Auto-upgrade free instructions to calls to the builtin free function.

Update all analysis passes and transforms to treat free calls just like FreeInst.
Remove RaiseAllocations and all its tests since FreeInst no longer needs to be raised.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84987 91177308-0d34-0410-b5e6-96231b3b80d8

17 files changed, 151 insertions, 200 deletions

diff --git a/lib/Analysis/IPA/Andersens.cpp b/lib/Analysis/IPA/Andersens.cpp
index b5129a7d3b..e37a9dbb7a 100644
--- a/lib/Analysis/IPA/Andersens.cpp
+++ b/lib/Analysis/IPA/Andersens.cpp
@@ -1017,6 +1017,8 @@ bool Andersens::AnalyzeUsesOfFunction(Value *V) {
       }
     } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
       if (AnalyzeUsesOfFunction(GEP)) return true;
+    } else if (isa<FreeInst>(*UI) || isFreeCall(*UI)) {
+      return false;
     } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
       // Make sure that this is just the function being called, not that it is
       // passing into the function.
@@ -1038,8 +1040,6 @@ bool Andersens::AnalyzeUsesOfFunction(Value *V) {
     } else if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) {
       if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
         return true;  // Allow comparison against null.
-    } else if (isa<FreeInst>(*UI)) {
-      return false;
     } else {
       return true;
     }
diff --git a/lib/Analysis/IPA/GlobalsModRef.cpp b/lib/Analysis/IPA/GlobalsModRef.cpp
index 7949288340..d83ea48080 100644
--- a/lib/Analysis/IPA/GlobalsModRef.cpp
+++ b/lib/Analysis/IPA/GlobalsModRef.cpp
@@ -240,6 +240,8 @@ bool GlobalsModRef::AnalyzeUsesOfPointer(Value *V,
     } else if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
       if (AnalyzeUsesOfPointer(BCI, Readers, Writers, OkayStoreDest))
         return true;
+    } else if (isa<FreeInst>(*UI) || isFreeCall(*UI)) {
+      Writers.push_back(cast<Instruction>(*UI)->getParent()->getParent());
     } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
       // Make sure that this is just the function being called, not that it is
       // passing into the function.
@@ -261,8 +263,6 @@ bool GlobalsModRef::AnalyzeUsesOfPointer(Value *V,
     } else if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) {
       if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
         return true;  // Allow comparison against null.
-    } else if (FreeInst *F = dyn_cast<FreeInst>(*UI)) {
-      Writers.push_back(F->getParent()->getParent());
     } else {
       return true;
     }
@@ -439,7 +439,8 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
           if (cast<StoreInst>(*II).isVolatile())
             // Treat volatile stores as reading memory somewhere.
             FunctionEffect |= Ref;
-        } else if (isMalloc(&cast<Instruction>(*II)) || isa<FreeInst>(*II)) {
+        } else if (isMalloc(&cast<Instruction>(*II)) || isa<FreeInst>(*II) ||
+                   isFreeCall(&cast<Instruction>(*II))) {
           FunctionEffect |= ModRef;
         }
 
diff --git a/lib/Analysis/MallocHelper.cpp b/lib/Analysis/MallocHelper.cpp
index e7bb41eeec..511de9d6a5 100644
--- a/lib/Analysis/MallocHelper.cpp
+++ b/lib/Analysis/MallocHelper.cpp
@@ -263,3 +263,29 @@ Value* llvm::getMallocArraySize(CallInst* CI, LLVMContext &Context,
   assert(BO && "getMallocArraySize not constant but not multiplication either");
   return BO->getOperand(0);
 }
+
+/// isFreeCall - Returns true if the the value is a call to the builtin free()
+bool llvm::isFreeCall(const Value* I) {
+  const CallInst *CI = dyn_cast<CallInst>(I);
+  if (!CI)
+    return false;
+
+  const Module* M = CI->getParent()->getParent()->getParent();
+  Function *FreeFunc = M->getFunction("free");
+
+  if (CI->getOperand(0) != FreeFunc)
+    return false;
+
+  // Check free prototype.
+  // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin 
+  // attribute will exist.
+  const FunctionType *FTy = FreeFunc->getFunctionType();
+  if (FTy->getReturnType() != Type::getVoidTy(M->getContext()))
+    return false;
+  if (FTy->getNumParams() != 1)
+    return false;
+  if (FTy->param_begin()->get() != Type::getInt8PtrTy(M->getContext()))
+    return false;
+
+  return true;
+}
diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index c3aa5bc930..ce7674003f 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -118,6 +118,10 @@ getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
       
