https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100677
Bug ID: 100677
Summary: False positive unused-but-set-parameter warning when
using VSX intrinsics
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: alexander.gr...@tu-dresden.de
Target Milestone: ---
On some code like the below the unused-but-set-parameter warning is incorrectly
triggered:
class Vec256 {
union {
struct {
vfloat32 _vec0;
vfloat32 _vec1;
};
struct {
vbool32 _vecb0;
vbool32 _vecb1;
};
} __attribute__((__may_alias__));
Vec256(float scalar)
: _vec0{vec_splats(scalar)}, _vec1{vec_splats(scalar)} {}
};
GCC seems to think "scalar" is unused even though it is passed to "vec_splats"
which is defined as "#define vec_splats __builtin_vec_splats"
This seems to also apply to other intrinsics, see e.g.
https://qlf-gitlab.inria.fr/guenneba/eigenci-junit-test/-/blob/85330d21b58bccbf95c90e874db2a0f6775ff63b/Eigen/src/Core/arch/AltiVec/PacketMath.h#L271-275
