[llvm-commits] [Review request] Instcombine: extractvalue from load --> load from gep

[Chris Lattner]

On Nov 29, 2010, at 3:20 PM, Dan Gohman wrote:
> If it emits both fields as gep+load, then there's no problem.
> 
> Basically, it's never desirable to actually do an aggregate load or store.
> It may be the case they they can be eliminated by optimization much of the
> time, but this can fail in various ways, and when it does, you can get
> quite unpleasant results. And even when it does work, the best you'll get
> is emit the same gep+load that the front-end could have emitted itself
> without any extra analysis.

Dan, we require frontends to generate first class aggregates for ABI reasons in some cases.  This happens on X86-64 for example.

-Chris