1 //===-- Instrumentation.cpp - TransformUtils Infrastructure ---------------===//
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 // This file defines the common initialization infrastructure for the
10 // Instrumentation library.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Transforms/Instrumentation.h"
15 #include "llvm-c/Initialization.h"
16 #include "llvm/ADT/Triple.h"
17 #include "llvm/IR/IntrinsicInst.h"
18 #include "llvm/IR/Module.h"
19 #include "llvm/InitializePasses.h"
20 #include "llvm/PassRegistry.h"
21 
22 using namespace llvm;
23 
24 /// Moves I before IP. Returns new insert point.
25 static BasicBlock::iterator moveBeforeInsertPoint(BasicBlock::iterator I, BasicBlock::iterator IP) {
26   // If I is IP, move the insert point down.
27   if (I == IP) {
28     ++IP;
29   } else {
30     // Otherwise, move I before IP and return IP.
31     I->moveBefore(&*IP);
32   }
33   return IP;
34 }
35 
36 /// Instrumentation passes often insert conditional checks into entry blocks.
37 /// Call this function before splitting the entry block to move instructions
38 /// that must remain in the entry block up before the split point. Static
39 /// allocas and llvm.localescape calls, for example, must remain in the entry
40 /// block.
41 BasicBlock::iterator llvm::PrepareToSplitEntryBlock(BasicBlock &BB,
42                                                     BasicBlock::iterator IP) {
43   assert(&BB.getParent()->getEntryBlock() == &BB);
44   for (auto I = IP, E = BB.end(); I != E; ++I) {
45     bool KeepInEntry = false;
46     if (auto *AI = dyn_cast<AllocaInst>(I)) {
47       if (AI->isStaticAlloca())
48         KeepInEntry = true;
49     } else if (auto *II = dyn_cast<IntrinsicInst>(I)) {
50       if (II->getIntrinsicID() == llvm::Intrinsic::localescape)
51         KeepInEntry = true;
52     }
53     if (KeepInEntry)
54       IP = moveBeforeInsertPoint(I, IP);
55   }
56   return IP;
57 }
58 
59 // Create a constant for Str so that we can pass it to the run-time lib.
60 GlobalVariable *llvm::createPrivateGlobalForString(Module &M, StringRef Str,
61                                                    bool AllowMerging,
62                                                    const char *NamePrefix) {
63   Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
64   // We use private linkage for module-local strings. If they can be merged
65   // with another one, we set the unnamed_addr attribute.
66   GlobalVariable *GV =
67       new GlobalVariable(M, StrConst->getType(), true,
68                          GlobalValue::PrivateLinkage, StrConst, NamePrefix);
69   if (AllowMerging)
70     GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
71   GV->setAlignment(Align(1)); // Strings may not be merged w/o setting
72                               // alignment explicitly.
73   return GV;
74 }
75 
76 Comdat *llvm::getOrCreateFunctionComdat(Function &F, Triple &T) {
77   if (auto Comdat = F.getComdat()) return Comdat;
78   assert(F.hasName());
79   Module *M = F.getParent();
80 
81   // Make a new comdat for the function. Use the "no duplicates" selection kind
82   // if the object file format supports it. For COFF we restrict it to non-weak
83   // symbols.
84   Comdat *C = M->getOrInsertComdat(F.getName());
85   if (T.isOSBinFormatELF() || (T.isOSBinFormatCOFF() && !F.isWeakForLinker()))
86     C->setSelectionKind(Comdat::NoDeduplicate);
87   F.setComdat(C);
88   return C;
89 }
90 
91 /// initializeInstrumentation - Initialize all passes in the TransformUtils
92 /// library.
93 void llvm::initializeInstrumentation(PassRegistry &Registry) {
94   initializeMemProfilerLegacyPassPass(Registry);
95   initializeModuleMemProfilerLegacyPassPass(Registry);
96   initializeBoundsCheckingLegacyPassPass(Registry);
97   initializeDataFlowSanitizerLegacyPassPass(Registry);
98 }
99 
100 /// LLVMInitializeInstrumentation - C binding for
101 /// initializeInstrumentation.
102 void LLVMInitializeInstrumentation(LLVMPassRegistryRef R) {
103   initializeInstrumentation(*unwrap(R));
104 }
105