1 //===- ReduceArguments.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 Arguments from declared and defined functions.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "ReduceArguments.h"
15 #include "Delta.h"
16 #include "Utils.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/IR/Constants.h"
19 #include "llvm/IR/Instructions.h"
20 #include "llvm/IR/Intrinsics.h"
21 #include <set>
22 #include <vector>
23
24 using namespace llvm;
25
26 /// Goes over OldF calls and replaces them with a call to NewF
replaceFunctionCalls(Function & OldF,Function & NewF,const std::set<int> & ArgIndexesToKeep)27 static void replaceFunctionCalls(Function &OldF, Function &NewF,
28 const std::set<int> &ArgIndexesToKeep) {
29 const auto &Users = OldF.users();
30 for (auto I = Users.begin(), E = Users.end(); I != E; )
31 if (auto *CI = dyn_cast<CallInst>(*I++)) {
32 // Skip uses in call instructions where OldF isn't the called function
33 // (e.g. if OldF is an argument of the call).
34 if (CI->getCalledFunction() != &OldF)
35 continue;
36 SmallVector<Value *, 8> Args;
37 for (auto ArgI = CI->arg_begin(), E = CI->arg_end(); ArgI != E; ++ArgI)
38 if (ArgIndexesToKeep.count(ArgI - CI->arg_begin()))
39 Args.push_back(*ArgI);
40
41 CallInst *NewCI = CallInst::Create(&NewF, Args);
42 NewCI->setCallingConv(NewF.getCallingConv());
43 if (!CI->use_empty())
44 CI->replaceAllUsesWith(NewCI);
45 ReplaceInstWithInst(CI, NewCI);
46 }
47 }
48
49 /// Returns whether or not this function should be considered a candidate for
50 /// argument removal. Currently, functions with no arguments and intrinsics are
51 /// not considered. Intrinsics aren't considered because their signatures are
52 /// fixed.
shouldRemoveArguments(const Function & F)53 static bool shouldRemoveArguments(const Function &F) {
54 return !F.arg_empty() && !F.isIntrinsic();
55 }
56
57 /// Removes out-of-chunk arguments from functions, and modifies their calls
58 /// accordingly. It also removes allocations of out-of-chunk arguments.
extractArgumentsFromModule(Oracle & O,ReducerWorkItem & WorkItem)59 static void extractArgumentsFromModule(Oracle &O, ReducerWorkItem &WorkItem) {
60 Module &Program = WorkItem.getModule();
61 std::vector<Argument *> InitArgsToKeep;
62 std::vector<Function *> Funcs;
63 // Get inside-chunk arguments, as well as their parent function
64 for (auto &F : Program)
65 if (shouldRemoveArguments(F)) {
66 Funcs.push_back(&F);
67 for (auto &A : F.args())
68 if (O.shouldKeep())
69 InitArgsToKeep.push_back(&A);
70 }
71
72 // We create a vector first, then convert it to a set, so that we don't have
73 // to pay the cost of rebalancing the set frequently if the order we insert
74 // the elements doesn't match the order they should appear inside the set.
75 std::set<Argument *> ArgsToKeep(InitArgsToKeep.begin(), InitArgsToKeep.end());
76
77 for (auto *F : Funcs) {
78 ValueToValueMapTy VMap;
79 std::vector<WeakVH> InstToDelete;
80 for (auto &A : F->args())
81 if (!ArgsToKeep.count(&A)) {
82 // By adding undesired arguments to the VMap, CloneFunction will remove
83 // them from the resulting Function
84 VMap[&A] = getDefaultValue(A.getType());
85 for (auto *U : A.users())
86 if (auto *I = dyn_cast<Instruction>(*&U))
87 InstToDelete.push_back(I);
88 }
89 // Delete any (unique) instruction that uses the argument
90 for (Value *V : InstToDelete) {
91 if (!V)
92 continue;
93 auto *I = cast<Instruction>(V);
94 I->replaceAllUsesWith(getDefaultValue(I->getType()));
95 if (!I->isTerminator())
96 I->eraseFromParent();
97 }
98
99 // No arguments to reduce
100 if (VMap.empty())
101 continue;
102
103 std::set<int> ArgIndexesToKeep;
104 for (const auto &[Index, Arg] : enumerate(F->args()))
105 if (ArgsToKeep.count(&Arg))
106 ArgIndexesToKeep.insert(Index);
107
108 auto *ClonedFunc = CloneFunction(F, VMap);
109 // In order to preserve function order, we move Clone after old Function
110 ClonedFunc->removeFromParent();
111 Program.getFunctionList().insertAfter(F->getIterator(), ClonedFunc);
112
113 replaceFunctionCalls(*F, *ClonedFunc, ArgIndexesToKeep);
114 // Rename Cloned Function to Old's name
115 std::string FName = std::string(F->getName());
116 F->replaceAllUsesWith(ClonedFunc);
117 F->eraseFromParent();
118 ClonedFunc->setName(FName);
119 }
120 }
121
reduceArgumentsDeltaPass(TestRunner & Test)122 void llvm::reduceArgumentsDeltaPass(TestRunner &Test) {
123 runDeltaPass(Test, extractArgumentsFromModule, "Reducing Arguments");
124 }
125