Clang: work around bogus warnings

Clang apparently doesn't expect the immediate to the permute intrinsics
to use 8 bits, otherwise it would use 'unsigned char' for the imm8
argument. Thus any value above 0x7f produces a warning. Work around the
warning by redefining the _mm256_permute2x128_si256,
_mm256_permute2f128_ps, and _mm256_permute2f128_si256 macros.

Signed-off-by: Matthias Kretz <kretz@kde.org>

avx/intrinsics.h

@@ -48,6 +48,28 @@ extern "C" {
 #include "macros.h"
 #include <cstdlib>
 
+#if (defined Vc_CLANG && Vc_CLANG >= 0x30900)
+#ifdef _mm256_permute2f128_si256
+#undef _mm256_permute2f128_si256
+#define _mm256_permute2f128_si256(V1, V2, M) __extension__ ({ \
+  (__m256i)__builtin_ia32_vperm2f128_si256((__v8si)(__m256i)(V1), \
+                                           (__v8si)(__m256i)(V2), (char)(M)); })
+#endif
+
+#ifdef _mm256_permute2f128_ps
+#undef _mm256_permute2f128_ps
+#define _mm256_permute2f128_ps(V1, V2, M) __extension__ ({ \
+  (__m256)__builtin_ia32_vperm2f128_ps256((__v8sf)(__m256)(V1), \
+                                          (__v8sf)(__m256)(V2), (char)(M)); })
+#endif
+
+#ifdef _mm256_permute2x128_si256
+#undef _mm256_permute2x128_si256
+#define _mm256_permute2x128_si256(V1, V2, M) __extension__ ({ \
+  (__m256i)__builtin_ia32_permti256((__m256i)(V1), (__m256i)(V2), (char)(M)); })
+#endif
+#endif
+
 namespace Vc_VERSIONED_NAMESPACE
 {
 namespace AvxIntrinsics