diff --git a/src/gallium/drivers/r600/sfn/sfn_instr_alugroup.cpp b/src/gallium/drivers/r600/sfn/sfn_instr_alugroup.cpp
index 6d40e185500..2b3987fa906 100644
--- a/src/gallium/drivers/r600/sfn/sfn_instr_alugroup.cpp
+++ b/src/gallium/drivers/r600/sfn/sfn_instr_alugroup.cpp
@@ -82,22 +82,21 @@ AluGroup::add_trans_instructions(AluInstr *instr)
       if (instr->dest() && instr->dest()->pin() == pin_free) {
          int used_slot = 3;
          auto dest = instr->dest();
-         int free_mask = 0xf;
+         int possible_dest_channel_mask = m_free_slots ^ 0xf;
 
          for (auto p : dest->parents()) {
             auto alu = p->as_alu();
             if (alu)
-               free_mask &= alu->allowed_dest_chan_mask();
+               possible_dest_channel_mask &= alu->allowed_dest_chan_mask();
          }
 
          for (auto u : dest->uses()) {
-            free_mask &= u->allowed_src_chan_mask();
-            if (!free_mask)
+            possible_dest_channel_mask &= u->allowed_src_chan_mask();
+            if (!possible_dest_channel_mask)
                return false;
          }
 
-         while (used_slot >= 0 &&
-                (!m_slots[used_slot] || !(free_mask & (1 << used_slot))))
+         while (used_slot >= 0 && (!(possible_dest_channel_mask & (1 << used_slot))))
             --used_slot;
 
          // if we schedule a non-trans instr into the trans slot,