Do we have the flexibility to do that for util/bufferiszero.c as well? Otherwise, we are using different mechanisms to detect (compile test.c with -mavx2) and actually use (GCC pragma & __attribute__((target(*))))) the feature in production.
Shu-Chun
On Wed, Jul 22, 2020 at 9:55 PM Thomas Huth <th...@redhat.com> wrote:
> On 23/07/2020 02.27, Shu-Chun Weng wrote:
> > Since clang does not support "#pragma GCC", the instruction sets are
> > always disabled. In this change, we
> >
> > 1. wrap "#pragma GCC" inside "#ifndef __clang__",
> > 2. only retain them around "#include <{e,i,s}mmintrin.h>" to work
> > around gcc bug,
> > 3. and annotate each function with `__attribute__((target(*)))` which
> > is recognized by both gcc and clang.
> >
> > Signed-off-by: Shu-Chun Weng <s...@google.com>
> > ---
> > configure | 16 ++++++++++++++--
> > util/bufferiszero.c | 33 +++++++++++++++++++++++----------
> > 2 files changed, 37 insertions(+), 12 deletions(-)
> >
> > diff --git a/configure b/configure
> > index 4bd80ed507..d9ce3aa5db 100755
> > --- a/configure
> > +++ b/configure
> > @@ -5808,10 +5808,16 @@ fi
> >
> > if test "$cpuid_h" = "yes" && test "$avx2_opt" != "no"; then
> > cat > $TMPC << EOF
> > +#include <cpuid.h>
> > +#ifndef __clang__
> > #pragma GCC push_options
> > #pragma GCC target("avx2")
> > -#include <cpuid.h>
> > +#endif
> > #include <immintrin.h>
> > +#ifndef __clang__
> > +#pragma GCC pop_options
> > +#endif
> > +__attribute__((target("avx2")))
> > static int bar(void *a) {
> > __m256i x = *(__m256i *)a;
> > return _mm256_testz_si256(x, x);
>
> I wonder whether it would make more sense to pass "-mavx2" to the
> compile_object call afterwards and simply remove the #pragmas here?
> Did you try that already?
>
> Thomas
>
>
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