DMD release compiler flags when building with LDC

[Seb]

On Tuesday, 22 October 2019 at 14:02:28 UTC, Per Nordlöw wrote:
> Have anybody experimented with release compilation flags when 
> building dmd with ldc?
> ...
> And I measure about a 20-25% drop in runtime compared to the 
> standard released version of dmd.

Last time I checked it was about 40-50% (depends a bit on what 
you use to test, your machine etc.). So, yup the released 
binaries could be easily twice as fast. This is well known.
The problem is that no one except Martin has a full running setup 
of the release pipeline:

https://github.com/dlang/installer

Hence, this change hasn't happened.
IMHO, we should build them directly in the respective CIs like 
e.g. LDC does, because then anyone can easily modify and improve 
the setup.

> Is profile guided optimization (PGO) worth a try?

Yes.