diff --git a/gcc/testsuite/gcc.dg/vect/bb-slp-pr97746.c b/gcc/testsuite/gcc.dg/vect/bb-slp-pr97746.c
new file mode 100644
index 0000000000000000000000000000000000000000..c5a615d1253f9f1ad8d42dd005a1d7b3aa271cb0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/bb-slp-pr97746.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+
+int a, b;
+short c;
+
+extern void f (short*);
+
+void d()
+{
+  short e[2] = {0, 0};
+  while (a)
+    {
+      f(e);
+      int g = 0 || a, h = 8 && c;
+      short i = c;
+      c = h & g;
+      if (b)
+	b = g || i;
+    }
+}
diff --git a/gcc/tree-vect-patterns.c b/gcc/tree-vect-patterns.c
index eefa7cf6799a7d846303aa6274d28bcc0a841158..f68a87e05ed54145a25ccff598eeef9e57f9a759 100644
--- a/gcc/tree-vect-patterns.c
+++ b/gcc/tree-vect-patterns.c
@@ -5182,15 +5182,15 @@ vect_determine_precisions (vec_info *vinfo)
       for (unsigned i = 0; i < bb_vinfo->bbs.length (); ++i)
 	{
 	  basic_block bb = bb_vinfo->bbs[i];
-	  for (auto gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+	  for (auto gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 	    {
-	      stmt_vec_info stmt_info = vinfo->lookup_stmt (gsi_stmt (gsi));
+	      stmt_vec_info stmt_info = vinfo->lookup_stmt (gsi.phi ());
 	      if (stmt_info && STMT_VINFO_VECTORIZABLE (stmt_info))
 		vect_determine_mask_precision (vinfo, stmt_info);
 	    }
-	  for (auto gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+	  for (auto gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 	    {
-	      stmt_vec_info stmt_info = vinfo->lookup_stmt (gsi.phi ());
+	      stmt_vec_info stmt_info = vinfo->lookup_stmt (gsi_stmt (gsi));
 	      if (stmt_info && STMT_VINFO_VECTORIZABLE (stmt_info))
 		vect_determine_mask_precision (vinfo, stmt_info);
 	    }