Small Extensions: Zicsr, Zifencei, Zicntr·Zihpm, B (Zba·Zbb·Zbs), Zicond, Zicbom
Part 12 of the RISC-V series. I check in QEMU the rule by which CSR instructions decide whether to read or write based on whether rd and rs1 are x0, and run the B and Zicond instructions over 2,772 combinations on RV32 and 3,720 on RV64, all matching a reference model. Enabling B shrank the code by 6.6–9.0%.
Sunhong'sSystem Blog
RISC-V