Add a random .LL file generator to stress-test different llvm components.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151479 91177308-0d34-0410-b5e6-96231b3b80d8

docs/CommandGuide/index.html

@@ -75,6 +75,9 @@ options) arguments to the tool you are interested in.</p>
 <li><a href="/cmds/llvm-cov.html"><b>llvm-cov</b></a> -
     emit coverage information</li>
 
+<li><a href="/cmds/llvm-stress.html"><b>llvm-stress</b></a> -
+    generate random .ll files to fuzz different llvm components</li>
+
 </ul>
 
 </div>

docs/CommandGuide/llvm-stress.pod

@@ -0,0 +1,42 @@
+=pod
+
+=head1 NAME
+
+llvm-stress - generate random .ll files
+
+=head1 SYNOPSIS
+
+B<llvm-cov> [-gcno=filename] [-gcda=filename] [dump]
+
+=head1 DESCRIPTION
+
+The B<llvm-stress> tool is used to generate random .ll files that can be used to
+test different components of LLVM.
+
+=head1 OPTIONS
+
+=over
+
+=item B<-o> I<filename>
+
+Specify the output filename.
+
+=item B<-size> I<size>
+
+Specify the size of the generated .ll file.
+
+=item B<-seed> I<seed>
+
+Specify the seed to be used for the randomly generated instructions.
+
+=back
+
+=head1 EXIT STATUS
+
+B<llvm-stress> returns 0.
+
+=head1 AUTHOR
+
+B<llvm-stress> is maintained by the LLVM Team (L<http://llvm.org/>).
+
+=cut

docs/ReleaseNotes.html

@@ -357,7 +357,7 @@ Release Notes</a>.</h1>
       closest user-defined super-class.</li>
   <li><code>MachineRegisterInfo</code> now allows the reserved registers to be
       frozen when register allocation starts.  Target hooks should use the
-      <code>MRI->canReserveReg(FramePtr)</code> method to avoid accidentally
+      <code>MRI-&gt;canReserveReg(FramePtr)</code> method to avoid accidentally
       disabling frame pointer elimination during register allocation.</li>
   <li>A new kind of <code>MachineOperand</code> provides a compact
       representation of large clobber lists on call instructions.  The register
@@ -490,6 +490,31 @@ syntax, there are still significant gaps in that support.</p>
 
 </div>
 
+<!--=========================================================================-->
+<h3>
+<a name="tools_changes">Tools Changes</a>
+</h3>
+
+<div>
+
+<p>In addition, some tools have changed in this release. Some of the changes
+   are:</p>
+
+
+<ul>
+  <li>llvm-stress is a command line tool for generating random .ll files to fuzz
+      different LLVM components. </li>
+  <li>....</li>
+</ul>
+
+<ul>
+  <li>....</li>
+</ul>
+
+</div>
+
+</div>
+
 <!-- *********************************************************************** -->
 <h2>
   <a name="knownproblems">Known Problems</a>

tools/CMakeLists.txt

@@ -44,6 +44,7 @@ add_subdirectory(bugpoint)
 add_subdirectory(bugpoint-passes)
 add_subdirectory(llvm-bcanalyzer)
 add_subdirectory(llvm-stub)
+add_subdirectory(llvm-stress)
 
 if( NOT WIN32 )
   add_subdirectory(lto)

tools/Makefile

@@ -34,7 +34,7 @@ PARALLEL_DIRS := opt llvm-as llvm-dis \
                  bugpoint llvm-bcanalyzer llvm-stub \
                  llvm-diff macho-dump llvm-objdump \
 	         llvm-rtdyld llvm-dwarfdump llvm-cov \
-	         llvm-size
+	         llvm-size llvm-stress
 
