[m-rev.] for review: ml_unused_assign.m

[Julien Fischer]

Hi Zoltan,

On Sat, 5 May 2018, Zoltan Somogyi wrote:

> Delete assignments to dead variables in the MLDS.

...

> compiler/mlds.m:
>     The new optimization needs extra information about loops.
>     When it enters into the loop body, it knows which variables
>     are needed *after* the loop, but it does not know which variables
>     the loop body first reads and then writes. Without this knowledge,
>     it would optimize away assignments to loop control variables,
>     such as the increment of i in the loop
>
>     i = 0;
>     while (...) {
>         ...; i = i+1; ...
>     }
>
>     Traditionlly, compilers have solved this problem by doing fixpoint

s/Traditionally/Traditionally/

>     iteration, adding to the live set at each program point until
>     no more additions are possible. We can do better, because we generate
>     loops in the MLDS in only two kinds of cases:

The diff itself looks fine.  (I assume you intend to apply the upcoming
in optimization to field updates in LLDS grade as well BTW?)

Julien.