[gcc r15-3069] tree-optimization/116380 - bogus SSA update with loop distribution

[Richard Biener via Gcc-cvs]

https://gcc.gnu.org/g:af0d2d95a5f767d92bd64f959679fb4612247b0b

commit r15-3069-gaf0d2d95a5f767d92bd64f959679fb4612247b0b
Author: Richard Biener <rguent...@suse.de>
Date:   Wed Aug 21 13:56:40 2024 +0200

    tree-optimization/116380 - bogus SSA update with loop distribution
    
    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.
    
            PR tree-optimization/116380
            * tree-loop-distribution.cc (copy_loop_before): Handle
            out-of-loop defs appropriately.
    
            * gcc.dg/torture/pr116380.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr116380.c | 16 ++++++++++++++++
 gcc/tree-loop-distribution.cc           |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/gcc/testsuite/gcc.dg/torture/pr116380.c 
b/gcc/testsuite/gcc.dg/torture/pr116380.c
new file mode 100644
index 000000000000..5ffd99459d26
--- /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 f87393ee94d6..10f261a8769b 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);
            }
        }