From patchwork Thu Nov 15 19:34:38 2012
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Subject: Fix PR middle-end/55321
Date: Thu, 15 Nov 2012 09:34:38 -0000
From: Eric Botcazou <ebotcazou@adacore.com>
X-Patchwork-Id: 199389
Message-Id: <1847684.pGViGHtxfN@polaris>
To: gcc-patches@gcc.gnu.org
Cc: Richard Henderson <rth@redhat.com>

Hi,

this is the build failure of the Ada runtime on the ARM:

+===========================GNAT BUG DETECTED==============================+
| 4.8.0 20121111 (experimental) (armv5tel-unknown-linux-gnueabi) GCC error:|
| in merge_latch_edges, at cfgloop.c:678                                   |
| Error detected around s-stposu.adb:565:8                                 |
| Please submit a bug report; see http://gcc.gnu.org/bugs.html.     

The problem is that get_loop_latch_edges finds no latch edges for a loop 
because the header of the loop doesn't dominate any of its predecessors.
The reason is that a new edge is added during RTL expansion, which changes the 
dominance info.  This edge is from a call to __sync_synchronize to a non-local 
label generated for a __builtin_setjmp_receiver.

Fixed by marking the call as "nononlocal", tested on x86_64-suse-linux, OK for 
the mainline?


2012-11-15  Eric Botcazou  <ebotcazou@adacore.com>

	PR middle-end/55321
	* optabs.c (mark_nothrow_nononlocal): New function extracted from...
	(emit_libcall_block_1): ...here.  Call it.
	(expand_mem_thread_fence): Call it for synchronize_libfunc.


2012-11-15  Eric Botcazou  <ebotcazou@adacore.com>

	* loop_optimization14.ad[sb]: New test.
	* loop_optimization14_pkg.ads: New helper.


Index: optabs.c
===================================================================
--- optabs.c	(revision 193528)
+++ optabs.c	(working copy)
@@ -3838,6 +3838,23 @@ no_conflict_move_test (rtx dest, const_r
 }
 
 
+/* Look for any CALL_INSNs in the insn chain starting at INSN and attach a
+   REG_EH_REGION reg note to indicate that this call cannot throw or execute
+   a nonlocal goto (unless there is already a REG_EH_REGION note, in which
+   case we update it).  */
+
+static void
+mark_nothrow_nononlocal (rtx insn)
+{
+  while (insn)
+    {
+      if (CALL_P (insn))
+	make_reg_eh_region_note_nothrow_nononlocal (insn);
+
+      insn = NEXT_INSN (insn);
+    }
+}
+
 /* Emit code to make a call to a constant function or a library call.
 
    INSNS is a list containing all insns emitted in the call.
@@ -3881,15 +3898,7 @@ emit_libcall_block_1 (rtx insns, rtx tar
 	  }
     }
   else
-    {
-      /* Look for any CALL_INSNs in this sequence, and attach a REG_EH_REGION
-	 reg note to indicate that this call cannot throw or execute a nonlocal
-	 goto (unless there is already a REG_EH_REGION note, in which case
-	 we update it).  */
-      for (insn = insns; insn; insn = NEXT_INSN (insn))
-	if (CALL_P (insn))
-	  make_reg_eh_region_note_nothrow_nononlocal (insn);
-    }
+    mark_nothrow_nononlocal (insns);
 
   /* First emit all insns that set pseudos.  Remove them from the list as
      we go.  Avoid insns that set pseudos which were referenced in previous
@@ -7404,7 +7413,15 @@ expand_mem_thread_fence (enum memmodel m
       if (HAVE_memory_barrier)
 	emit_insn (gen_memory_barrier ());
       else if (synchronize_libfunc != NULL_RTX)
-	emit_library_call (synchronize_libfunc, LCT_NORMAL, VOIDmode, 0);
+	{
+	  rtx insns;
+	  start_sequence ();
+	  emit_library_call (synchronize_libfunc, LCT_NORMAL, VOIDmode, 0);
+	  insns = get_insns ();
+	  end_sequence ();
+	  mark_nothrow_nononlocal (insns);
+	  emit_insn (insns);
+	}
       else
 	expand_asm_memory_barrier ();
     }