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 24 /// PointerMayBeCaptured - Return true if this pointer value may be captured 25 /// by the enclosing function (which is required to exist). This routine can 26 /// be expensive, so consider caching the results. The boolean ReturnCaptures 27 /// specifies whether returning the value (or part of it) from the function 28 /// counts as capturing it or not. The boolean StoreCaptures specified 29 /// whether storing the value (or part of it) into memory anywhere 30 /// automatically counts as capturing it or not. 31 bool PointerMayBeCaptured(const Value *V, 32 bool ReturnCaptures, 33 bool StoreCaptures); 34 35 /// PointerMayBeCapturedBefore - Return true if this pointer value may be 36 /// captured by the enclosing function (which is required to exist). If a 37 /// DominatorTree is provided, only captures which happen before the given 38 /// instruction are considered. This routine can be expensive, so consider 39 /// caching the results. The boolean ReturnCaptures specifies whether 40 /// returning the value (or part of it) from the function counts as capturing 41 /// it or not. The boolean StoreCaptures specified whether storing the value 42 /// (or part of it) into memory anywhere automatically counts as capturing it 43 /// or not. Captures by the provided instruction are considered if the 44 /// final parameter is true. 45 bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures, 46 bool StoreCaptures, const Instruction *I, 47 DominatorTree *DT, bool IncludeI = false); 48 49 /// This callback is used in conjunction with PointerMayBeCaptured. In 50 /// addition to the interface here, you'll need to provide your own getters 51 /// to see whether anything was captured. 52 struct CaptureTracker { 53 virtual ~CaptureTracker(); 54 55 /// tooManyUses - The depth of traversal has breached a limit. There may be 56 /// capturing instructions that will not be passed into captured(). 57 virtual void tooManyUses() = 0; 58 59 /// shouldExplore - This is the use of a value derived from the pointer. 60 /// To prune the search (ie., assume that none of its users could possibly 61 /// capture) return false. To search it, return true. 62 /// 63 /// U->getUser() is always an Instruction. 64 virtual bool shouldExplore(const Use *U); 65 66 /// captured - Information about the pointer was captured by the user of 67 /// use U. Return true to stop the traversal or false to continue looking 68 /// for more capturing instructions. 69 virtual bool captured(const Use *U) = 0; 70 }; 71 72 /// PointerMayBeCaptured - Visit the value and the values derived from it and 73 /// find values which appear to be capturing the pointer value. This feeds 74 /// results into and is controlled by the CaptureTracker object. 75 void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker); 76 } // end namespace llvm 77 78 #endif 79