C++ SSAUpdater::RewriteUseAfterInsertions方法代码示例

/// Handle a rare case where the disintegrated nodes instructions
/// no longer dominate all their uses. Not sure if this is really nessasary
void StructurizeCFG::rebuildSSA() {
  SSAUpdater Updater;
  for (const auto &BB : ParentRegion->blocks())
    for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
         II != IE; ++II) {

      bool Initialized = false;
      for (auto I = II->use_begin(), E = II->use_end(); I != E;) {
        Use &U = *I++;
        Instruction *User = cast<Instruction>(U.getUser());
        if (User->getParent() == BB) {
          continue;

        } else if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
          if (UserPN->getIncomingBlock(U) == BB)
            continue;
        }

        if (DT->dominates(II, User))
          continue;

        if (!Initialized) {
          Value *Undef = UndefValue::get(II->getType());
          Updater.Initialize(II->getType(), "");
          Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
          Updater.AddAvailableValue(BB, II);
          Initialized = true;
        }
        Updater.RewriteUseAfterInsertions(U);
      }
    }
}

void WebAssemblyLowerEmscriptenEHSjLj::rebuildSSA(Function &F) {
  DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
  DT.recalculate(F); // CFG has been changed
  SSAUpdater SSA;
  for (BasicBlock &BB : F) {
    for (Instruction &I : BB) {
      for (auto UI = I.use_begin(), UE = I.use_end(); UI != UE;) {
        Use &U = *UI;
        ++UI;
        SSA.Initialize(I.getType(), I.getName());
        SSA.AddAvailableValue(&BB, &I);
        Instruction *User = cast<Instruction>(U.getUser());
        if (User->getParent() == &BB)
          continue;

        if (PHINode *UserPN = dyn_cast<PHINode>(User))
          if (UserPN->getIncomingBlock(U) == &BB)
            continue;

        if (DT.dominates(&I, User))
          continue;
        SSA.RewriteUseAfterInsertions(U);
      }
    }
  }
}

/// Handle a rare case where the disintegrated nodes instructions
/// no longer dominate all their uses. Not sure if this is really nessasary
void StructurizeCFG::rebuildSSA() {
  SSAUpdater Updater;
  for (BasicBlock *BB : ParentRegion->blocks())
    for (Instruction &I : *BB) {
      bool Initialized = false;
      // We may modify the use list as we iterate over it, so be careful to
      // compute the next element in the use list at the top of the loop.
      for (auto UI = I.use_begin(), E = I.use_end(); UI != E;) {
        Use &U = *UI++;
        Instruction *User = cast<Instruction>(U.getUser());
        if (User->getParent() == BB) {
          continue;
        } else if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
          if (UserPN->getIncomingBlock(U) == BB)
            continue;
        }

        if (DT->dominates(&I, User))
          continue;

        if (!Initialized) {
          Value *Undef = UndefValue::get(I.getType());
          Updater.Initialize(I.getType(), "");
          Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
          Updater.AddAvailableValue(BB, &I);
          Initialized = true;
        }
        Updater.RewriteUseAfterInsertions(U);
      }
    }
}

/// Handle a rare case where the disintegrated nodes instructions
/// no longer dominate all their uses. Not sure if this is really nessasary
void StructurizeCFG::rebuildSSA() {
  SSAUpdater Updater;
  for (Region::block_iterator I = ParentRegion->block_begin(),
                              E = ParentRegion->block_end();
       I != E; ++I) {

    BasicBlock *BB = *I;
    for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
         II != IE; ++II) {

      bool Initialized = false;
      for (Use *I = &II->use_begin().getUse(), *Next; I; I = Next) {

        Next = I->getNext();

        Instruction *User = cast<Instruction>(I->getUser());
        if (User->getParent() == BB) {
          continue;

        } else if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
          if (UserPN->getIncomingBlock(*I) == BB)
            continue;
        }

        if (DT->dominates(II, User))
          continue;

        if (!Initialized) {
          Value *Undef = UndefValue::get(II->getType());
          Updater.Initialize(II->getType(), "");
          Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
          Updater.AddAvailableValue(BB, II);
          Initialized = true;
        }
        Updater.RewriteUseAfterInsertions(*I);
      }
    }
  }
}

