https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67366
--- Comment #3 from rguenther at suse dot de <rguenther at suse dot de> --- On Thu, 27 Aug 2015, rearnsha at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67366 > > --- Comment #2 from Richard Earnshaw <rearnsha at gcc dot gnu.org> --- > (In reply to Richard Biener from comment #1) > > I think this boils down to the fact that memcpy expansion is done too late > > and > > that (with more recent GCC) the "inlining" done on the GIMPLE level is > > restricted > > to !SLOW_UNALIGNED_ACCESS but arm defines STRICT_ALIGNMENT to 1 > > unconditionally. > > > > Yep, we have to define STRICT_ALIGNMENT to 1 because not all load instructions > work with misaligned addresses (ldm, for example). The only way to handle > misaligned copies is through the movmisalign API. Are the movmisalign handled ones reasonably efficient? That is, more efficient than memcpy/memmove? Then we should experiment with Index: gcc/gimple-fold.c =================================================================== --- gcc/gimple-fold.c (revision 227252) +++ gcc/gimple-fold.c (working copy) @@ -708,7 +708,9 @@ gimple_fold_builtin_memory_op (gimple_st /* If the destination pointer is not aligned we must be able to emit an unaligned store. */ && (dest_align >= GET_MODE_ALIGNMENT (TYPE_MODE (type)) - || !SLOW_UNALIGNED_ACCESS (TYPE_MODE (type), dest_align))) + || !SLOW_UNALIGNED_ACCESS (TYPE_MODE (type), dest_align) + || (optab_handler (movmisalign_optab, TYPE_MODE (type)) + != CODE_FOR_nothing))) { tree srctype = type; tree desttype = type; @@ -720,7 +722,10 @@ gimple_fold_builtin_memory_op (gimple_st srcmem = tem; else if (src_align < GET_MODE_ALIGNMENT (TYPE_MODE (type)) && SLOW_UNALIGNED_ACCESS (TYPE_MODE (type), - src_align)) + src_align) + && (optab_handler (movmisalign_optab, + TYPE_MODE (type)) + == CODE_FOR_nothing)) srcmem = NULL_TREE; if (srcmem) {
