Correct unsafe optimizations in beam_block

When attempting to eliminate the move/2 instruction in the following
code:

    {bif,self,{f,0},[],{x,0}}.
    {move,{x,0},{x,1}}.
       .
       .
       .
    {put_tuple,2,{x,1}}.
    {put,{atom,ok}}.
    {put,{x,0}}.

beam_block would produce the following unsafe code:

    {bif,self,{f,0},[],{x,1}}.
       .
       .
       .
    {put_tuple,2,{x,1}}.
    {put,{atom,ok}}.
    {put,{x,1}}.

It is unsafe because the tuple is self-referential.

The following code:

    {put_list,{y,6},nil,{x,4}}.
    {move,{x,4},{x,5}}.
    {put_list,{y,1},{x,5},{x,5}}.
         .
	 .
	 .
    {put_tuple,2,{x,6}}.
    {put,{x,4}}.
    {put,{x,5}}.

would be incorrectly transformed to:

    {put_list,{y,6},nil,{x,5}}.
    {put_list,{y,1},{x,5},{x,5}}.
         .
	 .
	 .
    {put_tuple,2,{x,6}}.
    {put,{x,5}}.
    {put,{x,5}}.

(Both elements in the built tuple get the same value.)

0 files changed, 0 insertions, 0 deletions