[LLVMdev] 16 bit floats

[Chris Lattner]

On Feb 5, 2009, at 12:51 PM, BGB wrote:

>
> ----- Original Message -----
> From: Villmow, Micah
> To: LLVM Developers Mailing List
> Sent: Friday, February 06, 2009 5:47 AM
> Subject: [LLVMdev] 16 bit floats
>
> I need to support 16 bit floats for some operations, outside of  
> datatypes.td and the constants class, is there anything else I will  
> need to modify to add f16 support?
>
> probably also code generation (can't give specifics, no real expert  
> on the LLVM codebase).
> this would be because, even if the core typesystem knows of the  
> type, the codegen might not know how to emit operations on that type.
>
> now, of note:
> in my project (not LLVM based), float16 had not been supported  
> directly (since it is not known to the CPU), rather, some loader and  
> saver thunks were used which converted to/from float32 (this used as  
> the 'internal' representation of the type). in most cases, I would  
> think this would be faster than directly operating on the float16,  
> since the CPU supports float32, but float16 would have to be emulated.
>
> (unless of course newer CPUs are adding native float16 support or  
> similar?...).
>

Right.  Micah, does your CPU support float16 operations like add/sub  
etc natively?

-Chirs
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