[PATH]: PR middlend/38385 fix

[Tomas Bily]

Hi,

 as Richard recommended this patch fixes pr38385 by propagation and
removing of phis from loop exit block.

Tested and bootstraped on x86_64-unknown-linux-gnu.
Ok for mainline ?

> >>>  This pr is caused because after removing bbs in generate_builtin
> >>> (tree-loop-distribution.c) some phis has bad incoming edges. This
> >>> patch tryes to fix it.
> >>>
> >>> Tested and bootstraped on x86_64-unknown-linux-gnu.
> >>> Ok for mainline ?
> >>>
> >>
> >> Looks good to me, but I cannot approve it.
> >
> > I don't follow.  You create an edge from the preheader to the loop exit
> > and now use the values from the exit edge for that edge?  If we
> > are in loop-closed SSA form we should not need to care at all here.
> > It is more likely that we need to split some block before removing the
> > loop.
> 
> Err, wait.  These _are_ the loop-closed PHI nodes.  You should be able
> to just remove them by propagation.
> 
> Richard.

Greetings
Tomas

Changelog:

        * tree-loop-distribution.c (prop_phis): New function.
        (generate_builtin): Call prop_phis.
        * testsuite/gcc.dg/tree-ssa/pr38385.c: New file.


Index: tree-loop-distribution.c
===================================================================
--- tree-loop-distribution.c	(revision 143184)
+++ tree-loop-distribution.c	(working copy)
@@ -331,6 +331,37 @@ generate_memset_zero (gimple stmt, tree 
   return res;
 }
 
+/* Propagate phis in bb b to their uses and remove them.  */
+
+static void
+prop_phis (basic_block b)
+{
+  gimple_stmt_iterator psi;
+  gimple_seq phis = phi_nodes (b);
+
+  for (psi = gsi_start (phis); !gsi_end_p (psi); )
+    {
+      gimple phi = gsi_stmt (psi);
+      tree def = gimple_phi_result (phi), use = gimple_phi_arg_def (phi, 0);
+      
+      if (!is_gimple_reg (def))
+	{
+	  imm_use_iterator iter;
+	  use_operand_p use_p;
+	  gimple stmt;
+
+	  FOR_EACH_IMM_USE_STMT (stmt, iter, def)
+	    FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
+	      SET_USE (use_p, use);
+	}
+      else
+	 replace_uses_by (def, use);
+
+      remove_phi_node (&psi, true);
+    }
+}
+
+
 /* Tries to generate a builtin function for the instructions of LOOP
    pointed to by the bits set in PARTITION.  Returns true when the
    operation succeeded.  */
@@ -400,12 +431,15 @@ generate_builtin (struct loop *loop, bit
       unsigned nbbs = loop->num_nodes;
       basic_block src = loop_preheader_edge (loop)->src;
       basic_block dest = single_exit (loop)->dest;
+      prop_phis (dest);
       make_edge (src, dest, EDGE_FALLTHRU);
       set_immediate_dominator (CDI_DOMINATORS, dest, src);
       cancel_loop_tree (loop);
 
       for (i = 0; i < nbbs; i++)
 	delete_basic_block (bbs[i]);
+
+      merge_blocks (src, dest);
     }
 
  end: