1 /* This plugin contains an analysis pass that detects and warns about
2 self-assignment statements. */
3 /* { dg-options "-O" } */
5 #include "gcc-plugin.h"
11 #include "basic-block.h"
14 #include "tree-pass.h"
18 int plugin_is_GPL_compatible;
20 /* Indicate whether to check overloaded operator '=', which is performed by
21 default. To disable it, use -fplugin-arg-NAME-no-check-operator-eq. */
22 bool check_operator_eq = true;
24 /* Given a rhs EXPR of a gimple assign statement, if it is
25 - SSA_NAME : returns its var decl, or, if it is a temp variable,
26 returns the rhs of its SSA def statement.
27 - VAR_DECL, PARM_DECL, FIELD_DECL, or a reference expression :
29 - any other expression : returns NULL_TREE. */
32 get_real_ref_rhs (tree expr)
34 switch (TREE_CODE (expr))
38 /* Given a self-assign statement, say foo.x = foo.x,
39 the IR (after SSA) looks like:
44 So if the rhs EXPR is an SSA_NAME of a temp variable,
45 e.g. D.1797_14, we need to grab the rhs of its SSA def
46 statement (i.e. foo.x). */
47 tree vdecl = SSA_NAME_VAR (expr);
48 if (DECL_ARTIFICIAL (vdecl)
49 && !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
51 gimple def_stmt = SSA_NAME_DEF_STMT (expr);
52 /* We are only interested in an assignment with a single
53 rhs operand because if it is not, the original assignment
54 will not possibly be a self-assignment. */
55 if (is_gimple_assign (def_stmt)
56 && (get_gimple_rhs_class (gimple_assign_rhs_code (def_stmt))
57 == GIMPLE_SINGLE_RHS))
58 return get_real_ref_rhs (gimple_assign_rhs1 (def_stmt));
77 /* Given an expression tree, EXPR, that may contains SSA names, returns an
78 equivalent tree with the SSA names converted to var/parm/field decls
79 so that it can be used with '%E' format modifier when emitting warning
82 This function currently only supports VAR/PARM/FIELD_DECL, reference
83 expressions (COMPONENT_REF, INDIRECT_REF, ARRAY_REF), integer constant,
84 and SSA_NAME. If EXPR contains any other tree nodes (e.g. an arithmetic
85 expression appears in array index), NULL_TREE is returned. */
88 get_non_ssa_expr (tree expr)
90 switch (TREE_CODE (expr))
103 tree base, orig_base = TREE_OPERAND (expr, 0);
104 tree component, orig_component = TREE_OPERAND (expr, 1);
105 base = get_non_ssa_expr (orig_base);
108 component = get_non_ssa_expr (orig_component);
111 /* If either BASE or COMPONENT is converted, build a new
112 component reference tree. */
113 if (base != orig_base || component != orig_component)
114 return build3 (COMPONENT_REF, TREE_TYPE (component),
115 base, component, NULL_TREE);
121 tree orig_base = TREE_OPERAND (expr, 0);
122 tree base = get_non_ssa_expr (orig_base);
125 /* If BASE is converted, build a new indirect reference tree. */
126 if (base != orig_base)
127 return build1 (INDIRECT_REF, TREE_TYPE (TREE_TYPE (base)), base);
133 tree array, orig_array = TREE_OPERAND (expr, 0);
134 tree index, orig_index = TREE_OPERAND (expr, 1);
135 array = get_non_ssa_expr (orig_array);
138 index = get_non_ssa_expr (orig_index);
141 /* If either ARRAY or INDEX is converted, build a new array
143 if (array != orig_array || index != orig_index)
144 return build4 (ARRAY_REF, TREE_TYPE (expr), array, index,
145 TREE_OPERAND (expr, 2), TREE_OPERAND (expr, 3));
151 tree vdecl = SSA_NAME_VAR (expr);
152 if (DECL_ARTIFICIAL (vdecl)
153 && !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
155 gimple def_stmt = SSA_NAME_DEF_STMT (expr);
156 if (is_gimple_assign (def_stmt)
157 && (get_gimple_rhs_class (gimple_assign_rhs_code (def_stmt))
158 == GIMPLE_SINGLE_RHS))
159 vdecl = gimple_assign_rhs1 (def_stmt);
161 return get_non_ssa_expr (vdecl);
166 /* Return NULL_TREE for any other kind of tree nodes. */
171 /* Given the LHS and (real) RHS of a gimple assign statement, STMT, check if
172 they are the same. If so, print a warning message about self-assignment. */
175 compare_and_warn (gimple stmt, tree lhs, tree rhs)
177 if (operand_equal_p (lhs, rhs, OEP_PURE_SAME))
180 location = (gimple_has_location (stmt)
181 ? gimple_location (stmt)
183 ? DECL_SOURCE_LOCATION (lhs)
185 /* If LHS contains any tree node not currently supported by
186 get_non_ssa_expr, simply emit a generic warning without
187 specifying LHS in the message. */
188 lhs = get_non_ssa_expr (lhs);
190 warning_at (location, 0, G_("%qE is assigned to itself"), lhs);
