migration/xbzrle: Use __attribute__((target)) for avx512

Use the attribute, which is supported by clang, instead of
the #pragma, which is not supported and, for some reason,
also not detected by the meson probe, so we fail by -Werror.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-Id: <20230501210555.289806-1-richard.henderson@linaro.org>

meson.build

@@ -2370,12 +2370,9 @@ config_host_data.set('CONFIG_AVX512F_OPT', get_option('avx512f') \
 config_host_data.set('CONFIG_AVX512BW_OPT', get_option('avx512bw') \
   .require(have_cpuid_h, error_message: 'cpuid.h not available, cannot enable AVX512BW') \
   .require(cc.links('''
-    #pragma GCC push_options
-    #pragma GCC target("avx512bw")
     #include <cpuid.h>
     #include <immintrin.h>
-    static int bar(void *a) {
-
+    static int __attribute__((target("avx512bw"))) bar(void *a) {
       __m512i *x = a;
       __m512i res= _mm512_abs_epi8(*x);
       return res[1];

migration/xbzrle.c

@@ -177,11 +177,11 @@ int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen)
 }
 
 #if defined(CONFIG_AVX512BW_OPT)
-#pragma GCC push_options
-#pragma GCC target("avx512bw")
 #include <immintrin.h>
-int xbzrle_encode_buffer_avx512(uint8_t *old_buf, uint8_t *new_buf, int slen,
-                             uint8_t *dst, int dlen)
+
+int __attribute__((target("avx512bw")))
+xbzrle_encode_buffer_avx512(uint8_t *old_buf, uint8_t *new_buf, int slen,
+                            uint8_t *dst, int dlen)
 {
     uint32_t zrun_len = 0, nzrun_len = 0;
     int d = 0, i = 0, num = 0;
@@ -296,5 +296,4 @@ int xbzrle_encode_buffer_avx512(uint8_t *old_buf, uint8_t *new_buf, int slen,
     }
     return d;
 }
-#pragma GCC pop_options
 #endif