[LLVMdev] [PATCH] OpenCL half support

[Anton Lokhmotov]

Hi Chris,

So what do you think about this proposal?  If you agree, it would be good to
include the patch into the 2.9 release (to avoid breaking compatibility
later).

Best regards,
Anton.


> -----Original Message-----
> From: Anton Lokhmotov [mailto:Anton.Lokhmotov at arm.com]
> Sent: 24 February 2011 10:19
> To: 'Chris Lattner'
> Cc: llvmdev at cs.uiuc.edu; cfe-dev at cs.uiuc.edu
> Subject: RE: [LLVMdev] [PATCH] OpenCL half support
> 
> Hi Chris,
> 
> > Does the spec force evaluation to happen in half mode, or does it
> > specify that there is a promotion to float (or some other type), an
> > operation, then truncation back to half?
> 
> The last paragraph in section 9.6 says: "NOTE: Implementations may
> perform floating-point operations on half scalar or vector data types
> by converting the half values to single precision floating-point values
> and performing the operation in single precision floating-point. In
> this case, the implementation will use the half scalar or vector data
> type as a storage only format."
> 
> That is, an implementation may perform operations on half scalar and
> vector values either using half-precision operations (if supported
> natively) or using single-precision operations (always supported
> natively).  In either case, it's desirable to represent half operations
> in the IR, and let the backend make the decision.
> 
> Cheers,
> Anton.