Forum Discussion
Occasional ContributorDoing low bit-width fixed precision FMA on DSP in OpenCL
The appropriate IP Core is either directly used by the OpenCL compiler, or eventually employed by the mapper depending on the width of your variables. I remember there were some topics in the forum about this subject before and the compiler's behavior was kinda buggy, though. You can also take a look at the variable-width integer extension and the instructions for correctly inferring fixed-point arithmetic in the Best Practices Guide.
Frequent ContributorThe most complex operation you can do using one Arria 10/Stratix 10 DSP is an "18 × 18 Sum of 2 fixed-point" operation. You cannot do more than one FMA per DSP on these devices regardless of bit-width since each DSP has only one adder and FP32 FMA is the only natively-supported FMA operation. You can refer to "Intel® Arria® 10 Native Fixed Point DSP IP Core User Guide" and "Intel® Stratix® 10 Variable Precision DSP Blocks User Guide" for more info.
P.S. You might be able to manually pack multiple low-bit-width FMAs into one 32-bit FMA by inserting zeroes between the numbers and using bit masking, but there is no guarantee you would get the intended DSP packing in the end.
