Teach TableGen to evaluate DAG expressions as set operations.

A TableGen backend can define how certain classes can be expanded into
ordered sets of defs, typically by evaluating a specific field in the
record. The SetTheory class can then evaluate DAG expressions that refer
to these named sets.

A number of standard set and list operations are predefined, and the
backend can add more specialized operators if needed. The -print-sets
backend is used by SetTheory.td to provide examples.

This is intended to simplify how register classes are defined:

  def GR32_NOSP : RegisterClass<"X86", [i32], 32, (sub GR32, ESP)>;

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132621 91177308-0d34-0410-b5e6-96231b3b80d8

test/TableGen/SetTheory.td

@@ -0,0 +1,167 @@
+// Test evaluation of set operations in dags.
+// RUN: tblgen -print-sets %s | FileCheck %s
+// XFAIL: vg_leak
+//
+// The -print-sets driver configures a primitive SetTheory instance that
+// understands these sets:
+
+class Set<dag d> {
+  dag Elements = d;
+}
+
+// It prints all Set instances and their ordered set interpretation.
+
+// Define some elements.
+def a;
+def b;
+def c;
+def d;
+
+// The 'add' operator evaluates and concatenates its arguments.
+def add;
+def S0a : Set<(add)>;
+def S0b : Set<(add a)>;
+def S0c : Set<(add a, b)>;
+def S0d : Set<(add b, a)>;
+def S0e : Set<(add a, a)>;
+def S0f : Set<(add a, a, b, a, c, b, d, a)>;
+def S0g : Set<(add b, a, b)>;
+// CHECK: S0a = [ ]
+// CHECK: S0b = [ a ]
+// CHECK: S0c = [ a b ]
+// CHECK: S0d = [ b a ]
+// CHECK: S0e = [ a ]
+// CHECK: S0f = [ a b c d ]
+// CHECK: S0g = [ b a ]
+
+// Defs of Set class expand into their elements.
+// Mixed sets and elements are flattened.
+def S1a : Set<(add S0a)>;
+def S1b : Set<(add S0a, S0a)>;
+def S1c : Set<(add S0d, S0f)>;
+def S1d : Set<(add d, S0d, S0f)>;
+// CHECK: S1a = [ ]
+// CHECK: S1b = [ ]
+// CHECK: S1c = [ b a c d ]
+// CHECK: S1d = [ d b a c ]
+
+// The 'sub' operator returns the first argument with the following arguments
+// removed.
+def sub;
+def S2a : Set<(sub S1a, S1c)>;
+def S2b : Set<(sub S1c, S1d)>;
+def S2c : Set<(sub S1c, b)>;
+def S2d : Set<(sub S1c, S0c)>;
+def S2e : Set<(sub S1c, S2d)>;
+// CHECK: S2a = [ ]
+// CHECK: S2b = [ ]
+// CHECK: S2c = [ a c d ]
+// CHECK: S2d = [ c d ]
+// CHECK: S2e = [ b a ]
+
+// The 'and' operator intersects two sets. The result has the same order as the
+// first argument.
+def and;
+def S3a : Set<(and S2d, S2e)>;
+def S3b : Set<(and S2d, S1d)>;
+// CHECK: S3a = [ ]
+// CHECK: S3b = [ c d ]
+
+// The 'shl' operator removes the first N elements.
+def shl;
+def S4a : Set<(shl S0f, 0)>;
+def S4b : Set<(shl S0f, 1)>;
+def S4c : Set<(shl S0f, 3)>;
+def S4d : Set<(shl S0f, 4)>;
+def S4e : Set<(shl S0f, 5)>;
+// CHECK: S4a = [ a b c d ]
