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"
16 #include "plugin-version.h"
17 #include "diagnostic.h"
19 int plugin_is_GPL_compatible;
21 /* Indicate whether to check overloaded operator '=', which is performed by
22 default. To disable it, use -fplugin-arg-NAME-no-check-operator-eq. */
23 bool check_operator_eq = true;
25 /* Given a rhs EXPR of a gimple assign statement, if it is
26 - SSA_NAME : returns its var decl, or, if it is a temp variable,
27 returns the rhs of its SSA def statement.
28 - VAR_DECL, PARM_DECL, FIELD_DECL, or a reference expression :
30 - any other expression : returns NULL_TREE. */
33 get_real_ref_rhs (tree expr)
35 switch (TREE_CODE (expr))
39 /* Given a self-assign statement, say foo.x = foo.x,
40 the IR (after SSA) looks like:
45 So if the rhs EXPR is an SSA_NAME of a temp variable,
46 e.g. D.1797_14, we need to grab the rhs of its SSA def
47 statement (i.e. foo.x). */
48 tree vdecl = SSA_NAME_VAR (expr);
49 if (DECL_ARTIFICIAL (vdecl)
50 && !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
52 gimple def_stmt = SSA_NAME_DEF_STMT (expr);
53 /* We are only interested in an assignment with a single
54 rhs operand because if it is not, the original assignment
55 will not possibly be a self-assignment. */
56 if (gimple_assign_single_p (def_stmt))
57 return get_real_ref_rhs (gimple_assign_rhs1 (def_stmt));
76 /* Given an expression tree, EXPR, that may contains SSA names, returns an
77 equivalent tree with the SSA names converted to var/parm/field decls
78 so that it can be used with '%E' format modifier when emitting warning
81 This function currently only supports VAR/PARM/FIELD_DECL, reference
82 expressions (COMPONENT_REF, INDIRECT_REF, ARRAY_REF), integer constant,
83 and SSA_NAME. If EXPR contains any other tree nodes (e.g. an arithmetic
84 expression appears in array index), NULL_TREE is returned. */
87 get_non_ssa_expr (tree expr)
89 switch (TREE_CODE (expr))
102 tree base, orig_base = TREE_OPERAND (expr, 0);
103 tree component, orig_component = TREE_OPERAND (expr, 1);
104 base = get_non_ssa_expr (orig_base);
107 component = get_non_ssa_expr (orig_component);
110 /* If either BASE or COMPONENT is converted, build a new
111 component reference tree. */
112 if (base != orig_base || component != orig_component)
113 return build3 (COMPONENT_REF, TREE_TYPE (component),
114 base, component, NULL_TREE);
120 tree orig_base = TREE_OPERAND (expr, 0);
121 if (TREE_CODE (orig_base) == SSA_NAME)
123 tree base = get_non_ssa_expr (orig_base);
126 return fold_build2 (MEM_REF, TREE_TYPE (expr),
127 base, TREE_OPERAND (expr, 1));
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 (gimple_assign_single_p (def_stmt))
157 vdecl = gimple_assign_rhs1 (def_stmt);
159 return get_non_ssa_expr (vdecl);
164 /* Return NULL_TREE for any other kind of tree nodes. */
169 /* Given the LHS and (real) RHS of a gimple assign statement, STMT, check if
170 they are the same. If so, print a warning message about self-assignment. */
173 compare_and_warn (gimple stmt, tree lhs, tree rhs)
175 if (operand_equal_p (lhs, rhs, OEP_PURE_SAME))
178 location = (gimple_has_location (stmt)
179 ? gimple_location (stmt)
181 ? DECL_SOURCE_LOCATION (lhs)
183 /* If LHS contains any tree node not currently supported by
184 get_non_ssa_expr, simply emit a generic warning without
185 specifying LHS in the message. */
186 lhs = get_non_ssa_expr (lhs);
188 warning_at (location, 0, G_("%qE is assigned to itself"), lhs);
190 warning_at (location, 0, G_("self-assignment detected"));
194 /* Check and warn if STMT is a self-assign statement. */
197 warn_self_assign (gimple stmt)
201 /* Check assigment statement. */
202 if (gimple_assign_single_p (stmt))
204 rhs = get_real_ref_rhs (gimple_assign_rhs1 (stmt));
208 lhs = gimple_assign_lhs (stmt);
209 if (TREE_CODE (lhs) == SSA_NAME)
