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//===- 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;
}
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