+// CHECK: S4b = [ b c d ]
+// CHECK: S4c = [ d ]
+// CHECK: S4d = [ ]
+// CHECK: S4e = [ ]
+
+// The 'trunc' operator truncates after the first N elements.
+def trunc;
+def S5a : Set<(trunc S0f, 0)>;
+def S5b : Set<(trunc S0f, 1)>;
+def S5c : Set<(trunc S0f, 3)>;
+def S5d : Set<(trunc S0f, 4)>;
+def S5e : Set<(trunc S0f, 5)>;
+// CHECK: S5a = [ ]
+// CHECK: S5b = [ a ]
+// CHECK: S5c = [ a b c ]
+// CHECK: S5d = [ a b c d ]
+// CHECK: S5e = [ a b c d ]
+
+// The 'rotl' operator rotates left, but also accepts a negative shift.
+def rotl;
+def S6a : Set<(rotl S0f, 0)>;
+def S6b : Set<(rotl S0f, 1)>;
+def S6c : Set<(rotl S0f, 3)>;
+def S6d : Set<(rotl S0f, 4)>;
+def S6e : Set<(rotl S0f, 5)>;
+def S6f : Set<(rotl S0f, -1)>;
+def S6g : Set<(rotl S0f, -4)>;
+def S6h : Set<(rotl S0f, -5)>;
+// CHECK: S6a = [ a b c d ]
+// CHECK: S6b = [ b c d a ]
+// CHECK: S6c = [ d a b c ]
+// CHECK: S6d = [ a b c d ]
+// CHECK: S6e = [ b c d a ]
+// CHECK: S6f = [ d a b c ]
+// CHECK: S6g = [ a b c d ]
+// CHECK: S6h = [ d a b c ]
+
+// The 'rotr' operator rotates right, but also accepts a negative shift.
+def rotr;
+def S7a : Set<(rotr S0f, 0)>;
+def S7b : Set<(rotr S0f, 1)>;
+def S7c : Set<(rotr S0f, 3)>;
+def S7d : Set<(rotr S0f, 4)>;
+def S7e : Set<(rotr S0f, 5)>;
+def S7f : Set<(rotr S0f, -1)>;
+def S7g : Set<(rotr S0f, -4)>;
+def S7h : Set<(rotr S0f, -5)>;
+// CHECK: S7a = [ a b c d ]
+// CHECK: S7b = [ d a b c ]
+// CHECK: S7c = [ b c d a ]
+// CHECK: S7d = [ a b c d ]
+// CHECK: S7e = [ d a b c ]
+// CHECK: S7f = [ b c d a ]
+// CHECK: S7g = [ a b c d ]
+// CHECK: S7h = [ b c d a ]
+
+// The 'decimate' operator picks every N'th element.
+def decimate;
+def e0;
+def e1;
+def e2;
+def e3;
+def e4;
+def e5;
+def e6;
+def e7;
+def e8;
+def e9;
+def E : Set<(add e0, e1, e2, e3, e4, e5, e6, e7, e8, e9)>;
+def S8a : Set<(decimate E, 3)>;
+def S8b : Set<(decimate E, 9)>;
+def S8c : Set<(decimate E, 10)>;
+def S8d : Set<(decimate (rotl E, 1), 2)>;
+def S8e : Set<(add (decimate E, 2), (decimate (rotl E, 1), 2))>;
+// CHECK: S8a = [ e0 e3 e6 e9 ]
+// CHECK: S8b = [ e0 e9 ]
+// CHECK: S8c = [ e0 ]
+// CHECK: S8d = [ e1 e3 e5 e7 e9 ]
+// CHECK: S8e = [ e0 e2 e4 e6 e8 e1 e3 e5 e7 e9 ]
+
+// The 'sequence' operator finds a sequence of records from their name.
+def sequence;
+def S9a : Set<(sequence "e%u", 3, 7)>;
+def S9b : Set<(sequence "e%u", 7, 3)>;
+def S9c : Set<(sequence "e%u", 0, 0)>;
+def S9d : Set<(sequence "S%ua", 7, 9)>;
+// CHECK: S9a = [ e3 e4 e5 e6 e7 ]
+// CHECK: S9b = [ e7 e6 e5 e4 e3 ]
+// CHECK: S9c = [ e0 ]
+// CHECK: S9d = [ a b c d e0 e3 e6 e9 e4 e5 e7 ]

utils/TableGen/CMakeLists.txt

@@ -34,6 +34,7 @@ add_llvm_utility(tblgen
   OptParserEmitter.cpp
   Record.cpp
   RegisterInfoEmitter.cpp
+  SetTheory.cpp
   StringMatcher.cpp
   SubtargetEmitter.cpp
   TGLexer.cpp

