blob: 2adb6446b1dbadd8e0a81914b5234685e126d0ce [file] [log] [blame]
/* This plugin contains an analysis pass that detects and warns about
self-assignment statements. */
/* { dg-options "-O" } */
#include "gcc-plugin.h"
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "stringpool.h"
#include "toplev.h"
#include "basic-block.h"
#include "hash-table.h"
#include "vec.h"
#include "ggc.h"
#include "basic-block.h"
#include "tree-ssa-alias.h"
#include "internal-fn.h"
#include "gimple-fold.h"
#include "tree-eh.h"
#include "gimple-expr.h"
#include "is-a.h"
#include "gimple.h"
#include "gimple-iterator.h"
#include "tree.h"
#include "tree-pass.h"
#include "intl.h"
#include "plugin-version.h"
#include "diagnostic.h"
#include "context.h"
int plugin_is_GPL_compatible;
/* Indicate whether to check overloaded operator '=', which is performed by
default. To disable it, use -fplugin-arg-NAME-no-check-operator-eq. */
bool check_operator_eq = true;
/* Given a rhs EXPR of a gimple assign statement, if it is
- SSA_NAME : returns its var decl, or, if it is a temp variable,
returns the rhs of its SSA def statement.
- VAR_DECL, PARM_DECL, FIELD_DECL, or a reference expression :
returns EXPR itself.
- any other expression : returns NULL_TREE. */
static tree
get_real_ref_rhs (tree expr)
{
switch (TREE_CODE (expr))
{
case SSA_NAME:
{
/* Given a self-assign statement, say foo.x = foo.x,
the IR (after SSA) looks like:
D.1797_14 = foo.x;
foo.x ={v} D.1797_14;
So if the rhs EXPR is an SSA_NAME of a temp variable,
e.g. D.1797_14, we need to grab the rhs of its SSA def
statement (i.e. foo.x). */
tree vdecl = SSA_NAME_VAR (expr);
if ((!vdecl || DECL_ARTIFICIAL (vdecl))
&& !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
{
gimple *def_stmt = SSA_NAME_DEF_STMT (expr);
/* We are only interested in an assignment with a single
rhs operand because if it is not, the original assignment
will not possibly be a self-assignment. */
if (gimple_assign_single_p (def_stmt))
return get_real_ref_rhs (gimple_assign_rhs1 (def_stmt));
else
return NULL_TREE;
}
else
return vdecl;
}
case VAR_DECL:
case PARM_DECL:
case FIELD_DECL:
case COMPONENT_REF:
case MEM_REF:
case ARRAY_REF:
return expr;
default:
return NULL_TREE;
}
}
/* Given an expression tree, EXPR, that may contains SSA names, returns an
equivalent tree with the SSA names converted to var/parm/field decls
so that it can be used with '%E' format modifier when emitting warning
messages.