 # Let users override the set of tools to build from the command line.
 ifdef ONLY_TOOLS

tools/llvm-stress/CMakeLists.txt

@@ -0,0 +1,5 @@
+set(LLVM_LINK_COMPONENTS bitreader asmparser bitwriter instrumentation scalaropts ipo)
+
+add_llvm_tool(llvm-stress
+  llvm-stress.cpp
+  )

tools/llvm-stress/LLVMBuild.txt

@@ -0,0 +1,22 @@
+;===- ./tools/llvm-stress/LLVMBuild.txt -------------------------*- Conf -*--===;
+;
+;                     The LLVM Compiler Infrastructure
+;
+; This file is distributed under the University of Illinois Open Source
+; License. See LICENSE.TXT for details.
+;
+;===------------------------------------------------------------------------===;
+;
+; This is an LLVMBuild description file for the components in this subdirectory.
+;
+; For more information on the LLVMBuild system, please see:
+;
+;   http://llvm.org/docs/LLVMBuild.html
+;
+;===------------------------------------------------------------------------===;
+
+[component_0]
+type = Tool
+name = llvm-stress
+parent = Tools
+required_libraries = AsmParser BitReader BitWriter IPO Instrumentation Scalar

tools/llvm-stress/Makefile

@@ -0,0 +1,18 @@
+##===- tools/llvm-stress/Makefile --------------------------*- Makefile -*-===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+LEVEL := ../..
+TOOLNAME := llvm-stress
+LINK_COMPONENTS := object
+LINK_COMPONENTS := bitreader bitwriter asmparser instrumentation scalaropts ipo
+
+# This tool has no plugins, optimize startup time.
+TOOL_NO_EXPORTS = 1
+
+include $(LEVEL)/Makefile.common

