On Wed, Oct 12, 2011 at 7:16 PM, Michael Matz <[email protected]> wrote:
> Hi,
>
> this adds a mean to retain restrict information without relying on
> restrict casts. In the patch it's emitted by the gimplifier when it sees
> a norestrict->restrict cast (which from then on is useless), at which
> point also the tag of that restrict pointer is generated. That's later
> used by the aliasing machinery to associate it with a restrict tag uid.
>
> In particular it will be possible to associate pointers coming from
> different inline instance of the same function with the same restrict tag,
> and hence make them conflict.
>
> This patch will fix the currently XFAILed tree-ssa/restrict-4.c again, as
> well as fix PR 50419. It also still fixes the original testcase of
> PR 49279. But it will break the checked in testcase for this bug report.
> I believe the checked in testcase is invalid as follows:
>
> struct S { int a; int *__restrict p; };
>
> int
> foo (int *p, int *q)
> {
> struct S s, *t;
> s.a = 1;
> s.p = p; // 1
> t = wrap(&s); // 2 t=&s in effect, but GCC doesn't see this
> t->p = q; // 3
> s.p[0] = 0; // 4
> t->p[0] = 1; // 5
> return s.p[0]; // 6
> }
>
> Assignment 2 means that t->p points to s.p. Assignment 3 changes t->p and
> s.p, but the change to s.p doesn't occur through a pointer based on t->p
> or any other restrict pointer, in fact it doesn't occur through any
> explicit initialization or assignment, but rather through in indirect
> access via a different pointer. Hence the accesses to the same memory
> object at s.p[0] and t->p[0] were undefined because both accesses weren't
> through pointers based on each other.
Ick, that actually shows a bug in points-to handling (well, in
pt_solutions_same_restrict_base handling). While we correctly
see that p escapes though wrap() and that t points to ESCAPED
we don't check in
bool
pt_solutions_same_restrict_base (struct pt_solution *pt1,
struct pt_solution *pt2)
{
/* If we deal with points-to solutions of two restrict qualified
pointers solely rely on the pointed-to variable bitmap intersection.
For two pointers that are based on each other the bitmaps will
intersect. */
if (pt1->vars_contains_restrict
&& pt2->vars_contains_restrict)
{
gcc_assert (pt1->vars && pt2->vars);
return bitmap_intersect_p (pt1->vars, pt2->vars);
}
whether the solutions overlap in the ESCAPED bit (remember
ESCAPED contents are not expanded into the pointers pt->vars
bitmaps but just noted as the pt->escaped flag). We ignore
pt->nonlocal as well, but that was by design ... so, re-try with
Index: tree-ssa-structalias.c
===================================================================
--- tree-ssa-structalias.c (revision 179962)
+++ tree-ssa-structalias.c (working copy)
@@ -6079,12 +6079,15 @@ pt_solutions_intersect_1 (struct pt_solu
return true;
/* If either points to unknown global memory and the other points to
- any global memory they alias. */
- if ((pt1->nonlocal
- && (pt2->nonlocal
- || pt2->vars_contains_global))
- || (pt2->nonlocal
- && pt1->vars_contains_global))
+ any global memory they alias. If both points-to sets are based
+ off a restrict qualified pointer ignore any overlaps with NONLOCAL. */
+ if (!(pt1->vars_contains_restrict
+ && pt2->vars_contains_restrict)
+ && ((pt1->nonlocal
+ && (pt2->nonlocal
+ || pt2->vars_contains_global))
+ || (pt2->nonlocal
+ && pt1->vars_contains_global)))
return true;
/* Check the escaped solution if required. */
@@ -6148,18 +6151,7 @@ bool
pt_solutions_same_restrict_base (struct pt_solution *pt1,
struct pt_solution *pt2)
{
- /* If we deal with points-to solutions of two restrict qualified
- pointers solely rely on the pointed-to variable bitmap intersection.
