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 "stringpool.h"
13 #include "basic-block.h"
14 #include "hash-table.h"
17 #include "basic-block.h"
18 #include "tree-ssa-alias.h"
19 #include "internal-fn.h"
20 #include "gimple-fold.h"
22 #include "gimple-expr.h"
25 #include "gimple-iterator.h"
27 #include "tree-pass.h"
29 #include "plugin-version.h"
30 #include "diagnostic.h"
33 int plugin_is_GPL_compatible
;
35 /* Indicate whether to check overloaded operator '=', which is performed by
36 default. To disable it, use -fplugin-arg-NAME-no-check-operator-eq. */
37 bool check_operator_eq
= true;
39 /* Given a rhs EXPR of a gimple assign statement, if it is
40 - SSA_NAME : returns its var decl, or, if it is a temp variable,
41 returns the rhs of its SSA def statement.
42 - VAR_DECL, PARM_DECL, FIELD_DECL, or a reference expression :
44 - any other expression : returns NULL_TREE. */
47 get_real_ref_rhs (tree expr
)
49 switch (TREE_CODE (expr
))
53 /* Given a self-assign statement, say foo.x = foo.x,
54 the IR (after SSA) looks like:
59 So if the rhs EXPR is an SSA_NAME of a temp variable,
60 e.g. D.1797_14, we need to grab the rhs of its SSA def
61 statement (i.e. foo.x). */
62 tree vdecl
= SSA_NAME_VAR (expr
);
63 if ((!vdecl
|| DECL_ARTIFICIAL (vdecl
))
64 && !gimple_nop_p (SSA_NAME_DEF_STMT (expr
)))
66 gimple def_stmt
= SSA_NAME_DEF_STMT (expr
);
67 /* We are only interested in an assignment with a single
68 rhs operand because if it is not, the original assignment
69 will not possibly be a self-assignment. */
70 if (gimple_assign_single_p (def_stmt
))
71 return get_real_ref_rhs (gimple_assign_rhs1 (def_stmt
));
90 /* Given an expression tree, EXPR, that may contains SSA names, returns an
91 equivalent tree with the SSA names converted to var/parm/field decls
92 so that it can be used with '%E' format modifier when emitting warning
95 This function currently only supports VAR/PARM/FIELD_DECL, reference
96 expressions (COMPONENT_REF, INDIRECT_REF, ARRAY_REF), integer constant,
97 and SSA_NAME. If EXPR contains any other tree nodes (e.g. an arithmetic
98 expression appears in array index), NULL_TREE is returned. */
101 get_non_ssa_expr (tree expr
)
105 switch (TREE_CODE (expr
))
111 if (DECL_NAME (expr
))
118 tree base
, orig_base
= TREE_OPERAND (expr
, 0);
119 tree component
, orig_component
= TREE_OPERAND (expr
, 1);
120 base
= get_non_ssa_expr (orig_base
);
123 component
= get_non_ssa_expr (orig_component
);
126 /* If either BASE or COMPONENT is converted, build a new
127 component reference tree. */
128 if (base
!= orig_base
|| component
!= orig_component
)
129 return build3 (COMPONENT_REF
, TREE_TYPE (component
),
130 base
, component
, NULL_TREE
);
136 tree orig_base
= TREE_OPERAND (expr
, 0);
137 if (TREE_CODE (orig_base
) == SSA_NAME
)
139 tree base
= get_non_ssa_expr (orig_base
);
142 return fold_build2 (MEM_REF
, TREE_TYPE (expr
),
143 base
, TREE_OPERAND (expr
, 1));
149 tree array
, orig_array
= TREE_OPERAND (expr
, 0);
150 tree index
, orig_index
= TREE_OPERAND (expr
, 1);
151 array
= get_non_ssa_expr (orig_array
);
154 index
= get_non_ssa_expr (orig_index
);
157 /* If either ARRAY or INDEX is converted, build a new array
159 if (array
!= orig_array
|| index
!= orig_index
)
160 return build4 (ARRAY_REF
, TREE_TYPE (expr
), array
, index
,
161 TREE_OPERAND (expr
, 2), TREE_OPERAND (expr
, 3));
167 tree vdecl
= SSA_NAME_VAR (expr
);
168 if ((!vdecl
|| DECL_ARTIFICIAL (vdecl
))
169 && !gimple_nop_p (SSA_NAME_DEF_STMT (expr
)))
171 gimple def_stmt
= SSA_NAME_DEF_STMT (expr
);
172 if (gimple_assign_single_p (def_stmt
))
173 vdecl
= gimple_assign_rhs1 (def_stmt
);
175 return get_non_ssa_expr (vdecl
);
180 /* Return NULL_TREE for any other kind of tree nodes. */
185 /* Given the LHS and (real) RHS of a gimple assign statement, STMT, check if
186 they are the same. If so, print a warning message about self-assignment. */
189 compare_and_warn (gimple stmt
, tree lhs
, tree rhs
)
191 if (operand_equal_p (lhs
, rhs
, OEP_PURE_SAME
))
194 location
= (gimple_has_location (stmt
)
195 ? gimple_location (stmt
)
197 ? DECL_SOURCE_LOCATION (lhs
)
199 /* If LHS contains any tree node not currently supported by
200 get_non_ssa_expr, simply emit a generic warning without
201 specifying LHS in the message. */
202 lhs
= get_non_ssa_expr (lhs
);
204 warning_at (location
, 0, G_("%qE is assigned to itself"), lhs
);
206 warning_at (location
, 0, G_("self-assignment detected"));
