Appendix A: MIPS Assembly Language

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Appendix A MIPS Assembly Language

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Instruction Format

• R-type
• I-type
• J-type

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SPIM and MIPS Architecture

• A MIPS processor consists of an integer
  processing unit (the CPU) and a collection of
  coprocessors.
• SPIM simulates two coprocessors
• coprocessor 0 handles exceptions, interrupts and
  the virtual memory system
• coprocessor 1 is the floating-point unit

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Addressing Modes

• MIPS is a load-store architecture
• Only load and store instructions access memory
• Computation instructions operates only on values
  in registers.
• The bare machine provides only one addressing
  mode c(rx), crx
• Virtual machine provides other modes.

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Data Alignment

• Most load and store instructions operate only on
  aligned data.
• A quantity is aligned if its memory address is a
  multiple of its size in bytes.
• Example a half-word object must be stored at a
  even address.
• MIPS provides some instructions to manipulate
  unaligned data. (lwl, lwr, swl, swr)

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Exceptions and Interrupts

• Will be discussed in Chapter 5.
• Deal with exceptions caused by errors during an
  instructions execution or external interrupts
  caused by I/O devices.
• SPIM only simulates part of MIPS exception
  facility.
• BadVAddr, Status, Cause, EPC

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Instruction Categories

• Arithmetic and Logical Instructions
• Constant-Manipulating Instructions
• Comparison Instructions
• Branch Instructions
• Jump Instructions
• Load Instructions
• Store Instructions
• Data Movement Instructions
• Floating-Point Instructions
• Exception and Interrupt Instructions

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Assembler Syntax

• .align n align the next datum on a 2n byte
  boundary.
• .ascii str , asciiz str
• .byte b1,,bn
• .data ltaddrgt
• .double d1,..,dn
• More on Pages A-47 and A-48

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System Calls

• System services (Figure A.9.1) print_int,
  print_float, print_double, print_string,
  read_int, read_float, read_double, read_string,
  srbk, exit

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Figure A.9.1
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Example

• .data
• str
• .asciiz the answer
• .text
• li v0,4 print_str
• la a0,str addr of string to print
• syscall

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Programming Assignment

• A.6 (due on 10/5/2005)
• A.7 (due on 10/5/2005)
• A.8 (due on 10/12/2005)
• Submit a hardcopy including the source code and
  the results of executing the program. Also send
  an electronic copy of the source code to your TA
  (g9304).