1 //===- ReduceFunctions.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 functions (and any instruction that calls it) in the provided
11 // Module.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "ReduceFunctions.h"
16 #include "Delta.h"
17 #include "llvm/ADT/SetVector.h"
18 #include "llvm/IR/Instructions.h"
19 #include <set>
20 
21 using namespace llvm;
22 
23 /// Removes all the Defined Functions (as well as their calls)
24 /// that aren't inside any of the desired Chunks.
25 static void extractFunctionsFromModule(const std::vector<Chunk> &ChunksToKeep,
26                                        Module *Program) {
27   // Get functions inside desired chunks
28   std::set<Function *> FuncsToKeep;
29   int I = 0, FunctionCount = 0;
30   for (auto &F : *Program)
31     if (I < (int)ChunksToKeep.size()) {
32       if (ChunksToKeep[I].contains(++FunctionCount))
33         FuncsToKeep.insert(&F);
34       if (FunctionCount == ChunksToKeep[I].end)
35         ++I;
36     }
37 
38   // Delete out-of-chunk functions, and replace their calls with undef
39   std::vector<Function *> FuncsToRemove;
40   SetVector<CallInst *> CallsToRemove;
41   for (auto &F : *Program)
42     if (!FuncsToKeep.count(&F)) {
43       for (auto U : F.users())
44         if (auto *Call = dyn_cast<CallInst>(U)) {
45           Call->replaceAllUsesWith(UndefValue::get(Call->getType()));
46           CallsToRemove.insert(Call);
47         }
48       F.replaceAllUsesWith(UndefValue::get(F.getType()));
49       FuncsToRemove.push_back(&F);
50     }
51 
52   for (auto *C : CallsToRemove)
53     C->eraseFromParent();
54 
55   for (auto *F : FuncsToRemove)
56     F->eraseFromParent();
57 }
58 
59 /// Counts the amount of non-declaration functions and prints their
60 /// respective name & index
61 static int countFunctions(Module *Program) {
62   // TODO: Silence index with --quiet flag
63   errs() << "----------------------------\n";
64   errs() << "Function Index Reference:\n";
65   int FunctionCount = 0;
66   for (auto &F : *Program)
67     errs() << "\t" << ++FunctionCount << ": " << F.getName() << "\n";
68 
69   errs() << "----------------------------\n";
70   return FunctionCount;
71 }
72 
73 void llvm::reduceFunctionsDeltaPass(TestRunner &Test) {
74   errs() << "*** Reducing Functions...\n";
75   int Functions = countFunctions(Test.getProgram());
76   runDeltaPass(Test, Functions, extractFunctionsFromModule);
77   errs() << "----------------------------\n";
78 }
79