When your assembler and linker are x86_64 versions, the options to produce i386 (32-bit) output are as –32 ld -m elf_i386 You don’t have to use as and ld just because you’re working with assembly code. gcc can be used, and in that case you would use -m32. gcc -m32 -nostdlib myprog.s -o myprog
In NASM syntax, that instruction should be MOV EBX, MY_TABLE. What MOV EBX, [MY_TABLE] would do is load the first 4 bytes located at MY_TABLE into EBX. Another alternative would be to use LEA, as in LEA EBX, [MY_TABLE]. In this case the tutorial is right. MY_TABLE is defined as an array of words. A … Read more
Add $t2 $t3 + $t4 $t5, result in $t0 $t1 addu $t1, $t3, $t5 # add least significant word sltu $t0, $t1, $t5 # set carry-in bit addu $t0, $t0, $t2 # add in first most significant word addu $t0, $t0, $t4 # add in second most significant word For the second part of your … Read more
Summary: try to allocate memory near your static code. But for calls that can’t reach with rel32, fall back to call qword [rel pointer] or inline mov r64,imm64 / call r64. Your mechanism 5. is probably best for performance if you can’t make 2. work, but 4. is easy and should be fine. Direct call … Read more
For two operand instructions using SIMD you can show that the number of operations necessary to transpose a nxn matrix is n*log_2(n) whereas using scalar operations it’s O(n^2). In fact, later I’ll show that the number of read and write operations using the scalar registers is 2*n*(n-1). Below is a table showing the number of … Read more
There are a few possibilities… here are a couple I can think of off the top of my head: You could access it relative to a label that comes after the .byte directive. Example: .byte 0x0a label: mov (label – 1), %eax Based on the final linked layout of the program, maybe the .byte directives … Read more
Your quote is from the “calling convention” part of the documentation. At the very least, you do not have to worry about this if you do not call other functions from your assembly code. If you do, then you must respect, among other things, “red zone” and stack alignment considerations, that the recommendation you quote … Read more
The call instruction actually does this for you. For example call my_func would do something like: push ret_address jmp my_func A subsequent ret call would just use the address you just pushed to jmp back in a sense. Is there a specific reason that you don’t want to use call or is it not available … Read more
There’s a patent for combined popcnt, bit scan forward / reverse: US8214414 B2 – Combined set bit count and detector logic Abstract A merged datapath for PopCount and BitScan is described. A hardware circuit includes a compressor tree utilized for a PopCount function, which is reused by a BitScan function (e.g., bit scan forward (BSF) … Read more
These are called instructions, and they specify operations that are to be performed by the processor. mov is a mnemonic for move, while mul is a mnemonic for multiply. Other common instructions include add, sub, and div. I trust you can figure out what operation these specify! Most instructions take two parameters. In the technical … Read more