Again: faster tracing when user tracing is off (#17947)
Another updated version of !5316.
I made userEventTracingEnabled
impure, and exported it.
I've verified that we get the code that we want, as before we end up with some redundant reads that get optimized away in Cmm. Unfortunately due to #24589 a mere inline
+ INLINABLE
on getTraceFlags
is insufficient and I had to mark it as INLINE
.