------- Comment #31 from ubizjak at gmail dot com 2008-02-14 12:48 -------
(In reply to comment #30)
> participate to the discussion, but I think this PR only expose an underlying
> bug that should be analyzed.
>
> From what I understand, if *STACK_BOUNDARY is larger than the size of what is
> pushed in the stack, some padding is performed. So the basic question is why
> this done for -O2 and not for -Os.
Well, _if_ we want STACK_BOUNDARY larger than PARM_BOUNDARY, then following
patch is needed:
ndex: function.c
===================================================================
--- function.c (revision 132313)
+++ function.c (working copy)
@@ -3436,7 +3436,7 @@ pad_to_arg_alignment (struct args_size *
sp_offset = 0;
#endif
- if (boundary > PARM_BOUNDARY && boundary > STACK_BOUNDARY)
+ if (boundary > PARM_BOUNDARY || boundary > STACK_BOUNDARY)
{
save_var = offset_ptr->var;
save_constant = offset_ptr->constant;
@@ -3462,7 +3462,7 @@ pad_to_arg_alignment (struct args_size *
offset_ptr->var = size_binop (MINUS_EXPR, rounded, sp_offset_tree);
/* ARGS_SIZE_TREE includes constant term. */
offset_ptr->constant = 0;
- if (boundary > PARM_BOUNDARY && boundary > STACK_BOUNDARY)
+ if (boundary > PARM_BOUNDARY || boundary > STACK_BOUNDARY)
alignment_pad->var = size_binop (MINUS_EXPR, offset_ptr->var,
save_var);
}
@@ -3474,7 +3474,7 @@ pad_to_arg_alignment (struct args_size *
#else
CEIL_ROUND (offset_ptr->constant + sp_offset, boundary_in_bytes);
#endif
- if (boundary > PARM_BOUNDARY && boundary > STACK_BOUNDARY)
+ if (boundary > PARM_BOUNDARY || boundary > STACK_BOUNDARY)
alignment_pad->constant = offset_ptr->constant - save_constant;
}
}
This patch fixes va-arg-25.c testcase I'm testing with STACK_BOUNDARY = 128.
The patch bootstraps and regression tests on i686-pc-linux-gnu, but due to
STACK_BOUNDARY == PARM_BOUNDARY on this target, it has not much effect there.
Without this patch, alignment pad is always 0, which is just wrong for
va-arg-25.c case with mixed int/SSE/int/SSE arguments pushed on stack. Note
that sse requires 16 byte alignment.
Using -maccumulate-outgoing-args (-O2), we subtract %esp and stick arguments
into the call frame using offseted moves. We have no other %esp manipulation in
this case.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34621
