MIPS Instructions Note: You can have this handout on both exams. Instruction Formats: Instruction formats: all 32 bits wide (one word): set less than unsigned: sltu instruction Identical as slt instruction, except: - funct = 43 dec - contents of R s and R t are considered as unsigned integers. The SPIM emulator implements instructions from the MIPS32 instruction set, as well as pseudo-instructions (which look like MIPS instructions, but which aren't provided on real hardware). Real MIPS instructions are marked with a . All other instructions are pseudo-instructions. Operators in expressions have the same meaning as their C counterparts. establishes a mapping from "instruction" to binary values which bit positions correspond to which parts of the instruction (operation, operands, etc.) MIPS Instruction Set (RISC) Instructions execute simple functions. Maintain regularity of format -each instruction is one word, contains opcode and arguments. Minimize memory accesses -whenever possible use registers as arguments. Three types of instructions: Register (R)-type -only registers as arguments. Instruction Set The words of a computer's language are called instructions and the MIPS instructions are encoded in binary, as 32-bit instruction words , called machine code . The layout of an instruction is called the instruction format. Only 3 different formats exist. MIPS Functions and Instruction Formats 1. Computer Science 61C Spring 2017 Friedland and Weaver The Contract: • Programs bound to specific instruction set • The "ABI": Application Binary Interface is a function of both the instruction set and the underlying operating system The MIPS32 architecture is based on a fixed-length, regularly encoded instruction set and uses a load/store data model. The architecture is streamlined to support optimized execution of high-level languages. Arithmetic and logic operations use a three-operand format, allowing compilers to optimize complex expressions formulation. The processor used a technique called pipelining to more efficiently process instructions. MIPS used 32 registers, each 32 bits wide (a bit pattern of this size is referred to as a word). Instruction Set The MIPS instruction set consists of about 111 total instructions, each represented in 32 bits. An example of a MIPS instruction is below: MIPS-I Assembly Language Instruction Set. Instruction Set (Integer instructions only) Arithmetic and Logical Instructions In all instructions below, src1, src2, and dest are general-purpose registers. imm is a 16-bit immediate value embedded within the instruction. EEL-4713C - Ann Gordon-Ross MIPS operations • See MIPS reference chart (green page of textbook) for full set of operations • Most common: addition and subtraction • MIPS assembly: add rd, rs, rt - register rd holds the sum of values currently in registers rs and rt EEL-4713C - Ann Gordon-Ross Operands • In MIPS, operands for arithmetic and logic operations •This doesn't have to be true in your new instruction set •This implies that in all modern computers, data is not intermingled with instructions in memory •Data and instructions may be intermingled in an assembly program so long as the assembler is able to separate all the instructions and all the data words • Instructions: a fixed set of built-in operations • Instructions and data are stored in memory − Allows general purpose computation! • Fetch-Execute Cycle while (!done) fetch instruction execute instructi