Richard Biener wrote: > Better - comments below. Jakub objections to the usefulness of the transform > remain - we do have the strlen pass that uses some global knowledge to decide > on profitability. One could argue that for -Os doing the reverse transform is > profitable?
In what way would it get more info to decide on profitability? The transform is profitable unless you messed up your strlen implementation badly. For -Os one could do the reverse, but I don't think it is going to give a substantial codesize gain compared to other simple improvements, so unlikely worth it. >> + if (optimize_function_for_size_p (cfun)) >> + return false; > > Hmm, I think we'd want a optimize_stmt_for_size_p (stmt) which > does the right thing for the case we have a CFG (look at the BB) > or when not (look at the function). Does that use the often incorrect BB probabilities? I used the function variant on purpose to avoid it making the wrong decision. A typical example I see is that GCC inlines a return sequence into an if marked with __builtin_expect (c, 0) but not in the hot code that follows... > I think you want to build a gimple_assign directly here, otherwise ... >... this may not reliably end up at the call stmt. OK, I revisit that once we've agreed how to proceed with this patch - we now have 3 variants... Wilco
