| From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: [PATCH] Small optimization across postgres (remove strlen duplicate usage) |
| Date: | 2020-04-19 22:00:28 |
| Message-ID: | CAApHDvo5rrUpOzQZogwEV5ZNteE4bTZNbWN4WUFza8oinGxy0A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, 20 Apr 2020 at 09:38, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> The cases where Ranier proposes to replace strlen(foo) == 0
> with a test on foo[0] do seem like wins, though. Asking for
> the full string length to be computed is more computation than
> necessary, and it's less clear that the compiler could be
> expected to save you from that. Anyway there's a coding style
> proposition that we should be doing this consistently, and
> certainly lots of places do do this without using strlen().
Looking at https://godbolt.org/z/6XsjbA it seems like GCC is pretty
good at getting rid of the strlen call even at -O0. It takes -O1 for
clang to use it and -O2 for icc.
David
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