This is the heart of this program. It aims to be able to produce a sustained output rate of 64 bytes of FizzBuzz per four clock cycles in its main loop

This is the heart of this program. It aims to be able to produce a sustained output rate of 64 bytes of FizzBuzz per four clock cycles in its main loop (with frequent breaks to do I/O, and rare breaks to do more expensive calculations). The third phase operates primarily using a bytecode interpreter; it generates a program in "FizzBuzz bytecode", for which each byte of bytecode generates one byte of output. The bytecode language is designed so that it can be interpreted using SIMD instructions; 32 bytes of bytecode can be loaded from memory, interpreted, and have its output stored back into memory using just four machine instructions. This makes it possible to speed up the FizzBuzz calculations by hardcoding some of the calculations into the bytecode (this is similar to how JIT compilers can create a version of the program with some variables hardcoded, and throw it away on the rare occasions that those variables' values change). The bytecode format is very simple (in order to allow it to be interpreted in just a couple of machine instructions): - A negative byte represents a literal character (e.g. to produce a literal 'F', you use the bytecode -'F', i.e. -70 = 0xba) - A byte 0..7 represents the hundreds..billions digit of the line number respectively, and asserts that the hundreds digit of the line number is even - A byte 8..15 represents the hundreds..billions digit of the line number respectively, and asserts that the hundreds digit of the line number is odd In other words, the bytecode program only ever needs to read from LINENO_MID; the information stored in LINENO_LOW and LINENO_TOP therefore has to be hardcoded into it. The program therefore needs to be able to generate 600 lines of output (as the smallest number that's divisible by 100 to be able to hardcode the two low digits, 200 to be able to get the assertions about the hundreds digits correct, and 3 and 5 to get the Fizzes and Buzzes in the right place). The bytecode interpreter consists of four instructions: 1. Load the bytecode from memory into %ymm2; 2. Use it as a shuffle mask to shuffle LINENO_MID_TEMP; 3. Subtract the bytecode from the shuffle result; 4. Output the result of the subtraction. #define INTERPRET_BYTECODE(bc_offset, buf_offset) \ vmovdqu %ymm2, [%rdx + bc_offset]; \ vpshufb %ymm0, LINENO_MID_TEMP, %ymm2; \ vpsubb %ymm0, %ymm0, %ymm2; \ vmovdqa [OUTPUT_PTR + buf_offset], %ymm0