[PATCH] Fix fold_stmt ICE (PR c++/49264)

[Jakub Jelinek]

On Mon, Jun 06, 2011 at 01:41:14PM +0200, Richard Guenther wrote:
> > I think NULL new_stmt would have the advantage that we wouldn't duplicate
> > the complex code looping through all kinds of clones.
> 
> Yeah, I'd prefer that variant.  Honza?

Ok, after further discussions with Honza on IRC here is what I've committed
to trunk and 4.6, after bootstrapping/regtesting it on x86_64-linux and
i686-linux again.

2011-06-06  Jakub Jelinek  <jakub@redhat.com>

	PR c++/49264
	* gimple-fold.c (fold_stmt_1): Don't try to fold *& on the lhs
	if stmt folded into nothing.
	* tree-inline.c (fold_marked_statements): If a builtin at the
	end of a bb folded into nothing, just update cgraph edges
	and move to next bb.
	* cgraph.c (cgraph_update_edges_for_call_stmt_node): Allow new_stmt
	to be NULL.  Don't compute count and frequency if new_call is NULL.

	* g++.dg/opt/pr49264.C: New test.

--- gcc/gimple-fold.c.jj	2011-06-03 10:31:32.000000000 +0200
+++ gcc/gimple-fold.c	2011-06-06 16:27:41.000000000 +0200
@@ -1577,6 +1577,11 @@ fold_stmt_1 (gimple_stmt_iterator *gsi, 
   bool changed = false;
   gimple stmt = gsi_stmt (*gsi);
   unsigned i;
+  gimple_stmt_iterator gsinext = *gsi;
+  gimple next_stmt;
+
+  gsi_next (&gsinext);
+  next_stmt = gsi_end_p (gsinext) ? NULL : gsi_stmt (gsinext);
 
   /* Fold the main computation performed by the statement.  */
   switch (gimple_code (stmt))
@@ -1665,10 +1670,19 @@ fold_stmt_1 (gimple_stmt_iterator *gsi, 
     default:;
     }
 
+  /* If stmt folds into nothing and it was the last stmt in a bb,
+     don't call gsi_stmt.  */
+  if (gsi_end_p (*gsi))
+    {
+      gcc_assert (next_stmt == NULL);
+      return changed;
+    }
+
   stmt = gsi_stmt (*gsi);
 
-  /* Fold *& on the lhs.  */
-  if (gimple_has_lhs (stmt))
+  /* Fold *& on the lhs.  Don't do this if stmt folded into nothing,
+     as we'd changing the next stmt.  */
+  if (gimple_has_lhs (stmt) && stmt != next_stmt)
     {
       tree lhs = gimple_get_lhs (stmt);
       if (lhs && REFERENCE_CLASS_P (lhs))
--- gcc/tree-inline.c.jj	2011-06-06 10:24:12.000000000 +0200
+++ gcc/tree-inline.c	2011-06-06 16:28:51.000000000 +0200
@@ -4055,6 +4055,14 @@ fold_marked_statements (int first, struc
 		  if (fold_stmt (&gsi))
 		    {
 		      gimple new_stmt;
+		      /* If a builtin at the end of a bb folded into nothing,
+			 the following loop won't work.  */
+		      if (gsi_end_p (gsi))
+			{
+			  cgraph_update_edges_for_call_stmt (old_stmt,
+							     old_decl, NULL);
+			  break;
+			}
 		      if (gsi_end_p (i2))
 			i2 = gsi_start_bb (BASIC_BLOCK (first));
 		      else
--- gcc/cgraph.c.jj	2011-06-03 10:31:32.000000000 +0200
+++ gcc/cgraph.c	2011-06-06 16:30:06.000000000 +0200
@@ -1233,13 +1233,17 @@ cgraph_make_edge_direct (struct cgraph_e
 
 /* Update or remove the corresponding cgraph edge if a GIMPLE_CALL
    OLD_STMT changed into NEW_STMT.  OLD_CALL is gimple_call_fndecl
-   of OLD_STMT if it was previously call statement.  */
+   of OLD_STMT if it was previously call statement.
+   If NEW_STMT is NULL, the call has been dropped without any
+   replacement.  */
 
 static void
 cgraph_update_edges_for_call_stmt_node (struct cgraph_node *node,
-					gimple old_stmt, tree old_call, gimple new_stmt)
+					gimple old_stmt, tree old_call,
+					gimple new_stmt)
 {
-  tree new_call = (is_gimple_call (new_stmt)) ? gimple_call_fndecl (new_stmt) : 0;
+  tree new_call = (new_stmt && is_gimple_call (new_stmt))
+		  ? gimple_call_fndecl (new_stmt) : 0;
 
   /* We are seeing indirect calls, then there is nothing to update.  */
   if (!new_call && !old_call)
@@ -1277,7 +1281,7 @@ cgraph_update_edges_for_call_stmt_node (
 	  frequency = e->frequency;
 	  cgraph_remove_edge (e);
 	}
-      else
+      else if (new_call)
 	{
 	  /* We are seeing new direct call; compute profile info based on BB.  */
 	  basic_block bb = gimple_bb (new_stmt);
--- gcc/testsuite/g++.dg/opt/pr49264.C.jj	2011-06-06 16:27:41.000000000 +0200
+++ gcc/testsuite/g++.dg/opt/pr49264.C	2011-06-06 16:27:41.000000000 +0200
@@ -0,0 +1,19 @@
+// PR c++/49264
+// { dg-do compile }
+// { dg-options "-O2" }
+
+struct B { };
+struct A { char a[sizeof (B) + 1]; } a;
+
+static inline void
+foo (const B &b)
+{
+  __builtin_memcpy (&a, &b, sizeof (b));
+}
+
+void
+bar ()
+{
+  B c;
+  foo (c);
+}


	Jakub