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Re: -mfence-as-lock-add option in binutils 2.27
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From: |
Ian Lance Taylor |
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Subject: |
Re: -mfence-as-lock-add option in binutils 2.27 |
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Date: |
Tue, 03 Oct 2017 05:46:14 -0700 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) |
Parul Chahar <address@hidden> writes:
> I found that a new option "-mfence-as-lock-add" is added in binutils 2.27.
> It generate lock instruction when "-mfence-as-lock-add=yes". Otherwise,
> mfence, lfence, sfence is generated.
>
> Please let me know why this option is required. Why lock instruction is
> needed.
It's not needed, but it can be more efficient. See, for example,
https://shipilev.net/blog/2014/on-the-fence-with-dependencies/#_hardware
Ian