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.
shouldAlwaysKeep(const Instruction & I)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.
extractInstrFromModule(Oracle & O,ReducerWorkItem & WorkItem)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
reduceInstructionsDeltaPass(TestRunner & Test)66 void llvm::reduceInstructionsDeltaPass(TestRunner &Test) {
67 runDeltaPass(Test, extractInstrFromModule, "Reducing Instructions");
68 }
69