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Re: Support for Runtime CPU type detection via builtins (issue5754058)


On Mon, Apr 2, 2012 at 5:38 AM, Richard Guenther
<richard.guenther@gmail.com> wrote:
> On Sat, Mar 31, 2012 at 1:03 AM, Sriraman Tallam <tmsriram@google.com> wrote:
>> On Fri, Mar 30, 2012 at 5:47 AM, Michael Matz <matz@suse.de> wrote:
>>> Hi,
>>>
>>> On Thu, 29 Mar 2012, Sriraman Tallam wrote:
>>>
>>>> +struct __processor_model
>>>> +{
>>>> + ?/* Vendor. */
>>>> + ?unsigned int __cpu_is_amd : 1;
>>>> + ?unsigned int __cpu_is_intel : 1;
>>>> + ?/* CPU type. */
>>>> + ?unsigned int __cpu_is_intel_atom : 1;
>>>> + ?unsigned int __cpu_is_intel_core2 : 1;
>>>> + ?unsigned int __cpu_is_intel_corei7 : 1;
>>>> + ?unsigned int __cpu_is_intel_corei7_nehalem : 1;
>>>> + ?unsigned int __cpu_is_intel_corei7_westmere : 1;
>>>> + ?unsigned int __cpu_is_intel_corei7_sandybridge : 1;
>>>> + ?unsigned int __cpu_is_amdfam10h : 1;
>>>> + ?unsigned int __cpu_is_amdfam10h_barcelona : 1;
>>>> + ?unsigned int __cpu_is_amdfam10h_shanghai : 1;
>>>> + ?unsigned int __cpu_is_amdfam10h_istanbul : 1;
>>>> + ?unsigned int __cpu_is_amdfam15h_bdver1 : 1;
>>>> + ?unsigned int __cpu_is_amdfam15h_bdver2 : 1;
>>>> +} __cpu_model;
>>>
>>> It doesn't make sense for the model to be a bitfield, a processor will
>>> have only ever exactly one model. ?Just make it an enum or even just an
>>> int.
>>
>> Not entirely true, nehalem and corei7 can be both set. However, I
>> modified this by dividing it into types and sub types and then did
>> what you said.
>
> Uh... ?then I suppose you need to document somewhere what names
> match to what cpuid family/model (supposedly thats where your two-layer
> hierarchy comes from, which incidentially misses one layer, the vendor?)

Yes, it is 3-layer. Vendor, family and model.

What is the right place to document these?

>
> Richard.
>
>> ? ? ? * config/i386/i386.c (build_processor_features_struct): New function.
>> ? ? ? (build_processor_model_struct): New function.
>> ? ? ? (make_var_decl): New function.
>> ? ? ? (get_field_from_struct): New function.
>> ? ? ? (fold_builtin_target): New function.
>> ? ? ? (ix86_fold_builtin): New function.
>> ? ? ? (ix86_expand_builtin): Expand new builtins by folding them.
>> ? ? ? (make_cpu_type_builtin): New functions.
>> ? ? ? (ix86_init_platform_type_builtins): Make the new builtins.
>> ? ? ? (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.
>>
>> ? ? ? * 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 symbols __cpu_model
>> ? ? ? and __cpu_features.
>>
>> Patch available for review here:
>> http://codereview.appspot.com/5754058
>>
>> Thanks,
>> -Sri.
>>
>>
>>>
>>>
>>> Ciao,
>>> Michael.


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