C++ SSATmp::getInstruction方法代码示例

void LinearScan::removeUnusedSpillsAux(Trace* trace) {
  IRInstruction::List& instList = trace->getInstructionList();
  for (IRInstruction::Iterator it = instList.begin();
       it != instList.end(); ) {
    IRInstruction::Iterator next = it; ++next;
    IRInstruction* inst = *it;
    if (inst->getOpcode() == Spill && inst->getDst()->getUseCount() == 0) {
      instList.erase(it);
      SSATmp* src = inst->getSrc(0);
      if (src->decUseCount() == 0) {
        Opcode srcOpc = src->getInstruction()->getOpcode();
        // Not all instructions are able to take noreg as its dest
        // reg.  We pick LdLoc and IncRef because they occur often.
        if (srcOpc == IncRef || srcOpc == LdLoc) {
          for (int locIndex = 0;
               locIndex < src->numNeededRegs();
               ++locIndex) {
            src->setReg(InvalidReg, locIndex);
          }
        }
      }
    }
    it = next;
  }
}

void LinearScan::removeUnusedSpills() {
  for (SlotInfo& slot : m_slots) {
    IRInstruction* spill = slot.m_spillTmp->getInstruction();
    if (spill->getDst()->getUseCount() == 0) {
      Block* block = spill->getBlock();
      block->erase(block->iteratorTo(spill));
      SSATmp* src = spill->getSrc(0);
      if (src->decUseCount() == 0) {
        Opcode srcOpc = src->getInstruction()->getOpcode();
        // Not all instructions are able to take noreg as its dest
        // reg.  We pick LdLoc and IncRef because they occur often.
        if (srcOpc == IncRef || srcOpc == LdLoc) {
          for (int i = 0, n = src->numNeededRegs(); i < n; ++i) {
            src->setReg(InvalidReg, i);
          }
        }
      }
    }
  }
}

void LinearScan::rematerializeAux(Trace* trace,
                                  SSATmp* curSp,
                                  SSATmp* curFp,
                                  std::vector<SSATmp*> localValues) {
  IRInstruction::List& instList = trace->getInstructionList();
  for (IRInstruction::Iterator it = instList.begin();
       it != instList.end();
       ++it) {
    IRInstruction* inst = *it;
    Opcode opc = inst->getOpcode();
    SSATmp* dst = inst->getDst();
    if (opc == DefFP || opc == FreeActRec) {
      curFp = dst;
      ASSERT(dst && dst->getReg() == rVmFp);
    }
    if (opc == Reload) {
      // s = Spill t0
      // t = Reload s
      SSATmp* spilledTmp = getSpilledTmp(dst);
      IRInstruction* spilledInst = spilledTmp->getInstruction();
      IRInstruction* newInst = NULL;
      if (spilledInst->isRematerializable() ||
          (spilledInst->getOpcode() == LdStack &&
           spilledInst->getSrc(0) == curSp)) {
        // XXX: could change <newInst> to the non-check version.
        // Rematerialize those rematerializable instructions (i.e.,
        // isRematerializable returns true) and LdStack.
        newInst = spilledInst->clone(m_irFactory);
        // The new instruction needn't have an exit label, because it is always
        // dominated by the original instruction.
        newInst->setLabel(NULL);
      } else {
        // Rematerialize LdLoc.
        std::vector<SSATmp*>::iterator pos =
          std::find(localValues.begin(),
                    localValues.end(),
                    canonicalize(spilledTmp));
        // Search for a local that stores the value of <spilledTmp>.
        if (pos != localValues.end()) {
          size_t locId = pos - localValues.begin();
          ASSERT(curFp != NULL);
          ConstInstruction constInst(curFp, Local(locId));
          IRInstruction* ldHomeInst =
            m_irFactory->cloneInstruction(&constInst);
          newInst = m_irFactory->ldLoc(m_irFactory->getSSATmp(ldHomeInst),
                                       dst->getType(),
                                       NULL);
        }
      }
      if (newInst) {
        newInst->setDst(dst);
        newInst->getDst()->setInstruction(newInst);
        *it = newInst;
        newInst->setParent(trace);
      }
    }

