[PATCH] D106426: [FuncSpec] Support specialising recursive functions

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer created this revision.
SjoerdMeijer added reviewers: ChuanqiXu, chill, jaykang10, fhahn.
Herald added subscribers: snehasish, ormris, hiraditya.
SjoerdMeijer requested review of this revision.
Herald added a project: LLVM.

This adds support for specialising recursive functions. For example, consider this program:

  int Global = 1;
  void recursiveFunc(int *arg) {
    if (*arg < 4) {
      print(*arg);
      recursiveFunc(*arg + 1);
    }
  }
  void main() {
    recursiveFunc(&Global);
  }

after 3 iterations of function specialisation, followed by inlining of the specialised versions of `recursiveFunc`, the main function looks like this:

  void main() {
      print(1);
      print(2);
      print(3);
    }

To support this, the following has been added:

- Update the solver and state of the new specialised functions,
- An optimisation to propagate constant stack values after each iteration of function specialisation, which is necessary for the next iteration to recognise the constant values and trigger.


https://reviews.llvm.org/D106426

Files:
  llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
  llvm/lib/Transforms/Utils/SCCPSolver.cpp
  llvm/test/Transforms/FunctionSpecialization/function-specialization-recursive.ll
  llvm/test/Transforms/FunctionSpecialization/function-specialization-recursive2.ll
  llvm/test/Transforms/FunctionSpecialization/function-specialization-recursive3.ll
  llvm/test/Transforms/FunctionSpecialization/function-specialization-recursive4.ll
  llvm/test/Transforms/FunctionSpecialization/function-specialization3.ll

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