diff --git a/gcc/function.c b/gcc/function.c
index 00b2fe70c7d..e47931a2695 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -3036,7 +3036,23 @@ assign_parm_setup_block (struct assign_parm_data_all *all,
 		  reg = gen_rtx_REG (word_mode, REGNO (entry_parm));
 		  reg = convert_to_mode (mode, copy_to_reg (reg), 1);
 		}
-	      emit_move_insn (change_address (mem, mode, 0), reg);
+
+	      /* We use change_address to get a new MEM with the mode
+		 changed.  But that new MEM will not have a full set
+		 of attributes such as MEM_EXPR.
+
+		 This can inhibit later optimizations like DSE which
+		 assumes if there is no MEM_EXPR, then the memory
+		 must escape the current function.
+
+		 The MEM_EXPR on the original MEM expression should be
+		 the PARM_DECL which should be safe to attach to the
+		 new MEM.  */
+	      gcc_assert (MEM_EXPR (mem));
+	      gcc_assert (TREE_CODE (MEM_EXPR (mem)) == PARM_DECL);
+	      rtx new_mem = change_address (mem, mode, 0);
+	      set_mem_attributes (new_mem, MEM_EXPR (mem), 1);
+	      emit_move_insn (new_mem, reg);
 	    }
 
 #ifdef BLOCK_REG_PADDING