llvm/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 Global Variables in the provided Module.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "ReduceGlobalVars.h"
  15 #include "Utils.h"
  16 #include "llvm/IR/Constants.h"
  17 #include "llvm/Transforms/Utils/ModuleUtils.h"
  18
  19 using namespace llvm;
  20
  21 static bool shouldAlwaysKeep(const GlobalVariable &GV) {
  22   return GV.getName() == "llvm.used" || GV.getName() == "llvm.compiler.used";
  23 }
  24
  25 /// Removes all the GVs that aren't inside the desired Chunks.
  26 static void extractGVsFromModule(Oracle &O, ReducerWorkItem &WorkItem) {
  27   Module &Program = WorkItem.getModule();
  28
  29   // Get GVs inside desired chunks
  30   std::vector<Constant *> InitGVsToKeep;
  31   for (auto &GV : Program.globals()) {
  32     if (shouldAlwaysKeep(GV) || O.shouldKeep())
  33       InitGVsToKeep.push_back(&GV);
  34   }
  35
  36   // We create a vector first, then convert it to a set, so that we don't have
  37   // to pay the cost of rebalancing the set frequently if the order we insert
  38   // the elements doesn't match the order they should appear inside the set.
  39   DenseSet<Constant *> GVsToKeep(InitGVsToKeep.begin(), InitGVsToKeep.end());
  40
  41   // Delete out-of-chunk GVs and their uses
  42   DenseSet<Constant *> ToRemove;
  43   for (auto &GV : Program.globals()) {
  44     if (!GVsToKeep.count(&GV))
  45       ToRemove.insert(&GV);
  46   }
  47
  48   removeFromUsedLists(Program,
  49                       [&ToRemove](Constant *C) { return ToRemove.count(C); });
  50
  51   for (auto *GV : ToRemove) {
  52     GV->replaceAllUsesWith(getDefaultValue(GV->getType()));
  53     cast<GlobalVariable>(GV)->eraseFromParent();
  54   }
  55 }
  56
  57 void llvm::reduceGlobalsDeltaPass(TestRunner &Test) {
  58   runDeltaPass(Test, extractGVsFromModule, "Reducing GlobalVariables");
  59 }