210 /* Check and warn if STMT is a self-assign statement. */
213 warn_self_assign (gimple stmt
)
217 /* Check assigment statement. */
218 if (gimple_assign_single_p (stmt
))
220 rhs
= get_real_ref_rhs (gimple_assign_rhs1 (stmt
));
224 lhs
= gimple_assign_lhs (stmt
);
225 if (TREE_CODE (lhs
) == SSA_NAME
)
227 lhs
= SSA_NAME_VAR (lhs
);
228 if (!lhs
|| DECL_ARTIFICIAL (lhs
))
232 compare_and_warn (stmt
, lhs
, rhs
);
234 /* Check overloaded operator '=' (if enabled). */
235 else if (check_operator_eq
&& is_gimple_call (stmt
))
237 tree fdecl
= gimple_call_fndecl (stmt
);
238 if (fdecl
&& (DECL_NAME (fdecl
) == maybe_get_identifier ("operator=")))
240 /* If 'operator=' takes reference operands, the arguments will be
241 ADDR_EXPR trees. In this case, just remove the address-taken
242 operator before we compare the lhs and rhs. */
243 lhs
= gimple_call_arg (stmt
, 0);
244 if (TREE_CODE (lhs
) == ADDR_EXPR
)
245 lhs
= TREE_OPERAND (lhs
, 0);
246 rhs
= gimple_call_arg (stmt
, 1);
247 if (TREE_CODE (rhs
) == ADDR_EXPR
)
248 rhs
= TREE_OPERAND (rhs
, 0);
250 compare_and_warn (stmt
, lhs
, rhs
);
257 const pass_data pass_data_warn_self_assign
=
259 GIMPLE_PASS
, /* type */
260 "warn_self_assign", /* name */
261 OPTGROUP_NONE
, /* optinfo_flags */
263 PROP_ssa
, /* properties_required */
264 0, /* properties_provided */
265 0, /* properties_destroyed */
266 0, /* todo_flags_start */
267 0, /* todo_flags_finish */
270 class pass_warn_self_assign
: public gimple_opt_pass
273 pass_warn_self_assign(gcc::context
*ctxt
)
274 : gimple_opt_pass(pass_data_warn_self_assign
, ctxt
)
277 /* opt_pass methods: */
278 virtual unsigned int execute (function
*);
280 }; // class pass_warn_self_assign
283 pass_warn_self_assign::execute (function
*fun
)
285 gimple_stmt_iterator gsi
;
288 FOR_EACH_BB_FN (bb
, fun
)
290 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
291 warn_self_assign (gsi_stmt (gsi
));
299 static gimple_opt_pass
*
300 make_pass_warn_self_assign (gcc::context
*ctxt
)
302 return new pass_warn_self_assign (ctxt
);
305 /* The initialization routine exposed to and called by GCC. The spec of this
306 function is defined in gcc/gcc-plugin.h.
308 PLUGIN_NAME - name of the plugin (useful for error reporting)
309 ARGC - the size of the ARGV array
310 ARGV - an array of key-value argument pair
312 Returns 0 if initialization finishes successfully.
314 Note that this function needs to be named exactly "plugin_init". */
317 plugin_init (struct plugin_name_args
*plugin_info
,
318 struct plugin_gcc_version
*version
)
320 struct register_pass_info pass_info
;
321 const char *plugin_name
= plugin_info
->base_name
;
322 int argc
= plugin_info
->argc
;
323 struct plugin_argument
*argv
= plugin_info
->argv
;
327 if (!plugin_default_version_check (version
, &gcc_version
))
330 /* Self-assign detection should happen after SSA is constructed. */
331 pass_info
.pass
= make_pass_warn_self_assign (g
);
332 pass_info
.reference_pass_name
= "ssa";
333 pass_info
.ref_pass_instance_number
= 1;
334 pass_info
.pos_op
= PASS_POS_INSERT_AFTER
;
336 /* Process the plugin arguments. This plugin takes the following arguments:
337 check-operator-eq, no-check-operator-eq, enable, and disable.
338 By default, the analysis is enabled with 'operator=' checked. */
339 for (i
= 0; i
< argc
; ++i
)
341 if (!strcmp (argv
[i
].key
, "check-operator-eq"))
344 warning (0, G_("option '-fplugin-arg-%s-check-operator-eq=%s'"
345 " ignored (superfluous '=%s')"),
346 plugin_name
, argv
[i
].value
, argv
[i
].value
);
348 check_operator_eq
= true;
350 else if (!strcmp (argv
[i
].key
, "no-check-operator-eq"))
353 warning (0, G_("option '-fplugin-arg-%s-no-check-operator-eq=%s'"
354 " ignored (superfluous '=%s')"),
355 plugin_name
, argv
[i
].value
, argv
[i
].value
);
357 check_operator_eq
= false;
359 else if (!strcmp (argv
[i
].key
, "enable"))
362 warning (0, G_("option '-fplugin-arg-%s-enable=%s' ignored"
363 " (superfluous '=%s')"),
364 plugin_name
, argv
[i
].value
, argv
[i
].value
);
368 else if (!strcmp (argv
[i
].key
, "disable"))
371 warning (0, G_("option '-fplugin-arg-%s-disable=%s' ignored"
372 " (superfluous '=%s')"),
373 plugin_name
, argv
[i
].value
, argv
[i
].value
);
378 warning (0, G_("plugin %qs: unrecognized argument %qs ignored"),
379 plugin_name
, argv
[i
].key
);
382 /* Register this new pass with GCC if the analysis is enabled. */
384 register_callback (plugin_name
, PLUGIN_PASS_MANAGER_SETUP
, NULL
,