[PATCH] Fix another __builtin_unreachable () ICE (PR bootstrap/42347)

[Jakub Jelinek]

Hi!

The http://gcc.gnu.org/ml/gcc-patches/2009-09/msg01046.html
fix apparently assumed only !onlyjump_p sideffects can lead into
an conditional jump not being redirected and/or optimized away.

But conditional return jumps apparently aren't redirected/removed either,
and comments like
/* A return instruction can't be redirected.  */
in cfgrtl.c suggest that is intentional.  So, this patch just allows
also conditional return jumps.

Ok for trunk/4.5?

2010-05-17  Jakub Jelinek  <jakub@redhat.com>

	PR bootstrap/42347
	* cfglayout.c (fixup_reorder_chain): Allow returnjump_p
	to have no fallthru edge.

	* gcc.c-torture/compile/pr42347.c: New test.

--- gcc/cfglayout.c.jj	2010-05-13 12:21:21.000000000 +0200
+++ gcc/cfglayout.c	2010-05-17 15:09:08.000000000 +0200
@@ -793,7 +793,8 @@ fixup_reorder_chain (void)
 		 to prevent rtl_verify_flow_info from complaining.  */
 	      if (!e_fall)
 		{
-		  gcc_assert (!onlyjump_p (bb_end_insn));
+		  gcc_assert (!onlyjump_p (bb_end_insn)
+			      || returnjump_p (bb_end_insn));
 		  bb->il.rtl->footer = emit_barrier_after (bb_end_insn);
 		  continue;
 		}
--- gcc/testsuite/gcc.c-torture/compile/pr42347.c.jj	2010-05-17 15:18:12.000000000 +0200
+++ gcc/testsuite/gcc.c-torture/compile/pr42347.c	2010-05-17 15:19:40.000000000 +0200
@@ -0,0 +1,16 @@
+/* PR bootstrap/42347 */
+
+long
+foo (long x, long y)
+{
+  x = x & y;
+  switch (y)
+    {
+    case 63L: x >>= 0; break;
+    case 4032L: x >>= 6; break;
+    case 258048L: x >>= 12; break;
+    case 16515072L: x >>= 18; break;
+    default: __builtin_unreachable ();
+    }
+  return x;
+}

	Jakub