Improve DCE of dead parts of a permute chain

gcc.dg/vect/bb-slp-pr78205.c is reported to have regressed with
the PR113073 change and in the end it's due to the DCE performed
by vect_transform_slp_perm_load_1 being imperfect.  The following
enhances it to also cover the CTOR and VIEW_CONVERT operations that
might be involved.

	* tree-vect-slp.cc (vect_transform_slp_perm_load_1): Also handle
	CTOR and VIEW_CONVERT up to the load when performing chain DCE.

1 files changed, 15 insertions, 4 deletions

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index a82fca4..1a357cb 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -8634,10 +8634,21 @@ vect_transform_slp_perm_load_1 (vec_info *vinfo, slp_tree node,
     for (unsigned i = 0; i < dr_chain.length (); ++i)
       if (!bitmap_bit_p (used_defs, i))
 	{
-	  gimple *stmt = SSA_NAME_DEF_STMT (dr_chain[i]);
-	  gimple_stmt_iterator rgsi = gsi_for_stmt (stmt);
-	  gsi_remove (&rgsi, true);
-	  release_defs (stmt);
+	  tree def = dr_chain[i];
+	  do
+	    {
+	      gimple *stmt = SSA_NAME_DEF_STMT (def);
+	      if (is_gimple_assign (stmt)
+		  && (gimple_assign_rhs_code (stmt) == VIEW_CONVERT_EXPR
+		      || gimple_assign_rhs_code (stmt) == CONSTRUCTOR))
+		def = single_ssa_tree_operand (stmt, SSA_OP_USE);
+	      else
+		def = NULL;
+	      gimple_stmt_iterator rgsi = gsi_for_stmt (stmt);
+	      gsi_remove (&rgsi, true);
+	      release_defs (stmt);
+	    }
+	  while (def);
 	}
 
   return true;