[PATCH, Pointer Bounds Checker 14/x] Passes [13/n] Optimize bounds intersections

Ilya Enkovich

2014-10-08 19:19:13 UTC

Hi,

This patch adds removal of unnecessary intersections into checker optimizations.

Thanks,
Ilya
--
2014-10-08 Ilya Enkovich <***@intel.com>

* tree-chkp.c (chkp_release_check_info): New.
(chkp_init_check_info): New.
(chkp_gather_checks_info): New.
(chkp_get_check_result): New.
(chkp_use_outer_bounds_if_possible): New.
(chkp_remove_excess_intersections): New.
(chkp_opt_execute): Run intersections removal
algorithm.

diff --git a/gcc/tree-chkp.c b/gcc/tree-chkp.c
index 5230d14..c9b616b 100644
--- a/gcc/tree-chkp.c
+++ b/gcc/tree-chkp.c
@@ -4569,6 +4569,348 @@ chkp_fill_check_info (gimple stmt, struct check_info *ci)
ci->stmt = stmt;
}

+/* Release structures holding check information
+ for current function. */
+void
+chkp_release_check_info (void)
+{
+ unsigned int n, m;
+
+ if (check_infos.exists ())
+ {
+ for (n = 0; n < check_infos.length (); n++)
+ {
+ for (m = 0; m < check_infos[n].checks.length (); m++)
+ if (check_infos[n].checks[m].addr.pol.exists ())
+ check_infos[n].checks[m].addr.pol.release ();
+ check_infos[n].checks.release ();
+ }
+ check_infos.release ();
+ }
+}
+
+/* Create structures to hold check information
+ for current function. */
+void
+chkp_init_check_info (void)
+{
+ struct bb_checks empty_bbc;
+ int n;
+
+ empty_bbc.checks = vNULL;
+
+ chkp_release_check_info ();
+
+ check_infos.create (last_basic_block_for_fn (cfun));
+ for (n = 0; n < last_basic_block_for_fn (cfun); n++)
+ {
+ check_infos.safe_push (empty_bbc);
+ check_infos.last ().checks.create (0);
+ }
+}
+
+/* Find all checks in current function and store info about them
+ in check_infos. */
+void
+chkp_gather_checks_info (void)
+{
+ basic_block bb;
+ gimple_stmt_iterator i;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Gathering information about checks...\n");
+
+ chkp_init_check_info ();
+
+ FOR_EACH_BB_FN (bb, cfun)
+ {
+ struct bb_checks *bbc = &check_infos[bb->index];
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Searching checks in BB%d...\n", bb->index);
+
+ for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
+ {
+ gimple stmt = gsi_stmt (i);
+
+ if (gimple_code (stmt) != GIMPLE_CALL)
+ continue;
+
+ if (gimple_call_fndecl (stmt) == chkp_checkl_fndecl
+ || gimple_call_fndecl (stmt) == chkp_checku_fndecl)
+ {
+ struct check_info ci;
+
+ chkp_fill_check_info (stmt, &ci);
+ bbc->checks.safe_push (ci);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Adding check information:\n");
+ fprintf (dump_file, " bounds: ");
+ print_generic_expr (dump_file, ci.bounds, 0);
+ fprintf (dump_file, "\n address: ");
+ chkp_print_addr (ci.addr);
+ fprintf (dump_file, "\n check: ");
+ print_gimple_stmt (dump_file, stmt, 0, 0);
+ }
+ }
+ }
+ }
+}
+
+/* Return 1 if check CI against BOUNDS always pass,
+ -1 if check CI against BOUNDS always fails and
+ 0 if we cannot compute check result. */
+int
+chkp_get_check_result (struct check_info *ci, tree bounds)
+{
+ gimple bnd_def;
+ address_t bound_val;
+ int sign, res = 0;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Trying to compute result of the check\n");
