llvm dev - Dec 2020 - Trying to use unordered_map

I implemented a map for Record fields using StringMap. The map is created when
the backend does a getAllDerivedDefinitions(), under the assumption that it will
then access the values from the returned vector of Record's.

This resulted in a noticeable slowdown of the backends, on the order of 10%. The
time to construct the maps appears to overwhelm any savings in accessing the
field values.

I'm going to try some other tricks, but I think this is a dead end.

> On Dec 7, 2020, at 10:39 AM, Paul C. Anagnostopoulos via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> 
> I implemented a map for Record fields using StringMap. The map is created
when the backend does a getAllDerivedDefinitions(), under the assumption that it
will then access the values from the returned vector of Record's.
> 
> This resulted in a noticeable slowdown of the backends, on the order of
10%. The time to construct the maps appears to overwhelm any savings in
accessing the field values.
> 
> I'm going to try some other tricks, but I think this is a dead end.
Hi Paul,

Have you profiled the result?  For example, on a Mac you can use the Instruments
tool that comes with Xcode.  On linux you can use a variety of perf tools, on
windows you can use Visual Studios profiler.

I wonder if you’re getting zero hits on the cache?

-Chris