Miscellaneous Assembly Code Examples

Cookbook
1

This is a collection of inline assembly examples.

BLSR - Reset Lowest Set Bit

BLSR, or Reset Lowest Set Bit, is an instruction that copies all bits from the source into the destination, and sets the least significant bit to zero. This is equivalent to a &= a-1.
You can find more information on BLSR here.

popbit :: (a: u64) -> u64 #expand {
  #asm { blsr.q a, a; }
  return a;
}

Here is an example of using BSLR.

a: u64 = 0xFF;
print("%\n", formatInt(a, 2));
a = popbit(a);
print("%\n", formatInt(a, 2));
a = popbit(a);
print("%\n", formatInt(a, 2));
a = popbit(a);
print("%\n", formatInt(a, 2));

When we run this code, we get:

11111111
11111110
11111100
11111000
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