On Wed, 25 Nov 2015, Jakub Jelinek wrote: > But finding out if you have an expression on which c_fully_fold has been > already called or not is non-trivial too.
The rule is that if the C front end needs to fold early for any reason (e.g. for warnings) then the result of folding gets wrapped in a C_MAYBE_CONST_EXPR as a signal that what's inside there doesn't need folding again - or in another kind of tree that also isn't folded inside, such as SAVE_EXPR or CALL_EXPR. > Wonder if we couldn't use some FE specific bit on the SAVE_EXPR to say > whether c_fully_fold_internal has already processed it or not, and just > get rid of c_save_expr, in c_fully_fold* recurse into SAVE_EXPRs too, but > only if that bit is not yet already set, and set it afterwards. I suppose you could do that, in line with the general principle of reducing early folding (as long as you ensure that folding the contents of a SAVE_EXPR results in modifying that SAVE_EXPR so that all pointers to it stay pointing to the same tree node). -- Joseph S. Myers jos...@codesourcery.com
