[LLVMdev] RFC: PerfGuide for frontend authors

[Hans Wennborg]

Yes, 3.7.

On Wed, Mar 4, 2015 at 2:55 PM, Philip Reames <listmail at philipreames.com> wrote:
> Just to be clear, you mean the release notes for 3.7 not 3.6 right?
>
>
> On 03/04/2015 02:15 PM, Hans Wennborg wrote:
>>
>> This is great. Can you add it to the release notes?
>>
>> On Fri, Feb 27, 2015 at 3:34 PM, Philip Reames
>> <listmail at philipreames.com> wrote:
>>>
>>> The first version of this document is now live:
>>> http://llvm.org/docs/Frontend/PerformanceTips.html
>>>
>>> Please feel free to add to it directly.  Alternatively, feel free to
>>> reply
>>> to this thread with text describing an issue that should be documented.
>>> I'll make sure text gets turned into patches.
>>>
>>> Philip
>>>
>>>
>>> On 02/23/2015 04:46 PM, Philip Reames wrote:
>>>>
>>>> I'd like to propose that we create a new Performance Guide document. The
>>>> target of this document will be frontend authors, not necessarily LLVM
>>>> contributors.  The content will be a collection of items a frontend
>>>> author
>>>> might want to know about how to generate LLVM IR which will optimize
>>>> well.
>>>>
>>>> Some ideas on topics that might be worthwhile:
>>>> - Prefer sext over zext when value is known to be positive in the
>>>> language
>>>> (e.g. range checked index on a GEP)
>>>> - Avoid loading and storing first class aggregates (i.e. they're not
>>>> well
>>>> supported in the optimizer)
>>>> - Mark invariant locations - i.e. link to !invariant.load and TBAA
>>>> constant flags
>>>> - Use globals not inttoptr for runtime structures - this gives you
>>>> dereferenceability information
>>>> - Use function attributes where possible (nonnull, deref, etc..)
>>>> - Be ware of ordered and atomic memory operations (not well optimized),
>>>> depending on source language, might be faster to use fences.
>>>> - Range checks - make sure you test with the IRCE pass
>>>>
>>>> If folks are happy with the idea of having such a document, I volunteer
>>>> to
>>>> create version 0.1 with one or two items.  After that, we can add to it
>>>> as
>>>> folks encounter ideas.  The initial content will be fairly minimal, I
>>>> just
>>>> want a link I can send to folks in reviews to record comments made.  :)
>>>>
>>>> Philip
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>>>
>>>
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>
>