diff options
Diffstat (limited to 'gcc/alias.c')
| -rw-r--r-- | gcc/alias.c | 153 |
1 files changed, 95 insertions, 58 deletions
diff --git a/gcc/alias.c b/gcc/alias.c index 2ebde8d73a5..2bc87024f55 100644 --- a/gcc/alias.c +++ b/gcc/alias.c @@ -518,6 +518,98 @@ component_uses_parent_alias_set (const_tree t) } } +/* Return the alias set for the memory pointed to by T, which may be + either a type or an expression. Return -1 if there is nothing + special about dereferencing T. */ + +static alias_set_type +get_deref_alias_set_1 (tree t) +{ + /* If we're not doing any alias analysis, just assume everything + aliases everything else. */ + if (!flag_strict_aliasing) + return 0; + + if (! TYPE_P (t)) + { + tree decl = find_base_decl (t); + + if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl)) + { + /* If we haven't computed the actual alias set, do it now. */ + if (DECL_POINTER_ALIAS_SET (decl) == -2) + { + tree pointed_to_type = TREE_TYPE (TREE_TYPE (decl)); + + /* No two restricted pointers can point at the same thing. + However, a restricted pointer can point at the same thing + as an unrestricted pointer, if that unrestricted pointer + is based on the restricted pointer. So, we make the + alias set for the restricted pointer a subset of the + alias set for the type pointed to by the type of the + decl. */ + alias_set_type pointed_to_alias_set + = get_alias_set (pointed_to_type); + + if (pointed_to_alias_set == 0) + /* It's not legal to make a subset of alias set zero. */ + DECL_POINTER_ALIAS_SET (decl) = 0; + else if (AGGREGATE_TYPE_P (pointed_to_type)) + /* For an aggregate, we must treat the restricted + pointer the same as an ordinary pointer. If we + were to make the type pointed to by the + restricted pointer a subset of the pointed-to + type, then we would believe that other subsets + of the pointed-to type (such as fields of that + type) do not conflict with the type pointed to + by the restricted pointer. */ + DECL_POINTER_ALIAS_SET (decl) + = pointed_to_alias_set; + else + { + DECL_POINTER_ALIAS_SET (decl) = new_alias_set (); + record_alias_subset (pointed_to_alias_set, + DECL_POINTER_ALIAS_SET (decl)); + } + } + + /* We use the alias set indicated in the declaration. */ + return DECL_POINTER_ALIAS_SET (decl); + } + + /* Now all we care about is the type. */ + t = TREE_TYPE (t); + } + + /* If we have an INDIRECT_REF via a void pointer, we don't + know anything about what that might alias. Likewise if the + pointer is marked that way. */ + if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE + || TYPE_REF_CAN_ALIAS_ALL (t)) + return 0; + + return -1; +} + +/* Return the alias set for the memory pointed to by T, which may be + either a type or an expression. */ + +alias_set_type +get_deref_alias_set (tree t) +{ + alias_set_type set = get_deref_alias_set_1 (t); + + /* Fall back to the alias-set of the pointed-to type. */ + if (set == -1) + { + if (! TYPE_P (t)) + t = TREE_TYPE (t); + set = get_alias_set (TREE_TYPE (t)); + } + + return set; +} + /* Return the alias set for T, which may be either a type or an expression. Call language-specific routine for help, if needed. */ @@ -558,66 +650,11 @@ get_alias_set (tree t) STRIP_NOPS (inner); } - /* Check for accesses through restrict-qualified pointers. */ if (INDIRECT_REF_P (inner)) { - tree decl; - - if (TREE_CODE (TREE_OPERAND (inner, 0)) == SSA_NAME) - decl = SSA_NAME_VAR (TREE_OPERAND (inner, 0)); - else - decl = find_base_decl (TREE_OPERAND (inner, 0)); - - if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl)) - { - /* If we haven't computed the actual alias set, do it now. */ - if (DECL_POINTER_ALIAS_SET (decl) == -2) - { - tree pointed_to_type = TREE_TYPE (TREE_TYPE (decl)); - - /* No two restricted pointers can point at the same thing. - However, a restricted pointer can point at the same thing - as an unrestricted pointer, if that unrestricted pointer - is based on the restricted pointer. So, we make the - alias set for the restricted pointer a subset of the - alias set for the type pointed to by the type of the - decl. */ - alias_set_type pointed_to_alias_set - = get_alias_set (pointed_to_type); - - if (pointed_to_alias_set == 0) - /* It's not legal to make a subset of alias set zero. */ - DECL_POINTER_ALIAS_SET (decl) = 0; - else if (AGGREGATE_TYPE_P (pointed_to_type)) - /* For an aggregate, we must treat the restricted - pointer the same as an ordinary pointer. If we - were to make the type pointed to by the - restricted pointer a subset of the pointed-to - type, then we would believe that other subsets - of the pointed-to type (such as fields of that - type) do not conflict with the type pointed to - by the restricted pointer. */ - DECL_POINTER_ALIAS_SET (decl) - = pointed_to_alias_set; - else - { - DECL_POINTER_ALIAS_SET (decl) = new_alias_set (); - record_alias_subset (pointed_to_alias_set, - DECL_POINTER_ALIAS_SET (decl)); - } - } - - /* We use the alias set indicated in the declaration. */ - return DECL_POINTER_ALIAS_SET (decl); - } - - /* If we have an INDIRECT_REF via a void pointer, we don't - know anything about what that might alias. Likewise if the - pointer is marked that way. */ - else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE - || (TYPE_REF_CAN_ALIAS_ALL - (TREE_TYPE (TREE_OPERAND (inner, 0))))) - return 0; + set = get_deref_alias_set_1 (TREE_OPERAND (inner, 0)); + if (set != -1) + return set; } /* Otherwise, pick up the outermost object that we could have a pointer |