Optimization advice for maintainers: go for low-hanging fruit

[Jan Hubicka]

> I've been staring at a lot of g++-generated x86 assembler, trying to
> coax g++ into creating better code, and creating a bunch of
> optimization-related PRs.  Overall, I'm disappointed by gcc's ability
> to optimize some very simple things like constant-folding.
> 
> The most distressing thing about the failures is that gcc is
> invariably capable of performing all the optimizations I care about,
> just not consistently.  Seemingly irrelevant random features of the
> source code seem to inhibit optimizations from being performed.

Can you send some testcases where GCC fails to do the transformation?

Honza