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Re: [i386] Replace builtins with vector extensions

On Tue, 9 Apr 2013, Richard Biener wrote:

On Mon, Apr 8, 2013 at 10:47 PM, Marc Glisse <> wrote:
On Sun, 7 Apr 2013, Marc Glisse wrote:

 extern __inline __m128i __attribute__((__gnu_inline__, __always_inline__,
 _mm_slli_epi16 (__m128i __A, int __B)
-  return (__m128i)__builtin_ia32_psllwi128 ((__v8hi)__A, __B);
+  return (__m128i) ((__v8hi)__A << __B);

Actually, I believe I have to keep using the builtins for shifts, because
the intrinsics have well defined behavior for large __B whereas << and >>

I seem to remember discussion in the PR(s) that the intrinsics should
(and do for other compilers) expand to the desired instructions even when
the corresponding instruction set is disabled.

emmintrin.h starts with:
#ifndef __SSE2__
# error "SSE2 instruction set not enabled"

The closest thing I can think of is issues with -mfpmath=387, but that shouldn't matter for full vector ops.

Using vector extension
makes that harder to achieve.  Other than that I am all for using the
vector extensions, but I think you need carefully wrapped __extension__
markers so that with -std=c89 -pedantic you still can compile programs
using the intrinsics?

The *intrin.h files already use __extension__ to create vectors, like:
  return __extension__ (__m128d){ __F, 0.0 };
but even when I remove it it does not warn with -std=c89 -pedantic.

Marc Glisse

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