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"
12 #include "basic-block.h"
14 #include "gimple-iterator.h"
16 #include "tree-pass.h"
18 #include "plugin-version.h"
19 #include "diagnostic.h"
22 int plugin_is_GPL_compatible
;
24 /* Indicate whether to check overloaded operator '=', which is performed by
25 default. To disable it, use -fplugin-arg-NAME-no-check-operator-eq. */
26 bool check_operator_eq
= true;
28 /* Given a rhs EXPR of a gimple assign statement, if it is
29 - SSA_NAME : returns its var decl, or, if it is a temp variable,
30 returns the rhs of its SSA def statement.
31 - VAR_DECL, PARM_DECL, FIELD_DECL, or a reference expression :
33 - any other expression : returns NULL_TREE. */
36 get_real_ref_rhs (tree expr
)
38 switch (TREE_CODE (expr
))
42 /* Given a self-assign statement, say foo.x = foo.x,
43 the IR (after SSA) looks like:
48 So if the rhs EXPR is an SSA_NAME of a temp variable,
49 e.g. D.1797_14, we need to grab the rhs of its SSA def
50 statement (i.e. foo.x). */
51 tree vdecl
= SSA_NAME_VAR (expr
);
52 if ((!vdecl
|| DECL_ARTIFICIAL (vdecl
))
53 && !gimple_nop_p (SSA_NAME_DEF_STMT (expr
)))
55 gimple def_stmt
= SSA_NAME_DEF_STMT (expr
);
56 /* We are only interested in an assignment with a single
57 rhs operand because if it is not, the original assignment
58 will not possibly be a self-assignment. */
59 if (gimple_assign_single_p (def_stmt
))
60 return get_real_ref_rhs (gimple_assign_rhs1 (def_stmt
));
79 /* Given an expression tree, EXPR, that may contains SSA names, returns an
80 equivalent tree with the SSA names converted to var/parm/field decls
81 so that it can be used with '%E' format modifier when emitting warning
84 This function currently only supports VAR/PARM/FIELD_DECL, reference
85 expressions (COMPONENT_REF, INDIRECT_REF, ARRAY_REF), integer constant,
86 and SSA_NAME. If EXPR contains any other tree nodes (e.g. an arithmetic
87 expression appears in array index), NULL_TREE is returned. */
90 get_non_ssa_expr (tree expr
)
94 switch (TREE_CODE (expr
))
100 if (DECL_NAME (expr
))
107 tree base
, orig_base
= TREE_OPERAND (expr
, 0);
108 tree component
, orig_component
= TREE_OPERAND (expr
, 1);
109 base
= get_non_ssa_expr (orig_base
);
112 component
= get_non_ssa_expr (orig_component
);
115 /* If either BASE or COMPONENT is converted, build a new
116 component reference tree. */
117 if (base
!= orig_base
|| component
!= orig_component
)
118 return build3 (COMPONENT_REF
, TREE_TYPE (component
),
119 base
, component
, NULL_TREE
);
125 tree orig_base
= TREE_OPERAND (expr
, 0);
126 if (TREE_CODE (orig_base
) == SSA_NAME
)
128 tree base
= get_non_ssa_expr (orig_base
);
131 return fold_build2 (MEM_REF
, TREE_TYPE (expr
),
132 base
, TREE_OPERAND (expr
, 1));
138 tree array
, orig_array
= TREE_OPERAND (expr
, 0);
139 tree index
, orig_index
= TREE_OPERAND (expr
, 1);
140 array
= get_non_ssa_expr (orig_array
);
143 index
= get_non_ssa_expr (orig_index
);
146 /* If either ARRAY or INDEX is converted, build a new array
148 if (array
!= orig_array
|| index
!= orig_index
)
149 return build4 (ARRAY_REF
, TREE_TYPE (expr
), array
, index
,
150 TREE_OPERAND (expr
, 2), TREE_OPERAND (expr
, 3));
156 tree vdecl
= SSA_NAME_VAR (expr
);
157 if ((!vdecl
|| DECL_ARTIFICIAL (vdecl
))
158 && !gimple_nop_p (SSA_NAME_DEF_STMT (expr
)))
160 gimple def_stmt
= SSA_NAME_DEF_STMT (expr
);
161 if (gimple_assign_single_p (def_stmt
))
162 vdecl
= gimple_assign_rhs1 (def_stmt
);
164 return get_non_ssa_expr (vdecl
);
169 /* Return NULL_TREE for any other kind of tree nodes. */
174 /* Given the LHS and (real) RHS of a gimple assign statement, STMT, check if
175 they are the same. If so, print a warning message about self-assignment. */
178 compare_and_warn (gimple stmt
, tree lhs
, tree rhs
)
180 if (operand_equal_p (lhs
, rhs
, OEP_PURE_SAME
))
183 location
= (gimple_has_location (stmt
)
184 ? gimple_location (stmt
)
186 ? DECL_SOURCE_LOCATION (lhs
)
188 /* If LHS contains any tree node not currently supported by
189 get_non_ssa_expr, simply emit a generic warning without
190 specifying LHS in the message. */
191 lhs
= get_non_ssa_expr (lhs
);
193 warning_at (location
, 0, G_("%qE is assigned to itself"), lhs
);
195 warning_at (location
, 0, G_("self-assignment detected"));
199 /* Check and warn if STMT is a self-assign statement. */
202 warn_self_assign (gimple stmt
)
206 /* Check assigment statement. */
207 if (gimple_assign_single_p (stmt
))
209 rhs
