https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98774
Bug ID: 98774
Summary: gcc -O3 does not vectorize multiplication
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vanyacpp at gmail dot com
Target Milestone: ---
Created attachment 50014
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50014&action=edit
nbody-update-velocity.cpp
In the following sample GCC (-O3 -ffast-math) fails to vectorize operations.
The results is that GCC 10.2 does 8 mulsd, while clang 11.0 does 4 mulpd.
struct vec3 { double x, y, z; };
void update_velocities(vec3* __restrict velocity,
double const* __restrict mass,
vec3 const* __restrict dpos,
double const* __restrict mag)
{
velocity[0] -= dpos[0] * (mass[1] * mag[0]);
velocity[1] += dpos[0] * (mass[0] * mag[0]);
}
See an attachment for the complete sample.
