Sparc Architecture Overview Natawut Nupairoj Assembly Language

Von Neumann Architecture Designed by John von Neumann in 1949. Machine = CPU + Memory Program is stored in memory along with data. CPU has Program Counter (PC) and Instruction Register (IR) Use PC to keep the current location of instruction being executed. Natawut Nupairoj Assembly Language

Von Neumann Architecture Control unit fetches an instruction from memory (located by PC) and stores in IR. Memory = Memory Address Register (MAR) + Memory Data Register (MDR) CPU puts an address in MAR and load/store from/to MDR. Natawut Nupairoj Assembly Language

Machine Organization Diagram Natawut Nupairoj Assembly Language

Instruction Execution Fetch-Decode-Execute cycles: Fetch the next instruction from memory. Change PC to point to next instruction. Determine the type of the instruction fetched. Find where the data being used by the instruction is kept. Fetch the data, if required. Execute the instruction. Store the results in the appropriate place. Go to step 1 and start all over again. Natawut Nupairoj Assembly Language

Instruction Cycles pc = 0; do { ir := memory[pc]; { Fetch the instruction. } pc := pc + INSTR_SIZE; { Move PC to next instruction. } decode(ir); { Decode the instruction. } fetch(operands); { Fetch the operands. } execute; { Execute the instruction. } store(results); { store the results. } } while(ir != HALT); Natawut Nupairoj Assembly Language

Sparc Architecture Overview Load/Store architecture ALU cannot access data from memory directly. Data must be loaded into registers before computing. RISC (Reduced Instruction Set Computer) architecture All instructions are one word (32 bits). 5-stage Pipelining CPU. Natawut Nupairoj Assembly Language

Sparc Registers There are 32 registers (%r0 - %r31). Each register is 64-bit for UltraSparc (128-bit for UltraSparc III). Registers are logically divided into 4 sets: global (%gx), in (%ix), local (%lx), and out (%ox). All registers are equal, can perform any operations. Special register: %g0 (%r0) - always discards writes and return zero. Natawut Nupairoj Assembly Language

Sparc Registers Global Output %g0 %r0 readonly / return zero %g1 %r1 %o0 %r8 %o1 %r9 %o2 %r10 %o3 %r11 %o4 %r12 %o5 %r13 %o6 %r14 %sp stack pointer %o7 %r15 called sub ret addr Natawut Nupairoj Assembly Language

Sparc Registers Local Input %l0 %r16 %l1 %r17 %l2 %r18 %l3 %r19 %i0 %r24 %i1 %r25 %i2 %r26 %i3 %r27 %i4 %r28 %i5 %r29 %i6 %r30 %fp frame pointer %i7 %r31 sub return addr Natawut Nupairoj Assembly Language

Format of Instructions Any instruction is made up of two parts: Opcode (the name of the instruction) Operands (the values or data manipulated by the instruction) -- can be omitted. L1: add %i2, 0x80, %o1 ! Add two numbers label opcode operands comment Natawut Nupairoj Assembly Language

Label Define the location of data or instruction. Start with: letter (A-Z and a-z), _, $, or . Followed by: letter (A-Z and a-z), number (0-9), _, $, or . Must end with color (:). Natawut Nupairoj Assembly Language

Operands Most instructions have three operands: three registers op reg, reg, reg add %g1, %i2, %g2 ! G2 is the destination. two registers and a literal constant op reg, imm, reg add %o1, 30, %o2 ! O2 is the destination. two registers op reg, reg mov %o4, %l3 ! L3 is the destination. Natawut Nupairoj Assembly Language

Operands a constant and a register op imm, reg mov 453, %g1 ! G1 is the destination. a register op reg clr %l2 a constant op imm call myfunc Notice: Last one is usually the destination. Natawut Nupairoj Assembly Language

Constant in Operand Constant (imm) must be 13-bit signed number: Format of constant ??? Natawut Nupairoj Assembly Language

Comment Inline comment (!): C-style comment (/* … */): ignore to the end of line. ! Inline comment here. Ignore to end of line. C-style comment (/* … */): ignore anything between the comment markers. /* comment here and it can be multiple line. */ Natawut Nupairoj Assembly Language

Our First Program Let try some simple C program (but not hello world !). /* first.c -- not hello world ! as usual */ main() { int x, y; x = 9; y = (x - 2)*(x + 14)/(x + 1); printf(“x = %d, y = %d\n”, x, y); } Natawut Nupairoj Assembly Language

printf(“x = %d, y = %d\n”, x, y); printf Function var1 printf(“x = %d, y = %d\n”, x, y); Display information formatted by the first string. Format: %d = integer %s = string %f = floating point \n = newline format var2 Natawut Nupairoj Assembly Language

Our First Program generate first.s gcc -S first.c .file "first.c" gcc2_compiled.: .global .umul .global .div .section ".rodata" .align 8 .LLC0: .asciz "x = %d and y = %d\n" .section ".text" .align 4 .global main .type main,#function .proc 04 main: !#PROLOGUE# 0 save %sp, -120, %sp !#PROLOGUE# 1 mov 9, %o0 st %o0, [%fp-20] ld [%fp-20], %o1 add %o1, -2, %o0 ld [%fp-20], %o2 add %o2, 14, %o1 call .umul, 0 nop add %o2, 1, %o1 call .div, 0 ... Natawut Nupairoj Assembly Language

