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SPEAR opt pass

If you want to use SPEAR as pass for llvm opt, use the following explanation:

Using the LLVM pass

We provided a custom LLVM pass to run with the opt tool. To run the analysis, use the following preset:

opt -disable-output 
    -load-pass-plugin <libpath>
    --passes="function(mem2reg,loop-rotate),energy"
    --profile <profilepath>
    --mode <mode> 
    --format <format> 
    --strategy <strategy> 
    --loopbound <loopbound> 
    --withCalls <withcalls>
    --program <llvmirpath>
    --forFunction <function>

<libpath>: Path to the compiled energy-library Energy.so

<profilepath>: Path to a profile calculated by spear with the -p flag

<mode>: Mode the analysis should run on. Choose between the following options

  • function - Analyses every function by itself. Takes no respect to calls
  • program - Analyses the whole program with respect to calls.
  • block- Analyses the whole program but will output the nodes of the programgraph for each function. Denotes the nodes with their energy usage.
  • instruction - Analyses the whole program and will output a JSON representing the programgraph down to the used instructions of each node.
  • graph- Analyses the program and will print out a DOT graph to stdout.

<format>: Outputformat to print after the calculation. Choose between the following options

  • json - Json-Format
  • plain - Human-readable plaintext

<strategy>: Analysis-strategy to calculate. Choose between the following options

  • worst - Worst case analysis. During the calculation the paths with the most energy consumption, will be used
  • best - Best case analysis. During the calculation the paths with the most energy consumption, will be used
  • average - Average case analysis. Attempts to balance the number of energy efficient and energy inefficient paths

<withcalls>: Determines if the analysis should use analyse called functions.

<loopbound>: A positive integer defining a value, loops will be over-approximated, if spear can't interfere the iteration count from a loop. E.g. in a while-loop

<llvmirpath> Path to compiled llvm-ir file, the analysis should run on

<function>: Name of the function to analysed. Can be used if only a single function should be analyzed. (Currently only used for graph generation)