tools/llvm-stress/llvm-stress.cpp

@@ -0,0 +1,623 @@
+//===-- llvm-stress.cpp - Print the size of each object section ------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This program is a utility that generates random .ll files to stress-test
+// different components in LLVM.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/LLVMContext.h"
+#include "llvm/Module.h"
+#include "llvm/PassManager.h"
+#include "llvm/Constants.h"
+#include "llvm/Instruction.h"
+#include "llvm/CallGraphSCCPass.h"
+#include "llvm/Assembly/PrintModulePass.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/Support/PassNameParser.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/PluginLoader.h"
+#include "llvm/Support/PrettyStackTrace.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include <memory>
+#include <sstream>
+#include <set>
+#include <vector>
+#include <algorithm>
+using namespace llvm;
+
+static cl::opt<unsigned> SeedCL("seed",
+  cl::desc("Seed used for randomness"), cl::init(0));
+static cl::opt<unsigned> SizeCL("size",
+  cl::desc("The estimated size of the generated function (# of instrs)"),
+  cl::init(100));
+static cl::opt<std::string>
+OutputFilename("o", cl::desc("Override output filename"),
+               cl::value_desc("filename"));
+
+/// A utility class to provide a pseudo-random number generator which is
+/// the same across all platforms. This is somewhat close to the libc
+/// implementation. Note: This is not a cryptographically secure pseudorandom
+/// number generator.
+class Random {
+public:
+  /// C'tor
+  Random(unsigned _seed):Seed(_seed) {}
+  /// Return the next random value.
+  unsigned Rand() {
+    unsigned Val = Seed + 0x000b07a1;
+    Seed = (Val * 0x3c7c0ac1);
+    // Only lowest 19 bits are random-ish.
+    return Seed & 0x7ffff;
+  }
+
+private:
+  unsigned Seed;
+};
+
+/// Generate an empty function with a default argument list.
+Function *GenEmptyFunction(Module *M) {
+  // Type Definitions
+  std::vector<Type*> ArgsTy;
+  // Define a few arguments
+  LLVMContext &Context = M->getContext();
+  ArgsTy.push_back(PointerType::get(IntegerType::getInt8Ty(Context), 0));
+  ArgsTy.push_back(PointerType::get(IntegerType::getInt32Ty(Context), 0));
+  ArgsTy.push_back(PointerType::get(IntegerType::getInt64Ty(Context), 0));
+  ArgsTy.push_back(IntegerType::getInt32Ty(Context));
+  ArgsTy.push_back(IntegerType::getInt64Ty(Context));
+  ArgsTy.push_back(IntegerType::getInt8Ty(Context));
+
+  FunctionType *FuncTy = FunctionType::get(Type::getVoidTy(Context), ArgsTy, 0);
+  // Pick a unique name to describe the input parameters
+  std::stringstream ss;
+  ss<<"autogen_SD"<<SeedCL;
+  Function *Func = Function::Create(FuncTy, GlobalValue::ExternalLinkage,
+                                    ss.str(), M);
+
+  Func->setCallingConv(CallingConv::C);
+  return Func;
+}
+
+/// A base class, implementing utilities needed for
+/// modifying and adding new random instructions.
+struct Modifier {
+  /// Used to store the randomly generated values.
+  typedef std::vector<Value*> PieceTable;
+
+public:
+  /// C'tor
+  Modifier(BasicBlock *_BB, PieceTable *PT, Random *R):
+    BB(_BB),PT(PT),Ran(R),Context(BB->getContext()) {};
+  /// Add a new instruction.
+  virtual void Act() = 0;
+  /// Add N new instructions,
+  virtual void ActN(unsigned n) {
+    for (unsigned i=0; i<n; ++i)
+      Act();
+  }
+
+protected:
+  /// Return a random value from the list of known values.
+  Value *getRandomVal() {
