Method FullyUnroll

source/opt/loop_unroller.cpp:592–626

Fully unroll the loop by partially unrolling it by the number of loop iterations minus one for the body already accounted for.

// Fully unroll the loop by partially unrolling it by the number of loop
// iterations minus one for the body already accounted for.
bool LoopUnrollerUtilsImpl::FullyUnroll(Loop* loop) {
  // We unroll the loop by number of iterations in the loop.
  if (!Unroll(loop, number_of_loop_iterations_)) {
    return false;
  }

  // The first condition block is preserved until now so it can be copied.
  if (!FoldConditionBlock(loop_condition_block_, 1)) {
    return false;
  }

  // Delete the OpLoopMerge and remove the backedge to the header.
  CloseUnrolledLoop(loop);

  // Mark the loop for later deletion. This allows us to preserve the loop
  // iterators but still disregard dead loops.
  loop->MarkLoopForRemoval();

  // If the loop has a parent add the new blocks to the parent.
  if (loop->GetParent()) {
    AddBlocksToLoop(loop->GetParent());
  }

  // Add the blocks to the function.
  AddBlocksToFunction(loop->GetMergeBlock());

  ReplaceInductionUseWithFinalValue(loop);

  RemoveDeadInstructions();
  // Invalidate all analyses.
  context_->InvalidateAnalysesExceptFor(
      IRContext::Analysis::kAnalysisLoopAnalysis |
      IRContext::Analysis::kAnalysisDefUse);
  return true;
}

void LoopUnrollerUtilsImpl::KillDebugDeclares(BasicBlock* bb) {
  // We cannot kill an instruction inside BasicBlock::ForEachInst()