Re: [Xen-devel] [PATCH v2 for-next 2/2] x86/string: Use compiler __builtin_str*() where possible

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 12/05/17 15:56, Jan Beulich wrote:
>>>> On 12.05.17 at 16:34, <andrew.cooper3@xxxxxxxxxx> wrote:
>> --- a/xen/include/asm-x86/string.h
>> +++ b/xen/include/asm-x86/string.h
>> @@ -10,4 +10,12 @@
>>  #define __HAVE_ARCH_MEMSET
>>  #define memset(s, c, n)       __builtin_memset(s, c, n)
>>  
>> +#define strcmp(s1, s2)        __builtin_strcmp(s1, s2)
>> +#define strncmp(s1, s2, n)    __builtin_strncmp(s1, s2, n)
>> +#define strcasecmp(s1, s2)    __builtin_strcasecmp(s1, s2)
>> +#define strchr(s1, c)         __builtin_strchr(s1, c)
>> +#define strrchr(s1, c)        __builtin_strrchr(s1, c)
>> +#define strstr(s1, s2)        __builtin_strstr(s1, s2)
>> +#define strlen(s1)            __builtin_strlen(s1)
> If the lack of __HAVE_ARCH_* additions is intentional here, 

Yes - it is deliberate.

> why do you keep them for mem*()?

We have x86-specific implementation of mem*(), while we use the common
implementation of str*().

Defining __HAVE_ARCH_STR* causes the common implementation to be
omitted, resulting in a link failure.


Given that all supported compilers have these builtins, I think it might
be better to make this adjustment in common code.  The arguments for
using them in x86 are the same as ARM.

Julien/Stefano: Thoughts?

~Andrew

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