-Wstack-protector -Wstack-usage=@var{len} -Wstrict-aliasing @gol
-Wstrict-aliasing=n -Wstrict-overflow -Wstrict-overflow=@var{n} @gol
-Wstringop-overflow=@var{n} @gol
--Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{]} @gol
+-Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{|}malloc@r{]} @gol
-Wsuggest-final-types @gol -Wsuggest-final-methods -Wsuggest-override @gol
-Wmissing-format-attribute -Wsubobject-linkage @gol
-Wswitch -Wswitch-bool -Wswitch-default -Wswitch-enum @gol
setting of the option may result in warnings for benign code.
@end table
-@item -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{|}cold@r{]}
+@item -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{|}cold@r{|}malloc@r{]}
@opindex Wsuggest-attribute=
@opindex Wno-suggest-attribute=
Warn for cases where adding an attribute may be beneficial. The
@item -Wsuggest-attribute=pure
@itemx -Wsuggest-attribute=const
@itemx -Wsuggest-attribute=noreturn
+@itemx -Wsuggest-attribute=malloc
@opindex Wsuggest-attribute=pure
@opindex Wno-suggest-attribute=pure
@opindex Wsuggest-attribute=const
@opindex Wno-suggest-attribute=const
@opindex Wsuggest-attribute=noreturn
@opindex Wno-suggest-attribute=noreturn
+@opindex Wsuggest-attribute=malloc
+@opindex Wno-suggest-attribute=malloc
Warn about functions that might be candidates for attributes
-@code{pure}, @code{const} or @code{noreturn}. The compiler only warns for
-functions visible in other compilation units or (in the case of @code{pure} and
-@code{const}) if it cannot prove that the function returns normally. A function
-returns normally if it doesn't contain an infinite loop or return abnormally
-by throwing, calling @code{abort} or trapping. This analysis requires option
-@option{-fipa-pure-const}, which is enabled by default at @option{-O} and
-higher. Higher optimization levels improve the accuracy of the analysis.
+@code{pure}, @code{const} or @code{noreturn} or @code{malloc}. The compiler
+only warns for functions visible in other compilation units or (in the case of
+@code{pure} and @code{const}) if it cannot prove that the function returns
+normally. A function returns normally if it doesn't contain an infinite loop or
+return abnormally by throwing, calling @code{abort} or trapping. This analysis
+requires option @option{-fipa-pure-const}, which is enabled by default at
+@option{-O} and higher. Higher optimization levels improve the accuracy
+of the analysis.
@item -Wsuggest-attribute=format
@itemx -Wmissing-format-attribute
#include "tree-scalar-evolution.h"
#include "intl.h"
#include "opts.h"
+#include "ssa.h"
+#include "alloc-pool.h"
+#include "symbol-summary.h"
+#include "ipa-prop.h"
+#include "ipa-fnsummary.h"
/* Lattice values for const and pure functions. Everything starts out
being const, then may drop to pure and then neither depending on
IPA_NEITHER
};
-const char *pure_const_names[3] = {"const", "pure", "neither"};
+static const char *pure_const_names[3] = {"const", "pure", "neither"};
+
+enum malloc_state_e
+{
+ STATE_MALLOC_TOP,
+ STATE_MALLOC,
+ STATE_MALLOC_BOTTOM
+};
+
+static const char *malloc_state_names[] = {"malloc_top", "malloc", "malloc_bottom"};
/* Holder for the const_state. There is one of these per function
decl. */
/* If function can call free, munmap or otherwise make previously
non-trapping memory accesses trapping. */
bool can_free;
+
+ enum malloc_state_e malloc_state;
};
/* State used when we know nothing about function. */
static struct funct_state_d varying_state
- = { IPA_NEITHER, IPA_NEITHER, true, true, true, true };
+ = { IPA_NEITHER, IPA_NEITHER, true, true, true, true, STATE_MALLOC_BOTTOM };
typedef struct funct_state_d * funct_state;
known_finite, warned_about, "const");
}
+/* Emit suggestion about __attribute__((malloc)) for DECL. */
+
+static void
+warn_function_malloc (tree decl)
+{
+ static hash_set<tree> *warned_about;
+ warned_about
+ = suggest_attribute (OPT_Wsuggest_attribute_malloc, decl,
+ false, warned_about, "malloc");
+}
+
+/* Emit suggestion about __attribute__((noreturn)) for DECL. */
+
static void
warn_function_noreturn (tree decl)
{
}
}
+/* Check that RETVAL is used only in STMT and in comparisons against 0.