       // FreeInsts erase the entire structure
       PointerSize = ~0ULL;
+    } else if (isFreeCall(Inst)) {
+      Pointer = Inst->getOperand(0);
+      // calls to free() erase the entire structure
+      PointerSize = ~0ULL;
     } else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) {
       // Debug intrinsics don't cause dependences.
       if (isa<DbgInfoIntrinsic>(Inst)) continue;
@@ -314,6 +318,10 @@ MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) {
       MemPtr = LI->getPointerOperand();
       MemSize = AA->getTypeStoreSize(LI->getType());
     }
+  } else if (isFreeCall(QueryInst)) {
+    MemPtr = QueryInst->getOperand(0);
+    // calls to free() erase the entire structure, not just a field.
+    MemSize = ~0UL;
   } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
     CallSite QueryCS = CallSite::get(QueryInst);
     bool isReadOnly = AA->onlyReadsMemory(QueryCS);
diff --git a/lib/AsmParser/LLParser.cpp b/lib/AsmParser/LLParser.cpp
index 271567bd1e..52fd2b21e1 100644
--- a/lib/AsmParser/LLParser.cpp
+++ b/lib/AsmParser/LLParser.cpp
@@ -2800,7 +2800,7 @@ bool LLParser::ParseInstruction(Instruction *&Inst, BasicBlock *BB,
   // Memory.
   case lltok::kw_alloca:         return ParseAlloc(Inst, PFS);
   case lltok::kw_malloc:         return ParseAlloc(Inst, PFS, BB, false);
-  case lltok::kw_free:           return ParseFree(Inst, PFS);
+  case lltok::kw_free:           return ParseFree(Inst, PFS, BB);
   case lltok::kw_load:           return ParseLoad(Inst, PFS, false);
   case lltok::kw_store:          return ParseStore(Inst, PFS, false);
   case lltok::kw_volatile:
@@ -3496,12 +3496,13 @@ bool LLParser::ParseAlloc(Instruction *&Inst, PerFunctionState &PFS,
 
 /// ParseFree
 ///   ::= 'free' TypeAndValue
-bool LLParser::ParseFree(Instruction *&Inst, PerFunctionState &PFS) {
+bool LLParser::ParseFree(Instruction *&Inst, PerFunctionState &PFS,
+                         BasicBlock* BB) {
   Value *Val; LocTy Loc;
   if (ParseTypeAndValue(Val, Loc, PFS)) return true;
   if (!isa<PointerType>(Val->getType()))
     return Error(Loc, "operand to free must be a pointer");
-  Inst = new FreeInst(Val);
+  Inst = CallInst::CreateFree(Val, BB);
   return false;
 }
 
