Help with Operators in Spin

Chris Merck

To the best of my knowledge the following lines of spin should be equivalent (where f is a long and a and b are constants in the range 0..31):

if f&|<a AND f&|<b
  ...

if f&(|<a | |<b)
 ...

However, these two lines give different behavior.

The interpretation here is that a and b are the names of bits in the flag register f, and the if-block is to be executed if both flags a and b are set.

Something must be wrong with how I am thinking about these operators. Can anyone clarify this?

Thanks,
Chris

kuroneko

The second one evaluates to non-zero (which propagates to TRUE) when either of the flags is set. You probably want something like

if (f&constant(|<a | |<b)) == constant(|<a | |<b)

Chris Merck

kuroneko,
Thanks for the fast response. You are totally right. I can't believe I missed that. (This has been bugging me for 2 hours).

VG

I think the following should also work.

if·f & (|<a·& |<b)
··...

Please correct me if I am wrong.

Sincerely,
Venkata.

Chris Merck

f & (|<a & |<b) will be true only when a=b and f.a=1