Hi Richard,
I was trying to have a look at PR35503.
The attached patch tries to warn when an argument is passed to a
restrict-qualified parameter
and the argument could alias with other argument.
For the following test-case:
int f2(int *restrict x, int *y);
void f(void)
{
int a;
f2 (&a, &a);
}
The patch warns:
test-1.c: In function âfâ:
test-1.c:6:3: warning: Passing argument 1 to restrict-qualified
parameter may alias with argument 2 [-Wrestrict]
f2 (&a, &a);
^~~~~~~~~~~
However it gives false positives if arg is a string constant as in
following case:
int foo (char *restrict buf, char *restrict fmt, ...);
int f(void)
{
char buf[10];
foo (buf, "%s-%s", buf, "hello");
}
The patch gives false positives for argument 2:
test-3.c: In function âfâ:
test-3.c:6:3: warning: Passing argument 1 to restrict-qualified
parameter may alias with argument 3 [-Wrestrict]
foo (buf, "%s-%s", buf, "hello");
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test-3.c:6:3: warning: Passing argument 2 to restrict-qualified
parameter may alias with argument 1 [-Wrestrict]
test-3.c:6:3: warning: Passing argument 2 to restrict-qualified
parameter may alias with argument 3 [-Wrestrict]
test-3.c:6:3: warning: Passing argument 2 to restrict-qualified
parameter may alias with argument 4 [-Wrestrict]
I am using compute_may_aliases() to obtain alias analysis info,
and then using ptr_derefs_may_alias_p(arg, current_arg) to check if
the arguments
could potentially alias. Is that incorrect ?
Thanks,
Prathamesh
diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 8d7cc51..5d8263d 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1549,6 +1549,7 @@ OBJS = \
varpool.o \
vmsdbgout.o \
vtable-verify.o \
+ warn-restrict.o \
web.o \
wide-int.o \
wide-int-print.o \
diff --git a/gcc/common.opt b/gcc/common.opt
index 65a9762..afb2327 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -732,6 +732,11 @@ Wmaybe-uninitialized
Common Var(warn_maybe_uninitialized) Warning EnabledBy(Wuninitialized)
Warn about maybe uninitialized automatic variables.
+Wrestrict
+Common Var(warn_restrict) Warning EanbledBy(Wall)
+Warn when a pointer argument is passed to a parameter qualified with restrict,
+and it potentially aliases with another arguments.
+
Wunreachable-code
Common Ignore Warning
Does nothing. Preserved for backward compatibility.
diff --git a/gcc/passes.def b/gcc/passes.def
index 533157d..2cccd6d 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -141,6 +141,7 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_ipa_increase_alignment);
NEXT_PASS (pass_ipa_tm);
NEXT_PASS (pass_ipa_lower_emutls);
+ NEXT_PASS (pass_ipa_warn_restrict);
TERMINATE_PASS_LIST (all_small_ipa_passes)
INSERT_PASSES_AFTER (all_regular_ipa_passes)
diff --git a/gcc/tree-pass.h b/gcc/tree-pass.h
index c0059de..90d06b5 100644
--- a/gcc/tree-pass.h
+++ b/gcc/tree-pass.h
@@ -485,6 +485,7 @@ extern ipa_opt_pass_d
*make_pass_ipa_whole_program_visibility (gcc::context
*ctxt);
extern simple_ipa_opt_pass *make_pass_ipa_increase_alignment (gcc::context
*ctxt);
+extern simple_ipa_opt_pass *make_pass_ipa_warn_restrict (gcc::context *ctxt);
