On Tue, Feb 21, 2012 at 9:54 AM, Jiangning Liu <jiangning....@arm.com> wrote: >> The MEM form is more "canonical", so the loop SM machinery to detect >> equality should be adjusted accordingly. Alternatively you can teach >> PRE insertion to strip off the MEM if possible (though >> fold_stmt_inplace should >> arelady do this if possible). > > Richard, > > Thank you! You are right. I noticed on latest trunk the problem in PRE was > already fixed by invoking fold_stmt_inplace. > > Unfortunately for this small case, the latest trunk code still can't do SM > for variable pos, because refs_may_alias_p(*D.4074_10, pos) is true, that > is, pos has alias with l[pos]. > > I think alias analysis should be able to know they don't have alias with > each other, unless there is an assignment statement like "l=&pos;". > > Can alias analysis fix the problem?
The problem is that 'pos' is marked TREE_ADDRESSABLE, so we think its address got taken. 'l' points to any global possibly address-taken variable. It get's the TREE_ADDRESSABLE flag via PRE insertion which re-gimplifies the tree it creates which marks the variable as addressable. I'll have a look. Richard. > Thanks, > -Jiangning > >> >> Richard. >> > > >
