http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47581
--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-02-02 12:12:23 UTC --- (In reply to comment #3) > Before Richard's commit apparently expand_one_var wasn't updating > stack_alignment_needed, just stack_alignment_estimated, now it updates both. > As PREFERRED_STACK_BOUNDARY is 128 (the default), ix86_minimum_alignment: > if (TARGET_64BIT || align != 64 || ix86_preferred_stack_boundary >= 64) > return align; > returns 64 instead of 32. > > So, to fix this, either the stack_alignment_needed updating in expand_one_var > isn't strictly necessary and we could undo that part of the changes. > > Or return 32 as MINIMUM_ALIGNMENT for DImode long long even for > ix86_preferred_stack_boundary >= 64. > > Or we could perhaps the > /* Align start of frame for local function. */ > offset = (offset + stack_alignment_needed - 1) & -stack_alignment_needed; > in ix86_compute_frame_layout perform only if > if (offset != frame->sse_reg_save_offset > || size != 0 > || !current_function_is_leaf > || cfun->calls_alloca > || ix86_current_function_calls_tls_descriptor) > (i.e. if frame size is 0 and no outgoing calls, it doesn't make sense to > align). I think we align the stack for reload (which might still happen without outgoing calls, simply with enough register pressure).