Daniel Berlin wrote: > On Sun, 2006-02-19 at 09:56 -0500, Kenneth Zadeck wrote: > >> Steven, Zdenek >> >> 1) single_set is built on top of single_set2. >> > Yes > >> 2) single_set_2 uses REG_UNUSED notes. >> > Only if there are multiple sets. > > >> 3) tree-ssa-loop-ivops.c:seq_cost uses single_set. >> > > This is because Zdenek builds RTL to determine target costs. > > >> I can find no indication that rtl dfa is run here to provide the >> information for single_set to produce the correct answer. >> > > I don't understand what you mean. > Why does the DFA need to be run to produce the correct answer? > (Our ports use Deterministic Finite Automaton based schedulers, so > saying DFA is an ambiguous term at best) > > Or do you mean DataFlow Analysis, in which case, i'm sure everyone > expects the notes are always up to date (even though they may not be). > > > I was refering to the reg_unused notes not being there at all when this is called. You are correct that this is not so much a correctness issue as a place where the code is pessimistic.
kenny
