Introduce optimizations of tail phis

Try to eliminate short blocks that starts with a phi node
and end in a return. For example:

    Result = phi { Res1, 4 }, { literal true, 5 }
    Ret = put_tuple literal ok, Result
    ret Ret

The code in this block can be inserted at the end blocks 4 and
5. Thus, the following code can be inserted into block 4:

    Ret:1 = put_tuple literal ok, Res1
    ret Ret:1

And the following code into block 5:

    Ret:2 = put_tuple literal ok, literal true
    ret Ret:2

Which can be further simplified to:

    ret literal {ok, true}

This transformation may lead to more code improvements, for example:

  * Stack trimming
  * Fewer test_heap instructions
  * Smaller stack frames

0 files changed, 0 insertions, 0 deletions