utils/TableGen/SetTheory.cpp

@@ -0,0 +1,272 @@
+//===- SetTheory.cpp - Generate ordered sets from DAG expressions ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the SetTheory class that computes ordered sets of
+// Records from DAG expressions.
+//
+//===----------------------------------------------------------------------===//
+
+#include "SetTheory.h"
+#include "Record.h"
+#include "llvm/Support/Format.h"
+
+using namespace llvm;
+
+// Define the standard operators.
+namespace {
+
+typedef SetTheory::RecSet RecSet;
+typedef SetTheory::RecVec RecVec;
+
+// (add a, b, ...) Evaluate and union all arguments.
+struct AddOp : public SetTheory::Operator {
+  void apply(SetTheory &ST, DagInit *Expr, RecSet &Elts) {
+    ST.evaluate(Expr->arg_begin(), Expr->arg_end(), Elts);
+  }
+};
+
+// (sub Add, Sub, ...) Set difference.
+struct SubOp : public SetTheory::Operator {
+  void apply(SetTheory &ST, DagInit *Expr, RecSet &Elts) {
+    if (Expr->arg_size() < 2)
+      throw "Set difference needs at least two arguments: " +
+        Expr->getAsString();
+    RecSet Add, Sub;
+    ST.evaluate(*Expr->arg_begin(), Add);
+    ST.evaluate(Expr->arg_begin() + 1, Expr->arg_end(), Sub);
+    for (RecSet::iterator I = Add.begin(), E = Add.end(); I != E; ++I)
+      if (!Sub.count(*I))
+        Elts.insert(*I);
+  }
+};
+
+// (and S1, S2) Set intersection.
+struct AndOp : public SetTheory::Operator {
+  void apply(SetTheory &ST, DagInit *Expr, RecSet &Elts) {
+    if (Expr->arg_size() != 2)
+      throw "Set intersection requires two arguments: " + Expr->getAsString();
+    RecSet S1, S2;
+    ST.evaluate(Expr->arg_begin()[0], S1);
+    ST.evaluate(Expr->arg_begin()[1], S2);
+    for (RecSet::iterator I = S1.begin(), E = S1.end(); I != E; ++I)
+      if (S2.count(*I))
+        Elts.insert(*I);
+  }
+};
+
+// SetIntBinOp - Abstract base class for (Op S, N) operators.
+struct SetIntBinOp : public SetTheory::Operator {
+  virtual void apply(SetTheory &ST, DagInit *Expr,
+                     RecSet &Set, int64_t N,
+                     RecSet &Elts) =0;
+
+  void apply(SetTheory &ST, DagInit *Expr, RecSet &Elts) {
+    if (Expr->arg_size() != 2)
+      throw "Operator requires (Op Set, Int) arguments: " + Expr->getAsString();
+    RecSet Set;
+    ST.evaluate(Expr->arg_begin()[0], Set);
+    IntInit *II = dynamic_cast<IntInit*>(Expr->arg_begin()[1]);
+    if (!II)
+      throw "Second argument must be an integer: " + Expr->getAsString();
+    apply(ST, Expr, Set, II->getValue(), Elts);
+  }
+};
+
+// (shl S, N) Shift left, remove the first N elements.
+struct ShlOp : public SetIntBinOp {
+  void apply(SetTheory &ST, DagInit *Expr,
+             RecSet &Set, int64_t N,
+             RecSet &Elts) {
+    if (N < 0)
+      throw "Positive shift required: " + Expr->getAsString();
+    if (unsigned(N) < Set.size())
+      Elts.insert(Set.begin() + N, Set.end());
+  }
+};
+
+// (trunc S, N) Truncate after the first N elements.
+struct TruncOp : public SetIntBinOp {
+  void apply(SetTheory &ST, DagInit *Expr,
+             RecSet &Set, int64_t N,
+             RecSet &Elts) {
+    if (N < 0)
+      throw "Positive length required: " + Expr->getAsString();
+    if (unsigned(N) > Set.size())
+      N = Set.size();
+    Elts.insert(Set.begin(), Set.begin() + N);
+  }
+};
+
+// Left/right rotation.
+struct RotOp : public SetIntBinOp {
+  const bool Reverse;
+
+  RotOp(bool Rev) : Reverse(Rev) {}
+
+  void apply(SetTheory &ST, DagInit *Expr,
+             RecSet &Set, int64_t N,
+             RecSet &Elts) {
+    if (Reverse)
+      N = -N;
+    // N > 0 -> rotate left, N < 0 -> rotate right.
+    if (Set.empty())
+      return;
+    if (N < 0)
+      N = Set.size() - (-N % Set.size());
+    else
+      N %= Set.size();
+    Elts.insert(Set.begin() + N, Set.end());
+    Elts.insert(Set.begin(), Set.begin() + N);
+  }
+};
+
+// (decimate S, N) Pick every N'th element of S.
+struct DecimateOp : public SetIntBinOp {
+  void apply(SetTheory &ST, DagInit *Expr,
+             RecSet &Set, int64_t N,
+             RecSet &Elts) {
+    if (N <= 0)
+      throw "Positive stride required: " + Expr->getAsString();
+    for (unsigned I = 0; I < Set.size(); I += N)
+      Elts.insert(Set[I]);
+  }
+};
+
+// (sequence "Format", From, To) Generate a sequence of records by name.
