Hm. I guess when thinking "SSE parsing" I didn't go with 4/8-wide parsing. I was thinking that they'd be grabbing 16/32-bytes, doing a compare against a fixed c

Hm. I guess when thinking "SSE parsing" I didn't go with 4/8-wide parsing. I was thinking that they'd be grabbing 16/32-bytes, doing a compare against a fixed constant literal of 16/32-copies of, say, '{', or '}', then extracting the index of the match, exactly. Something like this: d := _mm_loadu_ps <json> b := _mm_loadu_ps <token: '{'> n := _mm_cmpistrc(d, b) You'd have to be clever to skip around strings ("... \"sonuva ... "), but once that's handled, you'd have significant speed ups to scan for ',', '{', '}', etc. I think the double-quote escape might look something like this: d := _mm_loadu_ps <json> q := _mm_loadu_ps <token: '"'> e := _mm_loadu_ps <token: '\\'> n := _mm_cmpistrc(d, q) m := _mm_cmpistrc(d, e) if m+1 == n: branch-to-top ... process ... Looks like cmpistrc has 1/2 reciprocal throughput. If you unrolled the loop 8 deep, you're probably looking at 10c per 16bytes scanned.