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"
29 STATISTIC(NumBounceSites, "Number of sites modified");
30 STATISTIC(NumBounce , "Number of bounce functions created");
33 class VISIBILITY_HIDDEN IndMemRemPass : public ModulePass {
35 static char ID; // Pass identification, replacement for typeid
36 IndMemRemPass() : ModulePass(&ID) {}
38 virtual bool runOnModule(Module &M);
40 } // end anonymous namespace
42 char IndMemRemPass::ID = 0;
43 static RegisterPass<IndMemRemPass>
44 X("indmemrem","Indirect Malloc and Free Removal");
46 bool IndMemRemPass::runOnModule(Module &M) {
47 Context = &M.getContext();
49 // In theory, all direct calls of malloc and free should be promoted
50 // to intrinsics. Therefore, this goes through and finds where the
51 // address of free or malloc are taken and replaces those with bounce
52 // functions, ensuring that all malloc and free that might happen
53 // happen through intrinsics.
55 if (Function* F = M.getFunction("free")) {
56 if (F->isDeclaration() && F->arg_size() == 1 && !F->use_empty()) {
57 Function* FN = Function::Create(F->getFunctionType(),
58 GlobalValue::LinkOnceAnyLinkage,
59 "free_llvm_bounce", &M);
60 BasicBlock* bb = BasicBlock::Create("entry",FN);
61 Instruction* R = ReturnInst::Create(bb);
62 new FreeInst(FN->arg_begin(), R);
64 NumBounceSites += F->getNumUses();
65 F->replaceAllUsesWith(FN);
69 if (Function* F = M.getFunction("malloc")) {
70 if (F->isDeclaration() && F->arg_size() == 1 && !F->use_empty()) {
71 Function* FN = Function::Create(F->getFunctionType(),
72 GlobalValue::LinkOnceAnyLinkage,
73 "malloc_llvm_bounce", &M);
74 FN->setDoesNotAlias(0);
75 BasicBlock* bb = BasicBlock::Create("entry",FN);
76 Instruction* c = CastInst::CreateIntegerCast(
77 FN->arg_begin(), Type::Int32Ty, false, "c", bb);
78 Instruction* a = new MallocInst(Type::Int8Ty, c, "m", bb);
79 ReturnInst::Create(a, bb);
81 NumBounceSites += F->getNumUses();
82 F->replaceAllUsesWith(FN);
89 ModulePass *llvm::createIndMemRemPass() {
90 return new IndMemRemPass();