    // Updating <curSp> and <localValues>.
    if (dst && dst->getReg() == rVmSp) {
      // <inst> modifies the stack pointer.
      curSp = dst;
    }
    if (opc == LdLoc || opc == StLoc || opc == StLocNT) {
      // dst = LdLoc home
      // StLoc/StLocNT home, src
      int locId = getLocalIdFromHomeOpnd(inst->getSrc(0));
      SSATmp* localValue = (opc == LdLoc ? dst : inst->getSrc(1));
      if (int(localValues.size()) < locId + 1) {
        localValues.resize(locId + 1);
      }
      localValues[locId] = canonicalize(localValue);
    }

    if (inst->isControlFlowInstruction()) {
      LabelInstruction* label = inst->getLabel();
      if (label != NULL && label->getId() == inst->getId() + 1) {
        rematerializeAux(label->getTrace(), curSp, curFp, localValues);
      }
    }
  }
}

SSATmp* LinearScan::getSpilledTmp(SSATmp* tmp) {
  ASSERT(tmp->getInstruction()->getOpcode() == Reload);
  SSATmp* slot = tmp->getInstruction()->getSrc(0);
  ASSERT(slot->getInstruction()->getOpcode() == Spill);
  return slot->getInstruction()->getSrc(0);
}

void eliminateDeadCode(Trace* trace, IRFactory* irFactory) {
  IRInstruction::List wl; // worklist of live instructions
  Trace::List& exitTraces = trace->getExitTraces();
  // first mark all exit traces as unreachable by setting the id on
  // their labels to 0
  for (Trace::Iterator it = exitTraces.begin();
       it != exitTraces.end();
       it++) {
    Trace* trace = *it;
    trace->getLabel()->setId(DEAD);
  }

  // mark the essential instructions and add them to the initial
  // work list; also mark the exit traces that are reachable by
  // any control flow instruction in the main trace.
  initInstructions(trace, wl);
  for (Trace::Iterator it = exitTraces.begin();
       it != exitTraces.end();
       it++) {
    // only process those exit traces that are reachable from
    // the main trace
    Trace* trace = *it;
    if (trace->getLabel()->getId() != DEAD) {
      initInstructions(trace, wl);
    }
  }

  // process the worklist
  while (!wl.empty()) {
    IRInstruction* inst = wl.front();
    wl.pop_front();
    for (uint32 i = 0; i < inst->getNumSrcs(); i++) {
      SSATmp* src = inst->getSrc(i);
      if (src->getInstruction()->isDefConst()) {
        continue;
      }
      IRInstruction* srcInst = src->getInstruction();
      if (srcInst->getId() == DEAD) {
        srcInst->setId(LIVE);
        wl.push_back(srcInst);
      }
      // <inst> consumes <srcInst> which is an IncRef,
      // so we mark <srcInst> as REFCOUNT_CONSUMED.
      if (inst->consumesReference(i) && srcInst->getOpcode() == IncRef) {
        if (inst->getParent()->isMain() || !srcInst->getParent()->isMain()) {
          // <srcInst> is consumed from its own trace.
          srcInst->setId(REFCOUNT_CONSUMED);
        } else {
          // <srcInst> is consumed off trace.
          if (srcInst->getId() != REFCOUNT_CONSUMED) {
            // mark <srcInst> as REFCOUNT_CONSUMED_OFF_TRACE unless it is
            // also consumed from its own trace.
            srcInst->setId(REFCOUNT_CONSUMED_OFF_TRACE);
          }
        }
      }
    }
  }

  // Optimize IncRefs and DecRefs.
  optimizeRefCount(trace);
  for (Trace::Iterator it = exitTraces.begin(); it != exitTraces.end(); ++it) {
    optimizeRefCount(*it);
  }

  if (RuntimeOption::EvalHHIREnableSinking) {
    // Sink IncRefs consumed off trace.
    IRInstruction::List toSink;
    sinkIncRefs(trace, irFactory, toSink);
  }

