------- Comment #26 from hubicka at gcc dot gnu dot org 2009-02-21 13:00
-------
I had somehting along this lines in mind:
Index: config/i386/i386.c
===================================================================
*** config/i386/i386.c (revision 144352)
--- config/i386/i386.c (working copy)
*************** unsigned int
*** 19332,19337 ****
--- 19332,19343 ----
ix86_local_alignment (tree type, enum machine_mode mode,
unsigned int align)
{
+ /* We don't want to align DImode to 64bit for compilation with
+ -mpreferred-stack-boundary=2 to not enforce dynamic stack alignment
+ prologue. */
+ if (mode == DImode && !TARGET_64BIT && ix86_preferred_stack_boundary < 64)
+ align = 32;
+
/* If TYPE is NULL, we are allocating a stack slot for caller-save
register in MODE. We will return the largest alignment of XF
and DF. */
this will reduce alignment of long long as stack local variable. Because we
want to keep it aligned for DI->DF, I can do that only for
-mpreferred-stack-boundary=2 for now and perhaps on mainline we can invent new
macro PREFERRED_LOCAL_ALIGN that will return 64 and cfgexpand will allocate
64byte aligned slot but not increase alignment_needed (i.e. control slot
alignment via PREFERRED_LOCAL_ALIGN and stack alignment otherwise) and we will
increase the alignment when expanding full sized DImode instruction?
Honza
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39137
