3 ms·
It is slow to move data from SIMD to scalar registers, or can be.
by astrange 2y ago
It is slow to move data from SIMD to scalar registers, or can be.
- TinkersW 2y agoIt depends, for SIMD float-> scalar floats it is fast as they operate on the same registers. If pulling out of lane 0 you don't even need to do anything(just a type cast). For other lanes you need a shuffle. For SIMD integer to scalar integer, it has to move into separate register, so there is some short penalty(3 cycles iir).