CS334: MIPS language _Mars simulator Lab 2_1

Part1:MIPS assembly language. Questions. Contents: introduction. Part1:MIPS assembly language. Questions. Ins.Ebtesam AL-Etowi

Assembly Language Instructions are the primitive operations that the CPU may execute. Different CPUs implement different sets of instructions. The set of instructions a particular CPU implements is an Instruction Set Architecture (ISA). Examples: Intel 80x86 (Pentium 4), IBM/Motorola PowerPC (Macintosh), MIPS, Intel IA64, ... Ins.Ebtesam AL-Etowi

MIPS Architecture MIPS – semiconductor company that built one of the first commercial RISC architectures MIPS is simple, elegant. Assembly Operands are registers Groups of 32 bits called a word in MIPS The Text segment shows you: Address -- where this instruction is stored in memory Code -- the machine code of the instruction Basic -- [not too helpful at this point] Source -- the original instruction you typed in Ins.Ebtesam AL-Etowi

List of Instructions Ins.Ebtesam AL-Etowi

Part 1: MIPS .text $t1 = 3 + 5 + 9 addi $t1, $zero, 3 Start the program with: .text This says that the following are program instructions (and not, e.g.,data). Let's do the following: $t1 = 3 + 5 + 9 First, let's put 3 in $t1: addi $t1, $zero, 3 Ins.Ebtesam AL-Etowi

Part 1: MIPS (cont…) addi $t1, $t1, 5 addi $t1, $t1, 9 This says to take what is stored in register $zero, add 3 to it, and put the result in register $t1. $zero ALWAYS contains 0, so this puts 0 + 3 into register $t1 Now we want to add 5 to our running sum: addi $t1, $t1, 5 And then we want to add 9: addi $t1, $t1, 9 Save and Assemble the program (run it). You will see that $t1 contains 0x00000011 The 0x just means that the number following it is in hex. Ins.Ebtesam AL-Etowi

Performing the program Pc : Special register keeping the address of next instruction . Read the code from memory by pc . $at : assembler temporary as handle for save value . Ins.Ebtesam AL-Etowi

Questions Answer: 17 program counter = 0x00400000 Question 1: What decimal number is 0x00000011? Answer: 17 Question 2: before the first instruction is executed (the program counter is the register labeled "pc") program counter = __________ program counter = 0x00400000 Ins.Ebtesam AL-Etowi

Cont..)) Questions program counter = 0x00400004 $t1 = 0x00000003 Question 3: after the first instruction is executed: program counter = $t1 = program counter = 0x00400004 $t1 = 0x00000003 Question 4: after the second instruction is executed: program counter = $t1 = ____________ program counter = 0x00400008 $t1 = 0x00000008 Ins.Ebtesam AL-Etowi

Cont..)) Questions program counter = 0x0040000C $t1 = 0x00000011 Question 5: after the third instruction is executed: program counter = ___________ $t1 = _____________ program counter = 0x0040000C $t1 = 0x00000011 Question 6: Complete this sentence: After each instruction, the PC is incremented so that it contains: 1) A bit which is a 0 or 1. 2) A byte which is 8 bits. 3) A word which is 4 bytes. Ins.Ebtesam AL-Etowi

Cont..)) Questions Hint : In a MIPS architecture, each byte has its own address (the byte is the "addressable unit").   Question 7: How big are instructions in MIPS? Number of bits = Number of bytes = Number of words = 32 4 1 Ins.Ebtesam AL-Etowi

conclusion This shows a good way to learn assembly language. Enter and assemble instructions; this will show you the machine code that is produced. Then, step through execution so you can see the effects of the individual instructions. Ins.Ebtesam AL-Etowi

exercise to perform the calculation: f = (g + h) - (i + j) g= 5 h= -20 Ins.Ebtesam AL-Etowi

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H.W for absent You are given the following two numbers in two’s complement representation. Perform the binary addition and subtraction. Did signed overflow occur? determined whether or not overflow occurred. 00101100 - 00101100 00101100 Ins.Ebtesam AL-Etowi