+ fprintf (dump_file, " check: ");
+ print_gimple_stmt (dump_file, ci->stmt, 0, 0);
+ fprintf (dump_file, " address: ");
+ chkp_print_addr (ci->addr);
+ fprintf (dump_file, "\n bounds: ");
+ print_generic_expr (dump_file, bounds, 0);
+ fprintf (dump_file, "\n");
+ }
+
+ if (TREE_CODE (bounds) != SSA_NAME)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: bounds tree code is not ssa_name\n");
+ return 0;
+ }
+
+ if (bounds == zero_bounds)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: always pass with zero bounds\n");
+ return 1;
+ }
+
+ if (bounds == none_bounds)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: always fails with none bounds\n");
+ return -1;
+ }
+
+ bnd_def = SSA_NAME_DEF_STMT (bounds);
+ /* Currently we handle cases when bounds are result of bndmk
+ or loaded static bounds var. */
+ if (gimple_code (bnd_def) == GIMPLE_CALL
+ && gimple_call_fndecl (bnd_def) == chkp_bndmk_fndecl)
+ {
+ bound_val.pol.create (0);
+ chkp_collect_value (gimple_call_arg (bnd_def, 0), bound_val);
+ if (ci->type == CHECK_UPPER_BOUND)
+ {
+ address_t size_val;
+ size_val.pol.create (0);
+ chkp_collect_value (gimple_call_arg (bnd_def, 1), size_val);
+ chkp_add_addr_addr (bound_val, size_val);
+ size_val.pol.release ();
+ chkp_add_addr_item (bound_val, integer_minus_one_node, NULL);
+ }
+ }
+ else if (gimple_code (bnd_def) == GIMPLE_ASSIGN
+ && gimple_assign_rhs1 (bnd_def) == chkp_zero_bounds_var)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: always pass with zero bounds\n");
+ return 1;
+ }
+ else if (gimple_code (bnd_def) == GIMPLE_ASSIGN
+ && gimple_assign_rhs1 (bnd_def) == chkp_none_bounds_var)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: always fails with none bounds\n");
+ return -1;
+ }
+ else if (gimple_code (bnd_def) == GIMPLE_ASSIGN
+ && TREE_CODE (gimple_assign_rhs1 (bnd_def)) == VAR_DECL)
+ {
+ tree bnd_var = gimple_assign_rhs1 (bnd_def);
+ tree var;
+ tree size;
+
+ if (!DECL_INITIAL (bnd_var)
+ || DECL_INITIAL (bnd_var) == error_mark_node)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: cannot compute bounds\n");
+ return 0;
+ }
+
+ gcc_assert (TREE_CODE (DECL_INITIAL (bnd_var)) == ADDR_EXPR);
+ var = TREE_OPERAND (DECL_INITIAL (bnd_var), 0);
+
+ bound_val.pol.create (0);
+ chkp_collect_value (DECL_INITIAL (bnd_var), bound_val);
+ if (ci->type == CHECK_UPPER_BOUND)
+ {
+ if (TREE_CODE (var) == VAR_DECL)
+ {
+ if (DECL_SIZE (var)
+ && !chkp_variable_size_type (TREE_TYPE (var)))
+ size = DECL_SIZE_UNIT (var);
+ else
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: cannot compute bounds\n");
+ return 0;
+ }
+ }
+ else
+ {
+ gcc_assert (TREE_CODE (var) == STRING_CST);
+ size = build_int_cst (size_type_node,
+ TREE_STRING_LENGTH (var));
+ }
+
+ address_t size_val;
+ size_val.pol.create (0);
+ chkp_collect_value (size, size_val);
+ chkp_add_addr_addr (bound_val, size_val);
+ size_val.pol.release ();
+ chkp_add_addr_item (bound_val, integer_minus_one_node, NULL);
+ }
+ }
+ else
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: cannot compute bounds\n");
+ return 0;
+ }
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " bound value: ");
+ chkp_print_addr (bound_val);
+ fprintf (dump_file, "\n");