+ RETVAL is return value of the function and STMT is return stmt. */
+
+static bool
+check_retval_uses (tree retval, gimple *stmt)
+{
+ imm_use_iterator use_iter;
+ gimple *use_stmt;
+
+ FOR_EACH_IMM_USE_STMT (use_stmt, use_iter, retval)
+ if (gcond *cond = dyn_cast<gcond *> (use_stmt))
+ {
+ tree op2 = gimple_cond_rhs (cond);
+ if (!integer_zerop (op2))
+ RETURN_FROM_IMM_USE_STMT (use_iter, false);
+ }
+ else if (gassign *ga = dyn_cast<gassign *> (use_stmt))
+ {
+ enum tree_code code = gimple_assign_rhs_code (ga);
+ if (TREE_CODE_CLASS (code) != tcc_comparison)
+ RETURN_FROM_IMM_USE_STMT (use_iter, false);
+ if (!integer_zerop (gimple_assign_rhs2 (ga)))
+ RETURN_FROM_IMM_USE_STMT (use_iter, false);
+ }
+ else if (is_gimple_debug (use_stmt))
+ ;
+ else if (use_stmt != stmt)
+ RETURN_FROM_IMM_USE_STMT (use_iter, false);
+
+ return true;
+}
+
+/* malloc_candidate_p() checks if FUN can possibly be annotated with malloc
+ attribute. Currently this function does a very conservative analysis.
+ FUN is considered to be a candidate if
+ 1) It returns a value of pointer type.
+ 2) SSA_NAME_DEF_STMT (return_value) is either a function call or
+ a phi, and element of phi is either NULL or
+ SSA_NAME_DEF_STMT(element) is function call.
+ 3) The return-value has immediate uses only within comparisons (gcond or gassign)
+ and return_stmt (and likewise a phi arg has immediate use only within comparison
+ or the phi stmt). */
+
+static bool
+malloc_candidate_p (function *fun, bool ipa)
+{
+ basic_block exit_block = EXIT_BLOCK_PTR_FOR_FN (fun);
+ edge e;
+ edge_iterator ei;
+ cgraph_node *node = cgraph_node::get_create (fun->decl);
+
+#define DUMP_AND_RETURN(reason) \
+{ \
+ if (dump_file && (dump_flags & TDF_DETAILS)) \
+ fprintf (dump_file, "%s", (reason)); \
+ return false; \
+}
+
+ if (EDGE_COUNT (exit_block->preds) == 0)
+ return false;
+
+ FOR_EACH_EDGE (e, ei, exit_block->preds)
+ {
+ gimple_stmt_iterator gsi = gsi_last_bb (e->src);
+ greturn *ret_stmt = dyn_cast<greturn *> (gsi_stmt (gsi));
+
+ if (!ret_stmt)
+ return false;
+
+ tree retval = gimple_return_retval (ret_stmt);
+ if (!retval)
+ DUMP_AND_RETURN("No return value.")
+
+ if (TREE_CODE (retval) != SSA_NAME
+ || TREE_CODE (TREE_TYPE (retval)) != POINTER_TYPE)
+ DUMP_AND_RETURN("Return value is not SSA_NAME or not a pointer type.")
+
+ if (!check_retval_uses (retval, ret_stmt))
+ DUMP_AND_RETURN("Return value has uses outside return stmt"
+ " and comparisons against 0.")
+
+ gimple *def = SSA_NAME_DEF_STMT (retval);
+ if (gcall *call_stmt = dyn_cast<gcall *> (def))
+ {
+ tree callee_decl = gimple_call_fndecl (call_stmt);
+ if (!callee_decl)
+ return false;
+
+ if (!ipa && !DECL_IS_MALLOC (callee_decl))
+ DUMP_AND_RETURN("callee_decl does not have malloc attribute for"
+ " non-ipa mode.")
