[LLVMdev] disabling combining load/stores in optimizer.

[Alireza.Moshtaghi at microchip.com]

> > We are currently doing this, however I think disabling such
> > optimizations is a much better solution.
> 
> An LLVM design goal is that backends should be able to outsmart
> instcombine when necessary, rather than having instcombine be able
> to disable parts of itself in order to avoid foiling the backends.
> Practicality sometimes steers elsewhere of course. Please explain
> why you think suppressing this particular optimization is better;
> it isn't obvious how it would look different in the end.
> 

Well, for one thing, our port has no native operation other than 8-bit
so it does not make sense to promote operations to higher precisions.
Eventually all those operations will be lowered and the resulting code
is most likely worse than if it was not promoted in the first place. So
I think it should be at the discretion of port to enable or disable such
optimizations as needed.

A