From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id 68C6A3838F0D; Fri,  9 Dec 2022 14:55:57 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 68C6A3838F0D
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1670597757;
	bh=3n5AUraCddf1IOKldmQu0YjU/OUneySIQrMqsqb4ZJI=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=nielzdRNXzq33+q7l+e0E+wHRHPenLsofvB3JcHCFjjQ9T629+PadAJ7IxEgRkVP8
	 6TQ/LWnkX5CzwtXqs1a8IYpOW5MX+y72/3Tz1YCzOXnAKsaJAJDhlWYxhjoyCIexYU
	 la6ikZmW1eK2Seq+NbfXW7LBnCVfdghFJB9MCrVs=
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/108030] `std::experimental::simd` not inlined
Date: Fri, 09 Dec 2022 14:55:57 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 12.2.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jakub at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: mkretz at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 13.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-108030-4-qlEzLhhmO7@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-108030-4@http.gcc.gnu.org/bugzilla/>
References: <bug-108030-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108030

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Matthias Kretz (Vir) from comment #3)
> (In reply to Jakub Jelinek from comment #2)
> > I bet by adding too many always_inline functions that call normal inlin=
es
> > that is what is bound to happen, one runs into inline growth limits.  I=
t is
> > better to use always_inline on the leaf functions rather than on what c=
alls
> > them.
>=20
> How is the inline growth limit determined? I mean, in the cases where it
> really hurts, the resulting function compiles down to a single instruction
> (plus parameter passing boilerplate). The optimizer cannot know about the
> number of instructions, so what is the measure it uses?

I've CCed Honza, who should know the answers.
The inliner can't know if say some builtin will fold into a single instruct=
ion
or not,
it uses some heuristics on GIMPLE IL sizes.  Bet -fdump-ipa-inline-details
contain
all the reasons, but at least for me those dumps are hard to read.=