S0 and S1 register usage

[Tao Liu]

hi, folks, 

I am confused about using S0 and S1 register when reading the spec. What is "saved register"? It seems it can be used as frame pointer as well. Can I use it for other purpose? 

Thanks. 

[Tommy Murphy]

What specific text in what specification document/version are you having problems with?

You may also want to refer to the ABI spec if you haven't already:

* https://wiki.riscv.org/display/HOME/RISC-V+Technical+Specifications

  * https://drive.google.com/file/d/1Ja_Tpp_5Me583CGVD-BIZMlgGBnlKU4R/view?usp=drive_link

s0/s1 are callee saved registers.

The ABI spec says:

"The presence of a frame pointer is optional. If a frame pointer exists, it must reside in x8 (s0); the register remains callee-saved."

[Tao Liu]

thanks for the quick reply! wonderful guidance and problem sovled!