beam_jump: Optimize away unnecessary {move,nil,{x,0}}

The improved type inference optimizations will replace
a test for an empty list at the end of function with a move
of an empty list to {x,0}. Here is an example that shows
the BEAM code before the improved type inference:

      {test,is_nonempty_list,{f,3},[{x,0}]}.
	.
	.
	.
      return.
    {label,3}.
      {test,is_nil,{f,1},[{x,0}]}.
      return.

With the improved type inference the `is_nil`
test has been replaced by a `move` instruction:

      {test,is_nonempty_list,{f,3},[{x,0}]}.
	.
	.
	.
      return.
    {label,3}.
      {move,nil,{x,0}}.
      return.

This commit introduces a simple optimization that eliminates
the `move` instruction:

      {test,is_nonempty_list,{f,3},[{x,0}]}.
	.
	.
	.
      return.
    {label,3}.
      return.

Out of the more than 1000 modules compiled by the `scripts/diffable`
script, this optimization will bite in 578 functions spread among 200
modules.

0 files changed, 0 insertions, 0 deletions