[Bug c++/71885] Incorrect code generated with -01, memset() function call is missing

["hyc at symas dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71885

--- Comment #24 from hyc at symas dot com ---
(In reply to Manuel López-Ibáñez from comment #21)
> (In reply to hyc from comment #19)
> > That's all well and good. But, somebody had to go out of their way to
> > develop the code to identify this case of new as being a dead store. Why was
> > this worth anyone's time to do so? What performance benefit does this
> > "optimization" bring, and is it really worth all of the obviously known
> > breakage that it causes?
> 
> I don't know the answers to those questions, but somebody did do the effort
> to implement it and test it:
> https://gcc.gnu.org/ml/gcc-patches/2015-04/msg00782.html

I see a patch, I don't see justification / motivation / profiling / benchmark
results quantifying the impact of this patch.

> and then add various options to control it:
> https://gcc.gnu.org/ml/gcc-patches/2016-02/msg01651.html
> 
> so they probably have their own motivation to do this instead of something
> else. Nobody raised any objections at the time.
> 
> > We all have important things to be doing. It doesn't appear that the time
> > invested in this "feature" was time well spent.
> 
> For better or worse, we don't get to decide on what other people spent their
> own time unless we pay them.

No, but you get to decide whether to accept the work or not based on whether it
actually solved a problem that programmers care about. Or whether the added
complexity was worth any added maintenance cost or compile time.

This feature is enabled at -O1, which is usually reserved for non-aggressive,
benign optimizations. In what way is this feature an optimization? How does it
qualify as benign? Where was *any* critical review of this thing?

When I was a gcc maintainer (1988-1996) a patch like this wouldn't have
proceeded without answers to these questions.