Sparc Basic Assembly Instructions Load/Store Operations mov 75, %o2 ! %o2 = 75 mov %o2, %i3 ! %i3 = %o2 clr %l4 ! %l4 = 0 Arithmetics add %o1, %l2, %l3 ! %l3 = %o1 + %l2 add %o3, 19, %g4 ! %g4 = %o3 + 19 sub %i0, %g2, %o5 ! %o5 = %i0 + %g2 Natawut Nupairoj Assembly Language

Sparc Basic Assembly Instructions Multiply / Divide To multiply: 24 * %i2 mov 24, %o0 ! First operand mov %i2, %o1 ! Second operand call .mul ! Result stored in %o0 nop ! Delay slot, discussed later ! %o0 := %o0 * %o1 To divide: %o2 / %g3 mov %o2, %o0 ! First operand mov %g3, %o1 ! Second operand call .div ! Result stored in %o0 ! %o0 = %o0 / %o1 Natawut Nupairoj Assembly Language

Our First Program (Revisited) /* first.m */ /* * This programs compute: * y = (x - 2) * (x + 14) / (x + 8) * for x = 9 */ /* use %l0 and %l1 to store x and y */ define(x_r, l0) define(y_r, l1) /* define constants */ define(c1, 2) Natawut Nupairoj Assembly Language

Our First Program (Revisited) fmt: .asciz "x = %d and y = %d\n" .align 4 .global main main: save %sp, -64, %sp mov 9, %x_r ! x = 9 sub %x_r, c1, %o0 ! %o0 = x - 2 add %x_r, 14, %o1 ! %o1 = x + 14 call .mul ! %o0 = %o0 * %o1 nop add %x_r, 1, %o1 ! %o1 = x + 1 call .div ! %o0 = %o0 / %o1 mov %o0, %y_r ! store result in y Natawut Nupairoj Assembly Language

Our First Program (Revisited) set fmt, %o0 ! first argument for printf mov %x_r, %o1 ! second argument for printf mov %y_r, %o2 ! third argument for printf call printf ! print them out nop mov 1, %g1 ! prepare to exit ta 0 ! normal exit Natawut Nupairoj Assembly Language

Directives Information for the assembler. .global - tell the assembler the name of this function. .asciz - define a string. .align - align a location counter on a boundary. Natawut Nupairoj Assembly Language

Creating Executable File Use M4 macro-processor m4 < first.m > first.s (M4 produces first.s. Notice macro expansion.) Compile first.s gcc -S first.s -o first (this produces an executable file “first”.) Natawut Nupairoj Assembly Language

Running our First Program Run first first x = 9 and y = 16 Using printf to trace a program is not convenient. Natawut Nupairoj Assembly Language

The gdb Debugger To check the result, we will use a debugger. Run: gdb <filename> gdb first (gdb) Run your program: (gdb)r Starting program: /usr3/faculty/natawut/Class/Assembly/first ... Program exited with code 011. Natawut Nupairoj Assembly Language

Breakpoint Set a breakpoint: (gdb) b main Breakpoint 1 at 0x105a4 (gdb) r Starting program: /usr3/faculty/natawut/Class/Assembly/first ... Breakpoint 1, 0x105a4 in main () (gdb) Natawut Nupairoj Assembly Language

Print an Instruction We can examine memory by typing “x”. (gdb) x/i $pc 0x105a4 <main+4>: mov 9, %l0 (gdb) 0x105a8 <main+8>: sub %l0, 2, %o0 We can examine memory by typing “x”. Tell gdb to interpret the current memory as an instruction. Use current location pointed by %pc. Repeat last command by hitting enter key. Natawut Nupairoj Assembly Language

Print the Entire Program Assembley Language First Semester 2542 Print the Entire Program (gdb) disassemble Dump of assembler code for function main: 0x105a0 <main>: save %sp, -64, %sp 0x105a4 <main+4>: mov 9, %l0 0x105a8 <main+8>: sub %l0, 2, %o0 0x105ac <main+12>: add %l0, 0xe, %o1 0x105b0 <main+16>: call 0x2069c <.mul> 0x105b4 <main+20>: nop ... 0x105d4 <main+52>: add %o7, %l7, %l7 End of assembler dump. (gdb) Natawut Nupairoj Assembly Language Natawut Nupairoj

More Debugging Commands Advance breakpoint: (gdb) b *& main+16 Breakpoint 3 at 0x105cc (gdb) c Continuing. Breakpoint 3, 0x105cc in main () (gdb) We use “c” to continue execution after stopping at a breakpoint. Natawut Nupairoj Assembly Language

More Debugging Commands Print out the contents of a register: (gdb) p $l0 $1 = 9 (gdb) Automatically print out contents: (gdb) display/i $pc 1: x/i $pc 0x105a4 <main+4>: mov 9, %l0 (gdb) r The program being debugged has been started already. Start it from the beginning? (y or n) y Starting program: /usr3/faculty/natawut/Class/Assembly/first Natawut Nupairoj Assembly Language

More Debugging Commands Breakpoint 2, 0x105a4 in main () 1: x/i $pc 0x105a4 <main+4>: mov 9, %l0 (gdb) ni 0x105a8 in main () 1: x/i $pc 0x105a8 <main+8>: sub %l0, 2, %o0 (gdb) We use “r” to restart execution from the beginning and “ni” to execute the next instruction. Natawut Nupairoj Assembly Language

More Debugging Commands For other commands, try: help To exit from gdb: q Natawut Nupairoj Assembly Language