From: "George Spelvin" <linux@xxxxxxxxxxx> Date: 28 Apr 2016 17:21:26 -0400 > arch/sparc/lib/ffs.S is a custom implementation of __ffs, but it's a > function call and 33 instructions/18 cycles long. There are several > similar custom implementations that I also considered "NO". Read it again, it is patched if the cpu supports the necessary instructions in which case it's a very short sequence. The actual code used when the cpu support said instruction is simply: .section .popc_6insn_patch, "ax" .word ffs brz,pn %o0, 98f neg %o0, %g1 xnor %o0, %g1, %o1 popc %o1, %o0 98: retl nop .word __ffs neg %o0, %g1 xnor %o0, %g1, %o1 popc %o1, %o0 retl sub %o0, 1, %o0 nop .previous -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
