1 //===- MemDerefPrinter.cpp - Printer for isDereferenceablePointer ---------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "llvm/Analysis/MemDerefPrinter.h"
10 #include "llvm/Analysis/Loads.h"
11 #include "llvm/Analysis/Passes.h"
12 #include "llvm/IR/InstIterator.h"
13 #include "llvm/IR/Instructions.h"
14 #include "llvm/IR/Module.h"
15 #include "llvm/InitializePasses.h"
16 #include "llvm/Pass.h"
17 #include "llvm/Support/raw_ostream.h"
18 
19 using namespace llvm;
20 
21 namespace {
22   struct MemDerefPrinter : public FunctionPass {
23     SmallVector<Value *, 4> Deref;
24     SmallPtrSet<Value *, 4> DerefAndAligned;
25 
26     static char ID; // Pass identification, replacement for typeid
27     MemDerefPrinter() : FunctionPass(ID) {
28       initializeMemDerefPrinterPass(*PassRegistry::getPassRegistry());
29     }
30     void getAnalysisUsage(AnalysisUsage &AU) const override {
31       AU.setPreservesAll();
32     }
33     bool runOnFunction(Function &F) override;
34     void print(raw_ostream &OS, const Module * = nullptr) const override;
35     void releaseMemory() override {
36       Deref.clear();
37       DerefAndAligned.clear();
38     }
39   };
40 }
41 
42 char MemDerefPrinter::ID = 0;
43 INITIALIZE_PASS_BEGIN(MemDerefPrinter, "print-memderefs",
44                       "Memory Dereferenciblity of pointers in function", false, true)
45 INITIALIZE_PASS_END(MemDerefPrinter, "print-memderefs",
46                     "Memory Dereferenciblity of pointers in function", false, true)
47 
48 FunctionPass *llvm::createMemDerefPrinter() {
49   return new MemDerefPrinter();
50 }
51 
52 bool MemDerefPrinter::runOnFunction(Function &F) {
53   const DataLayout &DL = F.getParent()->getDataLayout();
54   for (auto &I: instructions(F)) {
55     if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
56       Value *PO = LI->getPointerOperand();
57       if (isDereferenceablePointer(PO, LI->getType(), DL))
58         Deref.push_back(PO);
59       if (isDereferenceableAndAlignedPointer(PO, LI->getType(), LI->getAlign(),
60                                              DL))
61         DerefAndAligned.insert(PO);
62     }
63   }
64   return false;
65 }
66 
67 void MemDerefPrinter::print(raw_ostream &OS, const Module *M) const {
68   OS << "The following are dereferenceable:\n";
69   for (Value *V: Deref) {
70     OS << "  ";
71     V->print(OS);
72     if (DerefAndAligned.count(V))
73       OS << "\t(aligned)";
74     else
75       OS << "\t(unaligned)";
76     OS << "\n";
77   }
78 }
79 
80 PreservedAnalyses MemDerefPrinterPass::run(Function &F,
81                                            FunctionAnalysisManager &AM) {
82   OS << "Memory Dereferencibility of pointers in function '" << F.getName()
83      << "'\n";
84 
85   SmallVector<Value *, 4> Deref;
86   SmallPtrSet<Value *, 4> DerefAndAligned;
87 
88   const DataLayout &DL = F.getParent()->getDataLayout();
89   for (auto &I : instructions(F)) {
90     if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
91       Value *PO = LI->getPointerOperand();
92       if (isDereferenceablePointer(PO, LI->getType(), DL))
93         Deref.push_back(PO);
94       if (isDereferenceableAndAlignedPointer(PO, LI->getType(), LI->getAlign(),
95                                              DL))
96         DerefAndAligned.insert(PO);
97     }
98   }
99 
100   OS << "The following are dereferenceable:\n";
101   for (Value *V : Deref) {
102     OS << "  ";
103     V->print(OS);
104     if (DerefAndAligned.count(V))
105       OS << "\t(aligned)";
106     else
107       OS << "\t(unaligned)";
108     OS << "\n";
109   }
110   return PreservedAnalyses::all();
111 }
112