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CSE 331 Computer Organization and Design Fall 2007 Week 5

CSE 331 Computer Organization and Design Fall 2007 Week 5. Section 1: Mary Jane Irwin ( www.cse.psu.edu/~mji ) Section 2: Krishna Narayanan Course material on ANGEL: cms.psu.edu [ adapted from D. Patterson slides ]. Head’s Up. Last week’s material Supporting procedure calls and returns

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CSE 331 Computer Organization and Design Fall 2007 Week 5

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  1. CSE 331Computer Organization and DesignFall 2007Week 5 Section 1: Mary Jane Irwin (www.cse.psu.edu/~mji) Section 2: Krishna Narayanan Course material on ANGEL: cms.psu.edu [adapted from D. Patterson slides]

  2. Head’s Up • Last week’s material • Supporting procedure calls and returns • This week’s material • Addressing modes; Assemblers, linkers and loaders • Reading assignment - PH: 2.10, A.1-A.5 • Next week’s material (after Exam #1) • Introduction to VHDL and basic VHDL constructs • Reading assignment – Y, Chapters 1 through 3 • Reminders • HW 4 is due Thursday, Sept 27th (by 11:55pm) • Quiz 3 will close Sunday, Sept 30th (at 11:55pm) • Exam #1 is Tuesday, Oct 2, 6:30 to 7:45pm, 113 IST

  3. CDT Article on IBM’s BlueGene/P (9/25/07) • Calculations per second • Gigaflop 1 billion (1,000,000,000) • Teraflop 1 trillion (1,000,000,000,000) • Petaflop 1 quadrillion (1,000,000,000,000,000) • Exaflop 1 quintrillion (1,000,000,000,000,000,000)

  4. 1. Register addressing op rs rt rd funct Register word operand 2. Base addressing op rs rt offset Memory word or byte operand base register 3. Immediate addressing op rs rt operand MIPS Operand Addressing Modes Summary • Register addressing – operand is in a register • Base (displacement) addressing – operand’s address in memory is the sum of a register and a 16-bit constant contained within the instruction • Immediate addressing – operand is a 16-bit constant contained within the instruction

  5. 4. PC-relative addressing op rs rt offset Memory branch destination instruction Program Counter (PC) 5. Pseudo-direct addressing Memory op jump address || jump destination instruction Program Counter (PC) MIPS Instruction Addressing Modes Summary • PC-relative addressing – instruction’s address in memory is the sum of the PC and a 16-bit constant contained within the instruction • Pseudo-direct addressing – instruction’saddress in memory is the 26-bit constant contained within the instruction concatenated with the upper 4 bits of the PC

  6. Review: MIPS Instructions, so far

  7. Review: MIPS Instructions, so far

  8. Review: MIPS R3000 ISA • Instruction Categories • Load/Store • Computational • Jump and Branch • Floating Point • coprocessor • Memory Management • Special • 3 Instruction Formats: all 32 bits wide Registers R0 - R31 PC HI LO 6 bits 5 bits 5 bits 5 bits 5 bits 6 bits R format OP rs rd shamt funct rt I format rt 16 bit number OP rs J format 26 bit jump target OP

  9. RISC Design Principles Review • Simplicity favors regularity • fixed size instructions – 32-bits • small number of instruction formats • Smaller is faster • limited instruction set • limited number of registers in register file • limited number of addressing modes • Good design demands good compromises • three instruction formats • Make the common case fast • arithmetic operands from the register file (load-store machine) • allow instructions to contain immediate operands

  10. compiler assembly code The Code Translation Hierarchy C program

  11. Compiler Transforms the C program into an assembly language program • Advantages of high-level languages • many fewer lines of code • easier to understand and debug • … • Today’s optimizing compilers can produce assembly code nearly as good as an assembly language programming expert and often better for large programs • smaller code size, faster execution • To learn more take CSE 421

  12. compiler assembly code assembler object code The Code Translation Hierarchy C program

  13. Assembler Does a syntactic check of the code (i.e., did you type it in correctly) and then transforms the symbolic assembler code into object (machine) code • Advantages of assembler • much easier than remembering instr’s binary codes • can use labels for addresses – and let the assembler do the arithmetic • can use pseudo-instructions • e.g., “move $t0, $t1” exists only in assembler (would be implemented using “add $t0,$t1,$zero”) • When considering performance, you should count instructions executed, not code size

