https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105175
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |dmalcolm at gcc dot gnu.org,
| |msebor at gcc dot gnu.org
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
@item -Wvector-operation-performance
@opindex Wvector-operation-performance
@opindex Wno-vector-operation-performance
Warn if vector operation is not implemented via SIMD capabilities of the
architecture. Mainly useful for the performance tuning.
Vector operation can be implemented @code{piecewise}, which means that the
scalar operation is performed on every vector element;
@code{in parallel}, which means that the vector operation is implemented
using scalars of wider type, which normally is more performance efficient;
and @code{as a single scalar}, which means that vector fits into a
scalar type.
--
So the point is the vector lowering pass cannot distinguish people writing
typedef int v2si __attribute__((vector_size(8)));
v2si a, b;
void foo()
{
a &= b;
}
and the vectorizer producing such code. So technically the diagnostic is
correct but it was the vectorizer producing the operation.
So a proper way would be to suppress OPT_Wvector_operation_performance for
the vectorizer generated stmt. Unfortunately
if (using_emulated_vectors_p)
suppress_warning (new_stmt, OPT_Wvector_operation_performance);
will not magically make
warning_at (loc, OPT_Wvector_operation_performance,
"vector operation will be expanded with a "
"single scalar operation");
not warn. suppress_warning_at returns true, and supp is true as well
(that parameter is not documented as far as I can see). So we need to
guard all the warning_at with stmt-based warning_suppressed_p and
there's no warning_at overload with a gimple * as location that would
automagically do that it seems? There is one with rich_location * but
AFAIK that doesn't cover gimple * or tree.
I'm testing a patch that is IMHO too verbose (adjusting all warning_at
in tree-vect-generic.cc).
