On Thu, Aug 27, 2015 at 11:21 AM, Kai Tietz <ktiet...@googlemail.com> wrote: > 2015-08-27 4:57 GMT+02:00 Jason Merrill <ja...@redhat.com>: >> Why does fold_simple fold so many patterns? I thought we wanted something >> that would just fold conversions and negations of constant values. > > Yes, initial variant was handling much less patterns. But actually we > need for functions (eg. like build_vec_init in init.c) a simple > routine to perform basic constant-value arithmetics (sizeof * / + - > trunc, etc) to avoid call of maybe_constant_value. Also for > overflow-diagnostics we want at least to resolve such simple patterns > for constant-values only. We could change those calls to use > maybe_constant_value instead, but the overhead (and some of its > folding) leads much further then working on constant-values only (as > fold_simple does). > > It might be that we can remove the ternary vector-cond expression from > this routine, The cond-expr itself seems to be necessary to resolve > patterns like (1 == 1 ? 32 : 64), which can appear pretty often via > macro-code. I will check if I what patterns I can remove here.
Note that fold-const.c has constant-only folding routines (handling only constant operands). const_unop, const_binop (no const_ternop split out yet). Richard. >> Jason > > > Kai
