Index: config/pdp11/pdp11.md
===================================================================
--- config/pdp11/pdp11.md	(revision 166978)
+++ config/pdp11/pdp11.md	(working copy)
@@ -1149,12 +1149,13 @@
   operands[1] = gen_rtx_REG (HImode, REGNO (operands[1]) + 1);
 
   output_asm_insn (\"com %0\", lateoperands);
-  output_asm_insn (\"neg %0\", operands);
+  output_asm_insn (\"com %0\", operands);
+  output_asm_insn (\"add $1, %0\", operands);
   output_asm_insn (\"adc %0\", lateoperands);
 
   return \"\";
 }
-  [(set_attr "length" "10")])
+  [(set_attr "length" "14")])
 
 (define_insn "neghi2"
   [(set (match_operand:HI 0 "nonimmediate_operand" "=rR,Q")