[PATCH] Add HLE target feature

[Krzysztof Parzyszek]

On 2/27/2013 6:01 PM, Jeffrey Yasskin wrote:
>
> This is why we need the langref patch before looking into the
> implementation. These annotations are something like the !nontemporal
> metadata on loads, in that they hint to the implementation that
> certain properties will hold on a particular use of the existing
> atomic instructions, and certain targets can take advantage of that to
> emit better code. On uses where those properties don't hold, the
> existing code is better.

Ok, so help me understand this---is the proposed metatada providing 
information that cannot be obtained by analysis of the code, or is this 
only meant to be a way for the programmer to provide an explicit hint to 
the compiler?

I can understand the need for platform-specific options (like pragmas), 
but I am not aware of any precedents for this in LLVM, and how that 
would be handled.  I guess metadata would be the way after all...

-Krzysztof

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