[PATCH] tree-optimization/97897 - complex lowering on abnormal edges

[Richard Biener]

This fixes complex lowering to not put constants into abnormal
edge PHI values by making sure abnormally used SSA names are
VARYING in its propagation lattice.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed to trunk.

2020-11-19  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/97897
        * tree-complex.c (complex_propagate::visit_stmt): Make sure
        abnormally used SSA names are VARYING.
        (complex_propagate::visit_phi): Likewise.
        * tree-ssa.c (verify_phi_args): Verify PHI arguments on abnormal
        edges are SSA names.

        * gcc.dg/pr97897.c: New testcase.
---
 gcc/testsuite/gcc.dg/pr97897.c | 13 +++++++++++++
 gcc/tree-complex.c             |  5 ++++-
 gcc/tree-ssa.c                 |  6 ++++++
 3 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr97897.c

diff --git a/gcc/testsuite/gcc.dg/pr97897.c b/gcc/testsuite/gcc.dg/pr97897.c
new file mode 100644
index 00000000000..775f34ca767
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr97897.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+
+void h ();
+void f () __attribute__ ((returns_twice));
+void g (_Complex int a)
+{
+  f ();
+  if (a != 0)
+  {
+    a = 0;
+    h ();
+  }
+}
diff --git a/gcc/tree-complex.c b/gcc/tree-complex.c
index f132e0f41c7..1cfb3e8d743 100644
--- a/gcc/tree-complex.c
+++ b/gcc/tree-complex.c
@@ -318,7 +318,7 @@ complex_propagate::visit_stmt (gimple *stmt, edge 
*taken_edge_p ATTRIBUTE_UNUSED
 
   lhs = gimple_get_lhs (stmt);
   /* Skip anything but GIMPLE_ASSIGN and GIMPLE_CALL with a lhs.  */
-  if (!lhs)
+  if (!lhs || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
     return SSA_PROP_VARYING;
 
   /* These conditions should be satisfied due to the initial filter
@@ -417,6 +417,9 @@ complex_propagate::visit_phi (gphi *phi)
      set up in init_dont_simulate_again.  */
   gcc_assert (TREE_CODE (TREE_TYPE (lhs)) == COMPLEX_TYPE);
 
+  if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
+    return SSA_PROP_VARYING;
+
   /* We've set up the lattice values such that IOR neatly models PHI meet.  */
   new_l = UNINITIALIZED;
   for (i = gimple_phi_num_args (phi) - 1; i >= 0; --i)
diff --git a/gcc/tree-ssa.c b/gcc/tree-ssa.c
index c47b963bbb2..b44361f8244 100644
--- a/gcc/tree-ssa.c
+++ b/gcc/tree-ssa.c
@@ -987,6 +987,12 @@ verify_phi_args (gphi *phi, basic_block bb, basic_block 
*definition_block)
          err = true;
        }
 
+      if ((e->flags & EDGE_ABNORMAL) && TREE_CODE (op) != SSA_NAME)
+       {
+         error ("PHI argument on abnormal edge is not SSA_NAME");
+         err = true;
+       }
+
       if (TREE_CODE (op) == SSA_NAME)
        {
          err = verify_ssa_name (op, virtual_operand_p (gimple_phi_result 
(phi)));
-- 
2.26.2