tree-optimization: only DSE trapping insn if -fdelete-dead-exceptions

gcc/ChangeLog:

	* tree-ssa-dse.cc (dse_optimize_stmt): Only delete a trapping
	statement if -fdelete-dead-exceptions.

gcc/testsuite/ChangeLog:

	* g++.dg/torture/except-1.C: New test.

gcc/testsuite/g++.dg/torture/except-1.C

@@ -0,0 +1,44 @@
+// { dg-do run { target { i?86-*-linux* i?86-*-gnu* x86_64-*-linux* } } }
+// { dg-additional-options "-fexceptions -fnon-call-exceptions -fno-delete-dead-exceptions" }
+
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void
+sighandler (int signo, siginfo_t* si, void* uc)
+{
+  throw (5);
+}
+
+struct S { void *p1, *p2; };
+
+struct S v;
+
+__attribute__ ((noinline))
+int
+dosegv ()
+{
+  struct S *p = 0;
+  struct S s __attribute__((unused)) = *p;
+  return 0;
+}
+
+int main ()
+{
+  struct sigaction sa;
+
+  memset (&sa, 0, sizeof sa);
+  sa.sa_sigaction = sighandler;
+  sigaction (SIGSEGV, &sa, NULL);
+  sigaction (SIGBUS, &sa, NULL);
+
+  try {
+    dosegv ();
+  }
+  catch (int x) {
+    return (x != 5);
+  }
+
+  return 1;
+}

gcc/tree-ssa-dse.cc

@@ -1463,7 +1463,8 @@ dse_optimize_stmt (function *fun, gimple_stmt_iterator *gsi, sbitmap live_bytes)
       gimple_call_set_lhs (stmt, NULL_TREE);
       update_stmt (stmt);
     }
-  else
+  else if (!stmt_could_throw_p (fun, stmt)
+	   || fun->can_delete_dead_exceptions)
     delete_dead_or_redundant_assignment (gsi, "dead", need_eh_cleanup,
 					 need_ab_cleanup);
 }