That instruction clears upper 4 bytes of the rdi register. Note the next instruction uses rdi in the address.
edi register is the lower 4 bytes of rdi. Instructions which write these smaller pieces zero out the unused higher bytes of the destination registers. This helps with performance because eliminates data dependencies on the old values in these higher bytes.
edi register is the lower 4 bytes of rdi. Instructions which write these smaller pieces zero out the unused higher bytes of the destination registers. This helps with performance because eliminates data dependencies on the old values in these higher bytes.