https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121669
Bug ID: 121669
Summary: -Wpsabi warnings should be suppressed for
always_inline functions
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: mkretz at gcc dot gnu.org
Target Milestone: ---
Target: x86_64-*-*
Test case (https://compiler-explorer.com/z/GzYe7qhTc):
using V [[gnu::vector_size(32)]] = int;
[[gnu::always_inline]]
inline V
f(V a)
{ return a; }
void g()
{
V x = {};
x = f(x);
}
Compiled with `-march=x86-64-v2 -Wpsabi` this code is diagnosed with:
<source>:5:6: warning: AVX vector return without AVX enabled changes the ABI
[-Wpsabi]
5 | f(V a)
| ^
<source>:5:1: note: the ABI for passing parameters with 32-byte alignment has
changed in GCC 4.6
5 | f(V a)
| ^
But that's a bogus warning because the function f is *always* inlined and any
potential ABI incompatibilities are therefore never going to matter. The
warning should, IMHO, be conditional on whether the function in question is
always_inline.
This issue is coming up in the std::simd internals all over the place, forcing
the use of -Wno-psabi. (One reason for using always_inline in std::simd is
exactly to avoid ABI issues.)
I'm only familiar with this warning coming up on x86. I don't know how relevant
this issue is for other targets.
