Replace size method call of containers to empty method where appropriate

[xazax.hun]

Summary

This patch was generated by a clang tidy checker that is being open sourced.
The documentation of that checker is the following:

/ The emptiness of a container should be checked using the empty method
/ instead of the size method. It is not guaranteed that size is a
/ constant-time function, and it is generally more efficient and also shows
/ clearer intent to use empty. Furthermore some containers may implement the
/ empty method but not implement the size method. Using empty whenever
/ possible makes it easier to switch to another container in the future.

[alexfh]

The patch looks good, but it would be nice to get an approval from the actual code owners.

[dblaikie]

This looks reasonable enough that I'm willing to sign off on it. We can do anything further in post-commit review.

[alexfh]

Gábor, do you have commit rights or you need someone to land the patch for you?

[xazax.hun]

I need someone to commit this.

Thanks,
Gábor

[alexfh]

Committed revision 226161.

Thanks for the patch!

lib/CodeGen/SelectionDAG/TargetLowering.cpp

   }
 
   // If we have multiple alternative constraints, select the best alternative.
-  if (ConstraintOperands.size()) {
+  if (!ConstraintOperands.empty()) {
     if (maCount) {
       unsigned bestMAIndex = 0;
       int bestWeight = -1;

lib/CodeGen/UnreachableBlockElim.cpp

     DeadBlocks[i]->eraseFromParent();
   }
 
-  return DeadBlocks.size();
+  return !DeadBlocks.empty();
 }
 
 

 
   F.RenumberBlocks();
 
-  return (DeadBlocks.size() || ModifiedPHI);
+  return (!DeadBlocks.empty() || ModifiedPHI);
 }

lib/MC/MCMachOStreamer.cpp

   if (!getAssembler().getBackend().hasDataInCodeSupport())
     return;
   std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
-  assert(Regions.size() && "Mismatched .end_data_region!");
+  assert(!Regions.empty() && "Mismatched .end_data_region!");
   DataRegionData &Data = Regions.back();
   assert(!Data.End && "Mismatched .end_data_region!");
   // Create a temporary label to mark the end of the data region.

lib/MC/MCParser/AsmParser.cpp

   MCAsmMacroParameters Parameters;
   while (getLexer().isNot(AsmToken::EndOfStatement)) {
 
-    if (Parameters.size() && Parameters.back().Vararg)
+    if (!Parameters.empty() && Parameters.back().Vararg)
       return Error(Lexer.getLoc(),
                    "Vararg parameter '" + Parameters.back().Name +
                    "' should be last one in the list of parameters.");

lib/ProfileData/CoverageMapping.cpp

       while (!ActiveRegions.empty() &&
              ActiveRegions.back()->endLoc() <= Region.startLoc())
         popRegion();
-      if (Segments.size() && Segments.back().Line == Region.LineStart &&
+      if (!Segments.empty() && Segments.back().Line == Region.LineStart &&
           Segments.back().Col == Region.ColumnStart) {
         if (Region.Kind != coverage::CounterMappingRegion::SkippedRegion)
           Segments.back().addCount(Region.ExecutionCount);

lib/TableGen/Record.cpp

   std::string Result = "(" + Val->getAsString();
   if (!ValName.empty())
     Result += ":" + ValName;
-  if (Args.size()) {
+  if (!Args.empty()) {
     Result += " " + Args[0]->getAsString();
     if (!ArgNames[0].empty()) Result += ":$" + ArgNames[0];
     for (unsigned i = 1, e = Args.size(); i != e; ++i) {

lib/TableGen/TGParser.cpp

   unsigned int ArgN = 0;
   if (ArgsRec && !EltTy) {
     const std::vector<Init *> &TArgs = ArgsRec->getTemplateArgs();
-    if (!TArgs.size()) {
+    if (TArgs.empty()) {
       TokError("template argument provided to non-template class");
       return std::vector<Init*>();
     }

lib/Transforms/Vectorize/BBVectorize.cpp

             CostSavings, FixedOrder)) continue;
 
         // J is a candidate for merging with I.
-        if (!PairableInsts.size() ||
+        if (PairableInsts.empty() ||
              PairableInsts[PairableInsts.size()-1] != I) {
           PairableInsts.push_back(I);
         }

lib/Transforms/Vectorize/LoopVectorize.cpp

   }
 
   // We can only vectorize innermost loops.
-  if (TheLoop->getSubLoopsVector().size()) {
+  if (!TheLoop->getSubLoopsVector().empty()) {
     emitAnalysis(Report() << "loop is not the innermost loop");
     return false;
   }

       if (I->getType()->isPointerTy() && isConsecutivePtr(I))
         Worklist.insert(Worklist.end(), I->op_begin(), I->op_end());
 
-  while (Worklist.size()) {
+  while (!Worklist.empty()) {
     Instruction *I = dyn_cast<Instruction>(Worklist.back());
     Worklist.pop_back();
 

lib/Transforms/Vectorize/SLPVectorizer.cpp

 
   // We only vectorize tiny trees if it is fully vectorizable.
   if (VectorizableTree.size() < 3 && !isFullyVectorizableTinyTree()) {
-    if (!VectorizableTree.size()) {
+    if (VectorizableTree.empty()) {
       assert(!ExternalUses.size() && "We should not have any external users");
     }
     return INT_MAX;

utils/TableGen/AsmMatcherEmitter.cpp

      << " bool matchingInlineAsm,\n"
      << "                                unsigned VariantID = 0);\n";
 
