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 
15 using namespace llvm;
16 
17 bool llvm::isGuard(const User *U) {
18   using namespace llvm::PatternMatch;
19   return match(U, m_Intrinsic<Intrinsic::experimental_guard>());
20 }
21 
22 bool llvm::isWidenableBranch(const User *U) {
23   Value *Condition, *WidenableCondition;
24   BasicBlock *GuardedBB, *DeoptBB;
25   return parseWidenableBranch(U, Condition, WidenableCondition, GuardedBB,
26                               DeoptBB);
27 }
28 
29 bool llvm::isGuardAsWidenableBranch(const User *U) {
30   Value *Condition, *WidenableCondition;
31   BasicBlock *GuardedBB, *DeoptBB;
32   if (!parseWidenableBranch(U, Condition, WidenableCondition, GuardedBB,
33                             DeoptBB))
34     return false;
35   using namespace llvm::PatternMatch;
36   for (auto &Insn : *DeoptBB) {
37     if (match(&Insn, m_Intrinsic<Intrinsic::experimental_deoptimize>()))
38       return true;
39     if (Insn.mayHaveSideEffects())
40       return false;
41   }
42   return false;
43 }
44 
45 bool llvm::parseWidenableBranch(const User *U, Value *&Condition,
46                                 Value *&WidenableCondition,
47                                 BasicBlock *&IfTrueBB, BasicBlock *&IfFalseBB) {
48   using namespace llvm::PatternMatch;
49   if (!match(U, m_Br(m_And(m_Value(Condition), m_Value(WidenableCondition)),
50                      IfTrueBB, IfFalseBB)))
51     return false;
52   // For the branch to be (easily) widenable, it must not correlate with other
53   // branches.  Thus, the widenable condition must have a single use.
54   if (!WidenableCondition->hasOneUse() ||
55       !cast<BranchInst>(U)->getCondition()->hasOneUse())
56     return false;
57   // TODO: At the moment, we only recognize the branch if the WC call in this
58   // specific position.  We should generalize!
59   return match(WidenableCondition,
60                m_Intrinsic<Intrinsic::experimental_widenable_condition>());
61 }
62