Support for Runtime CPU type detection via builtins (issue5754058)

H.J. Lu hjl.tools@gmail.com
Wed Apr 25 21:28:00 GMT 2012


On Wed, Apr 25, 2012 at 2:25 PM, Sriraman Tallam <tmsriram@google.com> wrote:
> On Tue, Apr 24, 2012 at 7:39 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Tue, Apr 24, 2012 at 7:06 PM, Sriraman Tallam <tmsriram@google.com> wrote:
>>> On Tue, Apr 24, 2012 at 5:24 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>> On Tue, Apr 24, 2012 at 5:10 PM, Sriraman Tallam <tmsriram@google.com> wrote:
>>>>> Hi,
>>>>>
>>>>>   Thanks for all the comments. I have made all the changes as
>>>>> mentioned and submiited the patch. Summary of changes made:
>>>>>
>>>>> * Add support for AVX
>>>>> * Fix documentation in extend.texi
>>>>> * Make it thread-safe according to H.J.'s comments.
>>>>>
>>>>> I have attached the patch. Boot-strapped and checked for test parity
>>>>> with pristine build.
>>>>>
>>>>>       * config/i386/i386.c (build_processor_model_struct): New function.
>>>>>        (make_var_decl): New function.
>>>>>        (fold_builtin_cpu): New function.
>>>>>        (ix86_fold_builtin): New function.
>>>>>        (make_cpu_type_builtin): New function.
>>>>>        (ix86_init_platform_type_builtins): New function.
>>>>>        (ix86_expand_builtin): Expand new builtins by folding them.
>>>>>        (ix86_init_builtins): Make new builtins to detect CPU type.
>>>>>        (TARGET_FOLD_BUILTIN): New macro.
>>>>>        (IX86_BUILTIN_CPU_INIT): New enum value.
>>>>>        (IX86_BUILTIN_CPU_IS): New enum value.
>>>>>        (IX86_BUILTIN_CPU_SUPPORTS): New enum value.
>>>>>        * config/i386/i386-builtin-types.def: New function type.
>>>>>        * testsuite/gcc.target/builtin_target.c: New testcase.
>>>>>        * doc/extend.texi: Document builtins.
>>>>>
>>>>>        * libgcc/config/i386/i386-cpuinfo.c: New file.
>>>>>        * libgcc/config/i386/t-cpuinfo: New file.
>>>>>        * libgcc/config.host: Include t-cpuinfo.
>>>>>        * libgcc/config/i386/libgcc-glibc.ver: Version symbol __cpu_model.
>>>>>
>>>>>
>>>>
>>>> +  /* This function needs to run just once.  */
>>>> +  if (__cpu_model.__cpu_vendor)
>>>> +    return 0;
>>>> +
>>>> +  /* Assume cpuid insn present. Run in level 0 to get vendor id. */
>>>> +  if (!__get_cpuid_output (0, &eax, &ebx, &ecx, &edx))
>>>> +    return -1;
>>>>
>>>> If __get_cpuid_output returns non-zero, it will be called
>>>> repeatedly.  I think you should set __cpu_model.__cpu_vendor
>>>> to non-zero in this case.
>>>
>>> Done now.
>>>
>>> 2012-04-24  Sriraman Tallam  <tmsriram@google.com>
>>>
>>>        * libgcc/config/i386/i386-cpuinfo.c: Set __cpu_vendor always.
>>>
>>>
>>> Index: libgcc/config/i386/i386-cpuinfo.c
>>> ===================================================================
>>> --- libgcc/config/i386/i386-cpuinfo.c   (revision 186789)
>>> +++ libgcc/config/i386/i386-cpuinfo.c   (working copy)
>>> @@ -256,16 +256,25 @@ __cpu_indicator_init (void)
>>>
>>>   /* Assume cpuid insn present. Run in level 0 to get vendor id. */
>>>   if (!__get_cpuid_output (0, &eax, &ebx, &ecx, &edx))
>>> -    return -1;
>>> +    {
>>> +      __cpu_model.__cpu_vendor = VENDOR_OTHER;
>>> +      return -1;
>>> +    }
>>>
>>>   vendor = ebx;
>>>   max_level = eax;
>>>
>>>   if (max_level < 1)
>>> -    return -1;
>>> +    {
>>> +      __cpu_model.__cpu_vendor = VENDOR_OTHER;
>>> +      return -1;
>>> +    }
>>>
>>>   if (!__get_cpuid_output (1, &eax, &ebx, &ecx, &edx))
>>> -    return -1;
>>> +    {
>>> +      __cpu_model.__cpu_vendor = VENDOR_OTHER;
>>> +      return -1;
>>> +    }
>>>
>>>   model = (eax >> 4) & 0x0f;
>>>   family = (eax >> 8) & 0x0f;
>>>
>>>
>>> Thanks,
>>
>> Should you also handle AVX2?
>
>  I cannot test it and thought will wait till I get access to a
> processor with AVX2.
>

You can download an AVX2 emulator (SDE) from

http://software.intel.com/en-us/avx/

to test AVX2 binaries.

-- 
H.J.



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