[LLVMdev] LLVA and WCET Analysis

Vikram S. Adve vadve at uiuc.edu
Tue Apr 3 14:48:10 PDT 2007

I do not know of any such work for LLVM.

Also, WCET for LLVM should be much simpler than for Java bytecode  
because LLVM is more low-level and translates to a very small (and  
highly predictable for any specific target) number of operations.  Of  
course, the general problems also present at the machine code level  
still remain -- cache misses, branch mispredicts, exceptions, etc.


On Apr 3, 2007, at 3:22 PM, Fabian Scheler wrote:

>>> LLVA specifically is refering to a research project offshoot of  
>>> llvm.
>>> LLVM instructions do not have 1:1 mappings to native instructions
>>> (sometimes multiple llvm instructions map to fewer native insts,
>>> sometimes the other way around).
>> That's correct, and furthermore, LLVA (now called SVA = Secure
>> Virtual Architecture) uses essentially the same virtual instruction
>> set as LLVM, so they have the same difficulty.
> Hm, when writing LLVA I rather meant this publication
> http://llvm.org/pubs/2003-10-01-LLVA.html
> Maybe the used abbreviations meanwhile changed or I mixed up something
> else. Regarding the fact, that it is not possible to have a 1:1
> mapping between LLVM instructions and native code instructions in the
> general case. That is clear, it is the same problem as it is with Java
> Byte Code. Some work dealing with WCET analysis of Java Byte Code
> already has been done:
> Iain Bate, Guillem Bernat, Greg Murphy, Peter Puschner:
> Low-Level Analysis of a Portable Java Byte Code WCET Analysis  
> Framework
> Guillem Bernat, Alan Burns, Andy Wellings:
> Portable Worst-Case Execution Time Analysis Using Java Byte Code
> I just wondered if anybody did something similar for the LLVM
> instruction set, but apparently this seems not to be the case.
> Ciao, Fabian
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