  // now remove instructions whose id == DEAD
  removeDeadInstructions(trace);
  for (Trace::Iterator it = exitTraces.begin(); it != exitTraces.end(); it++) {
    removeDeadInstructions(*it);
  }

  // If main trace ends with an unconditional jump, copy the target of
  // the jump to the end of the trace
  IRInstruction::List& instList = trace->getInstructionList();
  IRInstruction::Iterator lastInst = instList.end();
  lastInst--; // go back to the last instruction
  IRInstruction* jmpInst = *lastInst;
  if (jmpInst->getOpcode() == Jmp_) {
    Trace* targetTrace = jmpInst->getLabel()->getTrace();
    IRInstruction::List& targetInstList = targetTrace->getInstructionList();
    IRInstruction::Iterator instIter = targetInstList.begin();
    instIter++; // skip over label
    // update the parent trace of the moved instructions
    for (IRInstruction::Iterator it = instIter;
         it != targetInstList.end();
         ++it) {
      (*it)->setParent(trace);
    }
    instList.splice(lastInst, targetInstList, instIter, targetInstList.end());
    // delete the jump instruction
    instList.erase(lastInst);
  }

  // If main trace ends with a conditional jump with no side-effects on exit,
//.........这里部分代码省略.........

void LinearScan::rematerializeAux() {
  struct State {
    SSATmp *sp, *fp;
    std::vector<SSATmp*> values;
  };
  StateVector<Block, State*> states(m_irFactory, nullptr);
  SCOPE_EXIT { for (State* s : states) delete s; };
  SSATmp* curSp = nullptr;
  SSATmp* curFp = nullptr;
  std::vector<SSATmp*> localValues;
  auto killLocal = [&](IRInstruction& inst, unsigned src) {
    if (src < inst.getNumSrcs()) {
      unsigned loc = inst.getSrc(src)->getValInt();
      if (loc < localValues.size()) localValues[loc] = nullptr;
    }
  };
  auto setLocal = [&](unsigned loc, SSATmp* value) {
    // Note that when we implement inlining, we will need to deal
    // with the new local id space of the inlined function.
    if (loc >= localValues.size()) localValues.resize(loc + 1);
    localValues[loc] = canonicalize(value);
  };
  // Search for a local that stores <value>
  auto findLocal = [&](SSATmp* value) -> int {
    auto pos = std::find(localValues.begin(), localValues.end(),
                         canonicalize(value));
    return pos != localValues.end() ? pos - localValues.begin() : -1;
  };
  // save the current state for future use by block; merge if necessary.
  auto saveState = [&](Block* block) {
    if (State* state = states[block]) {
      // merge with saved state
      assert(curFp == state->fp);
      if (curSp != state->sp) state->sp = nullptr;
      for (unsigned i = 0; i < state->values.size(); ++i) {
        if (i >= localValues.size() || localValues[i] != state->values[i]) {
          state->values[i] = nullptr;
        }
      }
    } else {
      // snapshot state for use at target.
      state = states[block] = new State;
      state->sp = curSp;
      state->fp = curFp;
      state->values = localValues;
    }
  };

