1 //===- Transforms/Instrumentation.h - Instrumentation passes ----*- C++ -*-===// 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 constructor functions for instrumentation passes. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #ifndef LLVM_TRANSFORMS_INSTRUMENTATION_H 14 #define LLVM_TRANSFORMS_INSTRUMENTATION_H 15 16 #include "llvm/ADT/StringRef.h" 17 #include "llvm/IR/BasicBlock.h" 18 #include "llvm/IR/DebugInfoMetadata.h" 19 #include "llvm/IR/Function.h" 20 #include "llvm/IR/IRBuilder.h" 21 #include "llvm/IR/Instruction.h" 22 #include <cassert> 23 #include <cstdint> 24 #include <limits> 25 #include <string> 26 27 namespace llvm { 28 29 class Triple; 30 class OptimizationRemarkEmitter; 31 class Comdat; 32 class CallBase; 33 34 /// Instrumentation passes often insert conditional checks into entry blocks. 35 /// Call this function before splitting the entry block to move instructions 36 /// that must remain in the entry block up before the split point. Static 37 /// allocas and llvm.localescape calls, for example, must remain in the entry 38 /// block. 39 BasicBlock::iterator PrepareToSplitEntryBlock(BasicBlock &BB, 40 BasicBlock::iterator IP); 41 42 // Create a constant for Str so that we can pass it to the run-time lib. 43 GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str, 44 bool AllowMerging, 45 const char *NamePrefix = ""); 46 47 // Returns F.getComdat() if it exists. 48 // Otherwise creates a new comdat, sets F's comdat, and returns it. 49 // Returns nullptr on failure. 50 Comdat *getOrCreateFunctionComdat(Function &F, Triple &T); 51 52 // Place global in a large section for x86-64 ELF binaries to mitigate 53 // relocation overflow pressure. This can be be used for metadata globals that 54 // aren't directly accessed by code, which has no performance impact. 55 void setGlobalVariableLargeSection(const Triple &TargetTriple, 56 GlobalVariable &GV); 57 58 // Insert GCOV profiling instrumentation 59 struct GCOVOptions { 60 static GCOVOptions getDefault(); 61 62 // Specify whether to emit .gcno files. 63 bool EmitNotes; 64 65 // Specify whether to modify the program to emit .gcda files when run. 66 bool EmitData; 67 68 // A four-byte version string. The meaning of a version string is described in 69 // gcc's gcov-io.h 70 char Version[4]; 71 72 // Add the 'noredzone' attribute to added runtime library calls. 73 bool NoRedZone; 74 75 // Use atomic profile counter increments. 76 bool Atomic = false; 77 78 // Regexes separated by a semi-colon to filter the files to instrument. 79 std::string Filter; 80 81 // Regexes separated by a semi-colon to filter the files to not instrument. 82 std::string Exclude; 83 }; 84 85 // The pgo-specific indirect call promotion function declared below is used by 86 // the pgo-driven indirect call promotion and sample profile passes. It's a 87 // wrapper around llvm::promoteCall, et al. that additionally computes !prof 88 // metadata. We place it in a pgo namespace so it's not confused with the 89 // generic utilities. 90 namespace pgo { 91 92 // Helper function that transforms CB (either an indirect-call instruction, or 93 // an invoke instruction , to a conditional call to F. This is like: 94 // if (Inst.CalledValue == F) 95 // F(...); 96 // else 97 // Inst(...); 98 // end 99 // TotalCount is the profile count value that the instruction executes. 100 // Count is the profile count value that F is the target function. 101 // These two values are used to update the branch weight. 102 // If \p AttachProfToDirectCall is true, a prof metadata is attached to the 103 // new direct call to contain \p Count. 104 // Returns the promoted direct call instruction. 105 CallBase &promoteIndirectCall(CallBase &CB, Function *F, uint64_t Count, 106 uint64_t TotalCount, bool AttachProfToDirectCall, 107 OptimizationRemarkEmitter *ORE); 108 } // namespace pgo 109 110 /// Options for the frontend instrumentation based profiling pass. 111 struct InstrProfOptions { 112 // Add the 'noredzone' attribute to added runtime library calls. 113 bool NoRedZone = false; 114 115 // Do counter register promotion 116 bool DoCounterPromotion = false; 117 118 // Use atomic profile counter increments. 119 bool Atomic = false; 120 121 // Use BFI to guide register promotion 122 bool UseBFIInPromotion = false; 123 124 // Use sampling to reduce the profile instrumentation runtime overhead. 125 bool Sampling = false; 126 127 // Name of the profile file to use as output 128 std::string InstrProfileOutput; 129 130 InstrProfOptions() = default; 131 }; 132 133 // Create the variable for profile sampling. 134 void createProfileSamplingVar(Module &M); 135 136 // Options for sanitizer coverage instrumentation. 137 struct SanitizerCoverageOptions { 138 enum Type { 139 SCK_None = 0, 140 SCK_Function, 141 SCK_BB, 142 SCK_Edge 143 } CoverageType = SCK_None; 144 bool IndirectCalls = false; 145 bool TraceBB = false; 146 bool TraceCmp = false; 147 bool TraceDiv = false; 148 bool TraceGep = false; 149 bool Use8bitCounters = false; 150 bool TracePC = false; 151 bool TracePCGuard = false; 152 bool Inline8bitCounters = false; 153 bool InlineBoolFlag = false; 154 bool PCTable = false; 155 bool NoPrune = false; 156 bool StackDepth = false; 157 bool TraceLoads = false; 158 bool TraceStores = false; 159 bool CollectControlFlow = false; 160 161 SanitizerCoverageOptions() = default; 162 }; 163 164 /// Calculate what to divide by to scale counts. 165 /// 166 /// Given the maximum count, calculate a divisor that will scale all the 167 /// weights to strictly less than std::numeric_limits<uint32_t>::max(). 168 static inline uint64_t calculateCountScale(uint64_t MaxCount) { 169 return MaxCount < std::numeric_limits<uint32_t>::max() 170 ? 1 171 : MaxCount / std::numeric_limits<uint32_t>::max() + 1; 172 } 173 174 /// Scale an individual branch count. 175 /// 176 /// Scale a 64-bit weight down to 32-bits using \c Scale. 177 /// 178 static inline uint32_t scaleBranchCount(uint64_t Count, uint64_t Scale) { 179 uint64_t Scaled = Count / Scale; 180 assert(Scaled <= std::numeric_limits<uint32_t>::max() && "overflow 32-bits"); 181 return Scaled; 182 } 183 184 // Use to ensure the inserted instrumentation has a DebugLocation; if none is 185 // attached to the source instruction, try to use a DILocation with offset 0 186 // scoped to surrounding function (if it has a DebugLocation). 187 // 188 // Some non-call instructions may be missing debug info, but when inserting 189 // instrumentation calls, some builds (e.g. LTO) want calls to have debug info 190 // if the enclosing function does. 191 struct InstrumentationIRBuilder : IRBuilder<> { 192 static void ensureDebugInfo(IRBuilder<> &IRB, const Function &F) { 193 if (IRB.getCurrentDebugLocation()) 194 return; 195 if (DISubprogram *SP = F.getSubprogram()) 196 IRB.SetCurrentDebugLocation(DILocation::get(SP->getContext(), 0, 0, SP)); 197 } 198 199 explicit InstrumentationIRBuilder(Instruction *IP) : IRBuilder<>(IP) { 200 ensureDebugInfo(*this, *IP->getFunction()); 201 } 202 }; 203 } // end namespace llvm 204 205 #endif // LLVM_TRANSFORMS_INSTRUMENTATION_H 206