Hi, These are a few pointers on how to start modifying the RVV implementation.
- The previous gem5 bootcamp has details on how to implement instructions in gem5, and examples of implementing RISCV P extension, https://youtube.com/watch?v=Z5B02jkNpck&list=PL_hVbFs_loVSaSDPr1RJXP5RRFWjBMqq3&index=11&pp=iAQB . - The .isa files you're looking at contain the templates for generating the actual instruction. The instruction will be compiled to a couple of .cc and .hh files before being compiled and linked to the gem5.opt executable. In the case of riscv, you can find those generated files in build/RISCV/arch/riscv/generated/. - Typically, implementing an instruction will require implementing the decoder method, and execute method; and for memory instructions, you'll need to implement initiateAcc and completeAcc methods. - There are a few RVV memory instructions that are more complicated than other instructions (e.g. those scatter store/ gather load instructions). Those instructions act as a macro instructions spawning more micro instructions to perform loads/stores, which is necessary as the elements can be in different cache blocks. If you'd like to start with a simple implementation, I think you can start from by mimicking the implementation of simpler instructions in gem5's rvv implementation, like vadd_vv. Regards, Hoa Nguyen On Sat, Dec 23, 2023, 10:05 zahra butool via gem5-users <gem5-users@gem5.org> wrote: > Hi everyone, > > > For my project, I need to add a custom instruction to RISCV in Gem5 that > loads 2 sets of 128 elements (32-bit float) from the memory, computes the > dot product, and stores them back to the memory. A starting point is using > the RISCV vector instructions, but I want to reduce the instruction count > and have only one instruction doing all these operations. So I was checking > the vector .isa (decoder, memory, arith) files to get an idea of how to > merge vle32, vadd_vv, vredsum.vs, and vse32 into a single instruction, but > it looks a bit complicated to me and still couldn't figure out how I should > modify it. > > I would appreciate it if anyone could give me some pointers on starting > this or which files I need to check and modify. > > Thank you! > _______________________________________________ > gem5-users mailing list -- gem5-users@gem5.org > To unsubscribe send an email to gem5-users-le...@gem5.org >
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