On Thursday 09 February 2006 20:04, rajagopal, dwarak wrote: > The fact here is that in this case, A[k] will never trap because the > A[k] is already been written once along the path from Entry to the "A[k] > = g". So it is safe to convert it to a cmov statement.
But GCC doesn't know that this memory address has already been written to, so you don't have that information available in ifcvt. > I'm planning to add this heuristic to the compiler Where and how? This may be a lot harder than you think it is. > but I'm not sure > which level that information is available. Is it possible/better to do > this in rtl level inside the ifcvt.c or do we need SSA for this > information? Obviously, you need this information at the RTL level (that's where the if-conversion pass is) but computing this information on RTL is really not feasible. On the other hand, if you implement it on trees (ie. for GIMPLE in SSA form) then you need to figure out some scheme to propagate the information through the lowering process from GIMPLE to RTL. That's not an easy job, either. But, I wish you luck :-) Gr. Steven
