From: Richard Biener <rguenther@suse.de>
Date: Fri, 4 Nov 2016 08:54:42 +0000 (+0000)
Subject: re PR tree-optimization/78185 (Wrong branch optimization with -O1 on x86/x86_64)
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=964ef24cd591632a38c3e48154de389470df13df;p=gcc.git

re PR tree-optimization/78185 (Wrong branch optimization with -O1 on x86/x86_64)

2016-11-04  Richard Biener  <rguenther@suse.de>

	PR middle-end/78185
	* loop-invariant.c (find_exits): Record entering inner
	loops as possibly exiting to handle infinite sub-loops.
	* tree-ssa-loop-im.c: Include tree-ssa-loop-niter.h.
	(fill_always_executed_in_1): Honor infinite child loops.

	* gcc.dg/pr78185.c: New testcase.

From-SVN: r241841
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9222baaa498..8a455c1e1ef 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2016-11-04  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/78185
+	* loop-invariant.c (find_exits): Record entering inner
+	loops as possibly exiting to handle infinite sub-loops.
+	* tree-ssa-loop-im.c: Include tree-ssa-loop-niter.h.
+	(fill_always_executed_in_1): Honor infinite child loops.
+
 2016-11-03  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	PR target/78192
diff --git a/gcc/loop-invariant.c b/gcc/loop-invariant.c
index 551103fcf46..f617241ef0f 100644
--- a/gcc/loop-invariant.c
+++ b/gcc/loop-invariant.c
@@ -598,13 +598,17 @@ find_exits (struct loop *loop, basic_block *body,
 
 	  FOR_EACH_EDGE (e, ei, body[i]->succs)
 	    {
-	      if (flow_bb_inside_loop_p (loop, e->dest))
-		continue;
-
-	      bitmap_set_bit (may_exit, i);
-	      bitmap_set_bit (has_exit, i);
-	      outermost_exit = find_common_loop (outermost_exit,
-						 e->dest->loop_father);
+	      if (! flow_bb_inside_loop_p (loop, e->dest))
+		{
+		  bitmap_set_bit (may_exit, i);
+		  bitmap_set_bit (has_exit, i);
+		  outermost_exit = find_common_loop (outermost_exit,
+						     e->dest->loop_father);
+		}
+	      /* If we enter a subloop that might never terminate treat
+	         it like a possible exit.  */
+	      if (flow_loop_nested_p (loop, e->dest->loop_father))
+		bitmap_set_bit (may_exit, i);
 	    }
 	  continue;
 	}
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c62bb935966..9451ca975cf 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-11-04  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/78185
+	* gcc.dg/pr78185.c: New testcase.
+
 2016-10-04  David Edelsohn  <dje.gcc@gmail.com>
 
 	* g++.dg/debug/dwarf2/ref-3.C: XFAIL AIX.
diff --git a/gcc/testsuite/gcc.dg/pr78185.c b/gcc/testsuite/gcc.dg/pr78185.c
new file mode 100644
index 00000000000..405f7489dae
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr78185.c
@@ -0,0 +1,28 @@
+/* { dg-do run { target *-*-linux* *-*-gnu* } } */
+/* { dg-options "-O" } */
+
+#include <unistd.h>
+#include <signal.h>
+#include <stdlib.h>
+
+static char var1 = 0L;
+static char *var2 = &var1;
+
+void do_exit (int i)
+{
+  exit (0);
+}
+
+int main(void)
+{
+  struct sigaction s;
+  sigemptyset (&s.sa_mask);
+  s.sa_handler = do_exit;
+  s.sa_flags = 0;
+  sigaction (SIGALRM, &s, NULL);
+  alarm (1);
+  /* The following loop is infinite, the division by zero should not
+     be hoisted out of it.  */
+  for (; (var1 == 0 ? 0 : (100 / var1)) == *var2; );
+  return 0;
+}
diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c
index 463db048cb6..0524e57564f 100644
--- a/gcc/tree-ssa-loop-im.c
+++ b/gcc/tree-ssa-loop-im.c
@@ -44,6 +44,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "trans-mem.h"
 #include "gimple-fold.h"
 #include "tree-scalar-evolution.h"
+#include "tree-ssa-loop-niter.h"
 
 /* TODO:  Support for predicated code motion.  I.e.
 
@@ -2369,8 +2370,16 @@ fill_always_executed_in_1 (struct loop *loop, sbitmap contains_call)
 	    break;
 
 	  FOR_EACH_EDGE (e, ei, bb->succs)
-	    if (!flow_bb_inside_loop_p (loop, e->dest))
-	      break;
+	    {
+	      /* If there is an exit from this BB.  */
+	      if (!flow_bb_inside_loop_p (loop, e->dest))
+		break;
+	      /* Or we enter a possibly non-finite loop.  */
+	      if (flow_loop_nested_p (bb->loop_father,
+				      e->dest->loop_father)
+		  && ! finite_loop_p (e->dest->loop_father))
+		break;
+	    }
 	  if (e)
 	    break;