[stlee42]

Exactly this. Linker is threading given blocks together with fixups for position-independent code - this can be called rule application. Assembler is pattern matching.

This explanation confused me too:

  Each individual iteration: around 4x slower (register spilling)
  Cache pressure: around 2-3x additional penalty (instructions do not fit in L1/L2 cache)
  Combined over a billion iterations: 158,000x total slowdown

If each iteration is X percent slower, then a billion iterations will also be X percent slower. I wonder what is actually going on.