[m-rev.] for review: optimize merge_instmap_deltas

[Julien Fischer]

On Fri, 15 Apr 2022, Zoltan Somogyi wrote:

> Optimize merge_instmap_deltas.
> 
> compiler/instmap.m:
>     Until now, the merge_instmap_deltas predicate has always operated
>     by repeated invoking merge_instmap_delta in a two-level loop to fixpoint,

repeatedly

>     though how we do the inner loop has changed over the years. However,
>
>     - some of the work done by these invocations of merge_instmap_delta,
>       such as finding out which of the instmap_deltas is reachable,
>       is repeated in each iteration of the outer (fixpoint) loop, and
>     - some other work, such as finding out the types of the variables
>       whose insts need to be merged, is repeated many times even within
>       each iteration of the inner loop.
>
>     This diff moves such code out of the code of the nested fixpoint loop,
>     for invocations of merge_instmap_deltas that are given enough deltas
>     to make this worthwhile.
>
>     Carve merge_instmapping_delta_var out merge_instmapping_delta_vars,

out *of*

>     since this is the only part of part of merge_instmap_delta that the

Repeated "part of".

>     fixpoint iteration now repeatedly invokes.
>
>     Optimize even the base predicate merge_instmap_delta by testing whether
>     the *initial* instmap is reachable just once.
>
>     Standardize on capitalizating the M in InstMap/InstMapping.

The rest looks fine.

Julien.