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91 lines
3.4 KiB
C++
91 lines
3.4 KiB
C++
//===-- IndMemRemoval.cpp - Remove indirect allocations and frees ---------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass finds places where memory allocation functions may escape into
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// indirect land. Some transforms are much easier (aka possible) only if free
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// or malloc are not called indirectly.
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// Thus find places where the address of memory functions are taken and
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// construct bounce functions with direct calls of those functions.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "indmemrem"
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#include "llvm/Transforms/IPO.h"
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#include "llvm/Pass.h"
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#include "llvm/Module.h"
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#include "llvm/Instructions.h"
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#include "llvm/Type.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Support/Compiler.h"
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using namespace llvm;
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STATISTIC(NumBounceSites, "Number of sites modified");
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STATISTIC(NumBounce , "Number of bounce functions created");
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namespace {
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class VISIBILITY_HIDDEN IndMemRemPass : public ModulePass {
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public:
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static char ID; // Pass identification, replacement for typeid
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IndMemRemPass() : ModulePass(&ID) {}
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virtual bool runOnModule(Module &M);
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};
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} // end anonymous namespace
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char IndMemRemPass::ID = 0;
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static RegisterPass<IndMemRemPass>
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X("indmemrem","Indirect Malloc and Free Removal");
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bool IndMemRemPass::runOnModule(Module &M) {
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// In theory, all direct calls of malloc and free should be promoted
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// to intrinsics. Therefore, this goes through and finds where the
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// address of free or malloc are taken and replaces those with bounce
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// functions, ensuring that all malloc and free that might happen
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// happen through intrinsics.
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bool changed = false;
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if (Function* F = M.getFunction("free")) {
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if (F->isDeclaration() && F->arg_size() == 1 && !F->use_empty()) {
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Function* FN = Function::Create(F->getFunctionType(),
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GlobalValue::LinkOnceAnyLinkage,
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"free_llvm_bounce", &M);
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BasicBlock* bb = BasicBlock::Create(M.getContext(), "entry",FN);
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Instruction* R = ReturnInst::Create(M.getContext(), bb);
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new FreeInst(FN->arg_begin(), R);
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++NumBounce;
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NumBounceSites += F->getNumUses();
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F->replaceAllUsesWith(FN);
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changed = true;
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}
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}
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if (Function* F = M.getFunction("malloc")) {
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if (F->isDeclaration() && F->arg_size() == 1 && !F->use_empty()) {
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Function* FN = Function::Create(F->getFunctionType(),
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GlobalValue::LinkOnceAnyLinkage,
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"malloc_llvm_bounce", &M);
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FN->setDoesNotAlias(0);
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BasicBlock* bb = BasicBlock::Create(M.getContext(), "entry",FN);
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Instruction* c = CastInst::CreateIntegerCast(
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FN->arg_begin(), Type::getInt32Ty(M.getContext()), false, "c", bb);
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Instruction* a = new MallocInst(Type::getInt8Ty(M.getContext()),
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c, "m", bb);
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ReturnInst::Create(M.getContext(), a, bb);
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++NumBounce;
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NumBounceSites += F->getNumUses();
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F->replaceAllUsesWith(FN);
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changed = true;
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}
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}
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return changed;
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}
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ModulePass *llvm::createIndMemRemPass() {
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return new IndMemRemPass();
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}
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