http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50527
--- Comment #3 from vries at gcc dot gnu.org 2011-09-27 09:21:12 UTC --- > Or alternatively (given we re-compute alignment together with folding alloca), > assign the same alignment as folding would. At the point that we determine the alloca alignment during propagation in visit_stmt, we cannot predict whether that alloca will be folded (during the same or later ccp phase). So the only way to achieve other alignment is to be conservative a bit longer for vla-allocas with respect to alignment: - keep align at 1 byte during ccp. - if we fold during ccp, assign align calculated at folding - after we are sure there is no more folding (at expand, or f.i. at the end of the second ccp phase if we limit folding to the first 2 ccp phases, to take advantage of the larger alignment in the middle-end), we assign BIGGEST_ALIGNMENT. > The question is of course what standards say about the alignment of > alloca (4) I think alloca is non-standard. But in the context of fold_builtin_alloca_for_var, alloca is the implementation vehicle of vlas, so the question is what the standard says about alignment of vlas.
