1 //===----- llvm/Analysis/CaptureTracking.h - Pointer capture ----*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file contains routines that help determine which pointers are captured. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_ANALYSIS_CAPTURETRACKING_H 15 #define LLVM_ANALYSIS_CAPTURETRACKING_H 16 17 namespace llvm { 18 19 class Value; 20 class Use; 21 class Instruction; 22 class DominatorTree; 23 class OrderedBasicBlock; 24 25 /// PointerMayBeCaptured - Return true if this pointer value may be captured 26 /// by the enclosing function (which is required to exist). This routine can 27 /// be expensive, so consider caching the results. The boolean ReturnCaptures 28 /// specifies whether returning the value (or part of it) from the function 29 /// counts as capturing it or not. The boolean StoreCaptures specified 30 /// whether storing the value (or part of it) into memory anywhere 31 /// automatically counts as capturing it or not. 32 bool PointerMayBeCaptured(const Value *V, 33 bool ReturnCaptures, 34 bool StoreCaptures); 35 36 /// PointerMayBeCapturedBefore - Return true if this pointer value may be 37 /// captured by the enclosing function (which is required to exist). If a 38 /// DominatorTree is provided, only captures which happen before the given 39 /// instruction are considered. This routine can be expensive, so consider 40 /// caching the results. The boolean ReturnCaptures specifies whether 41 /// returning the value (or part of it) from the function counts as capturing 42 /// it or not. The boolean StoreCaptures specified whether storing the value 43 /// (or part of it) into memory anywhere automatically counts as capturing it 44 /// or not. Captures by the provided instruction are considered if the 45 /// final parameter is true. An ordered basic block in \p OBB could be used 46 /// to speed up capture-tracker queries. 47 bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures, 48 bool StoreCaptures, const Instruction *I, 49 DominatorTree *DT, bool IncludeI = false, 50 OrderedBasicBlock *OBB = nullptr); 51 52 /// This callback is used in conjunction with PointerMayBeCaptured. In 53 /// addition to the interface here, you'll need to provide your own getters 54 /// to see whether anything was captured. 55 struct CaptureTracker { 56 virtual ~CaptureTracker(); 57 58 /// tooManyUses - The depth of traversal has breached a limit. There may be 59 /// capturing instructions that will not be passed into captured(). 60 virtual void tooManyUses() = 0; 61 62 /// shouldExplore - This is the use of a value derived from the pointer. 63 /// To prune the search (ie., assume that none of its users could possibly 64 /// capture) return false. To search it, return true. 65 /// 66 /// U->getUser() is always an Instruction. 67 virtual bool shouldExplore(const Use *U); 68 69 /// captured - Information about the pointer was captured by the user of 70 /// use U. Return true to stop the traversal or false to continue looking 71 /// for more capturing instructions. 72 virtual bool captured(const Use *U) = 0; 73 }; 74 75 /// PointerMayBeCaptured - Visit the value and the values derived from it and 76 /// find values which appear to be capturing the pointer value. This feeds 77 /// results into and is controlled by the CaptureTracker object. 78 void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker); 79 } // end namespace llvm 80 81 #endif 82
