- /* Don't allow duplicate entries. */
- if (TREE_CODE (var) != SSA_NAME)
- {
- var_ann_t ann = get_var_ann (var);
-
- if (ann->in_vuse_list || ann->in_v_may_def_list)
- return;
- ann->in_vuse_list = 1;
- }
-
- VEC_safe_push (tree, heap, build_vuses, (tree)var);
-}
-
-
-/* Add VAR to the list of virtual must definitions for INFO. */
-
-static inline void
-append_v_must_def (tree var)
-{
- unsigned i;
-
- /* Don't allow duplicate entries. */
- for (i = 0; i < VEC_length (tree, build_v_must_defs); i++)
- if (var == VEC_index (tree, build_v_must_defs, i))
- return;
-
- VEC_safe_push (tree, heap, build_v_must_defs, (tree)var);
-}
-
-
-/* REF is a tree that contains the entire pointer dereference
- expression, if available, or NULL otherwise. ALIAS is the variable
- we are asking if REF can access. OFFSET and SIZE come from the
- memory access expression that generated this virtual operand. */
-
-static bool
-access_can_touch_variable (tree ref, tree alias, HOST_WIDE_INT offset,
- HOST_WIDE_INT size)
-{
- bool offsetgtz = offset > 0;
- unsigned HOST_WIDE_INT uoffset = (unsigned HOST_WIDE_INT) offset;
- tree base = ref ? get_base_address (ref) : NULL;
-
- /* If ALIAS is .GLOBAL_VAR then the memory reference REF must be
- using a call-clobbered memory tag. By definition, call-clobbered
- memory tags can always touch .GLOBAL_VAR. */
- if (alias == gimple_global_var (cfun))
- return true;
-
- /* If ALIAS is an SFT, it can't be touched if the offset
- and size of the access is not overlapping with the SFT offset and
- size. This is only true if we are accessing through a pointer
- to a type that is the same as SFT_PARENT_VAR. Otherwise, we may
- be accessing through a pointer to some substruct of the
- structure, and if we try to prune there, we will have the wrong
- offset, and get the wrong answer.
- i.e., we can't prune without more work if we have something like
-
- struct gcc_target
- {
- struct asm_out
- {
- const char *byte_op;
- struct asm_int_op
- {
- const char *hi;
- } aligned_op;
- } asm_out;
- } targetm;
-
- foo = &targetm.asm_out.aligned_op;
- return foo->hi;
-
- SFT.1, which represents hi, will have SFT_OFFSET=32 because in
- terms of SFT_PARENT_VAR, that is where it is.
- However, the access through the foo pointer will be at offset 0. */
- if (size != -1
- && TREE_CODE (alias) == STRUCT_FIELD_TAG
- && base
- && TREE_TYPE (base) == TREE_TYPE (SFT_PARENT_VAR (alias))
- && !overlap_subvar (offset, size, alias, NULL))
- {
-#ifdef ACCESS_DEBUGGING
- fprintf (stderr, "Access to ");
- print_generic_expr (stderr, ref, 0);
- fprintf (stderr, " may not touch ");
- print_generic_expr (stderr, alias, 0);
- fprintf (stderr, " in function %s\n", get_name (current_function_decl));
-#endif
- return false;
- }
-
- /* Without strict aliasing, it is impossible for a component access
- through a pointer to touch a random variable, unless that
- variable *is* a structure or a pointer.
-
- That is, given p->c, and some random global variable b,
- there is no legal way that p->c could be an access to b.
-
- Without strict aliasing on, we consider it legal to do something
- like:
-
- struct foos { int l; };
- int foo;
- static struct foos *getfoo(void);
- int main (void)
- {
- struct foos *f = getfoo();
- f->l = 1;
- foo = 2;
- if (f->l == 1)
- abort();
- exit(0);
- }
- static struct foos *getfoo(void)
- { return (struct foos *)&foo; }
-
- (taken from 20000623-1.c)
-
- The docs also say/imply that access through union pointers
- is legal (but *not* if you take the address of the union member,
- i.e. the inverse), such that you can do
-
- typedef union {
- int d;
- } U;
-
- int rv;
- void breakme()
- {
- U *rv0;
- U *pretmp = (U*)&rv;
- rv0 = pretmp;
- rv0->d = 42;
- }
- To implement this, we just punt on accesses through union
- pointers entirely.
- */
- else if (ref
- && flag_strict_aliasing
- && TREE_CODE (ref) != INDIRECT_REF
- && !MTAG_P (alias)
- && (TREE_CODE (base) != INDIRECT_REF
- || TREE_CODE (TREE_TYPE (base)) != UNION_TYPE)
- && !AGGREGATE_TYPE_P (TREE_TYPE (alias))
- && TREE_CODE (TREE_TYPE (alias)) != COMPLEX_TYPE
- && !var_ann (alias)->is_heapvar
- /* When the struct has may_alias attached to it, we need not to
- return true. */
- && get_alias_set (base))
- {
-#ifdef ACCESS_DEBUGGING
- fprintf (stderr, "Access to ");
- print_generic_expr (stderr, ref, 0);
- fprintf (stderr, " may not touch ");
- print_generic_expr (stderr, alias, 0);
- fprintf (stderr, " in function %s\n", get_name (current_function_decl));
-#endif
- return false;
- }
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