Re: [Qemu-devel] [PATCH v3 7/9] cutils: Rewrite x86 buffer zero checking

[Paolo Bonzini]

On 13/09/2016 16:17, Paolo Bonzini wrote:
> 
> 
> On 13/09/2016 15:26, Paolo Bonzini wrote:
>> I need this on top to fix compilation with older compilers:
>>
>> diff --git a/util/bufferiszero.c b/util/bufferiszero.c
>> index 3b39f82..1ce6b7a 100644
>> --- a/util/bufferiszero.c
>> +++ b/util/bufferiszero.c
>> @@ -71,13 +71,13 @@ buffer_zero_int(const void *buf, size_t len)
>>
>>  #if defined(CONFIG_AVX2_OPT) || defined(__SSE2__)
>>  #include <cpuid.h>
>> -#include <x86intrin.h>
>>
>>  /* Note that we're going to check for LEN >= 64 for all of these.  */
>>
>>  #ifdef CONFIG_AVX2_OPT
>>  #pragma GCC push_options
>>  #pragma GCC target("avx2")
>> +#include <immintrin.h>
>>
>>  static bool
>>  buffer_zero_avx2(const void *buf, size_t len)
>> @@ -181,6 +181,8 @@ buffer_zero_sse4(const void *buf, size_t len)
>>  #pragma GCC target("sse2")
>>  #endif /* CONFIG_AVX2_OPT */
>>
>> +#include <emmintrin.h>
>> +
>>  static bool
>>  buffer_zero_sse2(const void *buf, size_t len)
>>  {
>>
> 
> Nope, not enough on GCC 4.8:
> 
> $ nm util/bufferiszero.o
> 0000000000000000 b buffer_accel
> 0000000000000430 T buffer_is_zero
> 0000000000000240 t buffer_zero_avx
> 0000000000000330 t buffer_zero_avx2
> 0000000000000000 t buffer_zero_int
> 00000000000000b0 t buffer_zero_sse2
> 0000000000000190 t buffer_zero_sse4
> 0000000000000008 b cpuid_cache
>                  U _GLOBAL_OFFSET_TABLE_
> 0000000000000000 t init_cpuid_cache
>                  U _mm_cmpeq_epi8
>                  U _mm_loadu_si128
>                  U _mm_movemask_epi8
>                  U _mm_setzero_si128
>                  U _mm_testz_si128
> 00000000000003d0 T test_buffer_is_zero_next_accel
> 
> Since I have no idea what's going on, I'm dropping these the last three
> patches.

I still have no idea what's going on, but dropping this patch is enough.

Paolo