As Ben Tizer explained in a blog post TurboFan outperforms Crankshaft and copes better with:
some types of code that were challenging for our previous compiler to optimize, such as asm.js, class literals, with scopes, computed property names and for-of loops.
In a more technical blog post Tizer explains:
"An optimization engine applies these local rules in a systematic and thorough way. Transitioning out of the graphical representation involves an innovative scheduling algorithm that makes use of the reordering freedom to move code out of loops and into less frequently executed paths. Finally, architecture-specific optimizations like complex instruction selection exploit features of each target platform for the best quality code."
Having turned it on selectively Google has already seen some positive results, including a 29 per cent increase in the zlib compression score of its Octane benchmark suite.
Tizer concludes his post saying:
Amazon announced a raft of improvements to its databases at its AWS Summit in San Francisco, ranging from accelerators for DynamoDB to the ability to query exabytes of unstructured data directly in S3 [ ... ]