[PATCH] tree-optimization/95679 - properly signal changes from propagate_into_phi_args

[Richard Biener]

This restores a lost setting of something_changed with the
recent refactoring of the substitute and fold engine.  The
reported ICE in the PR was meanwhile mitigated in other ways
but the issue can still result in missed optimizations via
failed runs of CFG cleanup.

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

Richard.

2020-07-29  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/95679
        * tree-ssa-propagate.h
        (substitute_and_fold_engine::propagate_into_phi_args): Return
        whether anything changed.
        * tree-ssa-propagate.c
        (substitute_and_fold_engine::propagate_into_phi_args): Likewise.
        (substitute_and_fold_dom_walker::before_dom_children): Update
        something_changed.
---
 gcc/tree-ssa-propagate.c | 15 +++++++++++----
 gcc/tree-ssa-propagate.h |  2 +-
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/gcc/tree-ssa-propagate.c b/gcc/tree-ssa-propagate.c
index 01ee7fd33eb..1e057284154 100644
--- a/gcc/tree-ssa-propagate.c
+++ b/gcc/tree-ssa-propagate.c
@@ -1017,11 +1017,13 @@ substitute_and_fold_dom_walker::foreach_new_stmt_in_bb
     }
 }
 
-void
+bool
 substitute_and_fold_engine::propagate_into_phi_args (basic_block bb)
 {
   edge e;
   edge_iterator ei;
+  bool propagated = false;
+
   /* Visit BB successor PHI nodes and replace PHI args.  */
   FOR_EACH_EDGE (e, ei, bb->succs)
     {
@@ -1035,11 +1037,16 @@ substitute_and_fold_engine::propagate_into_phi_args 
(basic_block bb)
              || virtual_operand_p (arg))
            continue;
          tree val = get_value (arg, phi);
-         if (val && is_gimple_min_invariant (val)
+         if (val
+             && is_gimple_min_invariant (val)
              && may_propagate_copy (arg, val))
-           propagate_value (use_p, val);
+           {
+             propagate_value (use_p, val);
+             propagated = true;
+           }
        }
     }
+  return propagated;
 }
 
 edge
@@ -1229,7 +1236,7 @@ substitute_and_fold_dom_walker::before_dom_children 
(basic_block bb)
        }
     }
 
-  substitute_and_fold_engine->propagate_into_phi_args (bb);
+  something_changed |= substitute_and_fold_engine->propagate_into_phi_args 
(bb);
 
   return NULL;
 }
diff --git a/gcc/tree-ssa-propagate.h b/gcc/tree-ssa-propagate.h
index 24de43ebc6c..9406cdf8f51 100644
--- a/gcc/tree-ssa-propagate.h
+++ b/gcc/tree-ssa-propagate.h
@@ -115,7 +115,7 @@ class substitute_and_fold_engine
   virtual void pre_fold_stmt (gimple *) { }
   virtual void post_new_stmt (gimple *) { }
 
-  void propagate_into_phi_args (basic_block);
+  bool propagate_into_phi_args (basic_block);
 
   /* Users like VRP can set this when they want to perform
      folding for every propagation.  */
-- 
2.26.2