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//===- RaiseAllocations.cpp - Convert @malloc & @free calls to insts ------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the RaiseAllocations pass which convert malloc and free
// calls to malloc and free instructions.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "raiseallocs"
#include "llvm/Transforms/IPO.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.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 @malloc and @free calls into the appropriate
// instruction.
//
class VISIBILITY_HIDDEN RaiseAllocations : public ModulePass {
Function *MallocFunc; // Functions in the module we are processing
Function *FreeFunc; // Initialized by doPassInitializationVirt
public:
static char ID; // Pass identification, replacement for typeid
RaiseAllocations()
: ModulePass((intptr_t)&ID), MallocFunc(0), FreeFunc(0) {}
// doPassInitialization - For the raise allocations pass, this finds a
// declaration for malloc and free if they exist.
//
void doInitialization(Module &M);
// run - This method does the actual work of converting instructions over.
//
bool runOnModule(Module &M);
};
char RaiseAllocations::ID = 0;
RegisterPass<RaiseAllocations>
X("raiseallocs", "Raise allocations from calls to instructions");
} // end anonymous namespace
// 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 malloc and
// free functions. If this is the case, grab the method pointers that the
// module is using.
//
// Lookup @malloc and @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 Malloc and free prototypes if they exist!
MallocFunc = M.getFunction("malloc");
if (MallocFunc) {
const FunctionType* TyWeHave = MallocFunc->getFunctionType();
// Get the expected prototype for malloc
const FunctionType *Malloc1Type =
FunctionType::get(PointerType::get(Type::Int8Ty),
std::vector<const Type*>(1, Type::Int64Ty), false);
// Chck to see if we got the expected malloc
if (TyWeHave != Malloc1Type) {
// Check to see if the prototype is wrong, giving us sbyte*(uint) * malloc
// This handles the common declaration of: 'void *malloc(unsigned);'
const FunctionType *Malloc2Type =
FunctionType::get(PointerType::get(Type::Int8Ty),
std::vector<const Type*>(1, Type::Int32Ty), false);
if (TyWeHave != Malloc2Type) {
// Check to see if the prototype is missing, giving us
// sbyte*(...) * malloc
// This handles the common declaration of: 'void *malloc();'
const FunctionType *Malloc3Type =
FunctionType::get(PointerType::get(Type::Int8Ty),
std::vector<const Type*>(), true);
if (TyWeHave != Malloc3Type)
// Give up
MallocFunc = 0;
}
}
}
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::VoidTy,
std::vector<const Type*>(1, PointerType::get(Type::Int8Ty)), 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::VoidTy,
std::vector<const Type*>(),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::Int32Ty,
std::vector<const Type*>(),true);
if (TyWeHave != Free3Type) {
// Give up.
FreeFunc = 0;
}
}
}
}
// Don't mess with locally defined versions of these functions...
if (MallocFunc && !MallocFunc->isDeclaration()) MallocFunc = 0;
if (FreeFunc && !FreeFunc->isDeclaration()) FreeFunc = 0;
}
// run - Transform calls into instructions...
//
bool RaiseAllocations::runOnModule(Module &M) {
// Find the malloc/free prototypes...
doInitialization(M);
bool Changed = false;
// First, process all of the malloc calls...
if (MallocFunc) {
std::vector<User*> Users(MallocFunc->use_begin(), MallocFunc->use_end());
std::vector<Value*> EqPointers; // Values equal to MallocFunc
while (!Users.empty()) {
User *U = Users.back();
Users.pop_back();
if (Instruction *I = dyn_cast<Instruction>(U)) {
CallSite CS = CallSite::get(I);
if (CS.getInstruction() && CS.arg_begin() != CS.arg_end() &&
(CS.getCalledFunction() == MallocFunc ||
std::find(EqPointers.begin(), EqPointers.end(),
CS.getCalledValue()) != EqPointers.end())) {
Value *Source = *CS.arg_begin();
// If no prototype was provided for malloc, we may need to cast the
// source size.
if (Source->getType() != Type::Int32Ty)
Source =
CastInst::createIntegerCast(Source, Type::Int32Ty, false/*ZExt*/,
"MallocAmtCast", I);
MallocInst *MI = new MallocInst(Type::Int8Ty, Source, "", I);
MI->takeName(I);
I->replaceAllUsesWith(MI);
// 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))
new BranchInst(II->getNormalDest(), I);
// Delete the old call site
MI->getParent()->getInstList().erase(I);
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);
}
}
}
}
// Next, 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)) {
CallSite CS = CallSite::get(I);
if (CS.getInstruction() && CS.arg_begin() != CS.arg_end() &&
(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, PointerType::get(Type::Int8Ty),
"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))
new BranchInst(II->getNormalDest(), I);
// Delete the old call site
if (I->getType() != Type::VoidTy)
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;
}
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