- For two pointers that are based on each other the bitmaps will
- intersect. */
- if (pt1->vars_contains_restrict
- && pt2->vars_contains_restrict)
- {
- gcc_assert (pt1->vars && pt2->vars);
- return bitmap_intersect_p (pt1->vars, pt2->vars);
- }
-
- return true;
+ return pt_solutions_intersect (pt1, pt2);
}
> I expect some bike shedding about the name of the tree code, hence only
> RFC, no Changelog or anything. It's only ligthly tested in so far as it's
> currently in the target libs of a regstrap on x86_64-linux.
>
>
> Ciao,
> Michael.
>
> Index: tree-pretty-print.c
> ===================================================================
> *** tree-pretty-print.c (revision 179855)
> --- tree-pretty-print.c (working copy)
> *************** dump_generic_node (pretty_printer *buffe
> *** 1708,1713 ****
> --- 1708,1721 ----
> pp_character (buffer, '>');
> break;
>
> + case ADD_RESTRICT:
> + pp_string (buffer, "ADD_RESTRICT <");
> + dump_generic_node (buffer, TREE_OPERAND (node, 0), spc, flags, false);
> + pp_string (buffer, ", ");
> + dump_generic_node (buffer, TREE_OPERAND (node, 1), spc, flags, false);
> + pp_character (buffer, '>');
> + break;
> +
> case ABS_EXPR:
> pp_string (buffer, "ABS_EXPR <");
> dump_generic_node (buffer, TREE_OPERAND (node, 0), spc, flags, false);
> Index: expr.c
> ===================================================================
> *** expr.c (revision 179855)
> --- expr.c (working copy)
> *************** expand_expr_real_2 (sepops ops, rtx targ
> *** 7782,7787 ****
> --- 7782,7790 ----
>
> switch (code)
> {
> + case ADD_RESTRICT:
> + /* We can handle add_restrict like a conversion, treeop1 will be
> ignored.
> + FALLTHRU. */
> case NON_LVALUE_EXPR:
> case PAREN_EXPR:
> CASE_CONVERT:
> Index: gimple-pretty-print.c
> ===================================================================
> *** gimple-pretty-print.c (revision 179855)
> --- gimple-pretty-print.c (working copy)
> *************** dump_binary_rhs (pretty_printer *buffer,
> *** 334,339 ****
> --- 334,340 ----
> case COMPLEX_EXPR:
> case MIN_EXPR:
> case MAX_EXPR:
> + case ADD_RESTRICT:
> case VEC_WIDEN_MULT_HI_EXPR:
> case VEC_WIDEN_MULT_LO_EXPR:
> case VEC_PACK_TRUNC_EXPR:
> Index: gimplify.c
> ===================================================================
> *** gimplify.c (revision 179855)
> --- gimplify.c (working copy)
> *************** gimplify_modify_expr (tree *expr_p, gimp
> *** 4525,4530 ****
> --- 4525,4537 ----
> STRIP_USELESS_TYPE_CONVERSION (*from_p);
> if (!useless_type_conversion_p (TREE_TYPE (*to_p), TREE_TYPE
> (*from_p)))
> *from_p = fold_convert_loc (loc, TREE_TYPE (*to_p), *from_p);
> + else if (POINTER_TYPE_P (TREE_TYPE (*from_p))
> + && TYPE_RESTRICT (TREE_TYPE (*to_p))
> + && !TYPE_RESTRICT (TREE_TYPE (*from_p)))
> + *from_p = fold_build2_loc (loc, ADD_RESTRICT, TREE_TYPE (*to_p),
> + *from_p,
> + build_int_cst (integer_type_node,
> + allocate_decl_uid ()));
> }
>
> /* See if any simplifications can be done based on what the RHS is. */
> Index: tree.def
> ===================================================================
> *** tree.def (revision 179855)
> --- tree.def (working copy)
> *************** DEFTREECODE (WITH_SIZE_EXPR, "with_size_
> *** 961,966 ****
> --- 961,968 ----
> generated by the builtin targetm.vectorize.mask_for_load_builtin_decl. */
> DEFTREECODE (REALIGN_LOAD_EXPR, "realign_load", tcc_expression, 3)
>
> + DEFTREECODE (ADD_RESTRICT, "add_restrict", tcc_binary, 2)
> +
> /* Low-level memory addressing. Operands are BASE (address of static or
> global variable or register), OFFSET (integer constant),
> INDEX (register), STEP (integer constant), INDEX2 (register),
> Index: tree-inline.c
> ===================================================================
> *** tree-inline.c (revision 179855)
> --- tree-inline.c (working copy)
> *************** estimate_operator_cost (enum tree_code c
> *** 3279,3284 ****
> --- 3279,3285 ----
> case COMPLEX_EXPR:
> case PAREN_EXPR:
> case VIEW_CONVERT_EXPR:
> + case ADD_RESTRICT:
> return 0;
>
> /* Assign cost of 1 to usual operations.