+struct SequenceOp : public SetTheory::Operator {
+  RecordKeeper &Records;
+
+  SequenceOp(RecordKeeper&R) : Records(R) {}
+
+  void apply(SetTheory &ST, DagInit *Expr, RecSet &Elts) {
+    if (Expr->arg_size() != 3)
+      throw "Bad args to (sequence \"Format\", From, To): " +
+        Expr->getAsString();
+    std::string Format;
+    if (StringInit *SI = dynamic_cast<StringInit*>(Expr->arg_begin()[0]))
+      Format = SI->getValue();
+    else
+      throw "Format must be a string: " + Expr->getAsString();
+
+    int64_t From, To;
+    if (IntInit *II = dynamic_cast<IntInit*>(Expr->arg_begin()[1]))
+      From = II->getValue();
+    else
+      throw "From must be an integer: " + Expr->getAsString();
+    if (IntInit *II = dynamic_cast<IntInit*>(Expr->arg_begin()[2]))
+      To = II->getValue();
+    else
+      throw "From must be an integer: " + Expr->getAsString();
+
+    int Step = From <= To ? 1 : -1;
+    for (To += Step; From != To; From += Step) {
+      std::string Name;
+      raw_string_ostream OS(Name);
+      OS << format(Format.c_str(), From);
+      Record *Rec = Records.getDef(OS.str());
+      if (!Rec)
+        throw "No def named '" + Name + "': " + Expr->getAsString();
+      // Try to reevaluate Rec in case it is a set.
+      if (const RecVec *Result = ST.expand(Rec))
+        Elts.insert(Result->begin(), Result->end());
+      else
+        Elts.insert(Rec);
+    }
+  }
+};
+
+// Expand a Def into a set by evaluating one of its fields.
+struct FieldExpander : public SetTheory::Expander {
+  StringRef FieldName;
+
+  FieldExpander(StringRef fn) : FieldName(fn) {}
+
+  void expand(SetTheory &ST, Record *Def, RecSet &Elts) {
+    ST.evaluate(Def->getValueInit(FieldName), Elts);
+  }
+};
+} // end anonymous namespace
+
+SetTheory::SetTheory(RecordKeeper *Records) {
+  addOperator("add", new AddOp);
+  addOperator("sub", new SubOp);
+  addOperator("and", new AndOp);
+  addOperator("shl", new ShlOp);
+  addOperator("trunc", new TruncOp);
+  addOperator("rotl", new RotOp(false));
+  addOperator("rotr", new RotOp(true));
+  addOperator("decimate", new DecimateOp);
+  if (Records)
+    addOperator("sequence", new SequenceOp(*Records));
+}
+
+void SetTheory::addOperator(StringRef Name, Operator *Op) {
+  Operators[Name] = Op;
+}
+
+void SetTheory::addExpander(StringRef ClassName, Expander *E) {
+  Expanders[ClassName] = E;
+}
+
+void SetTheory::addFieldExpander(StringRef ClassName, StringRef FieldName) {
+  addExpander(ClassName, new FieldExpander(FieldName));
+}
+
+void SetTheory::evaluate(Init *Expr, RecSet &Elts) {
+  // A def in a list can be a just an element, or it may expand.
+  if (DefInit *Def = dynamic_cast<DefInit*>(Expr)) {
+    if (const RecVec *Result = expand(Def->getDef()))
+      return Elts.insert(Result->begin(), Result->end());
+    Elts.insert(Def->getDef());
+    return;
+  }
+
+  // Lists simply expand.
+  if (ListInit *LI = dynamic_cast<ListInit*>(Expr))
+    return evaluate(LI->begin(), LI->end(), Elts);
+
+  // Anything else must be a DAG.
+  DagInit *DagExpr = dynamic_cast<DagInit*>(Expr);
+  if (!DagExpr)
+    throw "Invalid set element: " + Expr->getAsString();
+  DefInit *OpInit = dynamic_cast<DefInit*>(DagExpr->getOperator());
+  if (!OpInit)
+    throw "Bad set expression: " + Expr->getAsString();
+  Operator *Op = Operators.lookup(OpInit->getDef()->getName());
+  if (!Op)
+    throw "Unknown set operator: " + Expr->getAsString();
+  Op->apply(*this, DagExpr, Elts);
+}
+
+const RecVec *SetTheory::expand(Record *Set) {
+  // Check existing entries for Set and return early.
+  ExpandMap::iterator I = Expansions.find(Set);
+  if (I != Expansions.end())
+    return &I->second;
+
+  // This is the first time we see Set. Find a suitable expander.
+  try {
+    const std::vector<Record*> &SC = Set->getSuperClasses();
+    for (unsigned i = 0, e = SC.size(); i != e; ++i)
+      if (Expander *Exp = Expanders.lookup(SC[i]->getName())) {
+        // This breaks recursive definitions.
+        RecVec &EltVec = Expansions[Set];
+        RecSet Elts;
+        Exp->expand(*this, Set, Elts);
+        EltVec.assign(Elts.begin(), Elts.end());
+        return &EltVec;
+      }
+  } catch (const std::string &Error) {
+    throw TGError(Set->getLoc(), Error);
+  }
+
+  // Set is not expandable.
+  return 0;
+}
+

