... > What _does_ work however are the following two approaches: > > 1) Perform the equality check on the original variables, creating > new versions (with OPTIMIZER_HIDE_VAR) of both variables for the > rest of their use, therefore making sure the pointer dereference > are not derived from versions of the variables which were compared > with another pointer. (as suggested by Boqun) If that is a1 = a; OPTIMISER_HIDE_VAR(a1); b1 = b; OPTIMISER_HIDE_BAR(b1); if (a != b} return; // code using a1 and b1 then can't the compiler first flip it to: if (a != b) return; a1 = a; OPTIMISER_HIDE_VAR(a1); b1 = b; OPTIMISER_HIDE_VAR(b1); and then replace the last line with: b1 = a; OPTIMISER_HIDE_VAR(b1); which isn't intended at all. OTOH if you do: a1 = a; OPTIMISER_HIDE_VAR(a1); b1 = b; OPTIMISER_HIDE_VAR(b1); if (a1 != b1) return; // code using a and b (which I think is) > 2) Perform the equality check on the versions resulting of hiding > both variables, making sure those versions of the variables are > not dereferenced afterwards. (as suggested by Linus) then the compiler can't possibly reverse the asm blocks. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