diff --git a/lib/AsmParser/LLParser.h b/lib/AsmParser/LLParser.h
index 5dd6a2e700..b6877bc7c1 100644
--- a/lib/AsmParser/LLParser.h
+++ b/lib/AsmParser/LLParser.h
@@ -280,7 +280,7 @@ namespace llvm {
     bool ParseCall(Instruction *&I, PerFunctionState &PFS, bool isTail);
     bool ParseAlloc(Instruction *&I, PerFunctionState &PFS,
                     BasicBlock *BB = 0, bool isAlloca = true);
-    bool ParseFree(Instruction *&I, PerFunctionState &PFS);
+    bool ParseFree(Instruction *&I, PerFunctionState &PFS, BasicBlock *BB);
     bool ParseLoad(Instruction *&I, PerFunctionState &PFS, bool isVolatile);
     bool ParseStore(Instruction *&I, PerFunctionState &PFS, bool isVolatile);
     bool ParseGetResult(Instruction *&I, PerFunctionState &PFS);
diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 3a385cbe38..ffd330c74e 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -2073,7 +2073,8 @@ bool BitcodeReader::ParseFunctionBody(Function *F) {
       if (getValueTypePair(Record, OpNum, NextValueNo, Op) ||
           OpNum != Record.size())
         return Error("Invalid FREE record");
-      I = new FreeInst(Op);
+      if (!CurBB) return Error("Invalid free instruction with no BB");
+      I = CallInst::CreateFree(Op, CurBB);
       InstructionList.push_back(I);
       break;
     }
diff --git a/lib/Transforms/IPO/CMakeLists.txt b/lib/Transforms/IPO/CMakeLists.txt
index 5c28801555..92bef3bb75 100644
--- a/lib/Transforms/IPO/CMakeLists.txt
+++ b/lib/Transforms/IPO/CMakeLists.txt
@@ -19,7 +19,6 @@ add_llvm_library(LLVMipo
   PartialInlining.cpp
   PartialSpecialization.cpp
   PruneEH.cpp
-  RaiseAllocations.cpp
   StripDeadPrototypes.cpp
   StripSymbols.cpp
   StructRetPromotion.cpp
diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp
index 9ced2e89a7..0bc086f432 100644
--- a/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/lib/Transforms/IPO/GlobalOpt.cpp
@@ -1364,10 +1364,11 @@ static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV,
                                                OrigBB->getParent());
     BasicBlock *NextBlock = BasicBlock::Create(Context, "next",
                                                OrigBB->getParent());
-    BranchInst::Create(FreeBlock, NextBlock, Cmp, NullPtrBlock);
+    Instruction *BI = BranchInst::Create(FreeBlock, NextBlock,
+                                         Cmp, NullPtrBlock);
 
     // Fill in FreeBlock.
-    new FreeInst(GVVal, FreeBlock);
+    CallInst::CreateFree(GVVal, BI);
     new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
                   FreeBlock);
     BranchInst::Create(NextBlock, FreeBlock);
diff --git a/lib/Transforms/IPO/IPO.cpp b/lib/Transforms/IPO/IPO.cpp
index 43066076ca..83e8624fe0 100644
--- a/lib/Transforms/IPO/IPO.cpp
+++ b/lib/Transforms/IPO/IPO.cpp
@@ -63,7 +63,7 @@ void LLVMAddPruneEHPass(LLVMPassManagerRef PM) {
 }
 
 void LLVMAddRaiseAllocationsPass(LLVMPassManagerRef PM) {
-  unwrap(PM)->add(createRaiseAllocationsPass());
+  // FIXME: Remove in LLVM 3.0.
 }
 
