On Mon, 2005-02-21 at 14:42 -0500, Kazu Hirata wrote: > Hi Jeff, > > > The second thought is to initialize all of cse_reg_info entries at the > > beginning of cse_main. Set aside a bitmap with as many bits as > > max_regs. Whenever we use one of these accessor macros for register > > k, set a bit k saying "cse_reg_info_table[k] is in use." This way, > > when we are done with a basic block, we can walk the bitmap and > > reinitialize those that are used. Again, a good optimizer should be > > able to eliminate most of these bit sets, but a non-pure/const > > function call will block the cleanup opportunities. Of course, this > > bitmap walk is far more expensive than cse_reg_info_timestamp++. > > I just tried this. It comes very close to the current timestamp > approach but loses by 0.3% or so in compile time. I'm attaching a > patch for completeness. Thanks. I suspect this won't cut the mustard either -- the SET_BIT twiddles memory, which, due to lameness in our aliasing code, is likely going to cause us to miss the CSE opportunities that are so important here.
Beyond that, I suspect we get killed zeroing the sbitmap every time we start a new cse block. I may play with it though. Who knows, maybe there'll be something that we can do with it. jeff