-  if (Info.OperandMatchInfo.size()) {
+  if (!Info.OperandMatchInfo.empty()) {
     OS << "\n  enum OperandMatchResultTy {\n";
     OS << "    MatchOperand_Success,    // operand matched successfully\n";
     OS << "    MatchOperand_NoMatch,    // operand did not match\n";

   OS << "  return Match_MissingFeature;\n";
   OS << "}\n\n";
 
-  if (Info.OperandMatchInfo.size())
+  if (!Info.OperandMatchInfo.empty())
     emitCustomOperandParsing(OS, Target, Info, ClassName, StringTable,
                              MaxMnemonicIndex);
 

utils/TableGen/AsmWriterEmitter.cpp

     return;
   }
 
-  if (MCOpPredicates.size())
+  if (!MCOpPredicates.empty())
     O << "static bool " << Target.getName() << ClassName
       << "ValidateMCOperand(\n"
       << "       const MCOperand &MCOp, unsigned PredicateIndex);\n";

   }    
   O << "}\n\n";
 
-  if (MCOpPredicates.size()) {
+  if (!MCOpPredicates.empty()) {
     O << "static bool " << Target.getName() << ClassName
       << "ValidateMCOperand(\n"
       << "       const MCOperand &MCOp, unsigned PredicateIndex) {\n"

utils/TableGen/CodeEmitterGen.cpp

     /// generated emitter, skip it.
     while (NumberedOp < NumberOps &&
            (CGI.Operands.isFlatOperandNotEmitted(NumberedOp) ||
-              (NamedOpIndices.size() && NamedOpIndices.count(
+              (!NamedOpIndices.empty() && NamedOpIndices.count(
                 CGI.Operands.getSubOperandNumber(NumberedOp).first)))) {
       ++NumberedOp;
 

utils/TableGen/CodeGenMapTable.cpp

     std::vector<Record*> ColInstrs = MapTable[CurInstr];
     std::string OutStr("");
     unsigned RelExists = 0;
-    if (ColInstrs.size()) {
+    if (!ColInstrs.empty()) {
       for (unsigned j = 0; j < NumCol; j++) {
         if (ColInstrs[j] != nullptr) {
           RelExists = 1;

   std::vector<Record*> InstrMapVec;
   InstrMapVec = Records.getAllDerivedDefinitions("InstrMapping");
 
-  if (!InstrMapVec.size())
+  if (InstrMapVec.empty())
     return;
 
   OS << "#ifdef GET_INSTRMAP_INFO\n";

utils/TableGen/DFAPacketizerEmitter.cpp

           current->canAddInsnClass(InsnClass)) {
         const State *NewState;
         current->AddInsnClass(InsnClass, NewStateResources);
-        assert(NewStateResources.size() && "New states must be generated");
+        assert(!NewStateResources.empty() && "New states must be generated");
 
         //
         // If we have seen this state before, then do not create a new state.

utils/TableGen/FixedLenDecoderEmitter.cpp

   // Starts by inheriting our parent filter chooser's filter bit values.
   std::vector<bit_value_t> BitValueArray(Owner->FilterBitValues);
 
-  if (VariableInstructions.size()) {
+  if (!VariableInstructions.empty()) {
     // Conservatively marks each segment position as BIT_UNSET.
     for (unsigned bitIndex = 0; bitIndex < NumBits; ++bitIndex)
       BitValueArray[StartBit + bitIndex] = BIT_UNSET;

 // Returns the number of fanout produced by the filter.  More fanout implies
 // the filter distinguishes more categories of instructions.
 unsigned Filter::usefulness() const {
-  if (VariableInstructions.size())
+  if (!VariableInstructions.empty())
     return FilteredInstructions.size();
   else
     return FilteredInstructions.size() + 1;

       unsigned NumberOps = CGI.Operands.size();
       while (NumberedOp < NumberOps &&
              (CGI.Operands.isFlatOperandNotEmitted(NumberedOp) ||
-              (NamedOpIndices.size() && NamedOpIndices.count(
+              (!NamedOpIndices.empty() && NamedOpIndices.count(
                 CGI.Operands.getSubOperandNumber(NumberedOp).first))))
         ++NumberedOp;
 

utils/TableGen/SubtargetEmitter.cpp

     OS << "}\n";
 
     std::vector<Record*> BPs = PI->ItinsDef->getValueAsListOfDefs("BP");
-    if (BPs.size()) {
+    if (!BPs.empty()) {
       OS << "\n// Pipeline forwarding pathes for itineraries \"" << Name
          << "\"\n" << "namespace " << Name << "Bypass {\n";
 

utils/TableGen/X86RecognizableInstr.cpp

   assert(numOperands <= X86_MAX_OPERANDS && "X86_MAX_OPERANDS is not large enough");
 
   for (unsigned operandIndex = 0; operandIndex < numOperands; ++operandIndex) {
-    if (OperandList[operandIndex].Constraints.size()) {
+    if (!OperandList[operandIndex].Constraints.empty()) {
       const CGIOperandList::ConstraintInfo &Constraint =
         OperandList[operandIndex].Constraints[0];
       if (Constraint.isTied()) {