  for (Block* block : m_blocks) {
    if (State* state = states[block]) {
      states[block] = nullptr;
      localValues = state->values;
      curSp = state->sp;
      curFp = state->fp;
      delete state;
    }
    for (auto it = block->begin(); it != block->end(); ++it) {
      IRInstruction& inst = *it;
      Opcode opc = inst.getOpcode();
      if (opc == DefFP || opc == FreeActRec) {
        assert(inst.getDst()->getReg() == rVmFp);
        curFp = inst.getDst();
      }
      else if (opc == Reload) {
        // s = Spill t0
        // t = Reload s
        SSATmp* dst = inst.getDst();
        SSATmp* spilledTmp = getSpilledTmp(dst);
        IRInstruction* spilledInst = spilledTmp->getInstruction();
        IRInstruction* newInst = NULL;
        if (spilledInst->isRematerializable() ||
            (spilledInst->getOpcode() == LdStack &&
             spilledInst->getSrc(0) == curSp)) {
          // XXX: could change <newInst> to the non-check version.
          // Rematerialize those rematerializable instructions (i.e.,
          // isRematerializable returns true) and LdStack.
          newInst = spilledInst->clone(m_irFactory);
          // The new instruction needn't have an exit label; it must always
          // be dominated by the original instruction because reloads are
          // inserted just before uses, which must be dominated by the
          // original (spilled) def.
          newInst->setTaken(nullptr);
        } else if (curFp) {
          // Rematerialize LdLoc.
          int loc = findLocal(spilledTmp);
          if (loc != -1) {
            LocalId localId(loc);
            newInst = m_irFactory->gen(LdLoc, dst->getType(), &localId, curFp);
          }
        }
        if (newInst) {
          UNUSED Type oldType = dst->getType();
          newInst->setDst(dst);
          dst->setInstruction(newInst);
          assert(outputType(newInst) == oldType);
          auto* block = inst.getBlock();
          auto newIt = block->insert(it, newInst);
          block->erase(it);
          it = newIt;
        }
//.........这里部分代码省略.........

void LinearScan::rematerializeAux(Trace* trace,
                                  SSATmp* curSp,
                                  SSATmp* curFp,
                                  std::vector<SSATmp*> localValues) {
  IRInstruction::List& instList = trace->getInstructionList();
  for (IRInstruction::Iterator it = instList.begin();
       it != instList.end();
       ++it) {
    IRInstruction* inst = *it;
    Opcode opc = inst->getOpcode();
    SSATmp* dst = inst->getDst();
    if (opc == DefFP || opc == FreeActRec) {
      curFp = dst;
      assert(dst && dst->getReg() == rVmFp);
    }
    if (opc == Reload) {
      // s = Spill t0
      // t = Reload s
      SSATmp* spilledTmp = getSpilledTmp(dst);
      IRInstruction* spilledInst = spilledTmp->getInstruction();
      IRInstruction* newInst = NULL;
      if (spilledInst->isRematerializable() ||
          (spilledInst->getOpcode() == LdStack &&
           spilledInst->getSrc(0) == curSp)) {
        // XXX: could change <newInst> to the non-check version.
        // Rematerialize those rematerializable instructions (i.e.,
        // isRematerializable returns true) and LdStack.
        newInst = spilledInst->clone(m_irFactory);
        // The new instruction needn't have an exit label, because it is always
        // dominated by the original instruction.
        newInst->setLabel(NULL);
      } else {
        // Rematerialize LdLoc.
        std::vector<SSATmp*>::iterator pos =
          std::find(localValues.begin(),
                    localValues.end(),
                    canonicalize(spilledTmp));
        // Search for a local that stores the value of <spilledTmp>.
        if (pos != localValues.end()) {
          size_t locId = pos - localValues.begin();
          assert(curFp != NULL);
          ConstInstruction constInst(curFp, Local(locId));
          IRInstruction* ldHomeInst =
            m_irFactory->cloneInstruction(&constInst);
          newInst = m_irFactory->gen(LdLoc,
                                     dst->getType(),
                                     m_irFactory->getSSATmp(ldHomeInst));
        }
      }
      if (newInst) {
        UNUSED Type::Tag oldType = dst->getType();
        newInst->setDst(dst);
        dst->setInstruction(newInst);
        assert(outputType(newInst) == oldType);
        *it = newInst;
        newInst->setParent(trace);
      }
    }

