1//===-- GuardUtils.cpp - Utils for work with guards -------------*- C++ -*-===//
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// Utils that are used to perform analyzes related to guards and their
9// conditions.
10//===----------------------------------------------------------------------===//
11
12#include "llvm/Analysis/GuardUtils.h"
13#include "llvm/IR/PatternMatch.h"
14
15using namespace llvm;
16using namespace llvm::PatternMatch;
17
18bool llvm::isGuard(const User *U) {
19 return match(V: U, P: m_Intrinsic<Intrinsic::experimental_guard>());
20}
21
22bool llvm::isWidenableCondition(const Value *V) {
23 return match(V, P: m_Intrinsic<Intrinsic::experimental_widenable_condition>());
24}
25
26bool llvm::isWidenableBranch(const User *U) {
27 Value *Condition, *WidenableCondition;
28 BasicBlock *GuardedBB, *DeoptBB;
29 return parseWidenableBranch(U, Condition, WidenableCondition, IfTrueBB&: GuardedBB,
30 IfFalseBB&: DeoptBB);
31}
32
33bool llvm::isGuardAsWidenableBranch(const User *U) {
34 if (!isWidenableBranch(U))
35 return false;
36 BasicBlock *DeoptBB = cast<BranchInst>(Val: U)->getSuccessor(i: 1);
37 SmallPtrSet<const BasicBlock *, 2> Visited;
38 Visited.insert(Ptr: DeoptBB);
39 do {
40 for (auto &Insn : *DeoptBB) {
41 if (match(V: &Insn, P: m_Intrinsic<Intrinsic::experimental_deoptimize>()))
42 return true;
43 if (Insn.mayHaveSideEffects())
44 return false;
45 }
46 DeoptBB = DeoptBB->getUniqueSuccessor();
47 if (!DeoptBB)
48 return false;
49 } while (Visited.insert(Ptr: DeoptBB).second);
50 return false;
51}
52
53bool llvm::parseWidenableBranch(const User *U, Value *&Condition,
54 Value *&WidenableCondition,
55 BasicBlock *&IfTrueBB, BasicBlock *&IfFalseBB) {
56
57 Use *C, *WC;
58 if (parseWidenableBranch(U: const_cast<User*>(U), Cond&: C, WC, IfTrueBB, IfFalseBB)) {
59 if (C)
60 Condition = C->get();
61 else
62 Condition = ConstantInt::getTrue(Context&: IfTrueBB->getContext());
63 WidenableCondition = WC->get();
64 return true;
65 }
66 return false;
67}
68
69bool llvm::parseWidenableBranch(User *U, Use *&C,Use *&WC,
70 BasicBlock *&IfTrueBB, BasicBlock *&IfFalseBB) {
71
72 auto *BI = dyn_cast<BranchInst>(Val: U);
73 if (!BI || !BI->isConditional())
74 return false;
75 auto *Cond = BI->getCondition();
76 if (!Cond->hasOneUse())
77 return false;
78
79 IfTrueBB = BI->getSuccessor(i: 0);
80 IfFalseBB = BI->getSuccessor(i: 1);
81
82 if (match(V: Cond, P: m_Intrinsic<Intrinsic::experimental_widenable_condition>())) {
83 WC = &BI->getOperandUse(i: 0);
84 C = nullptr;
85 return true;
86 }
87
88 // Check for two cases:
89 // 1) br (i1 (and A, WC())), label %IfTrue, label %IfFalse
90 // 2) br (i1 (and WC(), B)), label %IfTrue, label %IfFalse
91 // We do not check for more generalized and trees as we should canonicalize
92 // to the form above in instcombine. (TODO)
93 Value *A, *B;
94 if (!match(V: Cond, P: m_And(L: m_Value(V&: A), R: m_Value(V&: B))))
95 return false;
96 auto *And = dyn_cast<Instruction>(Val: Cond);
97 if (!And)
98 // Could be a constexpr
99 return false;
100
101 if (match(V: A, P: m_Intrinsic<Intrinsic::experimental_widenable_condition>()) &&
102 A->hasOneUse()) {
103 WC = &And->getOperandUse(i: 0);
104 C = &And->getOperandUse(i: 1);
105 return true;
106 }
107
108 if (match(V: B, P: m_Intrinsic<Intrinsic::experimental_widenable_condition>()) &&
109 B->hasOneUse()) {
110 WC = &And->getOperandUse(i: 1);
111 C = &And->getOperandUse(i: 0);
112 return true;
113 }
114 return false;
115}
116
117template <typename CallbackType>
118static void parseCondition(Value *Condition,
119 CallbackType RecordCheckOrWidenableCond) {
120 SmallVector<Value *, 4> Worklist(1, Condition);
121 SmallPtrSet<Value *, 4> Visited;
122 Visited.insert(Ptr: Condition);
123 do {
124 Value *Check = Worklist.pop_back_val();
125 Value *LHS, *RHS;
126 if (match(V: Check, P: m_And(L: m_Value(V&: LHS), R: m_Value(V&: RHS)))) {
127 if (Visited.insert(Ptr: LHS).second)
128 Worklist.push_back(Elt: LHS);
129 if (Visited.insert(Ptr: RHS).second)
130 Worklist.push_back(Elt: RHS);
131 continue;
132 }
133 if (!RecordCheckOrWidenableCond(Check))
134 break;
135 } while (!Worklist.empty());
136}
137
138void llvm::parseWidenableGuard(const User *U,
139 llvm::SmallVectorImpl<Value *> &Checks) {
140 assert((isGuard(U) || isWidenableBranch(U)) && "Should be");
141 Value *Condition = isGuard(U) ? cast<IntrinsicInst>(Val: U)->getArgOperand(i: 0)
142 : cast<BranchInst>(Val: U)->getCondition();
143
144 parseCondition(Condition, RecordCheckOrWidenableCond: [&](Value *Check) {
145 if (!isWidenableCondition(V: Check))
146 Checks.push_back(Elt: Check);
147 return true;
148 });
149}
150
151Value *llvm::extractWidenableCondition(const User *U) {
152 auto *BI = dyn_cast<BranchInst>(Val: U);
153 if (!BI || !BI->isConditional())
154 return nullptr;
155
156 auto Condition = BI->getCondition();
157 if (!Condition->hasOneUse())
158 return nullptr;
159
160 Value *WidenableCondition = nullptr;
161 parseCondition(Condition, RecordCheckOrWidenableCond: [&](Value *Check) {
162 // We require widenable_condition has only one use, otherwise we don't
163 // consider appropriate branch as widenable.
164 if (isWidenableCondition(V: Check) && Check->hasOneUse()) {
165 WidenableCondition = Check;
166 return false;
167 }
168 return true;
169 });
170 return WidenableCondition;
171}
172