https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111107
--- Comment #41 from Eric Botcazou <ebotcazou at gcc dot gnu.org> --- > This reads to me like `-mstackrealign` usually decreases > `incoming_stack_boundary` from 128 to 32; realignment is actually a result > of that, right? Yes, both -mstackrealign and force_align_arg_pointer work by decreasing incoming_stack_boundary, which later causes the realignment if a larger alignment is required on the stack. -mstackrealign does it for all functions that require 16-byte alignment, whereas force_align_arg_pointer does it for marked functions only but for all required alignments. > Is it right to say 'it has no effects for 8-byte alignment' because it's > 8-byte alignment that the function is asking for, which is not 16? Yes. > Because we want to decrease the preferred alignment to 4 bytes, > `incoming_stack_boundary` will be 32, which is same as MIN_STACK_BOUNDARY, > and the code above will not have an effect any more. Does it make sense to > remove `STACK_REALIGN_DEFAULT` from cygming.h? Yes, I think that, if the default incoming_stack_boundary is changed, then STACK_REALIGN_DEFAULT should be removed altogether. My understanding is that they are mutually exclusive mechanisms.
