[PATCH] tree-optimization/116380 - bogus SSA update with loop distribution

[Richard Biener]

When updating LC PHIs after copying loops we have to handle defs
defined outside of the loop appropriately (by not setting them to
NULL ...).  This mimics how we handle this in the SSA updating
code of the vectorizer.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

        PR tree-optimization/116380
        * tree-loop-distribution.cc (copy_loop_before): Handle
        out-of-loop defs appropriately.

        * gcc.dg/torture/pr116380.c: New testcase.
---
 gcc/testsuite/gcc.dg/torture/pr116380.c | 16 ++++++++++++++++
 gcc/tree-loop-distribution.cc           |  3 +++
 2 files changed, 19 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr116380.c

diff --git a/gcc/testsuite/gcc.dg/torture/pr116380.c 
b/gcc/testsuite/gcc.dg/torture/pr116380.c
new file mode 100644
index 00000000000..5ffd99459d2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr116380.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-fno-tree-scev-cprop" } */
+
+int a[3], d[3], c;
+int f(int e, int b)
+{
+  for (; e < 3; e++)
+    {
+      a[0] = 0;
+      if (b)
+       c = b;
+      d[e] = 0;
+      a[e] = 0;
+    }
+  return e;
+}
diff --git a/gcc/tree-loop-distribution.cc b/gcc/tree-loop-distribution.cc
index f87393ee94d..10f261a8769 100644
--- a/gcc/tree-loop-distribution.cc
+++ b/gcc/tree-loop-distribution.cc
@@ -980,6 +980,9 @@ copy_loop_before (class loop *loop, bool 
redirect_lc_phi_defs)
          if (TREE_CODE (USE_FROM_PTR (use_p)) == SSA_NAME)
            {
              tree new_def = get_current_def (USE_FROM_PTR (use_p));
+             if (!new_def)
+               /* Something defined outside of the loop.  */
+               continue;
              SET_USE (use_p, new_def);
            }
        }
-- 
2.43.0