[LLVMdev] RFC: PerfGuide for frontend authors

[Philip Reames]

Done.

On 03/04/2015 02:58 PM, Hans Wennborg wrote:
> 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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>>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
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>>>>
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