Cache the return values for GetIdForErrorCode

[sharwell]

Fixes #31964

[Therzok]

Wouldn't an ImmutableDictionary + Interlocked operations be a better option than Concurrent Dictionary?

I'm asking because this might regress from a lock contention perspective

[sharwell]

I'm asking because this might regress from a lock contention perspective

Assuming it lives up to its name, concurrent dictionary has a lock-free fast path 😄

[Therzok]

Still, would be good to have profiling numbers. YMMV, but there's even allocation regressions from using a ConcurrentDictionary that could be more than the allocated strings we're seeing here.

[sharwell]

Still, would be good to have profiling numbers.

Unfortunately this came from a customer trace, so I don't have a clean way to reproduce it locally.

YMMV, but there's even allocation regressions from using a ConcurrentDictionary that could be more than the allocated strings we're seeing here.

The trace that led to this showed over 125MiB of string allocations here. The only way to encounter this situation is for reads to overwhelmingly outnumber writes.

[333fred]

@dotnet/roslyn-compiler for a second review here.

[jcouv]

LGTM Thanks (iteration 1)

[sharwell]

@jaredpar for approval

[jcouv]

@sharwell This is approved to merge.