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//===- RaiseAllocations.cpp - Convert %malloc & %free calls to insts ------===//
//
// This file defines the RaiseAllocations pass which convert malloc and free
// calls to malloc and free instructions.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/ChangeAllocations.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Module.h"
#include "llvm/Function.h"
#include "llvm/DerivedTypes.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
#include "llvm/Pass.h"
#include "Support/StatisticReporter.h"
static Statistic<> NumRaised("raiseallocs\t- Number of allocations raised");
namespace {
// RaiseAllocations - Turn %malloc and %free calls into the appropriate
// instruction.
//
class RaiseAllocations : public BasicBlockPass {
Function *MallocFunc; // Functions in the module we are processing
Function *FreeFunc; // Initialized by doPassInitializationVirt
public:
inline RaiseAllocations() : MallocFunc(0), FreeFunc(0) {}
const char *getPassName() const { return "Raise Allocations"; }
// doPassInitialization - For the raise allocations pass, this finds a
// declaration for malloc and free if they exist.
//
bool doInitialization(Module &M);
// runOnBasicBlock - This method does the actual work of converting
// instructions over, assuming that the pass has already been initialized.
//
bool runOnBasicBlock(BasicBlock &BB);
};
} // end anonymous namespace
// createRaiseAllocationsPass - The interface to this file...
Pass *createRaiseAllocationsPass() {
return new RaiseAllocations();
}
bool RaiseAllocations::doInitialization(Module &M) {
// 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.
//
const FunctionType *MallocType = // Get the type for malloc
FunctionType::get(PointerType::get(Type::SByteTy),
std::vector<const Type*>(1, Type::UIntTy), false);
const FunctionType *FreeType = // Get the type for free
FunctionType::get(Type::VoidTy,
std::vector<const Type*>(1, PointerType::get(Type::SByteTy)),
false);
MallocFunc = M.getFunction("malloc", MallocType);
FreeFunc = M.getFunction("free" , FreeType);
// Check to see if the prototype is missing, giving us sbyte*(...) * malloc
// This handles the common declaration of: 'char *malloc();'
if (MallocFunc == 0) {
MallocType = FunctionType::get(PointerType::get(Type::SByteTy),
std::vector<const Type*>(), true);
MallocFunc = M.getFunction("malloc", MallocType);
}
// Check to see if the prototype was forgotten, giving us void (...) * free
// This handles the common forward declaration of: 'void free();'
if (FreeFunc == 0) {
FreeType = FunctionType::get(Type::VoidTy, std::vector<const Type*>(),true);
FreeFunc = M.getFunction("free", FreeType);
}
// Don't mess with locally defined versions of these functions...
if (MallocFunc && !MallocFunc->isExternal()) MallocFunc = 0;
if (FreeFunc && !FreeFunc->isExternal()) FreeFunc = 0;
return false;
}
// runOnBasicBlock - Process a basic block, fixing it up...
//
bool RaiseAllocations::runOnBasicBlock(BasicBlock &BB) {
bool Changed = false;
BasicBlock::InstListType &BIL = BB.getInstList();
for (BasicBlock::iterator BI = BB.begin(); BI != BB.end();) {
Instruction *I = BI;
if (CallInst *CI = dyn_cast<CallInst>(I)) {
if (CI->getCalledValue() == MallocFunc) { // Replace call to malloc?
const Type *PtrSByte = PointerType::get(Type::SByteTy);
Value *Source = CI->getOperand(1);
// If no prototype was provided for malloc, we may need to cast the
// source size.
if (Source->getType() != Type::UIntTy) {
CastInst *New = new CastInst(Source, Type::UIntTy, "MallocAmtCast");
BI = ++BIL.insert(BI, New);
Source = New;
}
MallocInst *MallocI = new MallocInst(PtrSByte, Source, CI->getName());
CI->setName("");
ReplaceInstWithInst(BIL, BI, MallocI);
Changed = true;
++NumRaised;
continue; // Skip the ++BI
} else if (CI->getCalledValue() == FreeFunc) { // Replace call to free?
// If no prototype was provided for free, we may need to cast the
// source pointer. This should be really uncommon, but it's neccesary
// just in case we are dealing with wierd code like this:
// free((long)ptr);
//
Value *Source = CI->getOperand(1);
if (!isa<PointerType>(Source->getType())) {
CastInst *New = new CastInst(Source, PointerType::get(Type::SByteTy),
"FreePtrCast");
BI = ++BIL.insert(BI, New);
Source = New;
}
ReplaceInstWithInst(BIL, BI, new FreeInst(Source));
Changed = true;
continue; // Skip the ++BI
++NumRaised;
}
}
++BI;
}
return Changed;
}
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