This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: Continue stmt branch prediction

On 3/5/08 2:28 PM, Jan Hubicka wrote:

I will give it one last try.  I think the misunderstanding can be here.
The prediction hint is not affecting edges *out* of the block it sits
in. When lowered, it is affecting all the edges that are going from
basic block not postdominated by the block to basic block postdominated
by the block (here the course of execution is crossing the point that it
inavoidably leads to the place PREDICT_EXPR is).  Think of abort call:
it is affecting all conditionals that are guarding it in the program.

Ah, I see now. Yes, I think I finally got your point. Adding PREDICT_EXPR is fine with me.

Instead of having to special-case it in places like DCE, how about we make it produce a value which is assigned to an artificial volatile global temporary? This way, we don't need to touch the optimizers, they will all naturally back away from moving and/or removing it.


Diego.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]