JIT compiling means that we need to obtain executable memory for the jitted code. That has a non-neglibile cost (in addition to the runtime cost of compiling the pattern). Thus, only compile the pattern if we suspect it to be worthwhile: - when we called match multiple times - or when the string we match against is quite large We also assume that the JIT generally works, and thus discard the bytecode immediately after jitting – if the JIT fails once (either to compile, or with offset failure), we recompile the bytecode and never JIT again. Change-Id: I91e9e10c5ab895af730dbb4a9bc85470dd794d1f Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>