Re: Discover nothorow functions before into_ssa

[Richard Biener <rguenther at suse dot de>]

On March 26, 2015 6:01:21 PM GMT+01:00, Jan Hubicka <hubicka@ucw.cz> wrote:
>Hi,
>this is updated patch I am testing (along with the fixes to verifiew
>and
>inliner I will commit independently).

OK.
Thanks,
Richard.

>	* passes.def: Add pass_nothrow.
>	* ipa-pure-const.c: (pass_data_nothrow): New.
>	(pass_nothrow): New.
>	(pass_nothrow::execute): New.
>	(make_pass_nothrow): New.
>	* tree-pass.h (make_pass_nothrow): Declare.
>Index: passes.def
>===================================================================
>--- passes.def	(revision 221682)
>+++ passes.def	(working copy)
>@@ -58,6 +58,7 @@ along with GCC; see the file COPYING3.
>       NEXT_PASS (pass_build_ssa);
>       NEXT_PASS (pass_ubsan);
>       NEXT_PASS (pass_early_warn_uninitialized);
>+      NEXT_PASS (pass_nothrow);
>   POP_INSERT_PASSES ()
> 
>   NEXT_PASS (pass_chkp_instrumentation_passes);
>Index: tree-pass.h
>===================================================================
>--- tree-pass.h	(revision 221682)
>+++ tree-pass.h	(working copy)
>@@ -436,6 +436,7 @@ extern gimple_opt_pass *make_pass_remove
> 							      *ctxt);
>extern gimple_opt_pass *make_pass_build_cgraph_edges (gcc::context
>*ctxt);
>extern gimple_opt_pass *make_pass_local_pure_const (gcc::context
>*ctxt);
>+extern gimple_opt_pass *make_pass_nothrow (gcc::context *ctxt);
> extern gimple_opt_pass *make_pass_tracer (gcc::context *ctxt);
>extern gimple_opt_pass *make_pass_warn_unused_result (gcc::context
>*ctxt);
>extern gimple_opt_pass *make_pass_diagnose_tm_blocks (gcc::context
>*ctxt);
>Index: ipa-pure-const.c
>===================================================================
>--- ipa-pure-const.c	(revision 221682)
>+++ ipa-pure-const.c	(working copy)
>@@ -710,6 +711,16 @@ check_stmt (gimple_stmt_iterator *gsip,
>   if (is_gimple_debug (stmt))
>     return;
> 
>+  /* Do consider clobber as side effects before IPA, so we rather
>inline
>+     C++ destructors and keep clobber semantics than eliminate them.
>+
>+     TODO: We may get smarter during early optimizations on these and
>let
>+     functions containing only clobbers to be optimized more.  This is
>a common
>+     case of C++ destructors.  */
>+
>+  if ((ipa || cfun->after_inlining) && gimple_clobber_p (stmt))
>+    return;
>+
>   if (dump_file)
>     {
>       fprintf (dump_file, "  scanning: ");
>@@ -1870,3 +1881,93 @@ make_pass_warn_function_noreturn (gcc::c
> {
>   return new pass_warn_function_noreturn (ctxt);
> }
>+
>+/* Simple local pass for pure const discovery reusing the analysis
>from
>+   ipa_pure_const.   This pass is effective when executed together
>with
>+   other optimization passes in early optimization pass queue.  */
>+
>+namespace {
>+
>+const pass_data pass_data_nothrow =
>+{
>+  GIMPLE_PASS, /* type */
>+  "nothrow", /* name */
>+  OPTGROUP_NONE, /* optinfo_flags */
>+  TV_IPA_PURE_CONST, /* tv_id */
>+  0, /* properties_required */
>+  0, /* properties_provided */
>+  0, /* properties_destroyed */
>+  0, /* todo_flags_start */
>+  0, /* todo_flags_finish */
>+};
>+
>+class pass_nothrow : public gimple_opt_pass
>+{
>+public:
>+  pass_nothrow (gcc::context *ctxt)
>+    : gimple_opt_pass (pass_data_nothrow, ctxt)
>+  {}
>+
>+  /* opt_pass methods: */
>+  opt_pass * clone () { return new pass_nothrow (m_ctxt); }
>+  virtual bool gate (function *) { return optimize; }
>+  virtual unsigned int execute (function *);
>+
>+}; // class pass_nothrow
>+
>+unsigned int
>+pass_nothrow::execute (function *)
>+{
>+  struct cgraph_node *node;
>+  basic_block this_block;
>+
>+  if (TREE_NOTHROW (current_function_decl))
>+    return 0;
>+
>+  node = cgraph_node::get (current_function_decl);
>+
>+  /* We run during lowering, we can not really use availability yet. 
>*/
>+  if (cgraph_node::get (current_function_decl)->get_availability ()
>+      <= AVAIL_INTERPOSABLE)
>+    {
>+      if (dump_file)
>+        fprintf (dump_file, "Function is interposable;"
>+	         " not analyzing.\n");
>+      return true;
>+    }
>+
>+  FOR_EACH_BB_FN (this_block, cfun)
>+    {
>+      gimple_stmt_iterator gsi;
>+      for (gsi = gsi_start_bb (this_block);
>+	   !gsi_end_p (gsi);
>+	   gsi_next (&gsi))
>+        if (stmt_can_throw_external (gsi_stmt (gsi)))
>+	  {
>+	    tree callee_t = gimple_call_fndecl (gsi_stmt (gsi));
>+	    if (callee_t && recursive_call_p (current_function_decl,
>callee_t))
>+	      continue;
>+	
>+	    if (dump_file)
>+	      {
>+		fprintf (dump_file, "Statement can throw: ");
>+		print_gimple_stmt (dump_file, gsi_stmt (gsi), 0, 0);
>+	      }
>+	    return 0;
>+	  }
>+    }
>+
>+  node->set_nothrow_flag (true);
>+  if (dump_file)
>+    fprintf (dump_file, "Function found to be nothrow: %s\n",
>+	     current_function_name ());
>+  return 0;
>+}
>+
>+} // anon namespace
>+
>+gimple_opt_pass *
>+make_pass_nothrow (gcc::context *ctxt)
>+{
>+  return new pass_nothrow (ctxt);
>+}