From: Matt Armstrong <matt@rfc20.org>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-devel@gnu.org
Subject: Re: Emacs' C: static inline considered useless nowadays?
Date: Sun, 16 Oct 2022 20:13:46 -0700 [thread overview]
Message-ID: <87a65vcfbp.fsf@rfc20.org> (raw)
In-Reply-To: <jwv7d0zffkq.fsf-monnier+emacs@gnu.org>
Stefan Monnier <monnier@iro.umontreal.ca> writes:
> Matt Armstrong [2022-10-16 15:08:51] wrote:
>> I've spent the last few decades coding with an undersanding that
>> "inline" is about linkage and allows one to place code in header files
>> so that it *may* be inlined, but that compilers long ago stopped using
>> it as a meaningful inlining hint. But this is mostly colored by how gcc
>> and clang behave with C++, and not much else.
>
> I believe what you say does hold true for "optimized builds".
> I'd be interested to know if it's true for lower levels of optimization
> as well.
>
> Stefan "compiling with -Og"
Seems the answer, thanks to godbolt, is "it depends", but "static
inline" does enable inlining in gcc's -Og, so it has its use.
For this program:
static inline int static_inline_add(int x, int y) { return x + y; }
static int static_add(int x, int y) { return x + y; }
int add_three(int x, int y, int z) {
return static_add(x, static_inline_add(y, z));
}
gcc and clang has the same behavior:
-O0: nither static functions are inlined into 'add_three'
-Og: only 'static_inline_add' is inlined
-O1: 'static_add' is also inlined
Microsoft Visual Studio has more optimization knobs.
/Od: neither are inlined
/Ot: neither are inlined
/Ox: both are inlined
/Odb1: only static_inline_add is inlined
/Odb2: only static_inline_add is inlined
/O1: both are inlined
/O2: both are inlined
I couldn't find a way to trigger Visual Studio into behaving like gcc.
next prev parent reply other threads:[~2022-10-17 3:13 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-16 22:08 Emacs' C: static inline considered useless nowadays? Matt Armstrong
2022-10-17 0:43 ` Stefan Monnier
2022-10-17 3:13 ` Matt Armstrong [this message]
2022-10-17 3:33 ` Óscar Fuentes
2022-10-17 6:10 ` Eli Zaretskii
2022-10-17 19:08 ` Matt Armstrong
2022-10-17 19:12 ` Eli Zaretskii
2022-10-17 20:33 ` Matt Armstrong
2022-10-18 2:30 ` Eli Zaretskii
2022-10-18 13:32 ` Stefan Monnier
2022-10-18 15:09 ` Eli Zaretskii
2022-10-18 17:01 ` tomas
2022-10-18 19:22 ` Stefan Monnier
2022-10-18 19:31 ` Eli Zaretskii
2022-10-18 11:58 ` Richard Stallman
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