Remove parameters after converting call to gcc_unreachable

[Jan Hubicka <hubicka at ucw dot cz>]

Hi,
this is second attempt to fix the issue with arguments being passed
to builtlin_unreachable after https://gcc.gnu.org/ml/gcc-patches/2014-12/msg01025.html

As suggested, I fixup the IL right after redirection instead waiting for tree-ssa-dce.

Bootstrapped/regtested x86_64-linux, OK?
	PR middle-end/64922
	* gimple.c: Include gimple-ssa.h
	(maybe_remove_unused_call_args): New function.
	* gimple.h (maybe_remove_unused_call_args): Declare.
	* craph.c (cgraph_edge::redirect_call_stmt_to_callee): Use it.
	* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children): Likewise.
	* gimple-fold.c (gimple_fold_call): Likewise.
Index: gimple.c
===================================================================
--- gimple.c	(revision 220411)
+++ gimple.c	(working copy)
@@ -67,6 +67,7 @@ along with GCC; see the file COPYING3.
 #include "ipa-ref.h"
 #include "lto-streamer.h"
 #include "cgraph.h"
+#include "gimple-ssa.h"
 
 
 /* All the tuples have their operand vector (if present) at the very bottom
@@ -2950,3 +2951,20 @@ gimple_seq_discard (gimple_seq seq)
       ggc_free (stmt);
     }
 }
+
+/* See if STMT now calls function that takes no parameters and if so, drop
+   call arguments.  This is used when devirtualization machinery redirects
+   to __builtiln_unreacahble or __cfa_pure_virutal.  */
+
+void
+maybe_remove_unused_call_args (struct function *fn, gimple stmt)
+{
+  tree decl = gimple_call_fndecl (stmt);
+  if (TYPE_ARG_TYPES (TREE_TYPE (decl))
+      && TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (decl))) == void_type_node
+      && gimple_call_num_args (stmt))
+    {
+      gimple_set_num_ops (stmt, 3);
+      update_stmt_fn (fn, stmt);
+    }
+}
Index: gimple.h
===================================================================
--- gimple.h	(revision 220411)
+++ gimple.h	(working copy)
@@ -1404,6 +1404,7 @@ extern void sort_case_labels (vec<tree>)
 extern void preprocess_case_label_vec_for_gimple (vec<tree>, tree, tree *);
 extern void gimple_seq_set_location (gimple_seq, location_t);
 extern void gimple_seq_discard (gimple_seq);
+extern void maybe_remove_unused_call_args (struct function *, gimple);
 
 /* Formal (expression) temporary table handling: multiple occurrences of
    the same scalar expression are evaluated into the same temporary.  */
Index: cgraph.c
===================================================================
--- cgraph.c	(revision 220411)
+++ cgraph.c	(working copy)
@@ -1324,7 +1324,8 @@ cgraph_edge::redirect_call_stmt_to_calle
 		     (int64_t)e->count);
 	  gcc_assert (e2->speculative);
 	  push_cfun (DECL_STRUCT_FUNCTION (e->caller->decl));
-	  new_stmt = gimple_ic (e->call_stmt, dyn_cast<cgraph_node *> (ref->referred),
+	  new_stmt = gimple_ic (e->call_stmt,
+				dyn_cast<cgraph_node *> (ref->referred),
 				e->count || e2->count
 				?  RDIV (e->count * REG_BR_PROB_BASE,
 					 e->count + e2->count)
@@ -1464,6 +1465,9 @@ cgraph_edge::redirect_call_stmt_to_calle
       update_stmt_fn (DECL_STRUCT_FUNCTION (e->caller->decl), new_stmt);
     }
 
+  maybe_remove_unused_call_args (DECL_STRUCT_FUNCTION (e->caller->decl),
+				 new_stmt);
+
   e->caller->set_call_stmt_including_clones (e->call_stmt, new_stmt, false);
 
   if (symtab->dump_file)
Index: tree-ssa-pre.c
===================================================================
--- tree-ssa-pre.c	(revision 220411)
+++ tree-ssa-pre.c	(working copy)
@@ -4406,6 +4406,7 @@ eliminate_dom_walker::before_dom_childre
 				       cgraph_node::get (fn)->name ());
 		    }
 		  gimple_call_set_fndecl (call_stmt, fn);
+		  maybe_remove_unused_call_args (cfun, call_stmt);
 		  gimple_set_modified (stmt, true);
 		}
 	    }
Index: gimple-fold.c
===================================================================
--- gimple-fold.c	(revision 220411)
+++ gimple-fold.c	(working copy)
@@ -3120,6 +3120,7 @@ gimple_fold_call (gimple_stmt_iterator *
 			}
 		      gimple_call_set_lhs (stmt, NULL_TREE);
 		    }
+		  maybe_remove_unused_call_args (cfun, stmt);
 		}
 	      else
 		{