+    assert(PT->size());
+    return PT->at(Ran->Rand() % PT->size());
+  }
+
+  /// Return a random value with a known type.
+  Value *getRandomValue(Type *Tp) {
+    unsigned index = Ran->Rand();
+    for (unsigned i=0; i<PT->size(); ++i) {
+      Value *V = PT->at((index + i) % PT->size());
+      if (V->getType() == Tp)
+        return V;
+    }
+
+    // If the requested type was not found, generate a constant value.
+    if (Tp->isIntegerTy()) {
+      if (Ran->Rand() & 1)
+        return ConstantInt::getAllOnesValue(Tp);
+      return ConstantInt::getNullValue(Tp);
+    } else if (Tp->isFloatingPointTy()) {
+      if (Ran->Rand() & 1)
+        return ConstantFP::getAllOnesValue(Tp);
+      return ConstantFP::getNullValue(Tp);
+    }
+
+    // TODO: return values for vector types.
+    return UndefValue::get(Tp);
+  }
+
+  /// Return a random value of any pointer type.
+  Value *getRandomPointerValue() {
+    unsigned index = Ran->Rand();
+    for (unsigned i=0; i<PT->size(); ++i) {
+      Value *V = PT->at((index + i) % PT->size());
+      if (V->getType()->isPointerTy())
+        return V;
+    }
+    return UndefValue::get(pickPointerType());
+  }
+
+  /// Return a random value of any vector type.
+  Value *getRandomVectorValue() {
+    unsigned index = Ran->Rand();
+    for (unsigned i=0; i<PT->size(); ++i) {
+      Value *V = PT->at((index + i) % PT->size());
+      if (V->getType()->isVectorTy())
+        return V;
+    }
+    return UndefValue::get(pickVectorType());
+  }
+
+  /// Pick a random type.
+  Type *pickType() {
+    return (Ran->Rand() & 1 ? pickVectorType() : pickScalarType());
+  }
+
+  /// Pick a random pointer type.
+  Type *pickPointerType() {
+    Type *Ty = pickType();
+    return PointerType::get(Ty, 0);
+  }
+
+  /// Pick a random vector type.
+  Type *pickVectorType(unsigned len = (unsigned)-1) {
+    Type *Ty = pickScalarType();
+    // Pick a random vector width in the range 2**0 to 2**4.
+    // by adding two randoms we are generating a normal-like distribution
+    // around 2**3.
+    unsigned width = 1<<((Ran->Rand() % 3) + (Ran->Rand() % 3));
+    if (len != (unsigned)-1)
+      width = len;
+    return VectorType::get(Ty, width);
+  }
+
+  /// Pick a random scalar type.
+  Type *pickScalarType() {
+    switch (Ran->Rand() % 15) {
+    case 0: return Type::getInt1Ty(Context);
+    case 1: return Type::getInt8Ty(Context);
+    case 2: return Type::getInt16Ty(Context);
+    case 3: case 4:
+    case 5: return Type::getFloatTy(Context);
+    case 6: case 7:
+    case 8: return Type::getDoubleTy(Context);
+    case 9: case 10:
+    case 11: return Type::getInt32Ty(Context);
+    case 12: case 13:
+    case 14: return Type::getInt64Ty(Context);
+    }
+    llvm_unreachable("Invalid scalar value");
+  }
+
+  /// Basic block to populate
+  BasicBlock *BB;
+  /// Value table
+  PieceTable *PT;
+  /// Random number generator
+  Random *Ran;
+  /// Context
+  LLVMContext &Context;
+};
+
+struct LoadModifier: public Modifier {
+  LoadModifier(BasicBlock *BB, PieceTable *PT, Random *R):Modifier(BB, PT, R) {};
+  virtual void Act() {
+    // Try to use predefined pointers. If non exist, use undef pointer value;
+    Value *Ptr = getRandomPointerValue();
+    Value *V = new LoadInst(Ptr, "L", BB->getTerminator());
+    PT->push_back(V);
+  }
+};
+
+struct StoreModifier: public Modifier {
+  StoreModifier(BasicBlock *BB, PieceTable *PT, Random *R):Modifier(BB, PT, R) {}
+  virtual void Act() {