> Index: tree-ssa-structalias.c
> ===================================================================
> *** tree-ssa-structalias.c (revision 179855)
> --- tree-ssa-structalias.c (working copy)
> *************** make_transitive_closure_constraints (var
> *** 3602,3632 ****
> /* Temporary storage for fake var decls. */
> struct obstack fake_var_decl_obstack;
>
> ! /* Build a fake VAR_DECL acting as referrer to a DECL_UID. */
>
> static tree
> ! build_fake_var_decl (tree type)
> {
> tree decl = (tree) XOBNEW (&fake_var_decl_obstack, struct tree_var_decl);
> memset (decl, 0, sizeof (struct tree_var_decl));
> TREE_SET_CODE (decl, VAR_DECL);
> TREE_TYPE (decl) = type;
> ! DECL_UID (decl) = allocate_decl_uid ();
> SET_DECL_PT_UID (decl, -1);
> layout_decl (decl, 0);
> return decl;
> }
>
> ! /* Create a new artificial heap variable with NAME.
> ! Return the created variable. */
>
> static varinfo_t
> ! make_heapvar (const char *name)
> {
> varinfo_t vi;
> tree heapvar;
>
> ! heapvar = build_fake_var_decl (ptr_type_node);
> DECL_EXTERNAL (heapvar) = 1;
>
> vi = new_var_info (heapvar, name);
> --- 3602,3644 ----
> /* Temporary storage for fake var decls. */
> struct obstack fake_var_decl_obstack;
>
> ! /* Build a fake VAR_DECL with DECL_UID being UID (which probably has
> ! to be ultimately allocated by allocate_decl_uid()). */
>
> static tree
> ! build_fake_var_decl_uid (tree type, int uid)
> {
> tree decl = (tree) XOBNEW (&fake_var_decl_obstack, struct tree_var_decl);
> memset (decl, 0, sizeof (struct tree_var_decl));
> TREE_SET_CODE (decl, VAR_DECL);
> TREE_TYPE (decl) = type;
> ! DECL_UID (decl) = uid;
> SET_DECL_PT_UID (decl, -1);
> layout_decl (decl, 0);
> return decl;
> }
>
> ! /* Build a fake VAR_DECL acting as referrer to a DECL_UID. */
> !
> ! static tree
> ! build_fake_var_decl (tree type)
> ! {
> ! return build_fake_var_decl_uid (type, allocate_decl_uid ());
> ! }
> !
> ! /* Create a new artificial heap variable with NAME and UID.
> ! If UID is -1 allocate a new one. Return the created variable. */
>
> static varinfo_t
> ! make_heapvar (const char *name, int uid)
> {
> varinfo_t vi;
> tree heapvar;
>
> ! if (uid == -1)
> ! heapvar = build_fake_var_decl (ptr_type_node);
> ! else
> ! heapvar = build_fake_var_decl_uid (ptr_type_node, uid);
> DECL_EXTERNAL (heapvar) = 1;
>
> vi = new_var_info (heapvar, name);
> *************** make_heapvar (const char *name)
> *** 3642,3657 ****
> return vi;
> }
>
> ! /* Create a new artificial heap variable with NAME and make a
> ! constraint from it to LHS. Return the created variable. */
>
> ! static varinfo_t
> ! make_constraint_from_heapvar (varinfo_t lhs, const char *name)
> {
> ! varinfo_t vi = make_heapvar (name);
> make_constraint_from (lhs, vi->id);
> !