+ }
+
+ chkp_sub_addr_addr (bound_val, ci->addr);
+
+ if (!chkp_is_constant_addr (bound_val, &sign))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: cannot compute result\n");
+
+ res = 0;
+ }
+ else if (sign == 0
+ || (ci->type == CHECK_UPPER_BOUND && sign > 0)
+ || (ci->type == CHECK_LOWER_BOUND && sign < 0))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: always pass\n");
+
+ res = 1;
+ }
+ else
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " result: always fail\n");
+
+ res = -1;
+ }
+
+ bound_val.pol.release ();
+
+ return res;
+}
+
+/* For bounds used in CI check if bounds are produced by
+ intersection and we may use outer bounds instead. If
+ transformation is possible then fix check statement and
+ recompute its info. */
+void
+chkp_use_outer_bounds_if_possible (struct check_info *ci)
+{
+ gimple bnd_def;
+ tree bnd1, bnd2, bnd_res = NULL;
+ int check_res1, check_res2;
+
+ if (TREE_CODE (ci->bounds) != SSA_NAME)
+ return;
+
+ bnd_def = SSA_NAME_DEF_STMT (ci->bounds);
+ if (gimple_code (bnd_def) != GIMPLE_CALL
+ || gimple_call_fndecl (bnd_def) != chkp_intersect_fndecl)
+ return;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Check if bounds intersection is redundant: \n");
+ fprintf (dump_file, " check: ");
+ print_gimple_stmt (dump_file, ci->stmt, 0, 0);
+ fprintf (dump_file, " intersection: ");
+ print_gimple_stmt (dump_file, bnd_def, 0, 0);
+ fprintf (dump_file, "\n");
+ }
+
+ bnd1 = gimple_call_arg (bnd_def, 0);
+ bnd2 = gimple_call_arg (bnd_def, 1);
+
+ check_res1 = chkp_get_check_result (ci, bnd1);
+ check_res2 = chkp_get_check_result (ci, bnd2);
+ if (check_res1 == 1)
+ bnd_res = bnd2;
+ else if (check_res1 == -1)
+ bnd_res = bnd1;
+ else if (check_res2 == 1)
+ bnd_res = bnd1;
+ else if (check_res2 == -1)
+ bnd_res = bnd2;
+
+ if (bnd_res)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " action: use ");
+ print_generic_expr (dump_file, bnd2, 0);
+ fprintf (dump_file, " instead of ");
+ print_generic_expr (dump_file, ci->bounds, 0);
+ }
+
+ ci->bounds = bnd_res;
+ gimple_call_set_arg (ci->stmt, 1, bnd_res);
+ update_stmt (ci->stmt);
+ }
+}
+
+/* Try to find checks whose bounds were produced by intersection
+ which does not affect check result. In such check outer bounds
+ are used instead. It allows to remove excess intersections
+ and helps to compare checks. */
+void
+chkp_remove_excess_intersections (void)
+{
+ basic_block bb;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Searching for redundant bounds intersections...\n");
+
+ FOR_EACH_BB_FN (bb, cfun)
+ {
+ struct bb_checks *bbc = &check_infos[bb->index];
+ unsigned int no;
+
+ /* Iterate throw all found checks in BB. */
+ for (no = 0; no < bbc->checks.length (); no++)
+ if (bbc->checks[no].stmt)
+ chkp_use_outer_bounds_if_possible (&bbc->checks[no]);
+ }
+}
+
/* Return fast version of string function FNCODE. */
tree
chkp_get_nobnd_fndecl (enum built_in_function fncode)
@@ -4848,6 +5190,12 @@ chkp_opt_execute (void)
and thus we put it before checks search. */
chkp_optimize_string_function_calls ();

+ chkp_gather_checks_info ();
+
+ chkp_remove_excess_intersections ();
+
+ chkp_release_check_info ();
+
chkp_opt_fini ();

return 0;