micro-optimization

I belive push/pop instructions will result in a more compact code, maybe will even run slightly faster. This requires disabling stack frames as well though. To check this, I will need to either rewrite a large enough program in assembly by hand (to compare them), or to install and study a few other compilers (to see if they have an option for this, and to compare the results). Here is the forum topic about this and simular problems. In short, I want to understand which code is better. Code like this: sub esp, c mov [esp+8],eax mov [esp+4],ecx mov [esp],edx ... add esp, c or code like this:

AMD CPUs handle 256b AVX instructions by decoding into two 128b operations. e.g. vaddps ymm0, ymm1,ymm1 on AMD Steamroller decodes to 2 macro-ops, with half the throughput of vaddps xmm0, xmm1,xmm1 . XOR-zeroing is a special case (no input dependency, and on Jaguar at least avoids consuming a physical register file entry , and enables movdqa from that register to be eliminated at issue/rename, like Bulldozer does all the time even for non-zerod regs). But is it detected early enough that vxorps ymm0,ymm0,ymm0 still only decodes to 1 macro-op with equal performance to vxorps xmm0,xmm0,xmm0 ?

This question already has an answer here: What's better to use in PHP $array[] = $value or array_push($array, $value)? 10 answers I need to add values received from MySQL into an array [PHP], here is what I've got: $players = array(); while ($homePlayerRow = mysql_fetch_array($homePlayerResult)) { $players[] = $homePlayerRow['player_id']; } Is this the only way of doing it? Also , is the following faster/better? $players = array(); while ($homePlayerRow = mysql_fetch_array($homePlayerResult)) { array_push($players, $homePlayerRow['player_id']); } Thanks in advance u can run and see that array

This question already has an answer here: What is the best way to set a register to zero in x86 assembly: xor, mov or and? 1 answer There're two well-known ways to set an integer register to zero value on x86. Either mov reg, 0 or xor reg, reg There's an opinion that the second variant is better since the value 0 is not stored in the code and that saves several bytes of produced machine code. This is definitely good - less instruction cache is used and this can sometimes allow for faster code execution. Many compilers produce such code. However there's formally an inter-instruction dependency

I am new to x86_64 assembly programming. I was writing simple "Hello World" program in x86_64 assembly. Below is my code, which runs perfectly fine. global _start section .data msg: db "Hello to the world of SLAE64", 0x0a mlen equ $-msg section .text _start: mov rax, 1 mov rdi, 1 mov rsi, msg mov rdx, mlen syscall mov rax, 60 mov rdi, 4 syscall Now when I disassemble in gdb, it gives below output: (gdb) disas Dump of assembler code for function _start: => 0x00000000004000b0 <+0>: mov eax,0x1 0x00000000004000b5 <+5>: mov edi,0x1 0x00000000004000ba <+10>: movabs rsi,0x6000d8 0x00000000004000c4 <