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 #include <set>
  16
  17 using namespace llvm;
  18
  19 /// Removes all the Initialized GVs that aren't inside the desired Chunks.
  20 static void extractGVsFromModule(std::vector<Chunk> ChunksToKeep,
  21                                  Module *Program) {
  22   // Get GVs inside desired chunks
  23   std::set<GlobalVariable *> GVsToKeep;
  24   int I = 0, GVCount = 0;
  25   for (auto &GV : Program->globals())
  26     if (GV.hasInitializer() && I < (int)ChunksToKeep.size()) {
  27       if (ChunksToKeep[I].contains(++GVCount))
  28         GVsToKeep.insert(&GV);
  29       if (GVCount == ChunksToKeep[I].end)
  30         ++I;
  31     }
  32
  33   // Delete out-of-chunk GVs and their uses
  34   std::vector<GlobalVariable *> ToRemove;
  35   std::vector<Instruction *> InstToRemove;
  36   for (auto &GV : Program->globals())
  37     if (GV.hasInitializer() && !GVsToKeep.count(&GV)) {
  38       for (auto U : GV.users())
  39         if (auto *Inst = dyn_cast<Instruction>(U))
  40           InstToRemove.push_back(Inst);
  41
  42       GV.replaceAllUsesWith(UndefValue::get(GV.getType()));
  43       ToRemove.push_back(&GV);
  44     }
  45
  46   // Delete Instruction uses of unwanted GVs
  47   for (auto *Inst : InstToRemove) {
  48     Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
  49     Inst->eraseFromParent();
  50   }
  51
  52   for (auto *GV : ToRemove)
  53     GV->eraseFromParent();
  54 }
  55
  56 /// Counts the amount of initialized GVs and displays their
  57 /// respective name & index
  58 static int countGVs(Module *Program) {
  59   // TODO: Silence index with --quiet flag
  60   outs() << "----------------------------\n";
  61   outs() << "GlobalVariable Index Reference:\n";
  62   int GVCount = 0;
  63   for (auto &GV : Program->globals())
  64     if (GV.hasInitializer())
  65       outs() << "\t" << ++GVCount << ": " << GV.getName() << "\n";
  66   outs() << "----------------------------\n";
  67   return GVCount;
  68 }
  69
  70 void llvm::reduceGlobalsDeltaPass(TestRunner &Test) {
  71   outs() << "*** Reducing GVs...\n";
  72   int GVCount = countGVs(Test.getProgram());
  73   runDeltaPass(Test, GVCount, extractGVsFromModule);
  74 }