1 /* This plugin contains an analysis pass that detects and warns about
2 self-assignment statements. */
3 /* { dg-options "-O" } */
10 #include "basic-block.h"
13 #include "tree-pass.h"
15 #include "gcc-plugin.h"
18 /* Indicate whether to check overloaded operator '=', which is performed by
19 default. To disable it, use -fplugin-arg-NAME-no-check-operator-eq. */
20 bool check_operator_eq = true;
22 /* Given a rhs EXPR of a gimple assign statement, if it is
23 - SSA_NAME : returns its var decl, or, if it is a temp variable,
24 returns the rhs of its SSA def statement.
25 - VAR_DECL, PARM_DECL, FIELD_DECL, or a reference expression :
27 - any other expression : returns NULL_TREE. */
30 get_real_ref_rhs (tree expr)
32 switch (TREE_CODE (expr))
36 /* Given a self-assign statement, say foo.x = foo.x,
37 the IR (after SSA) looks like:
42 So if the rhs EXPR is an SSA_NAME of a temp variable,
43 e.g. D.1797_14, we need to grab the rhs of its SSA def
44 statement (i.e. foo.x). */
45 tree vdecl = SSA_NAME_VAR (expr);
46 if (DECL_ARTIFICIAL (vdecl)
47 && !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
49 gimple def_stmt = SSA_NAME_DEF_STMT (expr);
50 /* We are only interested in an assignment with a single
51 rhs operand because if it is not, the original assignment
52 will not possibly be a self-assignment. */
53 if (is_gimple_assign (def_stmt)
54 && (get_gimple_rhs_class (gimple_assign_rhs_code (def_stmt))
55 == GIMPLE_SINGLE_RHS))
56 return get_real_ref_rhs (gimple_assign_rhs1 (def_stmt));
75 /* Given an expression tree, EXPR, that may contains SSA names, returns an
76 equivalent tree with the SSA names converted to var/parm/field decls
77 so that it can be used with '%E' format modifier when emitting warning
80 This function currently only supports VAR/PARM/FIELD_DECL, reference
81 expressions (COMPONENT_REF, INDIRECT_REF, ARRAY_REF), integer constant,
82 and SSA_NAME. If EXPR contains any other tree nodes (e.g. an arithmetic
83 expression appears in array index), NULL_TREE is returned. */
86 get_non_ssa_expr (tree expr)
88 switch (TREE_CODE (expr))
101 tree base, orig_base = TREE_OPERAND (expr, 0);
102 tree component, orig_component = TREE_OPERAND (expr, 1);
103 base = get_non_ssa_expr (orig_base);
106 component = get_non_ssa_expr (orig_component);
109 /* If either BASE or COMPONENT is converted, build a new
110 component reference tree. */
111 if (base != orig_base || component != orig_component)
112 return build3 (COMPONENT_REF, TREE_TYPE (component),
113 base, component, NULL_TREE);
119 tree orig_base = TREE_OPERAND (expr, 0);
120 tree base = get_non_ssa_expr (orig_base);
123 /* If BASE is converted, build a new indirect reference tree. */
124 if (base != orig_base)
125 return build1 (INDIRECT_REF, TREE_TYPE (TREE_TYPE (base)), base);
131 tree array, orig_array = TREE_OPERAND (expr, 0);
132 tree index, orig_index = TREE_OPERAND (expr, 1);
133 array = get_non_ssa_expr (orig_array);
136 index = get_non_ssa_expr (orig_index);
139 /* If either ARRAY or INDEX is converted, build a new array
141 if (array != orig_array || index != orig_index)
142 return build4 (ARRAY_REF, TREE_TYPE (expr), array, index,
143 TREE_OPERAND (expr, 2), TREE_OPERAND (expr, 3));
149 tree vdecl = SSA_NAME_VAR (expr);
150 if (DECL_ARTIFICIAL (vdecl)
151 && !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
153 gimple def_stmt = SSA_NAME_DEF_STMT (expr);
154 if (is_gimple_assign (def_stmt)
155 && (get_gimple_rhs_class (gimple_assign_rhs_code (def_stmt))
156 == GIMPLE_SINGLE_RHS))
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 (0, G_("%H%qE is assigned to itself"), &location, lhs);
190 warning (0, G_("%Hself-assignment detected"), &location);
194 /* Check and warn if STMT is a self-assign statement. */
197 warn_self_assign (gimple stmt)
201 /* Check assigment statement. */
202 if (is_gimple_assign (stmt)
