[PATCH] tree-optimization/96491 - avoid store commoning across abnormal edges

[Richard Biener]

This avoids store commoning across abnormal edges since that easily
can disrupt abnormal coalescing because it might create overlapping
lifetime of variables.

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

2020-08-06  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/96491
        * tree-ssa-sink.c (sink_common_stores_to_bb): Avoid
        sinking across abnormal edges.

        * gcc.dg/torture/pr96491.c: New testcase.
---
 gcc/testsuite/gcc.dg/torture/pr96491.c | 29 ++++++++++++++++++++++++++
 gcc/tree-ssa-sink.c                    |  3 ++-
 2 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr96491.c

diff --git a/gcc/testsuite/gcc.dg/torture/pr96491.c 
b/gcc/testsuite/gcc.dg/torture/pr96491.c
new file mode 100644
index 00000000000..784559f4754
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr96491.c
@@ -0,0 +1,29 @@
+/* { dg-do compile }  */
+
+int rj;
+
+void __attribute__ ((returns_twice))
+da (void)
+{
+  rj = 1;
+}
+
+void
+c5 (void)
+{
+  for (;;)
+    ++rj;
+}
+
+void
+ls (int kz)
+{
+  if (kz == 0)
+    {
+      rj = 0;
+      c5 ();
+    }
+
+  da ();
+  c5 ();
+}
diff --git a/gcc/tree-ssa-sink.c b/gcc/tree-ssa-sink.c
index 962ad076968..4cc5195f2f8 100644
--- a/gcc/tree-ssa-sink.c
+++ b/gcc/tree-ssa-sink.c
@@ -503,7 +503,8 @@ sink_common_stores_to_bb (basic_block bb)
              tree arg = gimple_phi_arg_def (phi, i);
              gimple *def = SSA_NAME_DEF_STMT (arg);
              if (! is_gimple_assign (def)
-                 || stmt_can_throw_internal (cfun, def))
+                 || stmt_can_throw_internal (cfun, def)
+                 || (gimple_phi_arg_edge (phi, i)->flags & EDGE_ABNORMAL))
                {
                  /* ???  We could handle some cascading with the def being
                     another PHI.  We'd have to insert multiple PHIs for
-- 
2.26.2