[Resent because of account funnies. Apologies to those who get this twice] Hi,
> > This problem is reported every once in a while, all targets with > small > > load-immediate instructions suffer from this, especially since GCC > 4.0 > > (i.e. since tree-ssa). But it seems there is just not enough > interest > > in having it fixed somehow, or someone would have taken care of it by > > now. > > > > I've summed up before how the problem _could_ be fixed, but I can't > > find where. So here we go again. > > > > This could be solved in CSE by extending the notion of "related > > expressions" to constants that can be generated from other constants > > by a shift. Alternatively, you could create a simple, separate pass > > that applies CSE's "related expressions" thing in dominator tree > walk. > > See http://gcc.gnu.org/ml/gcc-patches/2009-03/msg00158.html for > handling > something similar when related expressions differ by a small additive > constant. I am planning to finish this and submit it for 4.5. Wouldn't doing this in CSE only solve the problem within an extended basic block and not necessarily across the program ? Surely you'd want to do it globally or am I missing something very basic here ? Ramana
