2015-08-29 6:45 GMT+02:00 Jason Merrill <ja...@redhat.com>: > On 08/27/2015 05:21 AM, Kai Tietz 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). > > > For build_vec_init, since whether maxindex is constant has semantic meaning, > I think we want maybe_constant_value.
So you mean that handling of constexprs within vector-init is something we need. Ok. I will test a replace. > I think we also want it for overflow warnings, to get better diagnostics. Hmm, I don't think we want to call maybe_constant_value in functions like cp_build_binary_op. We are interested in overflow only on constant-values anyway, I don't see that we want to have here any constexpr-logic, nor specific address-manipulation logic. So I see here not much advantage in using maybe_constant_value. Maybe I simply not seeing the obvious here. Do you have a specific testcase, which shows what diagnostics could be missed? > Jason > Kai