+    // Try to use predefined pointers. If non exist, use undef pointer value;
+    Value *Ptr = getRandomPointerValue();
+    Type  *Tp = Ptr->getType();
+    Value *Val = getRandomValue(Tp->getContainedType(0));
+
+    // Do not store vectors of i1s because they are unsupported
+    //by the codegen.
+    if (Tp->isVectorTy() && Tp->getScalarSizeInBits() == 1)
+      return;
+
+    new StoreInst(Val, Ptr, BB->getTerminator());
+  }
+};
+
+struct BinModifier: public Modifier {
+  BinModifier(BasicBlock *BB, PieceTable *PT, Random *R):Modifier(BB, PT, R) {}
+
+  virtual void Act() {
+    Value *Val0 = getRandomVal();
+    Value *Val1 = getRandomValue(Val0->getType());
+
+    // Don't handle pointer types.
+    if (Val0->getType()->isPointerTy() ||
+        Val1->getType()->isPointerTy())
+      return;
+
+    // Don't handle i1 types.
+    if (Val0->getType()->getScalarSizeInBits() == 1)
+      return;
+
+
+    bool isFloat = Val0->getType()->getScalarType()->isFloatingPointTy();
+    Instruction* Term = BB->getTerminator();
+    unsigned R = Ran->Rand() % (isFloat ? 7 : 13);
+    Instruction::BinaryOps Op;
+
+    switch (R) {
+    default: llvm_unreachable("Invalid BinOp");
+    case 0:{Op = (isFloat?Instruction::FAdd : Instruction::Add); break; }
+    case 1:{Op = (isFloat?Instruction::FSub : Instruction::Sub); break; }
+    case 2:{Op = (isFloat?Instruction::FMul : Instruction::Mul); break; }
+    case 3:{Op = (isFloat?Instruction::FDiv : Instruction::SDiv); break; }
+    case 4:{Op = (isFloat?Instruction::FDiv : Instruction::UDiv); break; }
+    case 5:{Op = (isFloat?Instruction::FRem : Instruction::SRem); break; }
+    case 6:{Op = (isFloat?Instruction::FRem : Instruction::URem); break; }
+    case 7: {Op = Instruction::Shl;  break; }
+    case 8: {Op = Instruction::LShr; break; }
+    case 9: {Op = Instruction::AShr; break; }
+    case 10:{Op = Instruction::And;  break; }
+    case 11:{Op = Instruction::Or;   break; }
+    case 12:{Op = Instruction::Xor;  break; }
+    }
+
+    PT->push_back(BinaryOperator::Create(Op, Val0, Val1, "B", Term));
+  }
+};
+
+/// Generate constant values.
+struct ConstModifier: public Modifier {
+  ConstModifier(BasicBlock *BB, PieceTable *PT, Random *R):Modifier(BB, PT, R) {}
+  virtual void Act() {
+    Type *Ty = pickType();
+
+    if (Ty->isVectorTy()) {
+      switch (Ran->Rand() % 2) {
+      case 0: if (Ty->getScalarType()->isIntegerTy())
+                return PT->push_back(ConstantVector::getAllOnesValue(Ty));
+      case 1: if (Ty->getScalarType()->isIntegerTy())
+                return PT->push_back(ConstantVector::getNullValue(Ty));
+      }
+    }
+
+    if (Ty->isFloatingPointTy()) {
+      if (Ran->Rand() & 1)
+        return PT->push_back(ConstantFP::getNullValue(Ty));
+      return PT->push_back(ConstantFP::get(Ty,
+                                           static_cast<double>(1)/Ran->Rand()));
+    }
+
+    if (Ty->isIntegerTy()) {
+      switch (Ran->Rand() % 7) {
+      case 0: if (Ty->isIntegerTy())
+                return PT->push_back(ConstantInt::get(Ty,
+                  APInt::getAllOnesValue(Ty->getPrimitiveSizeInBits())));
+      case 1: if (Ty->isIntegerTy())
+                return PT->push_back(ConstantInt::get(Ty,
+                  APInt::getNullValue(Ty->getPrimitiveSizeInBits())));
+      case 2: case 3: case 4: case 5:
+      case 6: if (Ty->isIntegerTy())
+                PT->push_back(ConstantInt::get(Ty, Ran->Rand()));
+      }