192 warning_at (location, 0, G_("self-assignment detected"));
196 /* Check and warn if STMT is a self-assign statement. */
199 warn_self_assign (gimple stmt)
203 /* Check assigment statement. */
204 if (is_gimple_assign (stmt)
205 && (get_gimple_rhs_class (gimple_assign_rhs_code (stmt))
206 == GIMPLE_SINGLE_RHS))
208 rhs = get_real_ref_rhs (gimple_assign_rhs1 (stmt));
212 lhs = gimple_assign_lhs (stmt);
213 if (TREE_CODE (lhs) == SSA_NAME)
215 lhs = SSA_NAME_VAR (lhs);
216 if (DECL_ARTIFICIAL (lhs))
220 compare_and_warn (stmt, lhs, rhs);
222 /* Check overloaded operator '=' (if enabled). */
223 else if (check_operator_eq && is_gimple_call (stmt))
225 tree fdecl = gimple_call_fndecl (stmt);
226 if (fdecl && (DECL_NAME (fdecl) == maybe_get_identifier ("operator=")))
228 /* If 'operator=' takes reference operands, the arguments will be
229 ADDR_EXPR trees. In this case, just remove the address-taken
230 operator before we compare the lhs and rhs. */
231 lhs = gimple_call_arg (stmt, 0);
232 if (TREE_CODE (lhs) == ADDR_EXPR)
233 lhs = TREE_OPERAND (lhs, 0);
234 rhs = gimple_call_arg (stmt, 1);
235 if (TREE_CODE (rhs) == ADDR_EXPR)
236 rhs = TREE_OPERAND (rhs, 0);
238 compare_and_warn (stmt, lhs, rhs);
243 /* Entry point for the self-assignment detection pass. */
246 execute_warn_self_assign (void)
248 gimple_stmt_iterator gsi;
253 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
254 warn_self_assign (gsi_stmt (gsi));
260 /* Pass gate function. Currently always returns true. */
263 gate_warn_self_assign (void)
268 static struct gimple_opt_pass pass_warn_self_assign =
272 "warn_self_assign", /* name */
273 gate_warn_self_assign, /* gate */
274 execute_warn_self_assign, /* execute */
277 0, /* static_pass_number */
279 PROP_ssa, /* properties_required */
280 0, /* properties_provided */
281 0, /* properties_destroyed */
282 0, /* todo_flags_start */
283 TODO_dump_func /* todo_flags_finish */
287 /* The initialization routine exposed to and called by GCC. The spec of this
288 function is defined in gcc/gcc-plugin.h.
290 PLUGIN_NAME - name of the plugin (useful for error reporting)
291 ARGC - the size of the ARGV array
292 ARGV - an array of key-value argument pair
294 Returns 0 if initialization finishes successfully.
296 Note that this function needs to be named exactly "plugin_init". */
299 plugin_init (struct plugin_name_args *plugin_info,
300 struct plugin_gcc_version *version)
302 struct register_pass_info pass_info;
303 const char *plugin_name = plugin_info->base_name;
304 int argc = plugin_info->argc;
305 struct plugin_argument *argv = plugin_info->argv;
309 if (!plugin_default_version_check (version, version))
312 /* Self-assign detection should happen after SSA is constructed. */
313 pass_info.pass = &pass_warn_self_assign.pass;
314 pass_info.reference_pass_name = "ssa";
315 pass_info.ref_pass_instance_number = 1;
316 pass_info.pos_op = PASS_POS_INSERT_AFTER;
318 /* Process the plugin arguments. This plugin takes the following arguments:
319 check-operator-eq, no-check-operator-eq, enable, and disable.
320 By default, the analysis is enabled with 'operator=' checked. */
321 for (i = 0; i < argc; ++i)
323 if (!strcmp (argv[i].key, "check-operator-eq"))
326 warning (0, G_("option '-fplugin-arg-%s-check-operator-eq=%s'"
327 " ignored (superfluous '=%s')"),
328 plugin_name, argv[i].value, argv[i].value);
330 check_operator_eq = true;
332 else if (!strcmp (argv[i].key, "no-check-operator-eq"))
335 warning (0, G_("option '-fplugin-arg-%s-no-check-operator-eq=%s'"
336 " ignored (superfluous '=%s')"),
337 plugin_name, argv[i].value, argv[i].value);
339 check_operator_eq = false;
341 else if (!strcmp (argv[i].key, "enable"))
344 warning (0, G_("option '-fplugin-arg-%s-enable=%s' ignored"
345 " (superfluous '=%s')"),
346 plugin_name, argv[i].value, argv[i].value);
350 else if (!strcmp (argv[i].key, "disable"))
353 warning (0, G_("option '-fplugin-arg-%s-disable=%s' ignored"
354 " (superfluous '=%s')"),
355 plugin_name, argv[i].value, argv[i].value);
360 warning (0, G_("plugin %qs: unrecognized argument %qs ignored"),
361 plugin_name, argv[i].key);
364 /* Register this new pass with GCC if the analysis is enabled. */
366 register_callback (plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,