diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c9a48b0c02e6..b6a058bf4494 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2016-12-11  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
+
+	PR target/78695
+	* config/rs6000/rs6000.c (find_alignment_op): Discard from
+	consideration any artificial definition.
+
 2016-12-11  Iain Sandoe  <iain@codesourcery.com>
 
 	* configure.ac (CROSS directory tests): Remove the assumption that
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 55e9548f7669..6aa843697550 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -41433,6 +41433,12 @@ find_alignment_op (rtx_insn *insn, rtx base_reg)
       if (!base_def_link || base_def_link->next)
 	break;
 
+      /* With stack-protector code enabled, and possibly in other
+	 circumstances, there may not be an associated insn for 
+	 the def.  */
+      if (DF_REF_IS_ARTIFICIAL (base_def_link->ref))
+	break;
+
       rtx_insn *and_insn = DF_REF_INSN (base_def_link->ref);
       and_operation = alignment_mask (and_insn);
       if (and_operation != 0)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index aa9aae76e13f..cde6eefc8eeb 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-12-11  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
+
+	PR target/78695
+	* gcc.target/powerpc/swaps-stack-protector.c: New test.
+
 2016-12-11  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/70799
diff --git a/gcc/testsuite/gcc.target/powerpc/swaps-stack-protector.c b/gcc/testsuite/gcc.target/powerpc/swaps-stack-protector.c
new file mode 100644
index 000000000000..8093a26cc564
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/swaps-stack-protector.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-fstack-protector -O3" } */
+
+/* PR78695: This code used to ICE in rs6000.c:find_alignment_op because
+   the stack protector address definition isn't associated with an insn.  */
+
+void *a();
+long b() {
+  char c[1];
+  char *d = a(), *e = c;
+  long f = e ? b(e) : 0;
+  if (f > 54)
+    f = 1;
+  while (f--)
+    *d++ = *e++;
+}