PowerPoint PresentationReviewAssembly LanguageBook: Programming From the Ground UpInstruction Set ArchitecturesMIPS ArchitectureAssembly Variables: Registers (1/4)Assembly Variables: Registers (2/4)Assembly Variables: Registers (3/4)Assembly Variables: Registers (4/4)C, Java variables vs. registersComments in AssemblyAssembly InstructionsMIPS Addition and Subtraction (1/4)Addition and Subtraction of Integers (2/4)Addition and Subtraction of Integers (3/4)Addition and Subtraction of Integers (4/4)Register ZeroImmediatesSlide 20Peer Instruction“And in Conclusion…”AdministriviaCS61C L08 Introduction to MIPS Assembly Language : Arithmetic (1)Garcia, Spring 2008 © UCBLecturer SOE Dan Garciawww.cs.berkeley.edu/~ddgarciainst.eecs.berkeley.edu/~cs61c CS61C : Machine Structures Lecture 8 – Introduction to MIPSAssembly language : Arithmetic 2008-02-08$6 million theatre The Jeremy Kipnis $6Multimate home theatre presents amazing video (4,096 x 2,160) and audio (8.8 channel system, 16 18-inch subwoofers, 11,315 watts). Spare no expense, eh?crave.cnet.com/8301-1_105-9866428-1.htmlNi Hao to Yi Chen from CHINA!CS61C L08 Introduction to MIPS Assembly Language : Arithmetic (2)Garcia, Spring 2008 © UCBReview•Several techniques for managing heap w/ malloc/free: best-, first-, next-fit, slab,buddy•2 types of memory fragmentation: internal & external; all suffer from some kind of frag.•Each technique has strengths and weaknesses, none is definitively best•Automatic memory management relieves programmer from managing memory.•All require help from language and compiler•Reference Count: not for circular structures•Mark and Sweep: complicated and slow, works•Copying: move active objects back and forthCS61C L08 Introduction to MIPS Assembly Language : Arithmetic (3)Garcia, Spring 2008 © UCBAssembly Language•Basic job of a CPU: execute lots of instructions.•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, ...CS61C L08 Introduction to MIPS Assembly Language : Arithmetic (4)Garcia, Spring 2008 © UCBBook: Programming From the Ground Up“A new book was just released which isbased on a new concept - teachingcomputer science through assemblylanguage (Linux x86 assembly language, to be exact). This book teaches how themachine itself operates, rather than justthe language. I've found that the keydifference between mediocre and excellent programmers is whether or not they know assembly language. Those that do tend to understand computers themselves at a much deeper level. Although [almost!] unheard of today, this concept isn't really all that new -- there used to not be much choice in years past. Apple computers came with only BASIC and assembly language, and there were books available on assembly language for kids. This is why the old-timers are often viewed as 'wizards': they had to know assembly language programming.” -- slashdot.org comment, 2004-02-05CS61C L08 Introduction to MIPS Assembly Language : Arithmetic (5)Garcia, Spring 2008 © UCBInstruction Set Architectures•Early trend was to add more and more instructions to new CPUs to do elaborate operations•VAX architecture had an instruction to multiply polynomials!•RISC philosophy (Cocke IBM, Patterson, Hennessy, 1980s) – Reduced Instruction Set Computing•Keep the instruction set small and simple, makes it easier to build fast hardware.•Let software do complicated operations by composing simpler ones.CS61C L08 Introduction to MIPS Assembly Language : Arithmetic (6)Garcia, Spring 2008 © UCBMIPS Architecture•MIPS – semiconductor company that built one of the first commercial RISC architectures•We will study the MIPS architecture in some detail in this class (also used in upper division courses CS 152, 162, 164)•Why MIPS instead of Intel 80x86?•MIPS is simple, elegant. Don’t want to get bogged down in gritty details.•MIPS widely used in embedded apps, x86 little used in embedded, and more embedded computers than PCsCS61C L08 Introduction to MIPS Assembly Language : Arithmetic (7)Garcia, Spring 2008 © UCBAssembly Variables: Registers (1/4)•Unlike HLL like C or Java, assembly cannot use variables•Why not? Keep Hardware Simple•Assembly Operands are registers•limited number of special locations built directly into the hardware•operations can only be performed on these!•Benefit: Since registers are directly in hardware, they are very fast (faster than 1 billionth of a second)CS61C L08 Introduction to MIPS Assembly Language : Arithmetic (8)Garcia, Spring 2008 © UCBAssembly Variables: Registers (2/4)•Drawback: Since registers are in hardware, there are a predetermined number of them•Solution: MIPS code must be very carefully put together to efficiently use registers•32 registers in MIPS•Why 32? Smaller is faster•Each MIPS register is 32 bits wide•Groups of 32 bits called a word in MIPSCS61C L08 Introduction to MIPS Assembly Language : Arithmetic (9)Garcia, Spring 2008 © UCBAssembly Variables: Registers (3/4)•Registers are numbered from 0 to 31•Each register can be referred to by number or name•Number references:$0, $1, $2, … $30, $31CS61C L08 Introduction to MIPS Assembly Language : Arithmetic (10)Garcia, Spring 2008 © UCBAssembly Variables: Registers (4/4)•By convention, each register also has a name to make it easier to code•For now:$16 - $23 $s0 - $s7(correspond to C variables)$8 - $15 $t0 - $t7(correspond to temporary variables)Later will explain other 16 register names•In general, use names to make your code more readableCS61C L08 Introduction to MIPS Assembly Language : Arithmetic (11)Garcia, Spring 2008 © UCBC, Java variables vs. registers•In C (and most High Level Languages) variables declared first and given a type•Example: int fahr, celsius; char a, b, c, d, e;•Each variable can ONLY represent a value of the type it was declared as (cannot mix and match int and char variables).•In Assembly Language, the registers have no type; operation determines how register contents are treatedCS61C L08 Introduction to MIPS Assembly Language : Arithmetic (12)Garcia, Spring 2008 © UCBComments in Assembly•Another way to make your code more readable: comments!•Hash (#) is used for
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