211 lhs = SSA_NAME_VAR (lhs);
212 if (DECL_ARTIFICIAL (lhs))
216 compare_and_warn (stmt, lhs, rhs);
218 /* Check overloaded operator '=' (if enabled). */
219 else if (check_operator_eq && is_gimple_call (stmt))
221 tree fdecl = gimple_call_fndecl (stmt);
222 if (fdecl && (DECL_NAME (fdecl) == maybe_get_identifier ("operator=")))
224 /* If 'operator=' takes reference operands, the arguments will be
225 ADDR_EXPR trees. In this case, just remove the address-taken
226 operator before we compare the lhs and rhs. */
227 lhs = gimple_call_arg (stmt, 0);
228 if (TREE_CODE (lhs) == ADDR_EXPR)
229 lhs = TREE_OPERAND (lhs, 0);
230 rhs = gimple_call_arg (stmt, 1);
231 if (TREE_CODE (rhs) == ADDR_EXPR)
232 rhs = TREE_OPERAND (rhs, 0);
234 compare_and_warn (stmt, lhs, rhs);
239 /* Entry point for the self-assignment detection pass. */
242 execute_warn_self_assign (void)
244 gimple_stmt_iterator gsi;
249 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
250 warn_self_assign (gsi_stmt (gsi));
256 /* Pass gate function. Currently always returns true. */
259 gate_warn_self_assign (void)
264 static struct gimple_opt_pass pass_warn_self_assign =
268 "warn_self_assign", /* name */
269 gate_warn_self_assign, /* gate */
270 execute_warn_self_assign, /* execute */
273 0, /* static_pass_number */
275 PROP_ssa, /* properties_required */
276 0, /* properties_provided */
277 0, /* properties_destroyed */
278 0, /* todo_flags_start */
279 TODO_dump_func /* todo_flags_finish */
283 /* The initialization routine exposed to and called by GCC. The spec of this
284 function is defined in gcc/gcc-plugin.h.
286 PLUGIN_NAME - name of the plugin (useful for error reporting)
287 ARGC - the size of the ARGV array
288 ARGV - an array of key-value argument pair
290 Returns 0 if initialization finishes successfully.
292 Note that this function needs to be named exactly "plugin_init". */
295 plugin_init (struct plugin_name_args *plugin_info,
296 struct plugin_gcc_version *version)
298 struct register_pass_info pass_info;
299 const char *plugin_name = plugin_info->base_name;
300 int argc = plugin_info->argc;
301 struct plugin_argument *argv = plugin_info->argv;
305 if (!plugin_default_version_check (version, &gcc_version))
308 /* Self-assign detection should happen after SSA is constructed. */
309 pass_info.pass = &pass_warn_self_assign.pass;
310 pass_info.reference_pass_name = "ssa";
311 pass_info.ref_pass_instance_number = 1;
312 pass_info.pos_op = PASS_POS_INSERT_AFTER;
314 /* Process the plugin arguments. This plugin takes the following arguments:
315 check-operator-eq, no-check-operator-eq, enable, and disable.
316 By default, the analysis is enabled with 'operator=' checked. */
317 for (i = 0; i < argc; ++i)
319 if (!strcmp (argv[i].key, "check-operator-eq"))
322 warning (0, G_("option '-fplugin-arg-%s-check-operator-eq=%s'"
323 " ignored (superfluous '=%s')"),
324 plugin_name, argv[i].value, argv[i].value);
326 check_operator_eq = true;
328 else if (!strcmp (argv[i].key, "no-check-operator-eq"))
331 warning (0, G_("option '-fplugin-arg-%s-no-check-operator-eq=%s'"
332 " ignored (superfluous '=%s')"),
333 plugin_name, argv[i].value, argv[i].value);
335 check_operator_eq = false;
337 else if (!strcmp (argv[i].key, "enable"))
340 warning (0, G_("option '-fplugin-arg-%s-enable=%s' ignored"
341 " (superfluous '=%s')"),
342 plugin_name, argv[i].value, argv[i].value);
346 else if (!strcmp (argv[i].key, "disable"))
349 warning (0, G_("option '-fplugin-arg-%s-disable=%s' ignored"
350 " (superfluous '=%s')"),
351 plugin_name, argv[i].value, argv[i].value);
356 warning (0, G_("plugin %qs: unrecognized argument %qs ignored"),
357 plugin_name, argv[i].key);
360 /* Register this new pass with GCC if the analysis is enabled. */
362 register_callback (plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,