On Tuesday, 11 July 2017 at 20:05:43 UTC, Johan Engelen wrote:
On Tuesday, 11 July 2017 at 20:02:07 UTC, Johan Engelen wrote:
On Tuesday, 11 July 2017 at 19:57:06 UTC, Johan Engelen wrote:
On Tuesday, 11 July 2017 at 19:46:00 UTC, Johan Engelen wrote:
[...]
Also this nice hackery would need a workaround:
```
if ((y&(-y))==y)
```
http://www.exploringbinary.com/ten-ways-to-check-if-an-integer-is-a-power-of-two-in-c/
"The two’s complement of x is computed with ~x + 1, which
inverts the bits of x and adds 1 (~x + 1 is equivalent to -x,
but negation is technically illegal for an unsigned integer)."
Codegen is the same for both: https://godbolt.org/g/JiHiEe
So Phobos's `if ((y&(-y))==y)` can be rewritten to `if
((y&(~y+1))==y)` without consequence.
Interestingly returning a bool saves one register and a XOR.
