llvm dev - May 2018 - "Replace locked IO with unlocked IO" optimizations

Hello,

Please check this patch:
https://reviews.llvm.org/D45736

as Eli noted, other opinions are highly welcomed..

Thanks
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It's probably worth going into a little more detail... a lot of people 
read llvmdev, and most of them won't click the link or follow the whole 
discussion.

The transform in question is replacing "fputc(...)" with 
"fputc_unlocked(...)" when we can prove the FILE* doesn't escape.
The
question is whether it's safe for the compiler to emit a call to 
fputc_unlocked() on Linux, given it's a non-standard extension.  The bit 
I'm most worried about is some user defining a function named 
fputc_unlocked; it isn't a reserved name according to the C standard, so 
there's no way to ensure we're actually calling the glibc
fputc_unlocked.

Suggestions welcome.

-Eli

On 5/8/2018 4:59 PM, Dávid Bolvanský via llvm-dev wrote:
> Hello,
>
> Please check this patch:
> https://reviews.llvm.org/D45736
>
> as Eli noted, other opinions are highly welcomed..
>
> Thanks
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
Foundation Collaborative Project

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On 05/08/2018 07:13 PM, Friedman, Eli via llvm-dev
wrote:
> It's probably worth going into a little more detail... a lot of people
> read llvmdev, and most of them won't click the link or follow the
> whole discussion.
>
> The transform in question is replacing "fputc(...)" with
> "fputc_unlocked(...)" when we can prove the FILE* doesn't
escape.  The
> question is whether it's safe for the compiler to emit a call to
> fputc_unlocked() on Linux, given it's a non-standard extension.  The
> bit I'm most worried about is some user defining a function named
> fputc_unlocked; it isn't a reserved name according to the C standard,
> so there's no way to ensure we're actually calling the glibc
> fputc_unlocked.
Don't we generally assume the availability of glibc extensions when -gnu
is in the triple?

 -Hal
>
> Suggestions welcome.
>
> -Eli
>
> On 5/8/2018 4:59 PM, Dávid Bolvanský via llvm-dev wrote:
>> Hello,
>>
>> Please check this patch:
>> https://reviews.llvm.org/D45736
>>
>> as Eli noted, other opinions are highly welcomed..
>>
>> Thanks
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
> -- 
> Employee of Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
Foundation Collaborative Project
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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