GCC13 auto generated RVV instructions when RVV enabled¶

If you are using Nuclei SDK 0.5.0 with Nuclei RISC-V Toolchain 2023.10, and when compile some examples with RVV enabled, it may generate rvv instructions which called auto-vectorzation.

Take application/baremetal/benchmark/dhrystone for example:

cd application/baremetal/benchmark/dhrystone
# enable extra vector extension, which means the -march=rv64imafdcv
make CORE=nx900fd ARCH_EXT=v clean
make CORE=nx900fd ARCH_EXT=v dasm

Then if you check the dhrystone.dasm, you will be able to see rvv instructions:

This auto generated instructions may affect your hardware performance, so if you want to disable it, you don't need to pass rvv extension when compile application.

$ cat dhrystone.dasm |grep vs
    800003e2:   cc3ff057                vsetivli        zero,31,e8,m8,ta,ma
    800003f8:   02038427                vse8.v  v8,(t2)
    8000040c:   020b8027                vse8.v  v0,(s7)
    800004a2:   cc3ff057                vsetivli        zero,31,e8,m8,ta,ma
    800004b2:   02098827                vse8.v  v16,(s3)
    80000524:   cc3ff057                vsetivli        zero,31,e8,m8,ta,ma
    80000530:   02098c27                vse8.v  v24,(s3)
    80000df2:   cdb3f057                vsetivli        zero,7,e64,m8,ta,ma
    80000dfa:   0204f427                vse64.v v8,(s1)
    80000e20:   cdb3f057                vsetivli        zero,7,e64,m8,ta,ma
    80000e28:   02047027                vse64.v v0,(s0)

You can check https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112537 for more details.