[PATCH] Slightly altered backport for PR89572

[Richard Biener]

I am testing the following with additional hunks in 
tree-ssa-loop-ivcanon.c.

Bootstrap / regtest running on x86_64-unknown-linux-gnu (gcc-8-branch).

Richard.

2019-03-14  Richard Biener  <rguent...@suse.de>

        PR middle-end/89572
        * tree-scalar-evolution.c (get_loop_exit_condition): Use
        safe_dyn_cast.
        * tree-ssa-loop-ivcanon.c (canonicalize_loop_induction_variables):
        Use gimple_location_safe.

        * gcc.dg/torture/pr89572.c: New testcase.

Index: gcc/testsuite/gcc.dg/torture/pr89572.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr89572.c      (nonexistent)
+++ gcc/testsuite/gcc.dg/torture/pr89572.c      (working copy)
@@ -0,0 +1,28 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-finline-functions" } */
+
+int vh, it, k1;
+
+void
+vn (void)
+{
+  ++vh;
+  if (vh == 0 && it == 0)
+    k1 = -k1;
+}
+
+__attribute__ ((returns_twice)) void
+ef (int *uw)
+{
+  while (uw != (void *) 0)
+    {
+      vn ();
+      *uw = 0;
+    }
+}
+
+void
+gu (int *uw)
+{
+  ef (uw);
+}
Index: gcc/tree-scalar-evolution.c
===================================================================
--- gcc/tree-scalar-evolution.c (revision 269650)
+++ gcc/tree-scalar-evolution.c (working copy)
@@ -875,7 +875,7 @@ get_loop_exit_condition (const struct lo
       gimple *stmt;
 
       stmt = last_stmt (exit_edge->src);
-      if (gcond *cond_stmt = dyn_cast <gcond *> (stmt))
+      if (gcond *cond_stmt = safe_dyn_cast <gcond *> (stmt))
        res = cond_stmt;
     }
 
Index: gcc/tree-ssa-loop-ivcanon.c
===================================================================
--- gcc/tree-ssa-loop-ivcanon.c (revision 269650)
+++ gcc/tree-ssa-loop-ivcanon.c (working copy)
@@ -1177,7 +1177,7 @@ canonicalize_loop_induction_variables (s
        = niter_desc.may_be_zero && !integer_zerop (niter_desc.may_be_zero);
     }
   if (TREE_CODE (niter) == INTEGER_CST)
-    locus = gimple_location (last_stmt (exit->src));
+    locus = gimple_location_safe (last_stmt (exit->src));
   else
     {
       /* For non-constant niter fold may_be_zero into niter again.  */
@@ -1204,7 +1204,7 @@ canonicalize_loop_induction_variables (s
        niter = find_loop_niter_by_eval (loop, &exit);
 
       if (exit)
-        locus = gimple_location (last_stmt (exit->src));
+        locus = gimple_location_safe (last_stmt (exit->src));
 
       if (TREE_CODE (niter) != INTEGER_CST)
        exit = NULL;