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//===- LowerAllocations.cpp - Reduce free insts to calls ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// The LowerAllocations transformation is a target-dependent tranformation
// because it depends on the size of data types and alignment constraints.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "lowerallocs"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
#include "llvm/Module.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Constants.h"
#include "llvm/LLVMContext.h"
#include "llvm/Pass.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/Compiler.h"
using namespace llvm;
STATISTIC(NumLowered, "Number of allocations lowered");
namespace {
/// LowerAllocations - Turn free instructions into @free calls.
///
class LowerAllocations : public BasicBlockPass {
Constant *FreeFunc; // Functions in the module we are processing
// Initialized by doInitialization
public:
static char ID; // Pass ID, replacement for typeid
explicit LowerAllocations()
: BasicBlockPass(&ID), FreeFunc(0) {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetData>();
AU.setPreservesCFG();
// This is a cluster of orthogonal Transforms:
AU.addPreserved<UnifyFunctionExitNodes>();
AU.addPreservedID(PromoteMemoryToRegisterID);
AU.addPreservedID(LowerSwitchID);
AU.addPreservedID(LowerInvokePassID);
}
/// doPassInitialization - For the lower allocations pass, this ensures that
/// a module contains a declaration for a free function.
///
bool doInitialization(Module &M);
virtual bool doInitialization(Function &F) {
return doInitialization(*F.getParent());
}
/// runOnBasicBlock - This method does the actual work of converting
/// instructions over, assuming that the pass has already been initialized.
///
bool runOnBasicBlock(BasicBlock &BB);
};
}
char LowerAllocations::ID = 0;
static RegisterPass<LowerAllocations>
X("lowerallocs", "Lower allocations from instructions to calls");
// Publically exposed interface to pass...
const PassInfo *const llvm::LowerAllocationsID = &X;
// createLowerAllocationsPass - Interface to this file...
Pass *llvm::createLowerAllocationsPass() {
return new LowerAllocations();
}
// doInitialization - For the lower allocations pass, this ensures that a
// module contains a declaration for a free function.
//
// This function is always successful.
//
bool LowerAllocations::doInitialization(Module &M) {
const Type *BPTy = Type::getInt8PtrTy(M.getContext());
FreeFunc = M.getOrInsertFunction("free" , Type::getVoidTy(M.getContext()),
BPTy, (Type *)0);
return true;
}
// runOnBasicBlock - This method does the actual work of converting
// instructions over, assuming that the pass has already been initialized.
//
bool LowerAllocations::runOnBasicBlock(BasicBlock &BB) {
bool Changed = false;
assert(FreeFunc && "Pass not initialized!");
BasicBlock::InstListType &BBIL = BB.getInstList();
// 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)) {
// Insert a call to the free function...
CallInst::CreateFree(FI->getOperand(0), I);
// Delete the old free instruction
I = --BBIL.erase(I);
Changed = true;
++NumLowered;
}
}
return Changed;
}
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