[LLVMdev] LLVM Pass usable by all types of Passes

[Xin Tong]

Hi

I am modifying LLVM to enable runtime feedback directed optimizations. I
have modified the instrumentation part of LLVM to keep instrumentation data
in some pre-setup structures in memory and use the JIT to recompile some of
the hot functions with profiling information.

I need an analysis pass which loads the profiling data in memory and can be
used by different optimization passes in LLVM, e.g. loopunroller, inliner,
basicblockplacement, etc . Currently, I have an analysis pass that derives
from a functionpass that loads the instrumentation data in memory and the
basicblockplacement pass can then use that data as guide to place the
blocks.

However, when i add the same pass as an analysis dependence to the
loopunroller, i get some kind of infinite loop when the passes are
scheduled here.

I would like to know is it allowed in LLVM to have a LoopPass depending on
a FunctionPass ?

/// Schedule pass P for execution. Make sure that passes required by
/// P are run before P is run. Update analysis info maintained by
/// the manager. Remove dead passes. This is a recursive function.
void PMTopLevelManager::schedulePass(Pass *P) {

        ....

        else if (P->getPotentialPassManagerType () >
                 AnalysisPass->getPotentialPassManagerType()) {
      */// INFINITE LOOP HERE. maybe because checkAnalysis  is set to true
for some reasons not very clear based on the comments. *
    printf("Analysis Pass Name is %s\n", AnalysisPass->getPassName());
          // Schedule analysis pass that is managed by a new manager.
          schedulePass(AnalysisPass);
          // Recheck analysis passes to ensure that required analyses that
          // are already checked are still available.
          checkAnalysis = true;
 };

Thank you,
Trent
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