 void LLVMAddStripDeadPrototypesPass(LLVMPassManagerRef PM) {
diff --git a/lib/Transforms/IPO/RaiseAllocations.cpp b/lib/Transforms/IPO/RaiseAllocations.cpp
deleted file mode 100644
index deb4405754..0000000000
--- a/lib/Transforms/IPO/RaiseAllocations.cpp
+++ /dev/null
@@ -1,173 +0,0 @@
-//===- RaiseAllocations.cpp - Convert @free calls to insts ------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file defines the RaiseAllocations pass which convert free calls to free
-// instructions.
-//
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "raiseallocs"
-#include "llvm/Transforms/IPO.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Module.h"
-#include "llvm/Instructions.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/CallSite.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/ADT/Statistic.h"
-#include <algorithm>
-using namespace llvm;
-
-STATISTIC(NumRaised, "Number of allocations raised");
-
-namespace {
-  // RaiseAllocations - Turn @free calls into the appropriate
-  // instruction.
-  //
-  class VISIBILITY_HIDDEN RaiseAllocations : public ModulePass {
-    Function *FreeFunc;   // Functions in the module we are processing
-                          // Initialized by doPassInitializationVirt
-  public:
-    static char ID; // Pass identification, replacement for typeid
-    RaiseAllocations() 
-      : ModulePass(&ID), FreeFunc(0) {}
-
-    // doPassInitialization - For the raise allocations pass, this finds a
-    // declaration for free if it exists.
-    //
-    void doInitialization(Module &M);
-
-    // run - This method does the actual work of converting instructions over.
-    //
-    bool runOnModule(Module &M);
-  };
-}  // end anonymous namespace
-
-char RaiseAllocations::ID = 0;
-static RegisterPass<RaiseAllocations>
-X("raiseallocs", "Raise allocations from calls to instructions");
-
-// createRaiseAllocationsPass - The interface to this file...
-ModulePass *llvm::createRaiseAllocationsPass() {
-  return new RaiseAllocations();
-}
-
-
-// If the module has a symbol table, they might be referring to the free 
-// function.  If this is the case, grab the method pointers that the module is
-// using.
-//
-// Lookup @free in the symbol table, for later use.  If they don't
-// exist, or are not external, we do not worry about converting calls to that
-// function into the appropriate instruction.
-//
-void RaiseAllocations::doInitialization(Module &M) {
-  // Get free prototype if it exists!
-  FreeFunc = M.getFunction("free");
-  if (FreeFunc) {
-    const FunctionType* TyWeHave = FreeFunc->getFunctionType();
-    
-    // Get the expected prototype for void free(i8*)
-    const FunctionType *Free1Type =
-      FunctionType::get(Type::getVoidTy(M.getContext()),
-        std::vector<const Type*>(1, PointerType::getUnqual(
-                                 Type::getInt8Ty(M.getContext()))), 
-                                 false);
-
-    if (TyWeHave != Free1Type) {
-      // Check to see if the prototype was forgotten, giving us 
-      // void (...) * free
-      // This handles the common forward declaration of: 'void free();'
-      const FunctionType* Free2Type =
-                    FunctionType::get(Type::getVoidTy(M.getContext()), true);
-
-      if (TyWeHave != Free2Type) {
-        // One last try, check to see if we can find free as 
-        // int (...)* free.  This handles the case where NOTHING was declared.
-        const FunctionType* Free3Type =
-                    FunctionType::get(Type::getInt32Ty(M.getContext()), true);
-        
-        if (TyWeHave != Free3Type) {
-          // Give up.
-          FreeFunc = 0;
-        }
-      }
-    }
-  }
-
-  // Don't mess with locally defined versions of these functions...
-  if (FreeFunc && !FreeFunc->isDeclaration())     FreeFunc = 0;
-}
-
-// run - Transform calls into instructions...
-//
-bool RaiseAllocations::runOnModule(Module &M) {
-  // Find the free prototype...
-  doInitialization(M);
-  
-  bool Changed = false;
-
-  // Process all free calls...
-  if (FreeFunc) {
-    std::vector<User*> Users(FreeFunc->use_begin(), FreeFunc->use_end());
-    std::vector<Value*> EqPointers;   // Values equal to FreeFunc
-
-    while (!Users.empty()) {
-      User *U = Users.back();
-      Users.pop_back();
-
-      if (Instruction *I = dyn_cast<Instruction>(U)) {
-        if (isa<InvokeInst>(I))
-          continue;
-        CallSite CS = CallSite::get(I);
-        if (CS.getInstruction() && !CS.arg_empty() &&
-            (CS.getCalledFunction() == FreeFunc ||
-             std::find(EqPointers.begin(), EqPointers.end(),
-                       CS.getCalledValue()) != EqPointers.end())) {
-
-          // If no prototype was provided for free, we may need to cast the
-          // source pointer.  This should be really uncommon, but it's necessary
-          // just in case we are dealing with weird code like this:
-          //   free((long)ptr);
-          //
-          Value *Source = *CS.arg_begin();
-          if (!isa<PointerType>(Source->getType()))
-            Source = new IntToPtrInst(Source,           
-                        Type::getInt8PtrTy(M.getContext()), 
-                                      "FreePtrCast", I);
-          new FreeInst(Source, I);
-
-          // If the old instruction was an invoke, add an unconditional branch
-          // before the invoke, which will become the new terminator.
-          if (InvokeInst *II = dyn_cast<InvokeInst>(I))
-            BranchInst::Create(II->getNormalDest(), I);
-
-          // Delete the old call site
-          if (I->getType() != Type::getVoidTy(M.getContext()))
-            I->replaceAllUsesWith(UndefValue::get(I->getType()));
-          I->eraseFromParent();
-          Changed = true;
-          ++NumRaised;
-        }
-      } else if (GlobalValue *GV = dyn_cast<GlobalValue>(U)) {
-        Users.insert(Users.end(), GV->use_begin(), GV->use_end());
-        EqPointers.push_back(GV);
-      } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
-        if (CE->isCast()) {
-          Users.insert(Users.end(), CE->use_begin(), CE->use_end());
-          EqPointers.push_back(CE);
-        }
-      }
-    }
-  }
-
-  return Changed;
-}
diff --git a/lib/Transforms/Scalar/DeadStoreElimination.cpp b/lib/Transforms/Scalar/DeadStoreElimination.cpp
index a7b3e7524f..f55d8b2acc 100644
--- a/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -26,6 +26,7 @@
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/MallocHelper.h"
 #include "llvm/Analysis/MemoryDependenceAnalysis.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Transforms/Utils/Local.h"
@@ -49,7 +50,7 @@ namespace {
     }
     
