Em sáb., 5 de set. de 2020 às 14:29, Tom Lane <t...@sss.pgh.pa.us> escreveu:
> Ranier Vilela <ranier...@gmail.com> writes: > > Attached is a patch I made in March/2020, but due to problems, > > it was sent but did not make the list. > > Would you mind taking a look? > > I applied some of this, but other parts had been overtaken by > events, and there were other changes that I didn't agree with. > I fully agree with your judgment. > A general comment on the sort of "dead store" that I don't think > we should remove is where a function is trying to maintain an > internal invariant, such as "this pointer points past the last > data written to a buffer" or "these two variables are in sync". > If the update happens to be the last one in the function, the > compiler may be able to see that the store is dead ... but IMO > it should just optimize such a store away and not get in the > programmer's face about it. If we manually remove the dead > store then what we've done is broken the invariant, and we'll > pay for that in future bugs and maintenance costs. Somebody > may someday want to add more code after the step in question, > and if they fail to undo the manual optimization then they've > got a bug. Besides which, it's confusing when a function > does something the same way N-1 times and then differently the N'th time. > Good point. The last store is a little strange, but the compiler will certainly optimize. Maintenance is expensive, and the current code should be the best example. regards, Ranier Vilela
