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      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