[PATCH] Fix PR68017

[PATCH] Fix PR68017

[Richard Biener]

The usual stmt removing vs. debug stmts thing.

Bootstrapped and tested on x86_64-linux-gnu, applied to trunk.

Richard.

2015-10-20  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/68017
	* tree-tailcall.c (eliminate_tail_call): Remove stmts backwards.

	* gcc.dg/torture/pr68017.c: New testcase.

Index: gcc/tree-tailcall.c
===================================================================
--- gcc/tree-tailcall.c	(revision 228971)
+++ gcc/tree-tailcall.c	(working copy)
@@ -847,17 +847,21 @@ eliminate_tail_call (struct tailcall *t)
      possibly unreachable code in other blocks is removed later in
      cfg cleanup.  */
   gsi = t->call_gsi;
-  gsi_next (&gsi);
-  while (!gsi_end_p (gsi))
+  gimple_stmt_iterator gsi2 = gsi_last_bb (gimple_bb (gsi_stmt (gsi)));
+  while (gsi_stmt (gsi2) != gsi_stmt (gsi))
     {
-      gimple *t = gsi_stmt (gsi);
+      gimple *t = gsi_stmt (gsi2);
       /* Do not remove the return statement, so that redirect_edge_and_branch
 	 sees how the block ends.  */
-      if (gimple_code (t) == GIMPLE_RETURN)
-	break;
-
-      gsi_remove (&gsi, true);
-      release_defs (t);
+      if (gimple_code (t) != GIMPLE_RETURN)
+	{
+	  gimple_stmt_iterator gsi3 = gsi2;
+	  gsi_prev (&gsi2);
+	  gsi_remove (&gsi3, true);
+	  release_defs (t);
+	}
+      else
+	gsi_prev (&gsi2);
     }
 
   /* Number of executions of function has reduced by the tailcall.  */
Index: gcc/testsuite/gcc.dg/torture/pr68017.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr68017.c	(revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr68017.c	(working copy)
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-g" } */
+
+long long a;
+
+short
+fn1 (short p1, unsigned short p2)
+{
+  return p1 + p2;
+}
+
+short
+fn2 ()
+{
+  int b = a ? fn1 (fn2 (), a) : 0;
+  return b;
+}