Index: llvm/docs/TableGen/BackGuide.rst
===================================================================
--- llvm/docs/TableGen/BackGuide.rst
+++ llvm/docs/TableGen/BackGuide.rst
@@ -562,16 +562,16 @@
 * ``getDefs()`` returns a ``RecordMap`` reference for all the concrete
   records.
 
-* ``getDef(``\ *name*\ ``)`` return a ``Record`` reference for the named
+* ``getDef(``\ *name*\ ``)`` returns a ``Record`` reference for the named
   concrete record.
 
 * ``getAllDerivedDefinitions(``\ *classname*\ ``)`` returns a vector of
   ``Record`` references for the concrete records that derive from the
   given class.
 
-* ``getAllDerivedDefinitionsTwo(``\ *classname1*\ ``,`` *classname2*\ ``)`` returns
+* ``getAllDerivedDefinitions(``\ *classvector*\ ``)`` returns
   a vector of ``Record`` references for the concrete records that derive from
-  *both* of the given classes. [function to come]
+  *all* of the given classes.
 
 This statement obtains all the records that derive from the ``Attribute``
 class and iterates over them.
@@ -701,7 +701,7 @@
 defined through a sequence of multiclasses. Because of this, it can be
 difficult for backends to report clear error messages with accurate source
 file locations.  To make error reporting easier, five error reporting
-functions are provided, each with four overloads. [all combinations to come]
+functions are provided, each with four overloads.
 
 * ``PrintWarning`` prints a message tagged as a warning.
 
Index: llvm/include/llvm/TableGen/Record.h
===================================================================
--- llvm/include/llvm/TableGen/Record.h
+++ llvm/include/llvm/TableGen/Record.h
@@ -1784,7 +1784,12 @@
   //===--------------------------------------------------------------------===//
   // High-level helper methods, useful for tablegen backends.
 
-  /// Get all the concrete records that inherit from the specified
+  /// Get all the concrete records that inherit from all the specified
+  /// classes. The classes must be defined.
+  std::vector<Record *>
+  getAllDerivedDefinitions(const std::vector<std::string> &Classes) const;
+
+  /// Get all the concrete records that inherit from the one specified
   /// class. The class must be defined.
   std::vector<Record *> getAllDerivedDefinitions(StringRef ClassName) const;
 
Index: llvm/lib/TableGen/Record.cpp
===================================================================
--- llvm/lib/TableGen/Record.cpp
+++ llvm/lib/TableGen/Record.cpp
@@ -2319,10 +2319,10 @@
                                 "' exists but does not have a list value");
 }
 
-std::vector<Record*>
+std::vector<Record *>
 Record::getValueAsListOfDefs(StringRef FieldName) const {
   ListInit *List = getValueAsListInit(FieldName);
-  std::vector<Record*> Defs;
+  std::vector<Record *> Defs;
   for (Init *I : List->getValues()) {
     if (DefInit *DI = dyn_cast<DefInit>(I))
       Defs.push_back(DI->getDef());
@@ -2470,20 +2470,50 @@
   return StringInit::get("anonymous_" + utostr(AnonCounter++));
 }
 
+/// Get all the concrete records that inherit from all the specified
+/// classes. The classes must be defined.
 std::vector<Record *>
-RecordKeeper::getAllDerivedDefinitions(StringRef ClassName) const {
-  Record *Class = getClass(ClassName);
-  if (!Class)
-    PrintFatalError("ERROR: Couldn't find the `" + ClassName + "' class!\n");
-
-  std::vector<Record*> Defs;
-  for (const auto &D : getDefs())
-    if (D.second->isSubClassOf(Class))
-      Defs.push_back(D.second.get());
+RecordKeeper::getAllDerivedDefinitions(const std::vector<std::string> &Classes) const {
+  SmallVector<Record *, 2> ClassRecs;
+  std::vector<Record *> Defs;
+  bool AddDef;
+
+  // First get the class records for the specified classes and make
+  // sure they exist.
+  assert(Classes.size() > 0 && "At least one class must be passed.");
+  for (const auto ClassName : Classes) {
+    Record *Class = getClass(ClassName);
+    if (!Class)
+      PrintFatalError("The class '" + ClassName + "' is not defined\n");
+    ClassRecs.push_back(Class);
+  }
+
+  // Now scan all the concrete records and build the vector of records
+  // that inherit from all the classes.
+  for (const auto &OneDef : getDefs()) {
+    AddDef = true;
+    for (const auto Class : ClassRecs)
+      if (!OneDef.second->isSubClassOf(Class)) {
+        AddDef = false;
+        break;
+      }
+    if (AddDef)
+      Defs.push_back(OneDef.second.get());
+  }
 
   return Defs;
 }
 
+/// Get all the concrete records that inherit from the one specified
+/// class. The class must be defined.
+std::vector<Record *>
+RecordKeeper::getAllDerivedDefinitions(StringRef ClassName) const {
+  std::vector<std::string> ClassVec;
+  ClassVec.push_back(ClassName.str());
+
+  return getAllDerivedDefinitions(ClassVec);
+}
+
 Init *MapResolver::resolve(Init *VarName) {
   auto It = Map.find(VarName);
   if (It == Map.end())
Index: llvm/utils/TableGen/PseudoLoweringEmitter.cpp
===================================================================
--- llvm/utils/TableGen/PseudoLoweringEmitter.cpp
+++ llvm/utils/TableGen/PseudoLoweringEmitter.cpp
@@ -293,17 +293,8 @@
 }
 
 void PseudoLoweringEmitter::run(raw_ostream &o) {
-  Record *ExpansionClass = Records.getClass("PseudoInstExpansion");
-  Record *InstructionClass = Records.getClass("Instruction");
-  assert(ExpansionClass && "PseudoInstExpansion class definition missing!");
-  assert(InstructionClass && "Instruction class definition missing!");
-
-  std::vector<Record*> Insts;
-  for (const auto &D : Records.getDefs()) {
-    if (D.second->isSubClassOf(ExpansionClass) &&
-        D.second->isSubClassOf(InstructionClass))
-      Insts.push_back(D.second.get());
-  }
+  std::vector<std::string> Classes = {"PseudoInstExpansion", "Instruction"};
+  std::vector<Record *> Insts = Records.getAllDerivedDefinitions(Classes);
 
   // Process the pseudo expansion definitions, validating them as we do so.
   for (unsigned i = 0, e = Insts.size(); i != e; ++i)
Index: llvm/utils/TableGen/RISCVCompressInstEmitter.cpp
===================================================================
--- llvm/utils/TableGen/RISCVCompressInstEmitter.cpp
+++ llvm/utils/TableGen/RISCVCompressInstEmitter.cpp
@@ -884,13 +884,7 @@
 }
 
 void RISCVCompressInstEmitter::run(raw_ostream &o) {
-  Record *CompressClass = Records.getClass("CompressPat");
-  assert(CompressClass && "Compress class definition missing!");
-  std::vector<Record *> Insts;
-  for (const auto &D : Records.getDefs()) {
-    if (D.second->isSubClassOf(CompressClass))
-      Insts.push_back(D.second.get());
-  }
+  std::vector<Record *> Insts = Records.getAllDerivedDefinitions("CompressPat");
 
   // Process the CompressPat definitions, validating them as we do so.
   for (unsigned i = 0, e = Insts.size(); i != e; ++i)