c - matrix multiplication in ARM assembly -


a course of arm assembly started @ university, , or assignment create nxm * mxp matrix multiplication programm, called c code.

now have limited knowledge in assambler, i'm more willing learn. know this:

  1. how read/pass 2d arrays c asm?
  2. how output 2d array c?

i'm thinking, can figure rest of out myself, these 2 points find difficult.

i using arm assembly on qemu, on ubuntu code, it's not going on particular device.

c arrays merely pointers, when pass c array argument assemply function, pointer area of memory content of array.

for retrieving argument, depends on calling convention use. arm eabi stipulates that:

the first 4 registers r0-r3 (a1-a4) used pass argument values subroutine , return result value function. may used hold intermediate values within routine (but, in general, between subroutine calls).

for simple functions, them, should find pointer array in r0 r4 depending on function signature. otherwise, find on stack. technique find out abi disassemble object file of c code calls assembly function , check prior calling assembly function.

for instance, on linux, can compile following c code in file called testasm.c:

extern int myasmfunc(int *);  static int array[] = { 0, 1, 2 };  int mycfunc() {     return myasmfunc(array); }

then compile with:

arm-linux-gnueabi-gcc -c testasm.c

and disassembly with:

arm-linux-gnueabi-objdump -s testasm.o

the result is:

testasm.o:     file format elf32-littlearm   disassembly of section .text:  00000000 <mycfunc>:    0:   e92d4800    push    {fp, lr}    4:   e28db004    add fp, sp, #4    8:   e59f000c    ldr r0, [pc, #12]   ; 1c <mycfunc+0x1c>    c:   ebfffffe    bl  0 <myasmfunc>   10:   e1a03000    mov r3, r0   14:   e1a00003    mov r0, r3   18:   e8bd8800    pop {fp, pc}   1c:   00000000    andeq   r0, r0, r0

you can see single-parametered function myasmfunc called putting parameter register r0. meaning of ldr r0, [pc, #12] "load r0 content of memory address @ pc+12". pointer array stored.


Comments

Post a Comment

Popular posts from this blog

SPSS keyboard combination alters encoding -

my question not have programming practical issue on spss. accident keyword combination cannot remember because did not intend press changed encoding in spss , text in data in different language english shown small boxes. nevertheless, when kind of analysis performed different language text shown in output. does know reason? tried change encoding did not produce result. first, @ edit > options , see whether setting unicode or locale. might fix it. if have text in multiple languages, want unicode. otherwise, may have specific locale set wrong. can change set locale, need know locale want use.
Read more

Add new record to the table by click on the button in Microsoft Access -

in ms access form want implement separate button, adds new record table. in order added button , attached button event: private sub btnaddrec_click() refresh codecontextobject on error resume next docmd.gotorecord , , acnewrec if err.number <> 0 btnaddrec.enabled = false end if end end sub everything ok when open window , click btnaddrec button, problem when first of perform navigation through existed records , after click on button. got runtime error: 2105: «you can't go specified record. may @ end of recordset» . how solve issue, need have ability add new record on click on specific button, no matter, have walked or not walked through records before. thanks. i created simple form field call description (and autonumber) , created button code follows click event. filled number of records , navigated through them, clicked addnewrec button. form navigated new record without issues. able click addnewrec button directly after
Read more

CSS3 Transition to highlight new elements created in JQuery -

i want use css3 color transition apply highlight-fading color effect (yellow transparent) new elements appended markup using jquery. css #content div { background-color:transparent; -moz-transition:background-color 2s; -webkit-transition:background-color 2s; -o-transition:background-color 2s; transition:background-color 2s; } #content div.new { background-color:yellow; } html <div id="content"></div> <a id="add-element" href="#">add new element</a> js $('#add-element').click(function() { var newelement = $('<div class="new">new element</div>'); $('#content').append(newelement); newelement.removeclass('new'); }); when click link, new element created. class "new" (background color yellow) , it's appended html markup. should able remove "new" class trigger background color transition transparent (or whate
Read more