1 //===-- Annotation2Metadata.cpp - Add !annotation metadata. ---------------===//
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 // Add !annotation metadata for entries in @llvm.global.anotations, generated
10 // using __attribute__((annotate("_name"))) on functions in Clang.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Transforms/IPO/Annotation2Metadata.h"
15 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
16 #include "llvm/IR/Constants.h"
17 #include "llvm/IR/Function.h"
18 #include "llvm/IR/InstIterator.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/InitializePasses.h"
21 #include "llvm/Pass.h"
22 #include "llvm/Transforms/IPO.h"
23 
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "annotation2metadata"
27 
28 static bool convertAnnotation2Metadata(Module &M) {
29   // Only add !annotation metadata if the corresponding remarks pass is also
30   // enabled.
31   if (!OptimizationRemarkEmitter::allowExtraAnalysis(M.getContext(),
32                                                      "annotation-remarks"))
33     return false;
34 
35   auto *Annotations = M.getGlobalVariable("llvm.global.annotations");
36   auto *C = dyn_cast_or_null<Constant>(Annotations);
37   if (!C || C->getNumOperands() != 1)
38     return false;
39 
40   C = cast<Constant>(C->getOperand(0));
41 
42   // Iterate over all entries in C and attach !annotation metadata to suitable
43   // entries.
44   for (auto &Op : C->operands()) {
45     // Look at the operands to check if we can use the entry to generate
46     // !annotation metadata.
47     auto *OpC = dyn_cast<ConstantStruct>(&Op);
48     if (!OpC || OpC->getNumOperands() != 4)
49       continue;
50     auto *StrGEP = dyn_cast<ConstantExpr>(OpC->getOperand(1));
51     if (!StrGEP || StrGEP->getNumOperands() < 2)
52       continue;
53     auto *StrC = dyn_cast<GlobalValue>(StrGEP->getOperand(0));
54     if (!StrC)
55       continue;
56     auto *StrData = dyn_cast<ConstantDataSequential>(StrC->getOperand(0));
57     if (!StrData)
58       continue;
59     // Look through bitcast.
60     auto *Bitcast = dyn_cast<ConstantExpr>(OpC->getOperand(0));
61     if (!Bitcast || Bitcast->getOpcode() != Instruction::BitCast)
62       continue;
63     auto *Fn = dyn_cast<Function>(Bitcast->getOperand(0));
64     if (!Fn)
65       continue;
66 
67     // Add annotation to all instructions in the function.
68     for (auto &I : instructions(Fn))
69       I.addAnnotationMetadata(StrData->getAsCString());
70   }
71   return true;
72 }
73 
74 namespace {
75 struct Annotation2MetadataLegacy : public ModulePass {
76   static char ID;
77 
78   Annotation2MetadataLegacy() : ModulePass(ID) {
79     initializeAnnotation2MetadataLegacyPass(*PassRegistry::getPassRegistry());
80   }
81 
82   bool runOnModule(Module &M) override { return convertAnnotation2Metadata(M); }
83 
84   void getAnalysisUsage(AnalysisUsage &AU) const override {
85     AU.setPreservesAll();
86   }
87 };
88 
89 } // end anonymous namespace
90 
91 char Annotation2MetadataLegacy::ID = 0;
92 
93 INITIALIZE_PASS_BEGIN(Annotation2MetadataLegacy, DEBUG_TYPE,
94                       "Annotation2Metadata", false, false)
95 INITIALIZE_PASS_END(Annotation2MetadataLegacy, DEBUG_TYPE,
96                     "Annotation2Metadata", false, false)
97 
98 ModulePass *llvm::createAnnotation2MetadataLegacyPass() {
99   return new Annotation2MetadataLegacy();
100 }
101 
102 PreservedAnalyses Annotation2MetadataPass::run(Module &M,
103                                                ModuleAnalysisManager &AM) {
104   convertAnnotation2Metadata(M);
105   return PreservedAnalyses::all();
106 }
107