This fixes PR52571, we should not align DECL_COMMON variables as
they might be pre-empted by a definition with lower alignment.
At LTO/WPA level we might recover from missed optimizations by
promoting DECL_COMMON variables to non-common. Not sure if we
do that already.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
Richard.
2012-03-14 Richard Guenther <rguent...@suse.de>
PR tree-optimization/52571
* tree-vect-data-refs.c (vect_compute_data_ref_alignment): Move
flag_section_anchors check ...
(vect_can_force_dr_alignment_p): ... here. Do not re-align
DECL_COMMON variables.
Index: gcc/tree-vect-data-refs.c
===================================================================
*** gcc/tree-vect-data-refs.c (revision 185379)
--- gcc/tree-vect-data-refs.c (working copy)
*************** vect_compute_data_ref_alignment (struct
*** 872,881 ****
if (!base_aligned)
{
! /* Do not change the alignment of global variables if
! flag_section_anchors is enabled. */
! if (!vect_can_force_dr_alignment_p (base, TYPE_ALIGN (vectype))
! || (TREE_STATIC (base) && flag_section_anchors))
{
if (vect_print_dump_info (REPORT_DETAILS))
{
--- 872,878 ----
if (!base_aligned)
{
! if (!vect_can_force_dr_alignment_p (base, TYPE_ALIGN (vectype)))
{
if (vect_print_dump_info (REPORT_DETAILS))
{
*************** vect_can_force_dr_alignment_p (const_tre
*** 4546,4557 ****
if (TREE_CODE (decl) != VAR_DECL)
return false;
! if (DECL_EXTERNAL (decl))
return false;
if (TREE_ASM_WRITTEN (decl))
return false;
if (TREE_STATIC (decl))
return (alignment <= MAX_OFILE_ALIGNMENT);
else
--- 4543,4564 ----
if (TREE_CODE (decl) != VAR_DECL)
return false;
! /* We cannot change alignment of common or external symbols as another
! translation unit may contain a definition with lower alignment.
! The rules of common symbol linking mean that the definition
! will override the common symbol. */
! if (DECL_EXTERNAL (decl)
! || DECL_COMMON (decl))
return false;
if (TREE_ASM_WRITTEN (decl))
return false;
+ /* Do not change the alignment of global variables if flag_section_anchors
+ is enabled. */
+ if (TREE_STATIC (decl) && flag_section_anchors)
+ return false;
+
if (TREE_STATIC (decl))
return (alignment <= MAX_OFILE_ALIGNMENT);
else
