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