1//===----- llvm/Analysis/CaptureTracking.h - Pointer capture ----*- 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// 9// This file contains routines that help determine which pointers are captured. 10// 11//===----------------------------------------------------------------------===// 12 13#ifndef LLVM_ANALYSIS_CAPTURETRACKING_H 14#define LLVM_ANALYSIS_CAPTURETRACKING_H 15 16namespace llvm { 17 18 class Value; 19 class Use; 20 class DataLayout; 21 class Instruction; 22 class DominatorTree; 23 24 /// getDefaultMaxUsesToExploreForCaptureTracking - Return default value of 25 /// the maximal number of uses to explore before giving up. It is used by 26 /// PointerMayBeCaptured family analysis. 27 unsigned getDefaultMaxUsesToExploreForCaptureTracking(); 28 29 /// PointerMayBeCaptured - Return true if this pointer value may be captured 30 /// by the enclosing function (which is required to exist). This routine can 31 /// be expensive, so consider caching the results. The boolean ReturnCaptures 32 /// specifies whether returning the value (or part of it) from the function 33 /// counts as capturing it or not. The boolean StoreCaptures specified 34 /// whether storing the value (or part of it) into memory anywhere 35 /// automatically counts as capturing it or not. 36 /// MaxUsesToExplore specifies how many uses the analysis should explore for 37 /// one value before giving up due too "too many uses". If MaxUsesToExplore 38 /// is zero, a default value is assumed. 39 bool PointerMayBeCaptured(const Value *V, bool ReturnCaptures, 40 bool StoreCaptures, 41 unsigned MaxUsesToExplore = 0); 42 43 /// PointerMayBeCapturedBefore - Return true if this pointer value may be 44 /// captured by the enclosing function (which is required to exist). If a 45 /// DominatorTree is provided, only captures which happen before the given 46 /// instruction are considered. This routine can be expensive, so consider 47 /// caching the results. The boolean ReturnCaptures specifies whether 48 /// returning the value (or part of it) from the function counts as capturing 49 /// it or not. The boolean StoreCaptures specified whether storing the value 50 /// (or part of it) into memory anywhere automatically counts as capturing it 51 /// or not. Captures by the provided instruction are considered if the 52 /// final parameter is true. 53 /// MaxUsesToExplore specifies how many uses the analysis should explore for 54 /// one value before giving up due too "too many uses". If MaxUsesToExplore 55 /// is zero, a default value is assumed. 56 bool PointerMayBeCapturedBefore( 57 const Value *V, bool ReturnCaptures, bool StoreCaptures, 58 const Instruction *I, const DominatorTree *DT, bool IncludeI = false, 59 unsigned MaxUsesToExplore = 0); 60 61 /// This callback is used in conjunction with PointerMayBeCaptured. In 62 /// addition to the interface here, you'll need to provide your own getters 63 /// to see whether anything was captured. 64 struct CaptureTracker { 65 virtual ~CaptureTracker(); 66 67 /// tooManyUses - The depth of traversal has breached a limit. There may be 68 /// capturing instructions that will not be passed into captured(). 69 virtual void tooManyUses() = 0; 70 71 /// shouldExplore - This is the use of a value derived from the pointer. 72 /// To prune the search (ie., assume that none of its users could possibly 73 /// capture) return false. To search it, return true. 74 /// 75 /// U->getUser() is always an Instruction. 76 virtual bool shouldExplore(const Use *U); 77 78 /// captured - Information about the pointer was captured by the user of 79 /// use U. Return true to stop the traversal or false to continue looking 80 /// for more capturing instructions. 81 virtual bool captured(const Use *U) = 0; 82 83 /// isDereferenceableOrNull - Overload to allow clients with additional 84 /// knowledge about pointer dereferenceability to provide it and thereby 85 /// avoid conservative responses when a pointer is compared to null. 86 virtual bool isDereferenceableOrNull(Value *O, const DataLayout &DL); 87 }; 88 89 /// PointerMayBeCaptured - Visit the value and the values derived from it and 90 /// find values which appear to be capturing the pointer value. This feeds 91 /// results into and is controlled by the CaptureTracker object. 92 /// MaxUsesToExplore specifies how many uses the analysis should explore for 93 /// one value before giving up due too "too many uses". If MaxUsesToExplore 94 /// is zero, a default value is assumed. 95 void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker, 96 unsigned MaxUsesToExplore = 0); 97} // end namespace llvm 98 99#endif 100