> ! return vi;
> }
>
> /* Create a new artificial heap variable with NAME and make a
> --- 3654,3673 ----
> return vi;
> }
>
> ! /* Create a new artificial heap variable with NAME and UID and make a
> ! constraint from it to LHS. Set flags according to a tag used
> ! for tracking restrict pointers. */
>
> ! static void
> ! make_constraint_from_restrict_uid (varinfo_t lhs, const char *name, int uid)
> {
> ! varinfo_t vi;
> ! vi = make_heapvar (name, uid);
> make_constraint_from (lhs, vi->id);
> ! vi->is_restrict_var = 1;
> ! vi->is_global_var = 0;
> ! vi->is_special_var = 1;
> ! vi->may_have_pointers = 0;
> }
>
> /* Create a new artificial heap variable with NAME and make a
> *************** make_constraint_from_heapvar (varinfo_t
> *** 3661,3672 ****
> static void
> make_constraint_from_restrict (varinfo_t lhs, const char *name)
> {
> ! varinfo_t vi;
> ! vi = make_constraint_from_heapvar (lhs, name);
> ! vi->is_restrict_var = 1;
> ! vi->is_global_var = 0;
> ! vi->is_special_var = 1;
> ! vi->may_have_pointers = 0;
> }
>
> /* In IPA mode there are varinfos for different aspects of reach
> --- 3677,3683 ----
> static void
> make_constraint_from_restrict (varinfo_t lhs, const char *name)
> {
> ! make_constraint_from_restrict_uid (lhs, name, -1);
> }
>
> /* In IPA mode there are varinfos for different aspects of reach
> *************** handle_lhs_call (gimple stmt, tree lhs,
> *** 3846,3852 ****
> varinfo_t vi;
> struct constraint_expr tmpc;
> rhsc = NULL;
> ! vi = make_heapvar ("HEAP");
> /* We delay marking allocated storage global until we know if
> it escapes. */
> DECL_EXTERNAL (vi->decl) = 0;
> --- 3857,3863 ----
> varinfo_t vi;
> struct constraint_expr tmpc;
> rhsc = NULL;
> ! vi = make_heapvar ("HEAP", -1);
> /* We delay marking allocated storage global until we know if
> it escapes. */
> DECL_EXTERNAL (vi->decl) = 0;
> *************** find_func_aliases (gimple origt)
> *** 4494,4499 ****
> --- 4505,4515 ----
> && (!in_ipa_mode
> || DECL_EXTERNAL (lhsop) || TREE_PUBLIC (lhsop)))
> make_escape_constraint (rhsop);
> + /* Add the specified restrict tag. */
> + else if (gimple_assign_rhs_code (t) == ADD_RESTRICT)
> + make_constraint_from_restrict_uid (get_vi_for_tree (lhsop),
> + "RESTRICT_TAG",
> + TREE_INT_CST_LOW
> (gimple_assign_rhs2 (t)));
> }
> /* Handle escapes through return. */
> else if (gimple_code (t) == GIMPLE_RETURN
> Index: tree-cfg.c
> ===================================================================
> *** tree-cfg.c (revision 179855)
> --- tree-cfg.c (working copy)
> *************** do_pointer_plus_expr_check:
> *** 3567,3572 ****
> --- 3567,3587 ----
> return false;
> }
>
> + case ADD_RESTRICT:
> + {
> + if (!POINTER_TYPE_P (rhs1_type)
> + || !useless_type_conversion_p (lhs_type, rhs1_type)
> + || !useless_type_conversion_p (integer_type_node, rhs2_type))
> + {
> + error ("Invalid use of add_restrict");
> + debug_generic_stmt (lhs_type);
> + debug_generic_stmt (rhs1_type);
> + debug_generic_stmt (rhs2_type);
> + return true;
> + }
> + return false;
> + }
> +
> case TRUTH_ANDIF_EXPR:
> case TRUTH_ORIF_EXPR:
> case TRUTH_AND_EXPR:
>
