notes

Compiler optimization patterns

Loop counter

n := 255
for i := 0; i < 255; i++ {
  n--
  f(255-n)
}

n := 0
for i := 0; i < 255; i++ {
  n++
  f(n)
}

for i := 0; i < 255; i++ {
  f(i)
}

Sum as bitwise operations

func sum(a, b int) {
  for b != 0 {
    c := a & b
    a = a ^ b
    b = c << 1
  }
  return a
}

SWAR for nibbles

x >= 0xa0 || 0x0a <= x && x <= 0x0f
// ==>
(if x > 0x0f { x >> 4 } else { x }) >= 0x0a

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