Re: builtin_bswap plus enhancements

[Chris Lattner <clattner at apple dot com>]

On Aug 10, 2006, at 12:43 PM, Falk Hueffner wrote:
> Chris Lattner <clattner@apple.com> writes:
> > Why not add bswap16 as well?
>
> It should be unnecessary, since any attempt to express it should be
> picked up by the rot idiom recognizer, and the backends should then
> emit optimal code for constant-8 rots (and if that doesn't actually
> happen, we should rather fix that).

Sure, makes sense.  I was wondering more from the sake of consistency  
than from what GCC can and can not do.

LLVM, for example, recognizes the common bswap idioms for 16/32/64  
bits and generates good code for them, but also exposes intrinsics  
for each.  The intrinsics are important to clients who want to *know*  
they are going to get good code, without having to know that a  
particular version of the compiler will do the right thing, or worry  
about regressions in future versions.

In any case, I have no particular interest in what GCC does, it just  
seemed odd to have buildins for 32/64-bit but not 16-bit.

-Chris