Re: Time to merge scratch/correct-warning-pos into master, perhaps?

[Alan Mackenzie]

Hello, Mattias.

On Sun, Jan 16, 2022 at 16:50:23 +0100, Mattias Engdegård wrote:
> 16 jan. 2022 kl. 16.04 skrev Lars Ingebrigtsen <larsi@gnus.org>:

> > Yes.  I've now done a few more realistic non-micro benchmarks --
> > (eww-open-file "/tmp/foo.html") -- and I see no measurable performance
> > impact there at all.

> The time to run Relint on the Emacs tree is up about 3.0 ± 0.2 %. A
> lot of it is spent in reading files and in the regexp engine, neither
> of which use `eq` much.  It erases some (but not all) of the progress
> being made elsewhere.

> Micro-benchmarking code using `eq` a lot shows an overhead of about 50 %.

Would you clarify, please.  50% of what?  The new branch, except whilst
compiling, sees EQ extended from two machine instructions to four.  In
place of

CMP  ; the two operands.
JE

, we now have

CMP  ; the two operands.
JE
TEST ; symbols-with-pos-enabled.
JNE

..  More or less.  So if the Lisp EQ instruction is going to be matching
half the time, there would be an overhead of 50% on just that
instruction.  Presumably quite a bit less on a whole program.

-- 
Alan Mackenzie (Nuremberg, Germany).