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/Utils/Instrumentation.h"
15#include "llvm/IR/DiagnosticInfo.h"
16#include "llvm/IR/DiagnosticPrinter.h"
17#include "llvm/IR/IntrinsicInst.h"
18#include "llvm/IR/Module.h"
19#include "llvm/TargetParser/Triple.h"
20
21using namespace llvm;
22
23static cl::opt<bool> ClIgnoreRedundantInstrumentation(
24 "ignore-redundant-instrumentation",
25 cl::desc("Ignore redundant instrumentation"), cl::Hidden, cl::init(Val: false));
26
27/// Check if module has flag attached, if not add the flag.
28bool llvm::checkIfAlreadyInstrumented(Module &M, StringRef Flag) {
29 if (!M.getModuleFlag(Key: Flag)) {
30 M.addModuleFlag(Behavior: Module::ModFlagBehavior::Override, Key: Flag, Val: 1);
31 return false;
32 }
33 if (ClIgnoreRedundantInstrumentation)
34 return true;
35 std::string diagInfo =
36 "Redundant instrumentation detected, with module flag: " +
37 std::string(Flag);
38 M.getContext().diagnose(
39 DI: DiagnosticInfoInstrumentation(diagInfo, DiagnosticSeverity::DS_Warning));
40 return true;
41}
42
43/// Moves I before IP. Returns new insert point.
44static BasicBlock::iterator moveBeforeInsertPoint(BasicBlock::iterator I,
45 BasicBlock::iterator IP) {
46 // If I is IP, move the insert point down.
47 if (I == IP) {
48 ++IP;
49 } else {
50 // Otherwise, move I before IP and return IP.
51 I->moveBefore(InsertPos: IP);
52 }
53 return IP;
54}
55
56/// Instrumentation passes often insert conditional checks into entry blocks.
57/// Call this function before splitting the entry block to move instructions
58/// that must remain in the entry block up before the split point. Static
59/// allocas and llvm.localescape calls, for example, must remain in the entry
60/// block.
61BasicBlock::iterator llvm::PrepareToSplitEntryBlock(BasicBlock &BB,
62 BasicBlock::iterator IP) {
63 assert(&BB.getParent()->getEntryBlock() == &BB);
64 for (auto I = IP, E = BB.end(); I != E; ++I) {
65 bool KeepInEntry = false;
66 if (auto *AI = dyn_cast<AllocaInst>(Val&: I)) {
67 if (AI->isStaticAlloca())
68 KeepInEntry = true;
69 } else if (auto *II = dyn_cast<IntrinsicInst>(Val&: I)) {
70 if (II->getIntrinsicID() == llvm::Intrinsic::localescape)
71 KeepInEntry = true;
72 }
73 if (KeepInEntry)
74 IP = moveBeforeInsertPoint(I, IP);
75 }
76 return IP;
77}
78
79// Create a constant for Str so that we can pass it to the run-time lib.
80GlobalVariable *llvm::createPrivateGlobalForString(Module &M, StringRef Str,
81 bool AllowMerging,
82 Twine NamePrefix) {
83 Constant *StrConst = ConstantDataArray::getString(Context&: M.getContext(), Initializer: Str);
84 // We use private linkage for module-local strings. If they can be merged
85 // with another one, we set the unnamed_addr attribute.
86 GlobalVariable *GV =
87 new GlobalVariable(M, StrConst->getType(), true,
88 GlobalValue::PrivateLinkage, StrConst, NamePrefix);
89 if (AllowMerging)
90 GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
91 GV->setAlignment(Align(1)); // Strings may not be merged w/o setting
92 // alignment explicitly.
93 return GV;
94}
95
96Comdat *llvm::getOrCreateFunctionComdat(Function &F, Triple &T) {
97 if (auto Comdat = F.getComdat())
98 return Comdat;
99 assert(F.hasName());
100 Module *M = F.getParent();
101
102 // Make a new comdat for the function. Use the "no duplicates" selection kind
103 // if the object file format supports it. For COFF we restrict it to non-weak
104 // symbols.
105 Comdat *C = M->getOrInsertComdat(Name: F.getName());
106 if (T.isOSBinFormatELF() || (T.isOSBinFormatCOFF() && !F.isWeakForLinker()))
107 C->setSelectionKind(Comdat::NoDeduplicate);
108 F.setComdat(C);
109 return C;
110}
111
112void llvm::setGlobalVariableLargeSection(const Triple &TargetTriple,
113 GlobalVariable &GV) {
114 // Limit to x86-64 ELF.
115 if (TargetTriple.getArch() != Triple::x86_64 ||
116 TargetTriple.getObjectFormat() != Triple::ELF)
117 return;
118 // Limit to medium/large code models.
119 std::optional<CodeModel::Model> CM = GV.getParent()->getCodeModel();
120 if (!CM || (*CM != CodeModel::Medium && *CM != CodeModel::Large))
121 return;
122 GV.setCodeModel(CodeModel::Large);
123}
124