1 Assembly Language
1.1 Assemebly language programming
- Each assembly language is tied to a particular ISA (fits just a human readable version of machine language)
- Learn to program in assembly language:
- best way to understand what compilers do to generate machine code
- best way to understand what the cpu hardware does
1.2 Roadmap to Future Classes
- cs164: compilers
- all the processes in going from source code to assembly
- cs162: O/S
- OS needs a small amout of assembly for doing things the high level language does not support
- cs152: computer architecture
- how to build the computer support the assembly
- cs161: security
2. Registers
2.1 assembly variables: registers
- unlike c or java, assembly does not have variables as you know
- it’s more primitive, instead what simple CPU can directly support
- assembly operands are objects that called registers
- Limited number of special places to hold values, built directly into the hardware
- arithmetic operations can only be performed on these in a RISC
- Benefit: fast to access
2.2 Number of RISC-V Register
- Drawback: registers are in hardware. To keep them really fast, their number is limited
- 32 registers in RISC-V, referred to by number x0-x31:
- each register is 32 bits wide
- groups of 32 bits(4 bytes) called a word
- x0 is special, always holds the value zero
2.3 Type
- registers have no type
- operations determines how register contents are interpreted
2.4 Memory alignment
- RISC-V does not require that integers be word aligned, but it is very bad if you don’t
- so in practice, RISC-V requires integers to be aligned on 4-byte boundaries
2.5 Data Transfer
