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 #include <vector>
27 
28 namespace llvm {
29 
30 class Triple;
31 class OptimizationRemarkEmitter;
32 class Comdat;
33 class CallBase;
34 
35 /// Instrumentation passes often insert conditional checks into entry blocks.
36 /// Call this function before splitting the entry block to move instructions
37 /// that must remain in the entry block up before the split point. Static
38 /// allocas and llvm.localescape calls, for example, must remain in the entry
39 /// block.
40 BasicBlock::iterator PrepareToSplitEntryBlock(BasicBlock &BB,
41                                               BasicBlock::iterator IP);
42 
43 // Create a constant for Str so that we can pass it to the run-time lib.
44 GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str,
45                                              bool AllowMerging,
46                                              const char *NamePrefix = "");
47 
48 // Returns F.getComdat() if it exists.
49 // Otherwise creates a new comdat, sets F's comdat, and returns it.
50 // Returns nullptr on failure.
51 Comdat *getOrCreateFunctionComdat(Function &F, Triple &T);
52 
53 // Insert GCOV profiling instrumentation
54 struct GCOVOptions {
55   static GCOVOptions getDefault();
56 
57   // Specify whether to emit .gcno files.
58   bool EmitNotes;
59 
60   // Specify whether to modify the program to emit .gcda files when run.
61   bool EmitData;
62 
63   // A four-byte version string. The meaning of a version string is described in
64   // gcc's gcov-io.h
65   char Version[4];
66 
67   // Add the 'noredzone' attribute to added runtime library calls.
68   bool NoRedZone;
69 
70   // Use atomic profile counter increments.
71   bool Atomic = false;
72 
73   // Regexes separated by a semi-colon to filter the files to instrument.
74   std::string Filter;
75 
76   // Regexes separated by a semi-colon to filter the files to not instrument.
77   std::string Exclude;
78 };
79 
80 // The pgo-specific indirect call promotion function declared below is used by
81 // the pgo-driven indirect call promotion and sample profile passes. It's a
82 // wrapper around llvm::promoteCall, et al. that additionally computes !prof
83 // metadata. We place it in a pgo namespace so it's not confused with the
84 // generic utilities.
85 namespace pgo {
86 
87 // Helper function that transforms CB (either an indirect-call instruction, or
88 // an invoke instruction , to a conditional call to F. This is like:
89 //     if (Inst.CalledValue == F)
90 //        F(...);
91 //     else
92 //        Inst(...);
93 //     end
94 // TotalCount is the profile count value that the instruction executes.
95 // Count is the profile count value that F is the target function.
96 // These two values are used to update the branch weight.
97 // If \p AttachProfToDirectCall is true, a prof metadata is attached to the
98 // new direct call to contain \p Count.
99 // Returns the promoted direct call instruction.
100 CallBase &promoteIndirectCall(CallBase &CB, Function *F, uint64_t Count,
101                               uint64_t TotalCount, bool AttachProfToDirectCall,
102                               OptimizationRemarkEmitter *ORE);
103 } // namespace pgo
104 
105 /// Options for the frontend instrumentation based profiling pass.
106 struct InstrProfOptions {
107   // Add the 'noredzone' attribute to added runtime library calls.
108   bool NoRedZone = false;
109 
110   // Do counter register promotion
111   bool DoCounterPromotion = false;
112 
113   // Use atomic profile counter increments.
114   bool Atomic = false;
115 
116   // Use BFI to guide register promotion
117   bool UseBFIInPromotion = false;
118 
119   // Name of the profile file to use as output
120   std::string InstrProfileOutput;
121 
122   InstrProfOptions() = default;
123 };
124 
125 // Options for sanitizer coverage instrumentation.
126 struct SanitizerCoverageOptions {
127   enum Type {
128     SCK_None = 0,
129     SCK_Function,
130     SCK_BB,
131     SCK_Edge
132   } CoverageType = SCK_None;
133   bool IndirectCalls = false;
134   bool TraceBB = false;
135   bool TraceCmp = false;
136   bool TraceDiv = false;
137   bool TraceGep = false;
138   bool Use8bitCounters = false;
139   bool TracePC = false;
140   bool TracePCGuard = false;
141   bool Inline8bitCounters = false;
142   bool InlineBoolFlag = false;
143   bool PCTable = false;
144   bool NoPrune = false;
145   bool StackDepth = false;
146   bool TraceLoads = false;
147   bool TraceStores = false;
148   bool CollectControlFlow = false;
149 
150   SanitizerCoverageOptions() = default;
151 };
152 
153 /// Calculate what to divide by to scale counts.
154 ///
155 /// Given the maximum count, calculate a divisor that will scale all the
156 /// weights to strictly less than std::numeric_limits<uint32_t>::max().
157 static inline uint64_t calculateCountScale(uint64_t MaxCount) {
158   return MaxCount < std::numeric_limits<uint32_t>::max()
159              ? 1
160              : MaxCount / std::numeric_limits<uint32_t>::max() + 1;
161 }
162 
163 /// Scale an individual branch count.
164 ///
165 /// Scale a 64-bit weight down to 32-bits using \c Scale.
166 ///
167 static inline uint32_t scaleBranchCount(uint64_t Count, uint64_t Scale) {
168   uint64_t Scaled = Count / Scale;
169   assert(Scaled <= std::numeric_limits<uint32_t>::max() && "overflow 32-bits");
170   return Scaled;
171 }
172 
173 // Use to ensure the inserted instrumentation has a DebugLocation; if none is
174 // attached to the source instruction, try to use a DILocation with offset 0
175 // scoped to surrounding function (if it has a DebugLocation).
176 //
177 // Some non-call instructions may be missing debug info, but when inserting
178 // instrumentation calls, some builds (e.g. LTO) want calls to have debug info
179 // if the enclosing function does.
180 struct InstrumentationIRBuilder : IRBuilder<> {
181   static void ensureDebugInfo(IRBuilder<> &IRB, const Function &F) {
182     if (IRB.getCurrentDebugLocation())
183       return;
184     if (DISubprogram *SP = F.getSubprogram())
185       IRB.SetCurrentDebugLocation(DILocation::get(SP->getContext(), 0, 0, SP));
186   }
187 
188   explicit InstrumentationIRBuilder(Instruction *IP) : IRBuilder<>(IP) {
189     ensureDebugInfo(*this, *IP->getFunction());
190   }
191 };
192 } // end namespace llvm
193 
194 #endif // LLVM_TRANSFORMS_INSTRUMENTATION_H
195