Hi, while updating vect_can_force_dr_alignment_p for section API I noticed the predicate is bit confused about when it can update the alignment.
We need to check that decl_binds_to_current_def_p and in case we compile a partition also that the symbol is not homed in other partition. Previous code was wrong i.e. for COMDATs, weaks or -fpic. Also when having an alias, only way to promote the alignment is to bump up alignment of target. On the other hand comment about DECL_IN_CONSTANT_POOL seems confused - we have no sharing across partitions. I assume it was old hack and removed it. I also see no reason for disregarding DECL_PRESERVE - we only update alignment that should not disturb whatever magic user does. But I kept it. We probably should separate the logic into symtab predicate - it just checks if we can change definition of variable to meet our needs. I can do that incrementally. Bootstrapped/regtested x86_64-linux, comitted. Honza * tree-vect-data-refs.c (vect_can_force_dr_alignment_p): Reorg to use symtab and decl_binds_to_current_def_p * tree-vectorizer.c (increase_alignment): Increase alignment of alias target, too. Index: tree-vect-data-refs.c =================================================================== --- tree-vect-data-refs.c (revision 211489) +++ tree-vect-data-refs.c (working copy) @@ -58,6 +58,7 @@ along with GCC; see the file COPYING3. #include "expr.h" #include "optabs.h" #include "builtins.h" +#include "varasm.h" /* Return true if load- or store-lanes optab OPTAB is implemented for COUNT vectors of type VECTYPE. NAME is the name of OPTAB. */ @@ -5316,19 +5317,26 @@ vect_can_force_dr_alignment_p (const_tre 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. The same is true for constant - pool entries which may be shared and are not properly merged - by LTO. */ - if (DECL_EXTERNAL (decl) - || DECL_COMMON (decl) - || DECL_IN_CONSTANT_POOL (decl)) - return false; + gcc_assert (!TREE_ASM_WRITTEN (decl)); - if (TREE_ASM_WRITTEN (decl)) - return false; + if (TREE_PUBLIC (decl) || DECL_EXTERNAL (decl)) + { + symtab_node *snode; + + /* We cannot change alignment of symbols that may bind to symbols + in other translation unit that may contain a definition with lower + alignment. */ + if (!decl_binds_to_current_def_p (decl)) + return false; + + /* When compiling partition, be sure the symbol is not output by other + partition. */ + snode = symtab_get_node (decl); + if (flag_ltrans + && (snode->in_other_partition + || symtab_get_symbol_partitioning_class (snode) == SYMBOL_DUPLICATE)) + return false; + } /* Do not override the alignment as specified by the ABI when the used attribute is set. */ @@ -5343,6 +5351,18 @@ vect_can_force_dr_alignment_p (const_tre && !symtab_get_node (decl)->implicit_section) return false; + /* If symbol is an alias, we need to check that target is OK. */ + if (TREE_STATIC (decl)) + { + tree target = symtab_alias_ultimate_target (symtab_get_node (decl))->decl; + if (target != decl) + { + if (DECL_PRESERVE_P (target)) + return false; + decl = target; + } + } + if (TREE_STATIC (decl)) return (alignment <= MAX_OFILE_ALIGNMENT); else Index: tree-vectorizer.c =================================================================== --- tree-vectorizer.c (revision 211488) +++ tree-vectorizer.c (working copy) @@ -686,6 +686,12 @@ increase_alignment (void) { DECL_ALIGN (decl) = TYPE_ALIGN (vectype); DECL_USER_ALIGN (decl) = 1; + if (TREE_STATIC (decl)) + { + tree target = symtab_alias_ultimate_target (symtab_get_node (decl))->decl; + DECL_ALIGN (target) = TYPE_ALIGN (vectype); + DECL_USER_ALIGN (target) = 1; + } dump_printf (MSG_NOTE, "Increasing alignment of decl: "); dump_generic_expr (MSG_NOTE, TDF_SLIM, decl); dump_printf (MSG_NOTE, "\n");