     bool runOnBasicBlock(BasicBlock &BB);
-    bool handleFreeWithNonTrivialDependency(FreeInst *F, MemDepResult Dep);
+    bool handleFreeWithNonTrivialDependency(Instruction *F, MemDepResult Dep);
     bool handleEndBlock(BasicBlock &BB);
     bool RemoveUndeadPointers(Value* Ptr, uint64_t killPointerSize,
                               BasicBlock::iterator& BBI,
@@ -88,7 +89,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
     Instruction *Inst = BBI++;
     
     // If we find a store or a free, get its memory dependence.
-    if (!isa<StoreInst>(Inst) && !isa<FreeInst>(Inst))
+    if (!isa<StoreInst>(Inst) && !isa<FreeInst>(Inst) && !isFreeCall(Inst))
       continue;
     
     // Don't molest volatile stores or do queries that will return "clobber".
@@ -103,8 +104,8 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
     if (InstDep.isNonLocal()) continue;
   
     // Handle frees whose dependencies are non-trivial.
-    if (FreeInst *FI = dyn_cast<FreeInst>(Inst)) {
-      MadeChange |= handleFreeWithNonTrivialDependency(FI, InstDep);
+    if (isa<FreeInst>(Inst) || isFreeCall(Inst)) {
+      MadeChange |= handleFreeWithNonTrivialDependency(Inst, InstDep);
       continue;
     }
     
@@ -165,7 +166,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
 
 /// handleFreeWithNonTrivialDependency - Handle frees of entire structures whose
 /// dependency is a store to a field of that structure.
-bool DSE::handleFreeWithNonTrivialDependency(FreeInst *F, MemDepResult Dep) {
+bool DSE::handleFreeWithNonTrivialDependency(Instruction *F, MemDepResult Dep) {
   AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
   
   StoreInst *Dependency = dyn_cast_or_null<StoreInst>(Dep.getInst());
@@ -175,7 +176,8 @@ bool DSE::handleFreeWithNonTrivialDependency(FreeInst *F, MemDepResult Dep) {
   Value *DepPointer = Dependency->getPointerOperand()->getUnderlyingObject();
 
