On 04/10/2013 02:51 PM, Michel Dänzer wrote:
On Mit, 2013-04-10 at 12:59 +0200, Christian König wrote:
Am 10.04.2013 12:21, schrieb Michel Dänzer:
On Mit, 2013-04-10 at 12:07 +0200, Christian König wrote:
Am 10.04.2013 11:46, schrieb Michel Dänzer:
But why the heck is multiplying with 0x4f800000 fixing the result?
I'm afraid I can't explain how it works, I basically copied it from the
Cayman section in R600Instructions.td...
[...]
Anyway even if I can't explain exactly why it seems to work fine on both
Cayman and SI, so the patch is:
Reviewed-by: Christian König <christian.koe...@amd.com>
Thanks. I think I can actually explain again how it works:
The unsigned integer input value is converted to float, its reciprocal
value is computed and multiplied by (1 << 32) (encoded as 0x4f800000 in
floating point) and converted back to unsigned integer. I think this
might lose up to 8 of the least significant bits of the result...
Very interesting. This seems to be worth a comment in the source code.
Tobi
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