ganjing
a0fcbb7957
Rewrite arch_memcpy.S and arch_memset.S to be register-width aware on both RV32 and RV64 using REG_L/REG_S/SZREG macros from asm.h. memcpy gains: - 16xSZREG unrolled main loop (128B/iter on RV64, 64B on RV32). - Shift-merge path for misaligned src: reads two aligned words straddling each output word and shifts them together, so no load or store is ever misaligned. - Single SZREG and byte loops for remainder and small copies. memset gains: - 32xSZREG unrolled main loop (256B/iter on RV64, 128B on RV32) using Duff's device for non-power-of-two remainders. - .option norvc ensures fixed 4-byte instruction width for correct jump offset calculation in the Duff's device entry. - Zero-length input handled correctly (branch to guarded tail). The old memcpy always used lw/sw even on RV64, wasting half the memory bandwidth. The old memset unrolled only 16 bytes per iteration. Signed-off-by: ganjing <ganjing@xiaomi.com>
Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 64-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards. Additional standard APIs from Unix and other common RTOSs (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).
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