Sure, but if you look at the implementation in the article, that's a much longer dependency chain: *c = (uint32_t)(s[0] & masks[len]) << 18; *c |= (ui

Sure, but if you look at the implementation in the article, that's a much longer dependency chain: *c = (uint32_t)(s[0] & masks[len]) << 18; *c |= (uint32_t)(s[1] & 0x3f) << 12; *c |= (uint32_t)(s[2] & 0x3f) << 6; *c |= (uint32_t)(s[3] & 0x3f) << 0; *c >>= shiftc[len]; /* Accumulate the various error conditions. */ *e = (*c < mins[len]) << 6; *e |= ((*c >> 11) == 0x1b) << 7; // surrogate half? *e |= (s[1] & 0xc0) >> 2; *e |= (s[2] & 0xc0) >> 4; *e |= (s[3] ) >> 6; *e ^= 0x2a; // top two bits of each tail byte correct? *e >>= shifte[len]; Plus, all those loads are not making it easy for the processor to pipeline. And *e = (*c < mins[len]) << 6; is really a CMOV in disguise :)