tools/llvm-reduce/deltas/ReduceGlobalVars.cpp

   1 //===- ReduceGlobalVars.cpp - Specialized Delta Pass ----------------------===//
   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 implements a function which calls the Generic Delta pass in order
  10 // to reduce initialized Global Variables in the provided Module.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "ReduceGlobalVars.h"
  15
  16 /// Removes all the Initialized GVs that aren't inside the desired Chunks.
  17 static void extractGVsFromModule(std::vector<Chunk> ChunksToKeep,
  18                                  Module *Program) {
  19   // Get GVs inside desired chunks
  20   std::set<GlobalVariable *> GVsToKeep;
  21   unsigned I = 0, GVCount = 0;
  22   for (auto &GV : Program->globals())
  23     if (GV.hasInitializer() && I < ChunksToKeep.size()) {
  24       if (ChunksToKeep[I].contains(++GVCount))
  25         GVsToKeep.insert(&GV);
  26       if (GVCount == ChunksToKeep[I].end)
  27         ++I;
  28     }
  29
  30   // Delete out-of-chunk GVs and their uses
  31   std::vector<GlobalVariable *> ToRemove;
  32   std::vector<Instruction *> InstToRemove;
  33   for (auto &GV : Program->globals())
  34     if (GV.hasInitializer() && !GVsToKeep.count(&GV)) {
  35       for (auto U : GV.users())
  36         if (auto *Inst = dyn_cast<Instruction>(U))
  37           InstToRemove.push_back(Inst);
  38
  39       GV.replaceAllUsesWith(UndefValue::get(GV.getType()));
  40       ToRemove.push_back(&GV);
  41     }
  42
  43   // Delete Instruction uses of unwanted GVs
  44   for (auto *Inst : InstToRemove) {
  45     Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
  46     Inst->eraseFromParent();
  47   }
  48
  49   for (auto *GV : ToRemove)
  50     GV->eraseFromParent();
  51 }
  52
  53 /// Counts the amount of initialized GVs and displays their
  54 /// respective name & index
  55 static int countGVs(Module *Program) {
  56   // TODO: Silence index with --quiet flag
  57   outs() << "----------------------------\n";
  58   outs() << "GlobalVariable Index Reference:\n";
  59   int GVCount = 0;
  60   for (auto &GV : Program->globals())
  61     if (GV.hasInitializer())
  62       outs() << "\t" << ++GVCount << ": " << GV.getName() << "\n";
  63   outs() << "----------------------------\n";
  64   return GVCount;
  65 }
  66
  67 void llvm::reduceGlobalsDeltaPass(TestRunner &Test) {
  68   outs() << "*** Reducing GVs...\n";
  69   unsigned GVCount = countGVs(Test.getProgram());
  70   runDeltaPass(Test, GVCount, extractGVsFromModule);
  71 }