Notes on computers, programming and all the stuff

Conversion numbers to hexadecimal representation - SWAR, plain SSE, and draft of BMI2 implementation. Article SSSE3: printing hex values...

Few years ago I counted instructions from many Linux binaries --- 2014 is good year to repeated this experiment and see that nothing has ch...

I needed to iterate through all values of 32-bit unsigned integer, so I wrote: #include <stdint.h> for (uint32_t i=0; i <= UINT3...

Suppose we need to get mask when nonnegative argument is greater then some constant value; in other words, we want to evaluate following exp...

With help of BSWAP instruction or SSE instructions ( PSHUFD , PSHUFLW , PSHUFHW ) or SSSE3 instruction ( PSHUFB ) reversing table can be fas...

Method from Bit Twiddling Hacks : (x != 0) && (x & (x-1) == 0) . GCC compiles this to following code: ; input/ouput: eax ; dest...

Suppose we have to exchange (or just move) two registers A and B: C := A xor B C := 0 if condition is not true A := A xor C B := B xor...

Problem: calculate value of sign(x) : -1 when x < 0 0 when x = 0, +1 when x > 0. My solution do not involve any hardware specifi...

This is continuation of subproblem from previous post: we have a word (byte, dword, whatever) and want to fill it with selected bit. 1. Th...