It also says the multiplier must be one of 2, 4 or 8.
So I guess this trick then only works for multiplication by 2, 3, 4, 5, 8 or 9?
So I guess this trick then only works for multiplication by 2, 3, 4, 5, 8 or 9?
x * 6:
lea eax, [rdi+rdi*2]
add eax, eax
x * 7:
lea eax, [0+rdi*8]
sub eax, edi
x * 11:
lea eax, [rdi+rdi*4]
lea eax, [rdi+rax*2]
And on modern CPUs multiplication might not be actually all that slow (but there may be fewer multiply units).