[NFC] Revert SmallVector<T> -> SmallVector<T, N> fixes

With the change to include `SmallVector.h` directly in `LLVM.h` rather
than forward declaring in the only case it matters (ie. Clang <= 5),
these fixes are no longer needed. Since defaulted version is preferred
when there's no better choice (which is presumably the case if that's
how they were originally added), use it instead. Some uses were instead
changed to add `llvm::` so remove that too.

Author: bnbarham

lib/AST/RequirementMachine/ConcreteContraction.cpp

@@ -301,7 +301,7 @@ Optional<Type> ConcreteContraction::substTypeParameterRec(
 
     // An unresolved DependentMemberType stores an identifier. Handle this
     // by performing a name lookup into the base type.
-    SmallVector<TypeDecl *, 2> concreteDecls;
+    SmallVector<TypeDecl *> concreteDecls;
     lookupConcreteNestedType(*substBaseType, memberType->getName(), concreteDecls);
 
     auto *typeDecl = findBestConcreteNestedType(concreteDecls);

lib/AST/Type.cpp

@@ -882,7 +882,7 @@ Type TypeBase::lookThroughAllOptionalTypes(SmallVectorImpl<Type> &optionals){
 }
 
 unsigned int TypeBase::getOptionalityDepth() {
-  SmallVector<Type, 4> types;
+  SmallVector<Type> types;
   lookThroughAllOptionalTypes(types);
   return types.size();
 }

lib/ClangImporter/ClangDerivedConformances.cpp

@@ -88,7 +88,7 @@ static ValueDecl *getEqualEqualOperator(NominalTypeDecl *decl) {
   // If no member `func ==` was found, look for out-of-class definitions in the
   // same module.
   auto module = decl->getModuleContext();
-  llvm::SmallVector<ValueDecl *> nonMemberResults;
+  SmallVector<ValueDecl *> nonMemberResults;
   module->lookupValue(id, NLKind::UnqualifiedLookup, nonMemberResults);
   for (const auto &nonMember : nonMemberResults) {
     if (isValid(nonMember))

lib/DriverTool/swift_symbolgraph_extract_main.cpp

@@ -241,7 +241,7 @@ int swift_symbolgraph_extract_main(ArrayRef<const char *> Args,
   // don't need to print these errors.
   CI.removeDiagnosticConsumer(&DiagPrinter);
 
-  SmallVector<ModuleDecl *, 8> Overlays;
+  SmallVector<ModuleDecl *> Overlays;
   M->findDeclaredCrossImportOverlaysTransitive(Overlays);
   for (const auto *OM : Overlays) {
     auto CIM = CI.getASTContext().getModuleByName(OM->getNameStr());

lib/IRGen/IRGenModule.h

@@ -777,7 +777,7 @@ class IRGenModule {
 
 #ifdef CHECK_RUNTIME_EFFECT_ANALYSIS
   RuntimeEffect effectOfRuntimeFuncs = RuntimeEffect::NoEffect;
-  llvm::SmallVector<const char *> emittedRuntimeFuncs;
+  SmallVector<const char *> emittedRuntimeFuncs;
 
   void registerRuntimeEffect(ArrayRef<RuntimeEffect> realtime,
                              const char *funcName);
@@ -1263,7 +1263,7 @@ class IRGenModule {
   void emitLazyObjCProtocolDefinitions();
   void emitLazyObjCProtocolDefinition(ProtocolDecl *proto);
 
-  llvm::SmallVector<llvm::MDNode *> UsedConditionals;
+  SmallVector<llvm::MDNode *> UsedConditionals;
   void emitUsedConditionals();
 
   void emitGlobalLists();

lib/SIL/IR/SILArgument.cpp

@@ -236,7 +236,7 @@ bool SILPhiArgument::visitTransitiveIncomingPhiOperands(
   worklist.initialize(this);
 
   while (auto *argument = worklist.pop()) {
-    llvm::SmallVector<Operand *> operands;
+    SmallVector<Operand *> operands;
     argument->getIncomingPhiOperands(operands);
 
     for (auto *operand : operands) {

lib/SILOptimizer/Transforms/SILMem2Reg.cpp

@@ -919,7 +919,7 @@ void StackAllocationPromoter::fixPhiPredBlock(BlockSetVector &phiBlocks,
 
   LLVM_DEBUG(llvm::dbgs() << "*** Found the definition: " << def.stored);
 
-  llvm::SmallVector<SILValue> vals;
+  SmallVector<SILValue> vals;
   vals.push_back(def.stored);
   if (shouldAddLexicalLifetime(asi)) {
     vals.push_back(def.borrow);
@@ -964,7 +964,7 @@ void StackAllocationPromoter::propagateLiveness(
   // If liveness has not been propagated, go over the incoming operands and mark
   // any operand values that are proactivePhis as live
   livePhis.insert(proactivePhi);
-  SmallVector<SILValue, 4> incomingPhiVals;
+  SmallVector<SILValue> incomingPhiVals;
   proactivePhi->getIncomingPhiValues(incomingPhiVals);
   for (auto &inVal : incomingPhiVals) {
     auto *inPhi = dyn_cast<SILPhiArgument>(inVal);

lib/SILOptimizer/Utils/LexicalDestroyFolding.cpp

@@ -275,11 +275,11 @@ bool findIntroducerUsage(Context const &, IntroducerUsage &);
 /// How %borrowee is used.
 struct BorroweeUsage final {
   /// The operands that are uses of the borrowee.
-  SmallVector<Operand *, 16> uses;
+  SmallVector<Operand *> uses;
   /// The instructions that are users of the borrowee.
   ///
   /// A set of the users of uses for fast membership checking.
-  SmallPtrSet<SILInstruction *, 16> users;
+  SmallPtrSet<SILInstruction *> users;
 };
 
 /// Find all uses of %borrowee that are dominated by introducer.

lib/Sema/BuilderTransform.cpp

@@ -1355,7 +1355,7 @@ class ResultBuilderTransform
         }
       } else {
         auto *elseBraceStmt = cast<BraceStmt>(elseStmt);
-        SmallVector<ASTNode, 4> elseBody;
+        SmallVector<ASTNode> elseBody;
 
         std::tie(elseVar, unsupported) = transform(elseBraceStmt, elseBody);
         if (unsupported) {

lib/Sema/CSClosure.cpp

@@ -40,7 +40,7 @@ Expr *getVoidExpr(ASTContext &ctx, SourceLoc contextLoc = SourceLoc()) {
 /// Find any type variable references inside of an AST node.
 class TypeVariableRefFinder : public ASTWalker {
   /// A stack of all closures the walker encountered so far.
-  SmallVector<DeclContext *, 2> ClosureDCs;
+  SmallVector<DeclContext *> ClosureDCs;
 
   ConstraintSystem &CS;
   ASTNode Parent;

tools/swift-refactor/swift-refactor.cpp

@@ -449,7 +449,7 @@ int main(int argc, char *argv[]) {
     return 1;
   }
 
-  SmallVector<std::unique_ptr<SourceEditConsumer>, 32> Consumers;
+  SmallVector<std::unique_ptr<SourceEditConsumer>> Consumers;
   if (!options::RewrittenOutputFile.empty() ||
       options::DumpIn == options::DumpType::REWRITTEN) {
     Consumers.emplace_back(new SourceEditOutputConsumer(