llvm/tools/llvm-reduce/deltas/ReduceInstructions.cpp

   1 //===- ReduceInstructions.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 uninteresting Instructions from defined functions.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "ReduceInstructions.h"
  15 #include "Utils.h"
  16 #include "llvm/IR/Constants.h"
  17 #include <set>
  18
  19 using namespace llvm;
  20
  21 /// Filter out cases where deleting the instruction will likely cause the
  22 /// user/def of the instruction to fail the verifier.
  23 //
  24 // TODO: Technically the verifier only enforces preallocated token usage and
  25 // there is a none token.
  26 static bool shouldAlwaysKeep(const Instruction &I) {
  27   return I.isEHPad() || I.getType()->isTokenTy() || I.isSwiftError();
  28 }
  29
  30 /// Removes out-of-chunk arguments from functions, and modifies their calls
  31 /// accordingly. It also removes allocations of out-of-chunk arguments.
  32 static void extractInstrFromModule(Oracle &O, ReducerWorkItem &WorkItem) {
  33   Module &Program = WorkItem.getModule();
  34   std::vector<Instruction *> InitInstToKeep;
  35
  36   for (auto &F : Program)
  37     for (auto &BB : F) {
  38       // Removing the terminator would make the block invalid. Only iterate over
  39       // instructions before the terminator.
  40       InitInstToKeep.push_back(BB.getTerminator());
  41       for (auto &Inst : make_range(BB.begin(), std::prev(BB.end()))) {
  42         if (shouldAlwaysKeep(Inst) || O.shouldKeep())
  43           InitInstToKeep.push_back(&Inst);
  44       }
  45     }
  46
  47   // We create a vector first, then convert it to a set, so that we don't have
  48   // to pay the cost of rebalancing the set frequently if the order we insert
  49   // the elements doesn't match the order they should appear inside the set.
  50   std::set<Instruction *> InstToKeep(InitInstToKeep.begin(),
  51                                      InitInstToKeep.end());
  52
  53   std::vector<Instruction *> InstToDelete;
  54   for (auto &F : Program)
  55     for (auto &BB : F)
  56       for (auto &Inst : BB)
  57         if (!InstToKeep.count(&Inst)) {
  58           Inst.replaceAllUsesWith(getDefaultValue(Inst.getType()));
  59           InstToDelete.push_back(&Inst);
  60         }
  61
  62   for (auto &I : InstToDelete)
  63     I->eraseFromParent();
  64 }
  65
  66 void llvm::reduceInstructionsDeltaPass(TestRunner &Test) {
  67   runDeltaPass(Test, extractInstrFromModule, "Reducing Instructions");
  68 }