tree-optimization/96491 - avoid store commoning across abnormal edges

This avoids store commoning across abnormal edges since that easily
can disrupt abnormal coalescing because it might create overlapping
lifetime of variables.

2020-08-06  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/96491
	* tree-ssa-sink.c (sink_common_stores_to_bb): Avoid
	sinking across abnormal edges.

	* gcc.dg/torture/pr96491.c: New testcase.

gcc/testsuite/gcc.dg/torture/pr96491.c

@@ -0,0 +1,29 @@
+/* { dg-do compile }  */
+
+int rj;
+
+void __attribute__ ((returns_twice))
+da (void)
+{
+  rj = 1;
+}
+
+void
+c5 (void)
+{
+  for (;;)
+    ++rj;
+}
+
+void
+ls (int kz)
+{
+  if (kz == 0)
+    {
+      rj = 0;
+      c5 ();
+    }
+
+  da ();
+  c5 ();
+}

gcc/tree-ssa-sink.c

@@ -503,7 +503,8 @@ sink_common_stores_to_bb (basic_block bb)
 	      tree arg = gimple_phi_arg_def (phi, i);
 	      gimple *def = SSA_NAME_DEF_STMT (arg);
 	      if (! is_gimple_assign (def)
-		  || stmt_can_throw_internal (cfun, def))
+		  || stmt_can_throw_internal (cfun, def)
+		  || (gimple_phi_arg_edge (phi, i)->flags & EDGE_ABNORMAL))
 		{
 		  /* ???  We could handle some cascading with the def being
 		     another PHI.  We'd have to insert multiple PHIs for