  14. The Two Main Tasks of the Assembler • Builds a symbol table which holds the symbolic names (labels) and their corresponding addresses • A label is local if it is used only within the file where its defined. Labels are local by default. • A label is external (global) if it refers to code or data in another file or if it is referenced from another file. Global labels must be explicitly declared global (e.g., .globl main) • Translates each assembly language statement into object (machine) code by “assembling” the numeric equivalents of the opcodes, register specifiers, shift amounts, and jump/branch targets/offsets

  15. MIPS (spim) Memory Allocation Memory f f f f f f f c Mem Map I/O Kernel Code & Data $sp 7f f f f f fc Stack 230 words Dynamic data $gp 1000 8000 Static data 1000 0000 Text Segment PC 0040 0000 Reserved 0000 0000

  16. Other Tasks of the Assembler • Converts pseudo-instr’s to legal assembly code • register $at is reserved for the assembler to do this • Converts branches to far away locations into a branch followed by a jump • Converts instructions with large immediates into a lui followed by an ori • Converts numbers specified in decimal and hexidecimal into their binary equivalents and characters into their ASCII equivalents • Deals with data layout directives (e.g., .asciiz) • Expands macros (frequently used sequences of instructions)

  17. Typical Object File Pieces • Object file header: size and position of the following pieces of the file • Text (code) segment (.text) : assembled object (machine) code • Data segment (.data) : data accompanying the code • static data - allocated throughout the program • dynamic data - grows and shrinks as needed • Relocation information: identifies instructions (data) that use (are located at) absolute addresses – not relative to a register (including the PC) • on MIPS only j, jal, and some loads and stores (e.g., lw $t1, 100($zero) ) use absolute addresses • Symbol table: global labels with their addresses (if defined in this code segment) or without (if defined external to this code segment) • Debugging information

  18. An Example .data .align 0 str: .asciiz "The answer is " cr: .asciiz "\n" .text .align 2 .globl main .globl printf main: ori $2, $0, 5 syscall move $8, $2 loop: beq $8, $9, done blt $8, $9, brnc sub $8, $8, $9 j loop brnc: sub $9, $9, $8 j loop done: jal printf

  19. compiler assembly code assembler object code library routines linker executable The Code Translation Hierarchy C program main text segment printf text segment machine code

  20. Linker Takes all of the independently assembled code segments and “stitches” (links) them together • Faster to recompile and reassemble a patched segment, than it is to recompile and reassemble the entire program • Decides on memory allocation pattern for the code and data segments of each module • Remember, modules were assembled in isolation so each has assumed its code’s starting location is 0x0040 0000 and its static data starting location is 0x1000 0000 • Relocates absolute addresses to reflect the new starting location of the code segment and its data segment • Uses the symbol tables information to resolve all remaining undefined labels • branches, jumps, and data addresses to/in external modules • Linker produces an executable file

  21. Executable file main: . . . jal printf printf: . . . Linker Code Schematic Object file main: . . . jal ???? call, printf Linker C library printf: . . . Relocation info

  22. Linking Two Object Files Executable File 1 + File 2 Hdr Txtseg Dseg Reloc Hdr Txtseg Dseg Reloc Smtbl Dbg Hdr Txtseg Dseg Reloc Smtbl Dbg

  23. compiler assembly code assembler object code library routines linker executable loader memory The Code Translation Hierarchy C program machine code

  24. Loader • Loads (copies) the executable code now stored on disk into memory at the starting address specified by the operating system • Copies the parameters (if any) to the main routine onto the stack • Initializes the machine registers and sets the stack pointer to the first free location (0x7fff fffc) • Jumps to a start-up routine (at PC addr 0x0040 0000 on xspim) that copies the parameters into the argument registers and then calls the main routine of the program with a jal main • To learn more take CSE 311 and CSE 411

  25. Dynamically Linked Libraries • Statically linking libraries mean that the library becomes part of the executable code • It loads the whole library even if only a small part is used (e.g., standard C library is 2.5 MB) • What if a new version of the library is released ? • (Lazy) dynamically linked libraries (DLL) – library routines are not linked and loaded until a routine is called during execution • The first time the library routine called, a dynamic linker-loader must • find the desired routine, remap it, and “link” it to the calling routine (see book for more details) • DLLs require extra space for dynamic linking information, but do not require the whole library to be copied or linked

  26. First Evening Exam • Exam #1: Tuesday, Oct 2, 6:30 to 7:45pm, 113 IST • Look at the practice exam (and solutions) on ANGEL • In Section 1 – two people requesting a conflict exam • In Section 2 – one person requesting a conflict exam • Questions?

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