This function currently only supports VAR/PARM/FIELD_DECL, reference
expressions (COMPONENT_REF, INDIRECT_REF, ARRAY_REF), integer constant,
and SSA_NAME. If EXPR contains any other tree nodes (e.g. an arithmetic
expression appears in array index), NULL_TREE is returned. */
static tree
get_non_ssa_expr (tree expr)
{
if (!expr)
return NULL_TREE;
switch (TREE_CODE (expr))
{
case VAR_DECL:
case PARM_DECL:
case FIELD_DECL:
{
if (DECL_NAME (expr))
return expr;
else
return NULL_TREE;
}
case COMPONENT_REF:
{
tree base, orig_base = TREE_OPERAND (expr, 0);
tree component, orig_component = TREE_OPERAND (expr, 1);
base = get_non_ssa_expr (orig_base);
if (!base)
return NULL_TREE;
component = get_non_ssa_expr (orig_component);
if (!component)
return NULL_TREE;
/* If either BASE or COMPONENT is converted, build a new
component reference tree. */
if (base != orig_base || component != orig_component)
return build3 (COMPONENT_REF, TREE_TYPE (component),
base, component, NULL_TREE);
else
return expr;
}
case MEM_REF:
{
tree orig_base = TREE_OPERAND (expr, 0);
if (TREE_CODE (orig_base) == SSA_NAME)
{
tree base = get_non_ssa_expr (orig_base);
if (!base)
return NULL_TREE;
return fold_build2 (MEM_REF, TREE_TYPE (expr),
base, TREE_OPERAND (expr, 1));
}
return expr;
}
case ARRAY_REF:
{
tree array, orig_array = TREE_OPERAND (expr, 0);
tree index, orig_index = TREE_OPERAND (expr, 1);
array = get_non_ssa_expr (orig_array);
if (!array)
return NULL_TREE;
index = get_non_ssa_expr (orig_index);
if (!index)
return NULL_TREE;
/* If either ARRAY or INDEX is converted, build a new array
reference tree. */
if (array != orig_array || index != orig_index)
return build4 (ARRAY_REF, TREE_TYPE (expr), array, index,
TREE_OPERAND (expr, 2), TREE_OPERAND (expr, 3));
else
return expr;
}
case SSA_NAME:
{
tree vdecl = SSA_NAME_VAR (expr);
if ((!vdecl || DECL_ARTIFICIAL (vdecl))
&& !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
{
gimple *def_stmt = SSA_NAME_DEF_STMT (expr);
if (gimple_assign_single_p (def_stmt))
vdecl = gimple_assign_rhs1 (def_stmt);
}
return get_non_ssa_expr (vdecl);
}
case INTEGER_CST:
return expr;
default:
/* Return NULL_TREE for any other kind of tree nodes. */
return NULL_TREE;
}
}
/* Given the LHS and (real) RHS of a gimple assign statement, STMT, check if
they are the same. If so, print a warning message about self-assignment. */
static void
compare_and_warn (gimple *stmt, tree lhs, tree rhs)
{
if (operand_equal_p (lhs, rhs, OEP_PURE_SAME))
{
location_t location;
location = (gimple_has_location (stmt)
? gimple_location (stmt)
: (DECL_P (lhs)
? DECL_SOURCE_LOCATION (lhs)
: input_location));
/* If LHS contains any tree node not currently supported by
get_non_ssa_expr, simply emit a generic warning without
specifying LHS in the message. */
lhs = get_non_ssa_expr (lhs);
if (lhs)
warning_at (location, 0, G_("%qE is assigned to itself"), lhs);
else
warning_at (location, 0, G_("self-assignment detected"));
}
}
/* Check and warn if STMT is a self-assign statement. */
static void
warn_self_assign (gimple *stmt)
{
tree rhs, lhs;
/* Check assigment statement. */
if (gimple_assign_single_p (stmt))
{
rhs = get_real_ref_rhs (gimple_assign_rhs1 (stmt));
if (!rhs)
return;
lhs = gimple_assign_lhs (stmt);
if (TREE_CODE (lhs) == SSA_NAME)
{
lhs = SSA_NAME_VAR (lhs);
if (!lhs || DECL_ARTIFICIAL (lhs))
return;
}
compare_and_warn (stmt, lhs, rhs);
}
/* Check overloaded operator '=' (if enabled). */
else if (check_operator_eq && is_gimple_call (stmt))
{
tree fdecl = gimple_call_fndecl (stmt);
if (fdecl && (DECL_NAME (fdecl) == maybe_get_identifier ("operator=")))
{
/* If 'operator=' takes reference operands, the arguments will be
