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From: Terje Mathisen <terje.mathisen@tmsw.no>
Newsgroups: comp.arch
Subject: Re: Concertlina II: Full Circle
Date: Wed, 19 Jun 2024 22:49:40 +0200
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MitchAlsup1 wrote:
> Thomas Koenig wrote:
>=20
>> Terje Mathisen <terje.mathisen@tmsw.no> schrieb:
>>> This is partly due to programming languages that applies lifetimes to=
=20
>>> variables, so that an index register which is defined in the
>>> scaffolding
>>>
>>> of the loop (i.e. for (i =3D 0; i < limit; i++) {}) is invisible as=20
>>> soon as the loop terminates.
>=20
>> This makes things more clear to anybody reading the code (and
>> unambiguous to the compiler).=C2=A0 However, lifetime analysis has
>> also become very good, and if the value is not used afterwards,
>> I expect no difference in practice.
>=20
> When one writes::
>=20
>  =C2=A0=C2=A0=C2=A0 for( uint64_t i =3D 0; i < max; i++ )
>=20
> the lifetime of i is explicit--it terminates with the loop.
>=20
>>> Without such a restriction, there are many times when it would be=20
>>> very natural to inspect the index in order to determine if this was a=
=20
>>> normal
>>>
>>> (counting) exit, or an early exit due to some internal test.
>=20
>> Hmm... do you mean for the programmer, or for the compiler?

This is probably my asm background shining trough:

All asm loops have the counting register available directly after loop=20
exit, until it is reused. When I want to do the same in C I just have to =

define the variable before the loop starts, instead of inside the ().

Terje
--=20
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"