Re: [Mesa-dev] [Mesa-stable] [PATCH 2/3] gallivm: Override getHostCPUName() "generic" w/ "pwr8" (v3)

[Ben Crocker]

Hi Emil, 

Thanks for the feedback, and I agree. I'm adding such a comment now. 

-- Ben 


- Original Message -

From: "Emil Velikov"  
To: "Ben Crocker"  
Cc: "ML mesa-dev" , "12.0 13.0 17.0" 
 
Sent: Thursday, February 9, 2017 9:09:37 AM 
Subject: Re: [Mesa-stable] [PATCH 2/3] gallivm: Override getHostCPUName() 
"generic" w/ "pwr8" (v3) 

Hi Ben, 

On 19 January 2017 at 01:43, Ben Crocker  wrote: 
> If llvm::sys::getHostCPUName() returns "generic", override 
> it with "pwr8" (on PPC64LE). 
> 
> This is a work-around for a bug in LLVM: a table entry for "POWER8NVL" 
> is missing, resulting in (big-endian) "generic" being returned on 
> little-endian Power8NVL systems. The result is that code that 
> attempts to load the least significant 32 bits of a 64-bit quantity in 
> memory loads the wrong half. 
> 
> This omission should be fixed in the next version of LLVM (4.0), 
> but this work-around should be left in place in case some 
> future version of POWER also ends up unrepresented in LLVM's table. 
> 
Not sure how others feel, but imho you really want to have 
this/similar comment in the code. 

-Emil 

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Re: [Mesa-dev] [Mesa-stable] [PATCH 2/3] gallivm: Override getHostCPUName() "generic" w/ "pwr8" (v3)

[Emil Velikov]

Hi Ben,

On 19 January 2017 at 01:43, Ben Crocker  wrote:
> If llvm::sys::getHostCPUName() returns "generic", override
> it with "pwr8" (on PPC64LE).
>
> This is a work-around for a bug in LLVM: a table entry for "POWER8NVL"
> is missing, resulting in (big-endian) "generic" being returned on
> little-endian Power8NVL systems.  The result is that code that
> attempts to load the least significant 32 bits of a 64-bit quantity in
> memory loads the wrong half.
>
> This omission should be fixed in the next version of LLVM (4.0),
> but this work-around should be left in place in case some
> future version of POWER also ends up unrepresented in LLVM's table.
>
Not sure how others feel, but imho you really want to have
this/similar comment in the code.

-Emil
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