On Wed, 2020-01-08 at 12:58 +0800, bin.cheng wrote: > Hi, > > Function use_pred_not_overlap_with_undef_path_pred of > pass_late_warn_uninitialized > checks if predicate of variable use overlaps with predicate of undefined > control flow path. > For now, it only checks ssa_var comparing against constant, this can be > improved where > ssa_var compares against another ssa_var with value range info, as described > in comment: > > + /* Check value range info of rhs, do following transforms: > + flag_var < [min, max] -> flag_var < max > + flag_var > [min, max] -> flag_var > min > + > + We can also transform LE_EXPR/GE_EXPR to LT_EXPR/GT_EXPR: > + flag_var <= [min, max] -> flag_var < [min, max+1] > + flag_var >= [min, max] -> flag_var > [min-1, max] > + if no overflow/wrap. */ > > This change can avoid some false warning. Bootstrap and test on x86_64, any > comment? > > Thanks, > bin > > 2020-01-08 Bin Cheng <bin.li...@linux.alibaba.com> > > * tree-ssa-uninit.c (find_var_cmp_const): New function. > (use_pred_not_overlap_with_undef_path_pred): Call above. Totally agree with Richi in that it's a good idea. I've always expected that as we make ranges first class citizens that we'd find more places to use 'em.
Jeff
