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clinux-kernelmacrosglibc

what does the __insn_seqb() and __insn_ctz mean?

I was reading the Linux/arch/tile/lib/strlen_32.c to know about the accomplishment of the strlen_32. However I met two macros named __insn_seqb and __insn_ctz which I didn't know the meaning. The function strlen_32 is below:

size_t strlen(const char*s)
{
    const uintptr_t s_int = (uintptr_t)s;
    const uint32_t *p = (const uint32_t*)(s_int&-4);
    uint32_t v = *p | ((1<<(s_int<<3))-1);
    uint32_t bits;
    while((bits=__insn_seqb(v,0))==0)
         v = *++p;
    return ((const char*)p)+(__insn_ctz(bits)>>3)-s;
 }

I searched them on Google, but only found another macro definition: #define CFZ(x) __insn_ctz(x) in string_endian.h glib-ports string-endian.h Could someone tell me where the clear definition is or the real meaning and usage of these two macros?

Solution

  • They seem to be instruction intrinsics for Tilera processors.

    I would guess that __insn_ctz is a "count trailing zeroes" instruction.

    __insn_seqb seems to be testing for a 0 byte within a 4 byte word.

    The Tilera instruction is apparently somewhat similar to MIPS.