[LLVMdev] rol/ror llvm instruction set

[Paul Schlie]

Dale Johannesen wrote:
>On Feb 3, 2009, at 2:35 PMPST, Mike Stump wrote:
>> On Feb 3, 2009, at 2:28 PM, Kasra wrote:
>>> I was looking around the LLVM instruction set and I failed to find
>>> ROL and ROR instructions. Is there any plans on adding these
>>> instructions to LLVM?
>>
>> Not sure what you mean:
>
> He's referring to the LLVM IR, I think, and it's true that doesn't
> have rotates.  The LLVM back ends do know about rotate instructions on
> targets that have them, though, and the llvm optimizers are pretty
> smart about recognizing the usual ways to express rotate with shift/
> and/or, as below.

Similarly, ones-complement addition would be helpful (i.e. end around carry
checksums like Fletcher and such), as it's not apparent, at least to me, how
such sums may be otherwise cleanly defined in a efficient target independent
manner (especially when the sums may require precision equal to or exceeding
the natural operand size of the target machine)?