ADDR_EXPR trees. In this case, just remove the address-taken
operator before we compare the lhs and rhs. */
lhs = gimple_call_arg (stmt, 0);
if (TREE_CODE (lhs) == ADDR_EXPR)
lhs = TREE_OPERAND (lhs, 0);
rhs = gimple_call_arg (stmt, 1);
if (TREE_CODE (rhs) == ADDR_EXPR)
rhs = TREE_OPERAND (rhs, 0);
compare_and_warn (stmt, lhs, rhs);
}
}
}
namespace {
const pass_data pass_data_warn_self_assign =
{
GIMPLE_PASS, /* type */
"warn_self_assign", /* name */
OPTGROUP_NONE, /* optinfo_flags */
TV_NONE, /* tv_id */
PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
0, /* todo_flags_finish */
};
class pass_warn_self_assign : public gimple_opt_pass
{
public:
pass_warn_self_assign(gcc::context *ctxt)
: gimple_opt_pass(pass_data_warn_self_assign, ctxt)
{}
/* opt_pass methods: */
virtual unsigned int execute (function *);
}; // class pass_warn_self_assign
unsigned int
pass_warn_self_assign::execute (function *fun)
{
gimple_stmt_iterator gsi;
basic_block bb;
FOR_EACH_BB_FN (bb, fun)
{
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
warn_self_assign (gsi_stmt (gsi));
}
return 0;
}
} // anon namespace
static gimple_opt_pass *
make_pass_warn_self_assign (gcc::context *ctxt)
{
return new pass_warn_self_assign (ctxt);
}
/* The initialization routine exposed to and called by GCC. The spec of this
function is defined in gcc/gcc-plugin.h.
PLUGIN_NAME - name of the plugin (useful for error reporting)
ARGC - the size of the ARGV array
ARGV - an array of key-value argument pair
Returns 0 if initialization finishes successfully.
Note that this function needs to be named exactly "plugin_init". */
int
plugin_init (struct plugin_name_args *plugin_info,
struct plugin_gcc_version *version)
{
struct register_pass_info pass_info;
const char *plugin_name = plugin_info->base_name;
int argc = plugin_info->argc;
struct plugin_argument *argv = plugin_info->argv;
bool enabled = true;
int i;
if (!plugin_default_version_check (version, &gcc_version))
return 1;
/* Self-assign detection should happen after SSA is constructed. */
pass_info.pass = make_pass_warn_self_assign (g);
pass_info.reference_pass_name = "ssa";
pass_info.ref_pass_instance_number = 1;
pass_info.pos_op = PASS_POS_INSERT_AFTER;
/* Process the plugin arguments. This plugin takes the following arguments:
check-operator-eq, no-check-operator-eq, enable, and disable.
By default, the analysis is enabled with 'operator=' checked. */
for (i = 0; i < argc; ++i)
{
if (!strcmp (argv[i].key, "check-operator-eq"))
{
if (argv[i].value)
warning (0, G_("option '-fplugin-arg-%s-check-operator-eq=%s'"
" ignored (superfluous '=%s')"),
plugin_name, argv[i].value, argv[i].value);
else
check_operator_eq = true;
}
else if (!strcmp (argv[i].key, "no-check-operator-eq"))
{
if (argv[i].value)
warning (0, G_("option '-fplugin-arg-%s-no-check-operator-eq=%s'"
" ignored (superfluous '=%s')"),
plugin_name, argv[i].value, argv[i].value);
else
check_operator_eq = false;
}
else if (!strcmp (argv[i].key, "enable"))
{
if (argv[i].value)
warning (0, G_("option '-fplugin-arg-%s-enable=%s' ignored"
" (superfluous '=%s')"),
plugin_name, argv[i].value, argv[i].value);
else
enabled = true;
}
else if (!strcmp (argv[i].key, "disable"))
{
if (argv[i].value)
warning (0, G_("option '-fplugin-arg-%s-disable=%s' ignored"
" (superfluous '=%s')"),
plugin_name, argv[i].value, argv[i].value);
else
enabled = false;
}
else
warning (0, G_("plugin %qs: unrecognized argument %qs ignored"),
plugin_name, argv[i].key);
}
/* Register this new pass with GCC if the analysis is enabled. */
if (enabled)
register_callback (plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
&pass_info);
return 0;
}