   // Check for aliasing.
-  if (AA.alias(F->getPointerOperand(), 1, DepPointer, 1) !=
+  Value* FreeVal = isa<FreeInst>(F) ? F->getOperand(0) : F->getOperand(1);
+  if (AA.alias(FreeVal, 1, DepPointer, 1) !=
          AliasAnalysis::MustAlias)
     return false;
   
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 21554c108d..be4f775731 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -286,6 +286,7 @@ namespace {
     Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
     Instruction *visitAllocaInst(AllocaInst &AI);
     Instruction *visitFreeInst(FreeInst &FI);
+    Instruction *visitFree(Instruction &FI);
     Instruction *visitLoadInst(LoadInst &LI);
     Instruction *visitStoreInst(StoreInst &SI);
     Instruction *visitBranchInst(BranchInst &BI);
@@ -9747,6 +9748,9 @@ Instruction *InstCombiner::SimplifyMemSet(MemSetInst *MI) {
 /// the heavy lifting.
 ///
 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
+  if (isFreeCall(&CI))
+    return visitFree(CI);
+
   // If the caller function is nounwind, mark the call as nounwind, even if the
   // callee isn't.
   if (CI.getParent()->getParent()->doesNotThrow() &&
@@ -11337,6 +11341,42 @@ Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
   return 0;
 }
 
+Instruction *InstCombiner::visitFree(Instruction &FI) {
+  Value *Op = FI.getOperand(1);
+
+  // free undef -> unreachable.
+  if (isa<UndefValue>(Op)) {
+    // Insert a new store to null because we cannot modify the CFG here.
+    new StoreInst(ConstantInt::getTrue(*Context),
+           UndefValue::get(Type::getInt1PtrTy(*Context)), &FI);
+    return EraseInstFromFunction(FI);
+  }
+  
+  // If we have 'free null' delete the instruction.  This can happen in stl code
+  // when lots of inlining happens.
+  if (isa<ConstantPointerNull>(Op))
+    return EraseInstFromFunction(FI);
+
+  // FIXME: Bring back free (gep X, 0,0,0,0) into free(X) transform
+  
+  if (isMalloc(Op)) {
+    if (CallInst* CI = extractMallocCallFromBitCast(Op)) {
+      if (Op->hasOneUse() && CI->hasOneUse()) {
+        EraseInstFromFunction(FI);
+        EraseInstFromFunction(*CI);
+        return EraseInstFromFunction(*cast<Instruction>(Op));
+      }
+    } else {
+      // Op is a call to malloc
+      if (Op->hasOneUse()) {
+        EraseInstFromFunction(FI);
+        return EraseInstFromFunction(*cast<Instruction>(Op));
+      }
+    }
+  }
+
+  return 0;
+}
 
 /// InstCombineLoadCast - Fold 'load (cast P)' -> cast (load P)' when possible.
 static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI,
diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index e3dd54e8bc..1bb5f4ae7f 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -30,6 +30,7 @@
 #include "llvm/LLVMContext.h"
 #include "llvm/Pass.h"
 #include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/MallocHelper.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Support/CallSite.h"
@@ -400,7 +401,9 @@ private:
   void visitStoreInst     (Instruction &I);
   void visitLoadInst      (LoadInst &I);
   void visitGetElementPtrInst(GetElementPtrInst &I);
-  void visitCallInst      (CallInst &I) { 
+  void visitCallInst      (CallInst &I) {
+    if (isFreeCall(&I))
+      return;
     visitCallSite(CallSite::get(&I));
   }
   void visitInvokeInst    (InvokeInst &II) {
diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index b62261119c..940f5a9ec4 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -24,6 +24,7 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/DebugInfo.h"
+#include "llvm/Analysis/MallocHelper.h"
 #include "llvm/Analysis/ProfileInfo.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Support/GetElementPtrTypeIterator.h"
@@ -59,7 +60,7 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom) {
 
