[LLVMdev] Missed optimization opportunity with piecewise load shift-or'd together?

[David Nadlinger]

On Mon, Oct 28, 2013 at 10:09 AM, James Courtier-Dutton
<james.dutton at gmail.com> wrote:
> My guess is that this is a missed optimization, but in real life, all
> projects i have worked fix this in the C or C++ code using macros that
> change what instructions are used based on target platform and its
> endedness.

One reason for writing code like this, i.e. explicitly spelling out
the accesses to the individual bytes, would be to allow compile-time
evaluation of the fragment in the D programming language, where
arbitrarily reinterpreting memory is not supported (although
integer->integer pointer casts might be supported at some point).

Would a patch adding the capability to lower this to InstCombine or
similar have a chance of being accepted, or would that be considered
to be too rare a spacial case to be worth the added complexity?

David