Principles and necessities of TransposePreloadUnroller

[infinitexplore]

Hello companions in Gemmini:

TransposePreloadUnroller seems to expand a pair of preload and flip-compute instructions into three instructions. The C address is rearraged into another preload instruction.

This expansion really perplex me. Why do WS transposed instructions get such special treatment?

And I also found

 first_compute_cmd.cmd.inst.rs1 := Cat(cmds(1).cmd.rs1(63, 32), garbage_addr)
 first_compute_cmd.cmd.inst.rs2 := Cat(cmds(1).cmd.rs2(63, 32), garbage_addr)

inst is signal of RoCCInstruction type. They are used to exchange data between Gemmini and RISC-V CPU. In the downstream stages of Gemmini pipeline, it is not used anymore. So what is the point of above codes?

Thanks in advance for whoever might enlighten me in any way.

[infinitexplore]

@hngenc