| //===----- llvm/Analysis/CaptureTracking.h - Pointer capture ----*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file contains routines that help determine which pointers are captured. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_ANALYSIS_CAPTURETRACKING_H |
| #define LLVM_ANALYSIS_CAPTURETRACKING_H |
| |
| namespace llvm { |
| |
| class Value; |
| class Use; |
| class Instruction; |
| class DominatorTree; |
| class OrderedBasicBlock; |
| |
| /// The default value for MaxUsesToExplore argument. It's relatively small to |
| /// keep the cost of analysis reasonable for clients like BasicAliasAnalysis, |
| /// where the results can't be cached. |
| /// TODO: we should probably introduce a caching CaptureTracking analysis and |
| /// use it where possible. The caching version can use much higher limit or |
| /// don't have this cap at all. |
| unsigned constexpr DefaultMaxUsesToExplore = 20; |
| |
| /// PointerMayBeCaptured - Return true if this pointer value may be captured |
| /// by the enclosing function (which is required to exist). This routine can |
| /// be expensive, so consider caching the results. The boolean ReturnCaptures |
| /// specifies whether returning the value (or part of it) from the function |
| /// counts as capturing it or not. The boolean StoreCaptures specified |
| /// whether storing the value (or part of it) into memory anywhere |
| /// automatically counts as capturing it or not. |
| /// MaxUsesToExplore specifies how many uses should the analysis explore for |
| /// one value before giving up due too "too many uses". |
| bool PointerMayBeCaptured(const Value *V, |
| bool ReturnCaptures, |
| bool StoreCaptures, |
| unsigned MaxUsesToExplore = DefaultMaxUsesToExplore); |
| |
| /// PointerMayBeCapturedBefore - Return true if this pointer value may be |
| /// captured by the enclosing function (which is required to exist). If a |
| /// DominatorTree is provided, only captures which happen before the given |
| /// instruction are considered. This routine can be expensive, so consider |
| /// caching the results. The boolean ReturnCaptures specifies whether |
| /// returning the value (or part of it) from the function counts as capturing |
| /// it or not. The boolean StoreCaptures specified whether storing the value |
| /// (or part of it) into memory anywhere automatically counts as capturing it |
| /// or not. Captures by the provided instruction are considered if the |
| /// final parameter is true. An ordered basic block in \p OBB could be used |
| /// to speed up capture-tracker queries. |
| /// MaxUsesToExplore specifies how many uses should the analysis explore for |
| /// one value before giving up due too "too many uses". |
| bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures, |
| bool StoreCaptures, const Instruction *I, |
| const DominatorTree *DT, bool IncludeI = false, |
| OrderedBasicBlock *OBB = nullptr, |
| unsigned MaxUsesToExplore = DefaultMaxUsesToExplore); |
| |
| /// This callback is used in conjunction with PointerMayBeCaptured. In |
| /// addition to the interface here, you'll need to provide your own getters |
| /// to see whether anything was captured. |
| struct CaptureTracker { |
| virtual ~CaptureTracker(); |
| |
| /// tooManyUses - The depth of traversal has breached a limit. There may be |
| /// capturing instructions that will not be passed into captured(). |
| virtual void tooManyUses() = 0; |
| |
| /// shouldExplore - This is the use of a value derived from the pointer. |
| /// To prune the search (ie., assume that none of its users could possibly |
| /// capture) return false. To search it, return true. |
| /// |
| /// U->getUser() is always an Instruction. |
| virtual bool shouldExplore(const Use *U); |
| |
| /// captured - Information about the pointer was captured by the user of |
| /// use U. Return true to stop the traversal or false to continue looking |
| /// for more capturing instructions. |
| virtual bool captured(const Use *U) = 0; |
| }; |
| |
| /// PointerMayBeCaptured - Visit the value and the values derived from it and |
| /// find values which appear to be capturing the pointer value. This feeds |
| /// results into and is controlled by the CaptureTracker object. |
| /// MaxUsesToExplore specifies how many uses should the analysis explore for |
| /// one value before giving up due too "too many uses". |
| void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker, |
| unsigned MaxUsesToExplore = DefaultMaxUsesToExplore); |
| } // end namespace llvm |
| |
| #endif |