+    }
+
+  }
+};
+
+struct AllocaModifier: public Modifier {
+  AllocaModifier(BasicBlock *BB, PieceTable *PT, Random *R):Modifier(BB, PT, R){}
+
+  virtual void Act() {
+    Type *Tp = pickType();
+    PT->push_back(new AllocaInst(Tp, "A", BB->getFirstNonPHI()));
+  }
+};
+
+struct ExtractElementModifier: public Modifier {
+  ExtractElementModifier(BasicBlock *BB, PieceTable *PT, Random *R):
+    Modifier(BB, PT, R) {}
+
+  virtual void Act() {
+    Value *Val0 = getRandomVectorValue();
+    Value *V = ExtractElementInst::Create(Val0,
+             ConstantInt::get(Type::getInt32Ty(BB->getContext()),
+             Ran->Rand() % cast<VectorType>(Val0->getType())->getNumElements()), 
+             "E", BB->getTerminator());
+    return PT->push_back(V);
+  }
+};
+
+struct ShuffModifier: public Modifier {
+  ShuffModifier(BasicBlock *BB, PieceTable *PT, Random *R):Modifier(BB, PT, R) {}
+  virtual void Act() {
+
+    Value *Val0 = getRandomVectorValue();
+    Value *Val1 = getRandomValue(Val0->getType());
+
+    unsigned Width = cast<VectorType>(Val0->getType())->getNumElements();
+    std::vector<Constant*> Idxs;
+
+    Type *I32 = Type::getInt32Ty(BB->getContext());
+    for (unsigned i=0; i<Width; ++i) {
+      Constant *CI = ConstantInt::get(I32, Ran->Rand() % (Width*2));
+      // Pick some undef values.
+      if (!(Ran->Rand() % 5))
+        CI = UndefValue::get(I32);
+      Idxs.push_back(CI);
+    }
+
+    Constant *Mask = ConstantVector::get(Idxs);
+
+    Value *V = new ShuffleVectorInst(Val0, Val1, Mask, "Shuff",
+                                     BB->getTerminator());
+    PT->push_back(V);
+  }
+};
+
+struct InsertElementModifier: public Modifier {
+  InsertElementModifier(BasicBlock *BB, PieceTable *PT, Random *R):
+    Modifier(BB, PT, R) {}
+
+  virtual void Act() {
+    Value *Val0 = getRandomVectorValue();
+    Value *Val1 = getRandomValue(Val0->getType()->getScalarType());
+
+    Value *V = InsertElementInst::Create(Val0, Val1,
+              ConstantInt::get(Type::getInt32Ty(BB->getContext()),
+              Ran->Rand() % cast<VectorType>(Val0->getType())->getNumElements()),
+              "I",  BB->getTerminator());
+    return PT->push_back(V);
+  }
+
+};
+
+struct CastModifier: public Modifier {
+  CastModifier(BasicBlock *BB, PieceTable *PT, Random *R):Modifier(BB, PT, R) {}
+  virtual void Act() {
+
+    Value *V = getRandomVal();
+    Type *VTy = V->getType();
+    Type *DestTy = pickScalarType();
+
+    // Handle vector casts vectors.
+    if (VTy->isVectorTy()) {
+      VectorType *VecTy = cast<VectorType>(VTy);
+      DestTy = pickVectorType(VecTy->getNumElements());
+    }
+
+    // no need to casr.
+    if (VTy == DestTy) return;
+
+    // Pointers:
+    if (VTy->isPointerTy()) {
+      if (!DestTy->isPointerTy())
+        DestTy = PointerType::get(DestTy, 0);
+      return PT->push_back(
+        new BitCastInst(V, DestTy, "PC", BB->getTerminator()));
+    }
+
+    // Generate lots of bitcasts.
+    if ((Ran->Rand() & 1) &&
+        VTy->getPrimitiveSizeInBits() == DestTy->getPrimitiveSizeInBits()) {
+      return PT->push_back(
+        new BitCastInst(V, DestTy, "BC", BB->getTerminator()));
+    }
+
+    // Both types are integers:
+    if (VTy->getScalarType()->isIntegerTy() &&
+        DestTy->getScalarType()->isIntegerTy()) {
+      if (VTy->getScalarType()->getPrimitiveSizeInBits() >
+          DestTy->getScalarType()->getPrimitiveSizeInBits()) {
+        return PT->push_back(
