From: Richard Biener <rguenther@suse.de>
Date: Wed, 29 Jul 2020 07:59:01 +0000 (+0200)
Subject: tree-optimization/95679 - properly signal changes from propagate_into_phi_args
X-Git-Tag: basepoints/gcc-12~5857
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8e8792a347c87dbb82b4cf75ec3452bc5cd1d3db;p=thirdparty%2Fgcc.git

tree-optimization/95679 - properly signal changes from propagate_into_phi_args

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.

2020-07-29  Richard Biener  <rguenther@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.
---

diff --git a/gcc/tree-ssa-propagate.c b/gcc/tree-ssa-propagate.c
index 01ee7fd33eb1..1e0572841543 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 24de43ebc6c6..9406cdf8f515 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.  */