[llvm-commits] [PATCH]Implement getHostCPUFeatures for ARM Linux platform

[Evan Cheng]

I didn't see your new patch. But given the original patch only has a minor format issue it's ok to go in.

Evan

On Dec 11, 2012, at 5:39 PM, Hao Liu <Hao.Liu at arm.com> wrote:

> Is it OK to commit this patch?
>  
> As it’s my first time to do something about LLVM, I need to be more careful.
>  
> Thanks,
> -Hao
>  
> From: llvm-commits-bounces at cs.uiuc.edu [mailto:llvm-commits-bounces at cs.uiuc.edu] On Behalf Of Hao Liu
> Sent: 2012年12月11日 10:15
> To: 'Evan Cheng'
> Cc: llvm-commits at cs.uiuc.edu
> Subject: Re: [llvm-commits] [PATCH]Implement getHostCPUFeatures for ARM Linux platform
>  
> Hi,
>  
> Attached is the new reformatted patch.
>  
> I need to descript why this patch for getHostCPUFeatures is needed and why can’t detect all the features:
> 1)       A function getHostCPUName already exists in Host.cpp, it can detect CPU name. The getHostCPUFeatures is also defined in Host.cpp but it is default to do nothing.
> 2)       It can’t detect all the features, as /proc/cpuinfo only defines 19 features, which can be found in arch/arm/kernel/setup.c of source code of Linux kernel. LLVM defines it own features for ARM in ARM.td. The features in Linux and features in ARM have differect names, so I map the former to the latter names.
> 3)       Not all the 19 features in Linux have the corresponding features in LLVM, actually these features we don’t care about or have no use. So I only translate 7 features having corresponding features in LLVM.  As for v6,v7 and thumb2, they are not defined in /pro/cpuinfo, but we can know that information  from CPU name. But some features are optional for a CPU, such as NEON and VFP, it can’t get that information from CPU name, so getHostCPUFeatures is needed.
>  
>  
> Thanks
> -Hao
>  
> From: Evan Cheng [mailto:evan.cheng at apple.com] 
> Sent: 2012年12月11日 3:02
> To: Hao Liu
> Cc: llvm-commits at cs.uiuc.edu
> Subject: Re: [llvm-commits] [PATCH]Implement getHostCPUFeatures for ARM Linux platform
>  
> Nitpick:
> +  if (Implementer == "0x41"){ // ARM Ltd.
>  
> Please add a space after ')'.
>  
> This is a welcome fix. We need auto-detection since some benchmarking efforts do not specify target cpus. However, I can't help but noticing all the features this patch doesn't detect. Is it possible to detect whether the cpu supports v6, v7, thumb2, etc.? Or better yet, is it possible to detect CPU name?
>  
> Evan
>  
> On Dec 9, 2012, at 6:44 PM, Hao Liu <Hao.Liu at arm.com> wrote:
>  
> 
> Hi,
>  
> Attached is a patch to define getHostCPUFeatures for ARM Linux platform in Host.cpp. Currently the CPU features have default values. The getHostCPUFeatures function do nothing and only return false.
>  
> The implementation is like getHostCPUName for ARM Linux platform in Host.cpp:
> 1)       Read /proc/cpuinfo and get the ‘Features’ line.
> 2)       For each feature which has corresponding feature in LLVM, translate the feature name in /proc/cpuinfo to LLVM feature key name in ARM.td .
> 3)       Add all features to StringMap and set value to true.
> 4)       If success, return true, otherwise return false.
>  
>  
> Thanks,
> -Hao
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