extern ipa_opt_pass_d *make_pass_ipa_inline (gcc::context *ctxt);
extern simple_ipa_opt_pass *make_pass_ipa_free_lang_data (gcc::context *ctxt);
extern simple_ipa_opt_pass *make_pass_ipa_free_inline_summary (gcc::context
diff --git a/gcc/warn-restrict.c b/gcc/warn-restrict.c
new file mode 100644
index 0000000..fa6d9b1
--- /dev/null
+++ b/gcc/warn-restrict.c
@@ -0,0 +1,131 @@
+/*
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "backend.h"
+#include "target.h"
+#include "tree.h"
+#include "gimple.h"
+#include "tree-pass.h"
+#include "tree-streamer.h"
+#include "cgraph.h"
+#include "diagnostic.h"
+#include "calls.h"
+#include "cfganal.h"
+#include "tree-eh.h"
+#include "gimple-iterator.h"
+#include "gimple-walk.h"
+#include "tree-cfg.h"
+#include "tree-ssa-loop-niter.h"
+#include "langhooks.h"
+#include "ipa-utils.h"
+#include "gimple-pretty-print.h"
+#include "cfgloop.h"
+#include "tree-scalar-evolution.h"
+#include "intl.h"
+#include "opts.h"
+#include "fold-const.h"
+
+static void
+do_warn_restrict (function *fun)
+{
+ push_cfun (fun);
+ compute_may_aliases ();
+
+ cgraph_node *cnode = cgraph_node::get (current_function_decl);
+ for (cgraph_edge *e = cnode->callees; e; e = e->next_callee)
+ {
+ cgraph_node *callee = e->callee->function_symbol ();
+ tree callee_decl = callee->decl;
+ gcall *call_stmt = e->call_stmt;
+
+ unsigned param_pos = 0;
+ for (tree t = TYPE_ARG_TYPES (TREE_TYPE (callee_decl)); t; t =
TREE_CHAIN (t), param_pos++)
+ {
+ tree type = TREE_VALUE (t);
+ if (POINTER_TYPE_P (type) && TYPE_RESTRICT (type))
+ {
+ tree arg = gimple_call_arg (call_stmt, param_pos);
+ gcc_assert (POINTER_TYPE_P (TREE_TYPE (arg)));
+
+ for (unsigned i = 0; i < gimple_call_num_args (call_stmt); i++)
+ {
+ if (i == param_pos)
+ continue;
+
+ tree current_arg = gimple_call_arg (call_stmt, i);
+ if (POINTER_TYPE_P (TREE_TYPE (current_arg))
+ && ptr_derefs_may_alias_p (arg, current_arg))
+ warning_at (gimple_location (call_stmt), OPT_Wrestrict,
+ "Passing argument %d to restrict-qualified
parameter "
+ "may alias with argument %d",
+ param_pos + 1, i + 1);
+ }
+ }
+ }
+ }
+
+ pop_cfun ();
+}
+
+namespace {
+
+const pass_data pass_data_warn_restrict =
+{
+ SIMPLE_IPA_PASS, /* type */
+ "*warn-restrict", /* name */
+ OPTGROUP_NONE, /* optinfo_flags */
+ TV_NONE, /* tv_id */
+ 0, /* properties required */
+ 0, /* properties provided */
+ 0, /* properties destroyed */
+ 0, /* todo_flags_start */
+ 0, /* todo_flags_finish */
+};
+
+class pass_ipa_warn_restrict: public simple_ipa_opt_pass
+{
+public:
+ pass_ipa_warn_restrict (gcc::context *ctxt)
+ : simple_ipa_opt_pass (pass_data_warn_restrict, ctxt)
+ {}
+
+ /* opt_pass methods: */
+ virtual bool gate (function *) { return warn_restrict; }
+ virtual unsigned execute (function *);
+}; // class pass_warn_function_noreturn
+
+unsigned
+pass_ipa_warn_restrict::execute (function *)
+{
+ cgraph_node *cnode;
+
+ FOR_EACH_DEFINED_FUNCTION (cnode)
+ do_warn_restrict (DECL_STRUCT_FUNCTION (cnode->decl));
+
+ return 0;
+}
+
+} // anon namespace
+
+simple_ipa_opt_pass *
+make_pass_ipa_warn_restrict (gcc::context *ctxt)
+{
+ return new pass_ipa_warn_restrict (ctxt);
+}