+          new TruncInst(V, DestTy, "Tr", BB->getTerminator()));
+      } else {
+        if (Ran->Rand() & 1)
+          return PT->push_back(
+            new ZExtInst(V, DestTy, "ZE", BB->getTerminator()));
+        return PT->push_back(new SExtInst(V, DestTy, "Se", BB->getTerminator()));
+      }
+    }
+
+    // Fp to int.
+    if (VTy->getScalarType()->isFloatingPointTy() &&
+        DestTy->getScalarType()->isIntegerTy()) {
+      if (Ran->Rand() & 1)
+        return PT->push_back(
+          new FPToSIInst(V, DestTy, "FC", BB->getTerminator()));
+      return PT->push_back(new FPToUIInst(V, DestTy, "FC", BB->getTerminator()));
+    }
+
+    // Int to fp.
+    if (VTy->getScalarType()->isIntegerTy() &&
+        DestTy->getScalarType()->isFloatingPointTy()) {
+      if (Ran->Rand() & 1)
+        return PT->push_back(
+          new SIToFPInst(V, DestTy, "FC", BB->getTerminator()));
+      return PT->push_back(new UIToFPInst(V, DestTy, "FC", BB->getTerminator()));
+
+    }
+
+    // Both floats.
+    if (VTy->getScalarType()->isFloatingPointTy() &&
+        DestTy->getScalarType()->isFloatingPointTy()) {
+      if (VTy->getScalarType()->getPrimitiveSizeInBits() >
+          DestTy->getScalarType()->getPrimitiveSizeInBits()) {
+        return PT->push_back(
+          new FPTruncInst(V, DestTy, "Tr", BB->getTerminator()));
+      } else {
+        return PT->push_back(
+          new FPExtInst(V, DestTy, "ZE", BB->getTerminator()));
+      }
+    }
+  }
+
+};
+
+struct SelectModifier: public Modifier {
+  SelectModifier(BasicBlock *BB, PieceTable *PT, Random *R):
+    Modifier(BB, PT, R) {}
+
+  virtual void Act() {
+    // Try a bunch of different select configuration until a valid one is found.
+      Value *Val0 = getRandomVal();
+      Value *Val1 = getRandomValue(Val0->getType());
+
+      Type *CondTy = Type::getInt1Ty(Context);
+
+      // If the value type is a vector, and we allow vector select, then in 50%
+      // of the cases generate a vector select.
+      if (Val0->getType()->isVectorTy() && (Ran->Rand() % 1)) {
+        unsigned NumElem = cast<VectorType>(Val0->getType())->getNumElements();
+        CondTy = VectorType::get(CondTy, NumElem);
+      }
+
+      Value *Cond = getRandomValue(CondTy);
+      Value *V = SelectInst::Create(Cond, Val0, Val1, "Sl", BB->getTerminator());
+      return PT->push_back(V);
+  }
+};
+
+
+struct CmpModifier: public Modifier {
+  CmpModifier(BasicBlock *BB, PieceTable *PT, Random *R):Modifier(BB, PT, R) {}
+  virtual void Act() {
+
+    Value *Val0 = getRandomVal();
+    Value *Val1 = getRandomValue(Val0->getType());
+
+    if (Val0->getType()->isPointerTy()) return;
+    bool fp = Val0->getType()->getScalarType()->isFloatingPointTy();
+
+    int op;
+    if (fp) {
+      op = Ran->Rand() %
+      (CmpInst::LAST_FCMP_PREDICATE - CmpInst::FIRST_FCMP_PREDICATE) +
+       CmpInst::FIRST_FCMP_PREDICATE;
+    } else {
+      op = Ran->Rand() %
+      (CmpInst::LAST_ICMP_PREDICATE - CmpInst::FIRST_ICMP_PREDICATE) +
+       CmpInst::FIRST_ICMP_PREDICATE;
+    }
+
+    Value *V = CmpInst::Create(fp ? Instruction::FCmp : Instruction::ICmp,
+                               op, Val0, Val1, "Cmp", BB->getTerminator());
+    return PT->push_back(V);
+  }
+};
+
+void FillFunction(Function *F) {
+  // Create a legal entry block.
+  BasicBlock *BB = BasicBlock::Create(F->getContext(), "BB", F);
+  ReturnInst::Create(F->getContext(), BB);
+
+  // Create the value table.