+
+ cgraph_edge *cs = node->get_edge (call_stmt);
+ if (cs)
+ {
+ ipa_call_summary *es = ipa_call_summaries->get (cs);
+ gcc_assert (es);
+ es->is_return_callee_uncaptured = true;
+ }
+ }
+
+ else if (gphi *phi = dyn_cast<gphi *> (def))
+ for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
+ {
+ tree arg = gimple_phi_arg_def (phi, i);
+ if (TREE_CODE (arg) != SSA_NAME)
+ DUMP_AND_RETURN("phi arg is not SSA_NAME.")
+ if (!(arg == null_pointer_node || check_retval_uses (arg, phi)))
+ DUMP_AND_RETURN("phi arg has uses outside phi"
+ " and comparisons against 0.")
+
+ gimple *arg_def = SSA_NAME_DEF_STMT (arg);
+ gcall *call_stmt = dyn_cast<gcall *> (arg_def);
+ if (!call_stmt)
+ return false;
+ tree callee_decl = gimple_call_fndecl (call_stmt);
+ if (!callee_decl)
+ return false;
+ if (!ipa && !DECL_IS_MALLOC (callee_decl))
+ DUMP_AND_RETURN("callee_decl does not have malloc attribute for"
+ " non-ipa mode.")
+
+ cgraph_edge *cs = node->get_edge (call_stmt);
+ if (cs)
+ {
+ ipa_call_summary *es = ipa_call_summaries->get (cs);
+ gcc_assert (es);
+ es->is_return_callee_uncaptured = true;
+ }
+ }
+
+ else
+ DUMP_AND_RETURN("def_stmt of return value is not a call or phi-stmt.")
+ }
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "\nFound %s to be candidate for malloc attribute\n",
+ IDENTIFIER_POINTER (DECL_NAME (fun->decl)));
+ return true;
+
+#undef DUMP_AND_RETURN
+}
+
/* This is the main routine for finding the reference patterns for
global variables within a function FN. */
if (TREE_NOTHROW (decl))
l->can_throw = false;
+ l->malloc_state = STATE_MALLOC_BOTTOM;
+ if (DECL_IS_MALLOC (decl))
+ l->malloc_state = STATE_MALLOC;
+ else if (ipa && malloc_candidate_p (DECL_STRUCT_FUNCTION (decl), true))
+ l->malloc_state = STATE_MALLOC_TOP;
+ else if (malloc_candidate_p (DECL_STRUCT_FUNCTION (decl), false))
+ l->malloc_state = STATE_MALLOC;
+
pop_cfun ();
if (dump_file)
{
fprintf (dump_file, "Function is locally pure.\n");
if (l->can_free)
fprintf (dump_file, "Function can locally free.\n");
+ if (l->malloc_state == STATE_MALLOC)
+ fprintf (dump_file, "Function is locally malloc.\n");
}
return l;
}
bp_pack_value (&bp, fs->looping, 1);
bp_pack_value (&bp, fs->can_throw, 1);
bp_pack_value (&bp, fs->can_free, 1);
+ bp_pack_value (&bp, fs->malloc_state, 2);
streamer_write_bitpack (&bp);
}
}
fs->looping = bp_unpack_value (&bp, 1);
fs->can_throw = bp_unpack_value (&bp, 1);
fs->can_free = bp_unpack_value (&bp, 1);
+ fs->malloc_state
+ = (enum malloc_state_e) bp_unpack_value (&bp, 2);
+
if (dump_file)
{
int flags = flags_from_decl_or_type (node->decl);
fprintf (dump_file," function is locally throwing\n");
if (fs->can_free)
fprintf (dump_file," function can locally free\n");
+ fprintf (dump_file, "\n malloc state: %s\n",
+ malloc_state_names[fs->malloc_state]);
}
}
free (order);
}
+/* Debugging function to dump state of malloc lattice. */
+
+DEBUG_FUNCTION
+static void
+dump_malloc_lattice (FILE *dump_file, const char *s)
+{
+ if (!dump_file)
+ return;
+
+ fprintf (dump_file, "\n\nMALLOC LATTICE %s:\n", s);
+ cgraph_node *node;
+ FOR_EACH_FUNCTION (node)
+ {
+ funct_state fs = get_function_state (node);
+ malloc_state_e state = fs->malloc_state;
+ fprintf (dump_file, "%s: %s\n", node->name (), malloc_state_names[state]);
+ }
+}
+
+/* Propagate malloc attribute across the callgraph. */
+
+static void
+propagate_malloc (void)
+{
+ cgraph_node *node;
+ FOR_EACH_FUNCTION (node)