= get_real_ref_rhs (gimple_assign_rhs1 (stmt
));
213 lhs
= gimple_assign_lhs (stmt
);
214 if (TREE_CODE (lhs
) == SSA_NAME
)
216 lhs
= SSA_NAME_VAR (lhs
);
217 if (!lhs
|| DECL_ARTIFICIAL (lhs
))
221 compare_and_warn (stmt
, lhs
, rhs
);
223 /* Check overloaded operator '=' (if enabled). */
224 else if (check_operator_eq
&& is_gimple_call (stmt
))
226 tree fdecl
= gimple_call_fndecl (stmt
);
227 if (fdecl
&& (DECL_NAME (fdecl
) == maybe_get_identifier ("operator=")))
229 /* If 'operator=' takes reference operands, the arguments will be
230 ADDR_EXPR trees. In this case, just remove the address-taken
231 operator before we compare the lhs and rhs. */
232 lhs
= gimple_call_arg (stmt
, 0);
233 if (TREE_CODE (lhs
) == ADDR_EXPR
)
234 lhs
= TREE_OPERAND (lhs
, 0);
235 rhs
= gimple_call_arg (stmt
, 1);
236 if (TREE_CODE (rhs
) == ADDR_EXPR
)
237 rhs
= TREE_OPERAND (rhs
, 0);
239 compare_and_warn (stmt
, lhs
, rhs
);
244 /* Entry point for the self-assignment detection pass. */
247 execute_warn_self_assign (void)
249 gimple_stmt_iterator gsi
;
254 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
255 warn_self_assign (gsi_stmt (gsi
));
261 /* Pass gate function. Currently always returns true. */
264 gate_warn_self_assign (void)
271 const pass_data pass_data_warn_self_assign
=
273 GIMPLE_PASS
, /* type */
274 "warn_self_assign", /* name */
275 OPTGROUP_NONE
, /* optinfo_flags */
277 true, /* has_execute */
279 PROP_ssa
, /* properties_required */
280 0, /* properties_provided */
281 0, /* properties_destroyed */
282 0, /* todo_flags_start */
283 0, /* todo_flags_finish */
286 class pass_warn_self_assign
: public gimple_opt_pass
289 pass_warn_self_assign(gcc::context
*ctxt
)
290 : gimple_opt_pass(pass_data_warn_self_assign
, ctxt
)
293 /* opt_pass methods: */
294 bool gate () { return gate_warn_self_assign (); }
295 unsigned int execute () { return execute_warn_self_assign (); }
297 }; // class pass_warn_self_assign
301 static gimple_opt_pass
*
302 make_pass_warn_self_assign (gcc::context
*ctxt
)
304 return new pass_warn_self_assign (ctxt
);
307 /* The initialization routine exposed to and called by GCC. The spec of this
308 function is defined in gcc/gcc-plugin.h.
310 PLUGIN_NAME - name of the plugin (useful for error reporting)
311 ARGC - the size of the ARGV array
312 ARGV - an array of key-value argument pair
314 Returns 0 if initialization finishes successfully.
316 Note that this function needs to be named exactly "plugin_init". */
319 plugin_init (struct plugin_name_args
*plugin_info
,
320 struct plugin_gcc_version
*version
)
322 struct register_pass_info pass_info
;
323 const char *plugin_name
= plugin_info
->base_name
;
324 int argc
= plugin_info
->argc
;
325 struct plugin_argument
*argv
= plugin_info
->argv
;
329 if (!plugin_default_version_check (version
, &gcc_version
))
332 /* Self-assign detection should happen after SSA is constructed. */
333 pass_info
.pass
= make_pass_warn_self_assign (g
);
334 pass_info
.reference_pass_name
= "ssa";
335 pass_info
.ref_pass_instance_number
= 1;
336 pass_info
.pos_op
= PASS_POS_INSERT_AFTER
;
338 /* Process the plugin arguments. This plugin takes the following arguments:
339 check-operator-eq, no-check-operator-eq, enable, and disable.
340 By default, the analysis is enabled with 'operator=' checked. */
341 for (i
= 0; i
< argc
; ++i
)
343 if (!strcmp (argv
[i
].key
, "check-operator-eq"))
346 warning (0, G_("option '-fplugin-arg-%s-check-operator-eq=%s'"
347 " ignored (superfluous '=%s')"),
348 plugin_name
, argv
[i
].value
, argv
[i
].value
);
350 check_operator_eq
= true;
352 else if (!strcmp (argv
[i
].key
, "no-check-operator-eq"))
355 warning (0, G_("option '-fplugin-arg-%s-no-check-operator-eq=%s'"
356 " ignored (superfluous '=%s')"),
357 plugin_name
, argv
[i
].value
, argv
[i
].value
);
359 check_operator_eq
= false;
361 else if (!strcmp (argv
[i
].key
, "enable"))
364 warning (0, G_("option '-fplugin-arg-%s-enable=%s' ignored"
365 " (superfluous '=%s')"),
366 plugin_name
, argv
[i
].value
, argv
[i
].value
);
370 else if (!strcmp (argv
[i
].key
, "disable"))
373 warning (0, G_("option '-fplugin-arg-%s-disable=%s' ignored"
374 " (superfluous '=%s')"),
375 plugin_name
, argv
[i
].value
, argv
[i
].value
);
380 warning (0, G_("plugin %qs: unrecognized argument %qs ignored"),
381 plugin_name
, argv
[i
].key
);
384 /* Register this new pass with GCC if the analysis is enabled. */
386 register_callback (plugin_name
, PLUGIN_PASS_MANAGER_SETUP
, NULL
,