     // If we see a free or a call which may write to memory (i.e. which might do
     // a free) the pointer could be marked invalid.
-    if (isa<FreeInst>(BBI) || 
+    if (isa<FreeInst>(BBI) || isFreeCall(BBI) ||
         (isa<CallInst>(BBI) && BBI->mayWriteToMemory() &&
          !isa<DbgInfoIntrinsic>(BBI)))
       return false;
diff --git a/lib/Transforms/Utils/LowerAllocations.cpp b/lib/Transforms/Utils/LowerAllocations.cpp
index 9c9113daa9..f64a30f5e8 100644
--- a/lib/Transforms/Utils/LowerAllocations.cpp
+++ b/lib/Transforms/Utils/LowerAllocations.cpp
@@ -102,12 +102,8 @@ bool LowerAllocations::runOnBasicBlock(BasicBlock &BB) {
   // Loop over all of the instructions, looking for free instructions
   for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
     if (FreeInst *FI = dyn_cast<FreeInst>(I)) {
-      Value *PtrCast = 
-        new BitCastInst(FI->getOperand(0),
-               Type::getInt8PtrTy(BB.getContext()), "", I);
-
       // Insert a call to the free function...
-      CallInst::Create(FreeFunc, PtrCast, "", I)->setTailCall();
+      CallInst::CreateFree(FI->getOperand(0), I);
 
       // Delete the old free instruction
       I = --BBIL.erase(I);
diff --git a/lib/VMCore/Instructions.cpp b/lib/VMCore/Instructions.cpp
index 99a28594e6..60e203a7e0 100644
--- a/lib/VMCore/Instructions.cpp
+++ b/lib/VMCore/Instructions.cpp
@@ -559,6 +559,51 @@ Instruction *CallInst::CreateMalloc(BasicBlock *InsertAtEnd,
                       ArraySize, MallocF, Name);
 }
 
+static Instruction* createFree(Value* Source, Instruction *InsertBefore,
+                               BasicBlock *InsertAtEnd) {
+  assert(((!InsertBefore && InsertAtEnd) || (InsertBefore && !InsertAtEnd)) &&
+         "createFree needs either InsertBefore or InsertAtEnd");
+  assert(isa<PointerType>(Source->getType()) &&
+         "Can not free something of nonpointer type!");
+
+  BasicBlock* BB = InsertBefore ? InsertBefore->getParent() : InsertAtEnd;
+  Module* M = BB->getParent()->getParent();
+
+  const Type *VoidTy = Type::getVoidTy(M->getContext());
+  const Type *IntPtrTy = Type::getInt8PtrTy(M->getContext());
+  // prototype free as "void free(void*)"
+  Constant *FreeFunc = M->getOrInsertFunction("free", VoidTy, IntPtrTy, NULL);
+
+  CallInst* Result = NULL;
+  Value *PtrCast = Source;
+  if (InsertBefore) {
+    if (Source->getType() != IntPtrTy)
+      PtrCast = new BitCastInst(Source, IntPtrTy, "", InsertBefore);
+    Result = CallInst::Create(FreeFunc, PtrCast, "", InsertBefore);
+  } else {
+    if (Source->getType() != IntPtrTy)
+      PtrCast = new BitCastInst(Source, IntPtrTy, "", InsertAtEnd);
+    Result = CallInst::Create(FreeFunc, PtrCast, "");
+  }
+  Result->setTailCall();
+
+  return Result;
+}
+
+/// CreateFree - Generate the IR for a call to the builtin free function.
+void CallInst::CreateFree(Value* Source, Instruction *InsertBefore) {
+  createFree(Source, InsertBefore, NULL);
+}
+
+/// CreateFree - Generate the IR for a call to the builtin free function.
+/// Note: This function does not add the call to the basic block, that is the
+/// responsibility of the caller.
+Instruction* CallInst::CreateFree(Value* Source, BasicBlock *InsertAtEnd) {
+  Instruction* FreeCall = createFree(Source, NULL, InsertAtEnd);
+  assert(FreeCall && "CreateFree did not create a CallInst");
+  return FreeCall;
+}
+
 //===----------------------------------------------------------------------===//
 //                        InvokeInst Implementation
 //===----------------------------------------------------------------------===//