Appendix A: MIPS Assembly Language

Instruction Format R-type I-type J-type

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

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), c+rx Virtual machine provides other modes.

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 )

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

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

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

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

Figure A.9.1

Example.data str:.asciiz “the answer= “.text li $v0,4 # print_str la $a0,str # addr of string to print syscall

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).