+  Modifier::PieceTable PT;
+  // Pick an initial seed value
+  Random R(SeedCL);
+
+  // Consider arguments as legal values.
+  for (Function::arg_iterator it = F->arg_begin(), e = F->arg_end();
+       it != e; ++it)
+    PT.push_back(it);
+
+  // List of modifiers which add new random instructions.
+  std::vector<Modifier*> Modifiers;
+  std::auto_ptr<Modifier> LM(new LoadModifier(BB, &PT, &R));
+  std::auto_ptr<Modifier> SM(new StoreModifier(BB, &PT, &R));
+  std::auto_ptr<Modifier> EE(new ExtractElementModifier(BB, &PT, &R));
+  std::auto_ptr<Modifier> SHM(new ShuffModifier(BB, &PT, &R));
+  std::auto_ptr<Modifier> IE(new InsertElementModifier(BB, &PT, &R));
+  std::auto_ptr<Modifier> BM(new BinModifier(BB, &PT, &R));
+  std::auto_ptr<Modifier> CM(new CastModifier(BB, &PT, &R));
+  std::auto_ptr<Modifier> SLM(new SelectModifier(BB, &PT, &R));
+  std::auto_ptr<Modifier> PM(new CmpModifier(BB, &PT, &R));
+  Modifiers.push_back(LM.get());
+  Modifiers.push_back(SM.get());
+  Modifiers.push_back(EE.get());
+  Modifiers.push_back(SHM.get());
+  Modifiers.push_back(IE.get());
+  Modifiers.push_back(BM.get());
+  Modifiers.push_back(CM.get());
+  Modifiers.push_back(SLM.get());
+  Modifiers.push_back(PM.get());
+
+  // Generate the random instructions
+  AllocaModifier AM(BB, &PT, &R); AM.ActN(5); // Throw in a few allocas
+  ConstModifier COM(BB, &PT, &R);  COM.ActN(40); // Throw in a few constants
+
+  for (unsigned i=0; i< SizeCL / Modifiers.size(); ++i)
+    for (std::vector<Modifier*>::iterator it = Modifiers.begin(),
+         e = Modifiers.end(); it != e; ++it) {
+      (*it)->Act();
+    }
+
+  SM->ActN(5); // Throw in a few stores.
+}
+
+void IntroduceControlFlow(Function *F) {
+  std::set<Instruction*> BoolInst;
+  for (BasicBlock::iterator it = F->begin()->begin(),
+       e = F->begin()->end(); it != e; ++it) {
+    if (it->getType() == IntegerType::getInt1Ty(F->getContext()))
+      BoolInst.insert(it);
+  }
+
+  for (std::set<Instruction*>::iterator it = BoolInst.begin(),
+       e = BoolInst.end(); it != e; ++it) {
+    Instruction *Instr = *it;
+    BasicBlock *Curr = Instr->getParent();
+    BasicBlock::iterator Loc= Instr;
+    BasicBlock *Next = Curr->splitBasicBlock(Loc, "CF");
+    Instr->moveBefore(Curr->getTerminator());
+    if (Curr != &F->getEntryBlock()) {
+      BranchInst::Create(Curr, Next, Instr, Curr->getTerminator());
+      Curr->getTerminator()->eraseFromParent();
+    }
+  }
+}
+
+int main(int argc, char **argv) {
+  // Init LLVM, call llvm_shutdown() on exit, parse args, etc.
+  llvm::PrettyStackTraceProgram X(argc, argv);
+  cl::ParseCommandLineOptions(argc, argv, "llvm codegen stress-tester\n");
+  llvm_shutdown_obj Y;
+
+  std::auto_ptr<Module> M(new Module("/tmp/autogen.bc", getGlobalContext()));
+  Function *F = GenEmptyFunction(M.get());
+  FillFunction(F);
+  IntroduceControlFlow(F);
+
+  // Figure out what stream we are supposed to write to...
+  OwningPtr<tool_output_file> Out;
+  // Default to standard output.
+  if (OutputFilename.empty())
+    OutputFilename = "-";
+
+  std::string ErrorInfo;
+  Out.reset(new tool_output_file(OutputFilename.c_str(), ErrorInfo,
+                                 raw_fd_ostream::F_Binary));
+  if (!ErrorInfo.empty()) {
+    errs() << ErrorInfo << '\n';
+    return 1;
+  }
+
+  PassManager Passes;
+  Passes.add(createVerifierPass());
+  Passes.add(createPrintModulePass(&Out->os()));
+  Passes.run(*M.get());
+  Out->keep();
+
+  return 0;
+}