//.........这里部分代码省略.........
          EdgeTargetsFunclet = (CRI->getCatchSwitchParentPad() == FuncletToken);
        } else {
          ColorVector &IncomingColors = BlockColors[IncomingBlock];
          assert(!IncomingColors.empty() && "Block not colored!");
          assert((IncomingColors.size() == 1 ||
                  llvm::all_of(IncomingColors,
                               [&](BasicBlock *Color) {
                                 return Color != FuncletPadBB;
                               })) &&
                 "Cloning should leave this funclet's blocks monochromatic");
          EdgeTargetsFunclet = (IncomingColors.front() == FuncletPadBB);
        }
        if (IsForOldBlock != EdgeTargetsFunclet)
          continue;
        PN->removeIncomingValue(IncomingBlock, /*DeletePHIIfEmpty=*/false);
        // Revisit the next entry.
        --PredIdx;
        --PredEnd;
      }
    };

    for (auto &BBMapping : Orig2Clone) {
      BasicBlock *OldBlock = BBMapping.first;
      BasicBlock *NewBlock = BBMapping.second;
      for (PHINode &OldPN : OldBlock->phis()) {
        UpdatePHIOnClonedBlock(&OldPN, /*IsForOldBlock=*/true);
      }
      for (PHINode &NewPN : NewBlock->phis()) {
        UpdatePHIOnClonedBlock(&NewPN, /*IsForOldBlock=*/false);
      }
    }

    // Check to see if SuccBB has PHI nodes. If so, we need to add entries to
    // the PHI nodes for NewBB now.
    for (auto &BBMapping : Orig2Clone) {
      BasicBlock *OldBlock = BBMapping.first;
      BasicBlock *NewBlock = BBMapping.second;
      for (BasicBlock *SuccBB : successors(NewBlock)) {
        for (PHINode &SuccPN : SuccBB->phis()) {
          // Ok, we have a PHI node.  Figure out what the incoming value was for
          // the OldBlock.
          int OldBlockIdx = SuccPN.getBasicBlockIndex(OldBlock);
          if (OldBlockIdx == -1)
            break;
          Value *IV = SuccPN.getIncomingValue(OldBlockIdx);

          // Remap the value if necessary.
          if (auto *Inst = dyn_cast<Instruction>(IV)) {
            ValueToValueMapTy::iterator I = VMap.find(Inst);
            if (I != VMap.end())
              IV = I->second;
          }

          SuccPN.addIncoming(IV, NewBlock);
        }
      }
    }

    for (ValueToValueMapTy::value_type VT : VMap) {
      // If there were values defined in BB that are used outside the funclet,
      // then we now have to update all uses of the value to use either the
      // original value, the cloned value, or some PHI derived value.  This can
      // require arbitrary PHI insertion, of which we are prepared to do, clean
      // these up now.
      SmallVector<Use *, 16> UsesToRename;

      auto *OldI = dyn_cast<Instruction>(const_cast<Value *>(VT.first));
      if (!OldI)
        continue;
      auto *NewI = cast<Instruction>(VT.second);
      // Scan all uses of this instruction to see if it is used outside of its
      // funclet, and if so, record them in UsesToRename.
      for (Use &U : OldI->uses()) {
        Instruction *UserI = cast<Instruction>(U.getUser());
        BasicBlock *UserBB = UserI->getParent();
        ColorVector &ColorsForUserBB = BlockColors[UserBB];
        assert(!ColorsForUserBB.empty());
        if (ColorsForUserBB.size() > 1 ||
            *ColorsForUserBB.begin() != FuncletPadBB)
          UsesToRename.push_back(&U);
      }

      // If there are no uses outside the block, we're done with this
      // instruction.
      if (UsesToRename.empty())
        continue;

      // We found a use of OldI outside of the funclet.  Rename all uses of OldI
      // that are outside its funclet to be uses of the appropriate PHI node
      // etc.
      SSAUpdater SSAUpdate;
      SSAUpdate.Initialize(OldI->getType(), OldI->getName());
      SSAUpdate.AddAvailableValue(OldI->getParent(), OldI);
      SSAUpdate.AddAvailableValue(NewI->getParent(), NewI);

      while (!UsesToRename.empty())
        SSAUpdate.RewriteUseAfterInsertions(*UsesToRename.pop_back_val());
    }
  }
}