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mul24_hi in OpenCL

Question asked by Bdot on Oct 11, 2012

Hi,

 

the GPUs as well as the AMD-IL have an instruction for mul24_hi (unsigned as an example, but exists also for signed):

Evergreen/Cayman: MULHI_UINT24

GCN: V_MUL_HI_U32_U24

IL: UMUL24_high ( IL_OP_U_MUL24_HIGH )

 

However, in OpenCL I'm still missing this. If it is so difficult to get this into the OpenCL standard, could you not add an AMD-specific extension to add this important performance-feature?

 

I found this old thread about it, but it still seems to be unresolved

http://devgurus.amd.com/thread/149862

 

Is there some feasible way to tweak the IL or ISA code into using this instruction? Has anyone done that?

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