+ {
+ if (DECL_IS_MALLOC (node->decl))
+ if (!has_function_state (node))
+ {
+ funct_state l = XCNEW (struct funct_state_d);
+ *l = varying_state;
+ l->malloc_state = STATE_MALLOC;
+ set_function_state (node, l);
+ }
+ }
+
+ dump_malloc_lattice (dump_file, "Initial");
+ struct cgraph_node **order
+ = XNEWVEC (struct cgraph_node *, symtab->cgraph_count);
+ int order_pos = ipa_reverse_postorder (order);
+ bool changed = true;
+
+ while (changed)
+ {
+ changed = false;
+ /* Walk in postorder. */
+ for (int i = order_pos - 1; i >= 0; --i)
+ {
+ cgraph_node *node = order[i];
+ if (node->alias
+ || !node->definition
+ || !has_function_state (node))
+ continue;
+
+ funct_state l = get_function_state (node);
+
+ /* FIXME: add support for indirect-calls. */
+ if (node->indirect_calls)
+ {
+ l->malloc_state = STATE_MALLOC_BOTTOM;
+ continue;
+ }
+
+ if (node->get_availability () <= AVAIL_INTERPOSABLE)
+ {
+ l->malloc_state = STATE_MALLOC_BOTTOM;
+ continue;
+ }
+
+ if (l->malloc_state == STATE_MALLOC_BOTTOM)
+ continue;
+
+ vec<cgraph_node *> callees = vNULL;
+ for (cgraph_edge *cs = node->callees; cs; cs = cs->next_callee)
+ {
+ ipa_call_summary *es = ipa_call_summaries->get (cs);
+ if (es && es->is_return_callee_uncaptured)
+ callees.safe_push (cs->callee);
+ }
+
+ malloc_state_e new_state = l->malloc_state;
+ for (unsigned j = 0; j < callees.length (); j++)
+ {
+ cgraph_node *callee = callees[j];
+ if (!has_function_state (callee))
+ {
+ new_state = STATE_MALLOC_BOTTOM;
+ break;
+ }
+ malloc_state_e callee_state = get_function_state (callee)->malloc_state;
+ if (new_state < callee_state)
+ new_state = callee_state;
+ }
+ if (new_state != l->malloc_state)
+ {
+ changed = true;
+ l->malloc_state = new_state;
+ }
+ }
+ }
+
+ FOR_EACH_DEFINED_FUNCTION (node)
+ if (has_function_state (node))
+ {
+ funct_state l = get_function_state (node);
+ if (!node->alias
+ && l->malloc_state == STATE_MALLOC
+ && !node->global.inlined_to)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Function %s found to be malloc\n",
+ node->name ());
+
+ bool malloc_decl_p = DECL_IS_MALLOC (node->decl);
+ node->set_malloc_flag (true);
+ if (!malloc_decl_p && warn_suggest_attribute_malloc)
+ warn_function_malloc (node->decl);
+ }
+ }
+
+ dump_malloc_lattice (dump_file, "after propagation");
+ ipa_free_postorder_info ();
+ free (order);
+}
/* Produce the global information by preforming a transitive closure
on the local information that was produced by generate_summary. */
/* Nothrow makes more function to not lead to return and improve
later analysis. */
propagate_nothrow ();
+ propagate_malloc ();
remove_p = propagate_pure_const ();
/* Cleanup. */
if (has_function_state (node))
free (get_function_state (node));
funct_state_vec.release ();
+
+ /* In WPA we use inline summaries for partitioning process. */
+ if (!flag_wpa)
+ ipa_free_fn_summary ();
return remove_p ? TODO_remove_functions : 0;
}
fprintf (dump_file, "Function found to be nothrow: %s\n",
current_function_name ());
}
+
+ if (l->malloc_state == STATE_MALLOC
+ && !DECL_IS_MALLOC (current_function_decl))
+ {
+ node->set_malloc_flag (true);
+ if (warn_suggest_attribute_malloc)
+ warn_function_malloc (node->decl);
+ changed = true;
+ if (dump_file)
+ fprintf (dump_file, "Function found to be malloc: %s\n",
+ node->name ());
+ }
+
free (l);
if (changed)
return execute_fixup_cfg ();
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