utils/TableGen/SetTheory.h

@@ -0,0 +1,133 @@
+//===- SetTheory.h - Generate ordered sets from DAG expressions -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the SetTheory class that computes ordered sets of
+// Records from DAG expressions.  Operators for standard set operations are
+// predefined, and it is possible to add special purpose set operators as well.
+//
+// The user may define named sets as Records of predefined classes. Set
+// expanders can be added to a SetTheory instance to teach it how to find the
+// elements of such a named set.
+//
+// These are the predefined operators. The argument lists can be individual
+// elements (defs), other sets (defs of expandable classes), lists, or DAG
+// expressions that are evaluated recursively.
+//
+// - (add S1, S2 ...) Union sets. This is also how sets are created from element
+//   lists.
+//
+// - (sub S1, S2, ...) Set difference. Every element in S1 except for the
+//   elements in S2, ...
+//
+// - (and S1, S2) Set intersection. Every element in S1 that is also in S2.
+//
+// - (shl S, N) Shift left. Remove the first N elements from S.
+//
+// - (trunc S, N) Truncate. The first N elements of S.
+//
+// - (rotl S, N) Rotate left. Same as (add (shl S, N), (trunc S, N)).
+//
+// - (rotr S, N) Rotate right.
+//
+// - (decimate S, N) Decimate S by picking every N'th element, starting with
+//   the first one. For instance, (decimate S, 2) returns the even elements of
+//   S.
+//
+// - (sequence "Format", From, To) Generate a sequence of defs with printf.
+//   For instance, (sequence "R%u", 0, 3) -> [ R0, R1, R2, R3 ]
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SETTHEORY_H
+#define SETTHEORY_H
+
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/SetVector.h"
+#include <map>
+#include <vector>
+
+namespace llvm {
+
+class DagInit;
+struct Init;
+class Record;
+class RecordKeeper;
+
+class SetTheory {
+public:
+  typedef std::vector<Record*> RecVec;
+  typedef SmallSetVector<Record*, 16> RecSet;
+
+  /// Operator - A callback representing a DAG operator.
+  struct Operator {
+    /// apply - Apply this operator to Expr's arguments and insert the result
+    /// in Elts.
+    virtual void apply(SetTheory&, DagInit *Expr, RecSet &Elts) =0;
+  };
+
+  /// Expander - A callback function that can transform a Record representing a
+  /// set into a fully expanded list of elements. Expanders provide a way for
+  /// users to define named sets that can be used in DAG expressions.
+  struct Expander {
+    virtual void expand(SetTheory&, Record*, RecSet &Elts) =0;
+  };
+
+private:
+  // Map set defs to their fully expanded contents. This serves as a memoization
+  // cache and it makes it possible to return const references on queries.
+  typedef std::map<Record*, RecVec> ExpandMap;
+  ExpandMap Expansions;
+
+  // Known DAG operators by name.
+  StringMap<Operator*> Operators;
+
+  // Typed expanders by class name.
+  StringMap<Expander*> Expanders;
