[PATCH] D19821: [EarlyCSE] Optionally use MemorySSA. NFC.

[Daniel Berlin via llvm-commits]

Ah, this is a file that takes <100ms to run in release mode.
Yeah, gonna be hard to beat that.
You can see what the time is without any use optimization by using
-memssa-check-limit=0 (but again, you have to use getClobberingMemoryAccess
as you are now to get sane results).

It looks like all the build time is in use opt.
Better alias caching would help with this.

Profiling is hard, it takes so little time instruments on my mac won't
profile it :)




On Mon, Aug 22, 2016 at 3:00 PM, Geoff Berry <gberry at codeaurora.org> wrote:

> Sure, here is the .bc file for z44.c:
>
>
>
> On 8/22/2016 5:39 PM, Daniel Berlin wrote:
>
> Can you send me bc files so i can profile?
> We haven't really begun to speed anything up yet :)
>
> We also could, if it really mattered, turn off use optimization, which is
> usually the slow part of building.
>
> It would require updating defining accesses in the walker (otherwise, it
> will slow down every query that asks about a given load. Caching is a
> non-starter since you are basically caching something the size of memoryssa
> ;)).
>
>
> On Mon, Aug 22, 2016 at 2:27 PM, Geoff Berry <gberry at codeaurora.org>
> wrote:
>
>> gberry added a comment.
>>
>> I've collected some compile time stats when enabling MemorySSA EarlyCSE
>> just for the EarlyCSE pass added at the beginning of
>> addFunctionSimplificationPasses at O2 and higher.
>> There were 8 benchmarks in the llvm test-suite whose compile time
>> increased by more than 1%.  The biggest increase was in consumer-typeset.
>> Drilling down a bit, the MemorySSA construction time for compiling the
>> z44.c input to this benchmark is reported as 2% of runtime.
>>
>>
>> https://reviews.llvm.org/D19821
>>
>>
>>
>>
>
> --
> Geoff Berry
> Employee of Qualcomm Datacenter Technologies, Inc.
>  Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.  Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
>
>
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