203 && (get_gimple_rhs_class (gimple_assign_rhs_code (stmt))
204 == GIMPLE_SINGLE_RHS))
206 rhs = get_real_ref_rhs (gimple_assign_rhs1 (stmt));
210 lhs = gimple_assign_lhs (stmt);
211 if (TREE_CODE (lhs) == SSA_NAME)
213 lhs = SSA_NAME_VAR (lhs);
214 if (DECL_ARTIFICIAL (lhs))
218 compare_and_warn (stmt, lhs, rhs);
220 /* Check overloaded operator '=' (if enabled). */
221 else if (check_operator_eq && is_gimple_call (stmt))
223 tree fdecl = gimple_call_fndecl (stmt);
224 if (fdecl && (DECL_NAME (fdecl) == maybe_get_identifier ("operator=")))
226 /* If 'operator=' takes reference operands, the arguments will be
227 ADDR_EXPR trees. In this case, just remove the address-taken
228 operator before we compare the lhs and rhs. */
229 lhs = gimple_call_arg (stmt, 0);
230 if (TREE_CODE (lhs) == ADDR_EXPR)
231 lhs = TREE_OPERAND (lhs, 0);
232 rhs = gimple_call_arg (stmt, 1);
233 if (TREE_CODE (rhs) == ADDR_EXPR)
234 rhs = TREE_OPERAND (rhs, 0);
236 compare_and_warn (stmt, lhs, rhs);
241 /* Entry point for the self-assignment detection pass. */
244 execute_warn_self_assign (void)
246 gimple_stmt_iterator gsi;
251 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
252 warn_self_assign (gsi_stmt (gsi));
258 /* Pass gate function. Currently always returns true. */
261 gate_warn_self_assign (void)
266 static struct gimple_opt_pass pass_warn_self_assign =
270 "warn_self_assign", /* name */
271 gate_warn_self_assign, /* gate */
272 execute_warn_self_assign, /* execute */
275 0, /* static_pass_number */
277 PROP_ssa, /* properties_required */
278 0, /* properties_provided */
279 0, /* properties_destroyed */
280 0, /* todo_flags_start */
281 TODO_dump_func /* todo_flags_finish */
285 /* The initialization routine exposed to and called by GCC. The spec of this
286 function is defined in gcc/gcc-plugin.h.
288 PLUGIN_NAME - name of the plugin (useful for error reporting)
289 ARGC - the size of the ARGV array
290 ARGV - an array of key-value argument pair
292 Returns 0 if initialization finishes successfully.
294 Note that this function needs to be named exactly "plugin_init". */
297 plugin_init (const char *plugin_name, struct plugin_gcc_version *version,
298 int argc, struct plugin_argument *argv)
300 struct plugin_pass pass_info;
304 if (!plugin_default_version_check (version, version))
307 /* Self-assign detection should happen after SSA is constructed. */
308 pass_info.pass = &pass_warn_self_assign.pass;
309 pass_info.reference_pass_name = "ssa";
310 pass_info.ref_pass_instance_number = 1;
311 pass_info.pos_op = PASS_POS_INSERT_AFTER;
313 /* Process the plugin arguments. This plugin takes the following arguments:
314 check-operator-eq, no-check-operator-eq, enable, and disable.
315 By default, the analysis is enabled with 'operator=' checked. */
316 for (i = 0; i < argc; ++i)
318 if (!strcmp (argv[i].key, "check-operator-eq"))
321 warning (0, G_("option '-fplugin-arg-%s-check-operator-eq=%s'"
322 " ignored (superfluous '=%s')"),
323 plugin_name, argv[i].value, argv[i].value);
325 check_operator_eq = true;
327 else if (!strcmp (argv[i].key, "no-check-operator-eq"))
330 warning (0, G_("option '-fplugin-arg-%s-no-check-operator-eq=%s'"
331 " ignored (superfluous '=%s')"),
332 plugin_name, argv[i].value, argv[i].value);
334 check_operator_eq = false;
336 else if (!strcmp (argv[i].key, "enable"))
339 warning (0, G_("option '-fplugin-arg-%s-enable=%s' ignored"
340 " (superfluous '=%s')"),
341 plugin_name, argv[i].value, argv[i].value);
345 else if (!strcmp (argv[i].key, "disable"))
348 warning (0, G_("option '-fplugin-arg-%s-disable=%s' ignored"
349 " (superfluous '=%s')"),
350 plugin_name, argv[i].value, argv[i].value);
355 warning (0, G_("plugin %qs: unrecognized argument %qs ignored"),
356 plugin_name, argv[i].key);
359 /* Register this new pass with GCC if the analysis is enabled. */
361 register_callback (plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,