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 "llvm/IR/Constants.h"
  16 #include <set>
  17
  18 using namespace llvm;
  19
  20 /// Removes all the GVs that aren't inside the desired Chunks.
  21 static void extractGVsFromModule(Oracle &O, Module &Program) {
  22   // Get GVs inside desired chunks
  23   std::vector<GlobalVariable *> InitGVsToKeep;
  24   for (auto &GV : Program.globals())
  25     if (O.shouldKeep())
  26       InitGVsToKeep.push_back(&GV);
  27
  28   // We create a vector first, then convert it to a set, so that we don't have
  29   // to pay the cost of rebalancing the set frequently if the order we insert
  30   // the elements doesn't match the order they should appear inside the set.
  31   std::set<GlobalVariable *> GVsToKeep(InitGVsToKeep.begin(),
  32                                        InitGVsToKeep.end());
  33
  34   // Delete out-of-chunk GVs and their uses
  35   std::vector<GlobalVariable *> ToRemove;
  36   std::vector<WeakVH> InstToRemove;
  37   for (auto &GV : Program.globals())
  38     if (!GVsToKeep.count(&GV)) {
  39       for (auto *U : GV.users())
  40         if (auto *Inst = dyn_cast<Instruction>(U))
  41           InstToRemove.push_back(Inst);
  42
  43       GV.replaceAllUsesWith(UndefValue::get(GV.getType()));
  44       ToRemove.push_back(&GV);
  45     }
  46
  47   // Delete (unique) Instruction uses of unwanted GVs
  48   for (Value *V : InstToRemove) {
  49     if (!V)
  50       continue;
  51     auto *Inst = cast<Instruction>(V);
  52     Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
  53     Inst->eraseFromParent();
  54   }
  55
  56   for (auto *GV : ToRemove)
  57     GV->eraseFromParent();
  58 }
  59
  60 void llvm::reduceGlobalsDeltaPass(TestRunner &Test) {
  61   outs() << "*** Reducing GVs...\n";
  62   runDeltaPass(Test, extractGVsFromModule);
  63 }