builtinclzll

Builtinclzll is a terminal instruction in Intel Architecture (IA-32) and x86-64 instruction sets. It is a built-in instruction that is designed to perform a population count operation on a single operand.

Population count, also known as Hamming weight, is the total number of single bits set to 1 in a binary number. The builtinclzll instruction calculates the population count of each byte in the input data by examining each bit in the 128-bit operand.

Upon executing the builtinclzll instruction, the most significant bit (MSB) of the result is set to 1 to indicate that the population count of each byte may be different. Then, the next 8 bits of the result are used to store the population count of the first byte, followed by the count of the second byte and so on.

The built-in instruction has four input operands labeled EAX through R8D and two output operands labeled RCX and RDX. It has several input and output configurations; this is because it involves various bit masking operations. The configuration determines which bytes of the input operand are into consideration.

The builtinclzll instruction has several uses in data processing, particularly in the calculation of the Hamming code, which is required to detect if any bits in a binary code have been altered. It also comes in handy in estimation of median value.