    // Updating <curSp> and <localValues>.
    if (dst && dst->getReg() == rVmSp) {
      // <inst> modifies the stack pointer.
      curSp = dst;
    }
    if (opc == LdLoc || opc == StLoc || opc == StLocNT) {
      // dst = LdLoc home
      // StLoc/StLocNT home, src
      int locId = getLocalIdFromHomeOpnd(inst->getSrc(0));
      // Note that when we implement inlining, we will need to deal
      // with the new local id space of the inlined function.
      SSATmp* localValue = (opc == LdLoc ? dst : inst->getSrc(1));
      if (int(localValues.size()) < locId + 1) {
        localValues.resize(locId + 1);
      }
      localValues[locId] = canonicalize(localValue);
    }
    // Other instructions that may have side effects on locals must
    // kill the local variable values.
    else if (opc == IterInit) {
      int valLocId = inst->getSrc(3)->getConstValAsInt();
      localValues[valLocId] = NULL;
      if (inst->getNumSrcs() == 5) {
        int keyLocId = inst->getSrc(4)->getConstValAsInt();
        localValues[keyLocId] = NULL;
      }
    } else if (opc == IterNext) {
      int valLocId = inst->getSrc(2)->getConstValAsInt();
      localValues[valLocId] = NULL;
      if (inst->getNumSrcs() == 4) {
        int keyLocId = inst->getSrc(3)->getConstValAsInt();
        localValues[keyLocId] = NULL;
      }
    }

    if (inst->isControlFlowInstruction()) {
      LabelInstruction* label = inst->getLabel();
      if (label != NULL && label->getId() == inst->getId() + 1) {
        rematerializeAux(label->getParent(), curSp, curFp, localValues);
      }
    }
//.........这里部分代码省略.........

void eliminateDeadCode(Trace* trace, IRFactory* irFactory) {
  auto removeEmptyExitTraces = [&] {
    trace->getExitTraces().remove_if([](Trace* exit) {
      return exit->getBlocks().empty();
    });
  };

  // kill unreachable code and remove any traces that are now empty
  BlockList blocks = removeUnreachable(trace, irFactory);
  removeEmptyExitTraces();

  // mark the essential instructions and add them to the initial
  // work list; this will also mark reachable exit traces. All
  // other instructions marked dead.
  DceState state(irFactory, DceFlags());
  WorkList wl = initInstructions(trace, blocks, state, irFactory);

  // process the worklist
  while (!wl.empty()) {
    auto* inst = wl.front();
    wl.pop_front();
    for (uint32_t i = 0; i < inst->getNumSrcs(); i++) {
      SSATmp* src = inst->getSrc(i);
      if (src->getInstruction()->getOpcode() == DefConst) {
        continue;
      }
      IRInstruction* srcInst = src->getInstruction();
      if (state[srcInst].isDead()) {
        state[srcInst].setLive();
        wl.push_back(srcInst);
      }
      // <inst> consumes <srcInst> which is an IncRef, so we mark <srcInst> as
      // REFCOUNT_CONSUMED. If the source instruction is a GuardType and guards
      // to a maybeCounted type, we need to trace through to the source for
      // refcounting purposes.
      while (srcInst->getOpcode() == GuardType &&
             srcInst->getTypeParam().maybeCounted()) {
        srcInst = srcInst->getSrc(0)->getInstruction();
      }
      if (inst->consumesReference(i) && srcInst->getOpcode() == IncRef) {
        if (inst->getTrace()->isMain() || !srcInst->getTrace()->isMain()) {
          // <srcInst> is consumed from its own trace.
          state[srcInst].setCountConsumed();
        } else {
          // <srcInst> is consumed off trace.
          if (!state[srcInst].countConsumed()) {
            // mark <srcInst> as REFCOUNT_CONSUMED_OFF_TRACE unless it is
            // also consumed from its own trace.
            state[srcInst].setCountConsumedOffTrace();
          }
        }
      }
    }
  }

  // Optimize IncRefs and DecRefs.
  forEachTrace(trace, [&](Trace* t) { optimizeRefCount(t, state); });

  if (RuntimeOption::EvalHHIREnableSinking) {
    // Sink IncRefs consumed off trace.
    sinkIncRefs(trace, irFactory, state);
  }

  // now remove instructions whose id == DEAD
  removeDeadInstructions(trace, state);
  for (Trace* exit : trace->getExitTraces()) {
    removeDeadInstructions(exit, state);
  }

  // and remove empty exit traces
  removeEmptyExitTraces();
}