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Date: Fri, 26 Mar 2021 08:44:54 -0700 (PDT)
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Subject: Re: Performance of records with variant parts
From: John Perry <john.perry@usm.edu>
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Xref: reader02.eternal-september.org comp.lang.ada:61658
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On Friday, March 26, 2021 at 10:38:22 AM UTC-5, Stephen Leake wrote:
> As a workaround, you can suppress checks in that block of code:=20
>=20
> pragma Suppress (Discriminant_Check);=20

Sorry, I should have updated earlier. I discovered tried this a couple of n=
ights ago, and it did nothing to help. I checked the IR and that did change=
, so it certainly did something; it just didn't improve the performance as =
I expected. It has made me think that perhaps the problem is elsewhere, but=
 I have no idea where.

So, thank you very much for remembering this and getting back to me! But by=
 now I've concluded that gprof misled me. Wouldn't be the first time. The d=
ifference in performance is real, but must be caused elsewhere. I don't eve=
n feel confidence submitting an enhancement request to AdaCore because by n=
ow I have no idea what the problem is.

For what it's worth: I reimplemented it a fourth time as tagged records, an=
d while the code is quite a bit wordier, it was more efficient than variant=
 records.

(I also tried examining the generated assembly code, but I'm not strong eno=
ugh in assembly to work that out.)