1 //===-- IndMemRemoval.cpp - Remove indirect allocations and frees ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass finds places where memory allocation functions may escape into
11 // indirect land. Some transforms are much easier (aka possible) only if free
12 // or malloc are not called indirectly.
13 // Thus find places where the address of memory functions are taken and
14 // construct bounce functions with direct calls of those functions.
16 //===----------------------------------------------------------------------===//
18 #define DEBUG_TYPE "indmemrem"
19 #include "llvm/Transforms/IPO.h"
20 #include "llvm/Pass.h"
21 #include "llvm/Module.h"
22 #include "llvm/Instructions.h"
23 #include "llvm/Type.h"
24 #include "llvm/DerivedTypes.h"
25 #include "llvm/ADT/Statistic.h"
26 #include "llvm/Support/Compiler.h"
27 #include "llvm/Target/TargetData.h"
30 STATISTIC(NumBounceSites, "Number of sites modified");
31 STATISTIC(NumBounce , "Number of bounce functions created");
34 class VISIBILITY_HIDDEN IndMemRemPass : public ModulePass {
36 static char ID; // Pass identification, replacement for typeid
37 IndMemRemPass() : ModulePass(&ID) {}
39 virtual bool runOnModule(Module &M);
41 } // end anonymous namespace
43 char IndMemRemPass::ID = 0;
44 static RegisterPass<IndMemRemPass>
45 X("indmemrem","Indirect Malloc and Free Removal");
47 bool IndMemRemPass::runOnModule(Module &M) {
48 // In theory, all direct calls of malloc and free should be promoted
49 // to intrinsics. Therefore, this goes through and finds where the
50 // address of free or malloc are taken and replaces those with bounce
51 // functions, ensuring that all malloc and free that might happen
52 // happen through intrinsics.
54 if (Function* F = M.getFunction("free")) {
55 if (F->isDeclaration() && F->arg_size() == 1 && !F->use_empty()) {
56 Function* FN = Function::Create(F->getFunctionType(),
57 GlobalValue::LinkOnceAnyLinkage,
58 "free_llvm_bounce", &M);
59 BasicBlock* bb = BasicBlock::Create(M.getContext(), "entry",FN);
60 Instruction* R = ReturnInst::Create(M.getContext(), bb);
61 new FreeInst(FN->arg_begin(), R);
63 NumBounceSites += F->getNumUses();
64 F->replaceAllUsesWith(FN);
68 if (Function* F = M.getFunction("malloc")) {
69 if (F->isDeclaration() && F->arg_size() == 1 && !F->use_empty()) {
70 TargetData* TD = getAnalysisIfAvailable<TargetData>();
72 Function* FN = Function::Create(F->getFunctionType(),
73 GlobalValue::LinkOnceAnyLinkage,
74 "malloc_llvm_bounce", &M);
75 F->replaceAllUsesWith(FN);
76 FN->setDoesNotAlias(0);
77 BasicBlock* bb = BasicBlock::Create(M.getContext(), "entry", FN);
78 const Type* IntPtrTy = TD->getIntPtrType(M.getContext());
79 Value* c = FN->arg_begin();
80 if (FN->arg_begin()->getType() != IntPtrTy)
81 c = CastInst::CreateIntegerCast(FN->arg_begin(), IntPtrTy, false,
83 Value* a = CallInst::CreateMalloc(bb, IntPtrTy,
84 Type::getInt8Ty(M.getContext()),
86 bb->getInstList().push_back(cast<Instruction>(a));
87 ReturnInst::Create(M.getContext(), a, bb);
89 NumBounceSites += F->getNumUses();
97 ModulePass *llvm::createIndMemRemPass() {
98 return new IndMemRemPass();