[LLVMdev] WCET optimizations

[John Criswell]

Dear Chao,

Yes, you can use LLVM to transform code to improve its Worse Case 
Execution Time (WCET).  I was involved in the PREM project that used a 
combination of LLVM and special hardware to reduce WCET by storing the 
data needed by a computation in the cache so that the bus could be used 
exclusively for I/O 
(http://dl.acm.org/citation.cfm?id=1989765.1990504&coll=DL&dl=GUIDE). I 
suspect there are other transforms that can improve WCET, but since I 
know nothing about them, you'll have to read up on them on your own.

As for including your changes into the LLVM distribution, that has a 
higher bar for entry.  Whatever transforms you write to improve WCET 
will need to be usable by others, and you'll need someone committed to 
maintaining the transforms long term (which usually means having enough 
users interested in using your transforms that it's worth making a long 
term maintenance commitment).

Regards,

John Criswell

On 9/9/14, 8:16 AM, Chao Peng wrote:
>
> Hi,
>
> I want to add some WCET optimizations into LLVM. Is it possible? Is 
> there any existing work to follow? Or some advices?
>
> Thanks
>
> Chao.
>
>
>
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