+
+public:
+  /// Create a SetTheory instance with only the standard operators.
+  /// A 'sequence' operator will only be added if a RecordKeeper is given.
+  SetTheory(RecordKeeper *Records = 0);
+
+  /// addExpander - Add an expander for Records with the named super class.
+  void addExpander(StringRef ClassName, Expander*);
+
+  /// addFieldExpander - Add an expander for ClassName that simply evaluates
+  /// FieldName in the Record to get the set elements.  That is all that is
+  /// needed for a class like:
+  ///
+  ///   class Set<dag d> {
+  ///     dag Elts = d;
+  ///   }
+  ///
+  void addFieldExpander(StringRef ClassName, StringRef FieldName);
+
+  /// addOperator - Add a DAG operator.
+  void addOperator(StringRef Name, Operator*);
+
+  /// evaluate - Evaluate Expr and append the resulting set to Elts.
+  void evaluate(Init *Expr, RecSet &Elts);
+
+  /// evaluate - Evaluate a sequence of Inits and append to Elts.
+  template<typename Iter>
+  void evaluate(Iter begin, Iter end, RecSet &Elts) {
+    while (begin != end)
+      evaluate(*begin++, Elts);
+  }
+
+  /// expand - Expand a record into a set of elements if possible.  Return a
+  /// pointer to the expanded elements, or NULL if Set cannot be expanded
+  /// further.
+  const RecVec *expand(Record *Set);
+};
+
+} // end namespace llvm
+
+#endif
+

utils/TableGen/TableGen.cpp

@@ -37,6 +37,7 @@
 #include "RegisterInfoEmitter.h"
 #include "ARMDecoderEmitter.h"
 #include "SubtargetEmitter.h"
+#include "SetTheory.h"
 #include "TGParser.h"
 #include "llvm/ADT/OwningPtr.h"
 #include "llvm/Support/CommandLine.h"
@@ -80,7 +81,8 @@ enum ActionType {
   GenArmNeon,
   GenArmNeonSema,
   GenArmNeonTest,
-  PrintEnums
+  PrintEnums,
+  PrintSets
 };
 
 namespace {
@@ -162,6 +164,8 @@ namespace {
                                "Generate ARM NEON tests for clang"),
                     clEnumValN(PrintEnums, "print-enums",
                                "Print enum values for a class"),
+                    clEnumValN(PrintSets, "print-sets",
+                               "Print expanded sets for testing DAG exprs"),
                     clEnumValEnd));
 
   cl::opt<std::string>
@@ -374,6 +378,21 @@ int main(int argc, char **argv) {
       Out.os() << "\n";
       break;
     }
+    case PrintSets:
+    {
+      SetTheory Sets(&Records);
+      Sets.addFieldExpander("Set", "Elements");
+      std::vector<Record*> Recs = Records.getAllDerivedDefinitions("Set");
+      for (unsigned i = 0, e = Recs.size(); i != e; ++i) {
+        Out.os() << Recs[i]->getName() << " = [";
+        const std::vector<Record*> *Elts = Sets.expand(Recs[i]);
+        assert(Elts && "Couldn't expand Set instance");
+        for (unsigned ei = 0, ee = Elts->size(); ei != ee; ++ei)
+          Out.os() << ' ' << (*Elts)[ei]->getName();
+        Out.os() << " ]\n";
+      }
+      break;
+    }
     default:
       assert(1 && "Invalid Action");
       return 1;