carry out the computations in our C code

Next lecture

• Introduction
  • C program -> assembly code -> machine level code
• Assembly language basics: data, move operation
  • Memory addressing modes
• Operation leaq and Arithmetic & logical operations
• Conditional Statement – Condition Code + cmov*
• Loops
• Function call – Stack
• Array
• Buffer Overflow
• Floating-point operations