C++ BranchInst::getDebugLoc方法代码示例

//.........这里部分代码省略.........
    Value *V = SimplifyInstruction(C);
    if (V && LI->replacementPreservesLCSSAForm(C, V)) {
      // If so, then delete the temporary instruction and stick the folded value
      // in the map.
      delete C;
      ValueMap[Inst] = V;
    } else {
      // Otherwise, stick the new instruction into the new block!
      C->setName(Inst->getName());
      C->insertBefore(LoopEntryBranch);
      ValueMap[Inst] = C;
    }
  }

  // Along with all the other instructions, we just cloned OrigHeader's
  // terminator into OrigPreHeader. Fix up the PHI nodes in each of OrigHeader's
  // successors by duplicating their incoming values for OrigHeader.
  TerminatorInst *TI = OrigHeader->getTerminator();
  for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
    for (BasicBlock::iterator BI = TI->getSuccessor(i)->begin();
         PHINode *PN = dyn_cast<PHINode>(BI); ++BI)
      PN->addIncoming(PN->getIncomingValueForBlock(OrigHeader), OrigPreheader);

  // Now that OrigPreHeader has a clone of OrigHeader's terminator, remove
  // OrigPreHeader's old terminator (the original branch into the loop), and
  // remove the corresponding incoming values from the PHI nodes in OrigHeader.
  LoopEntryBranch->eraseFromParent();

  // If there were any uses of instructions in the duplicated block outside the
  // loop, update them, inserting PHI nodes as required
  RewriteUsesOfClonedInstructions(OrigHeader, OrigPreheader, ValueMap);

  // NewHeader is now the header of the loop.
  L->moveToHeader(NewHeader);
  assert(L->getHeader() == NewHeader && "Latch block is our new header");


  // At this point, we've finished our major CFG changes.  As part of cloning
  // the loop into the preheader we've simplified instructions and the
  // duplicated conditional branch may now be branching on a constant.  If it is
  // branching on a constant and if that constant means that we enter the loop,
  // then we fold away the cond branch to an uncond branch.  This simplifies the
  // loop in cases important for nested loops, and it also means we don't have
  // to split as many edges.
  BranchInst *PHBI = cast<BranchInst>(OrigPreheader->getTerminator());
  assert(PHBI->isConditional() && "Should be clone of BI condbr!");
  if (!isa<ConstantInt>(PHBI->getCondition()) ||
      PHBI->getSuccessor(cast<ConstantInt>(PHBI->getCondition())->isZero())
          != NewHeader) {
    // The conditional branch can't be folded, handle the general case.
    // Update DominatorTree to reflect the CFG change we just made.  Then split
    // edges as necessary to preserve LoopSimplify form.
    if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>()) {
      // Since OrigPreheader now has the conditional branch to Exit block, it is
      // the dominator of Exit.
      DT->changeImmediateDominator(Exit, OrigPreheader);
      DT->changeImmediateDominator(NewHeader, OrigPreheader);

      // Update OrigHeader to be dominated by the new header block.
      DT->changeImmediateDominator(OrigHeader, OrigLatch);
    }

    // Right now OrigPreHeader has two successors, NewHeader and ExitBlock, and
    // thus is not a preheader anymore.
    // Split the edge to form a real preheader.
    BasicBlock *NewPH = SplitCriticalEdge(OrigPreheader, NewHeader, this);
    NewPH->setName(NewHeader->getName() + ".lr.ph");

    // Preserve canonical loop form, which means that 'Exit' should have only
    // one predecessor.
    BasicBlock *ExitSplit = SplitCriticalEdge(L->getLoopLatch(), Exit, this);
    ExitSplit->moveBefore(Exit);
  } else {
    // We can fold the conditional branch in the preheader, this makes things
    // simpler. The first step is to remove the extra edge to the Exit block.
    Exit->removePredecessor(OrigPreheader, true /*preserve LCSSA*/);
    BranchInst *NewBI = BranchInst::Create(NewHeader, PHBI);
    NewBI->setDebugLoc(PHBI->getDebugLoc());
    PHBI->eraseFromParent();

    // With our CFG finalized, update DomTree if it is available.
    if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>()) {
      // Update OrigHeader to be dominated by the new header block.
      DT->changeImmediateDominator(NewHeader, OrigPreheader);
      DT->changeImmediateDominator(OrigHeader, OrigLatch);
    }
  }

  assert(L->getLoopPreheader() && "Invalid loop preheader after loop rotation");
  assert(L->getLoopLatch() && "Invalid loop latch after loop rotation");

  // Now that the CFG and DomTree are in a consistent state again, try to merge
  // the OrigHeader block into OrigLatch.  This will succeed if they are
  // connected by an unconditional branch.  This is just a cleanup so the
  // emitted code isn't too gross in this common case.
  MergeBlockIntoPredecessor(OrigHeader, this);

  ++NumRotated;
  return true;
}