| 1 | //===- TypeMetadataUtils.h - Utilities related to type metadata --*- C++ -*-==// |
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| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | // |
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| 9 | // This file contains functions that make it easier to manipulate type metadata |
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| 10 | // for devirtualization. |
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| 11 | // |
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| 12 | //===----------------------------------------------------------------------===// |
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| 13 | |
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| 14 | #ifndef LLVM_ANALYSIS_TYPEMETADATAUTILS_H |
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| 15 | #define LLVM_ANALYSIS_TYPEMETADATAUTILS_H |
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| 16 | |
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| 17 | #include <cstdint> |
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| 18 | #include <utility> |
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| 19 | |
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| 20 | namespace llvm { |
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| 21 | |
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| 22 | template <typename T> class SmallVectorImpl; |
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| 23 | class CallBase; |
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| 24 | class CallInst; |
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| 25 | class Constant; |
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| 26 | class Function; |
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| 27 | class DominatorTree; |
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| 28 | class GlobalVariable; |
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| 29 | class Instruction; |
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| 30 | class Module; |
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| 31 | |
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| 32 | /// The type of CFI jumptable needed for a function. |
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| 33 | enum CfiFunctionLinkage { |
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| 34 | CFL_Definition = 0, |
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| 35 | CFL_Declaration = 1, |
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| 36 | CFL_WeakDeclaration = 2 |
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| 37 | }; |
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| 38 | |
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| 39 | /// A call site that could be devirtualized. |
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| 40 | struct DevirtCallSite { |
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| 41 | /// The offset from the address point to the virtual function. |
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| 42 | uint64_t Offset; |
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| 43 | /// The call site itself. |
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| 44 | CallBase &CB; |
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| 45 | }; |
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| 46 | |
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| 47 | /// Given a call to the intrinsic \@llvm.type.test, find all devirtualizable |
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| 48 | /// call sites based on the call and return them in DevirtCalls. |
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| 49 | void findDevirtualizableCallsForTypeTest( |
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| 50 | SmallVectorImpl<DevirtCallSite> &DevirtCalls, |
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| 51 | SmallVectorImpl<CallInst *> &Assumes, const CallInst *CI, |
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| 52 | DominatorTree &DT); |
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| 53 | |
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| 54 | /// Given a call to the intrinsic \@llvm.type.checked.load, find all |
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| 55 | /// devirtualizable call sites based on the call and return them in DevirtCalls. |
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| 56 | void findDevirtualizableCallsForTypeCheckedLoad( |
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| 57 | SmallVectorImpl<DevirtCallSite> &DevirtCalls, |
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| 58 | SmallVectorImpl<Instruction *> &LoadedPtrs, |
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| 59 | SmallVectorImpl<Instruction *> &Preds, bool &HasNonCallUses, |
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| 60 | const CallInst *CI, DominatorTree &DT); |
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| 61 | |
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| 62 | /// Processes a Constant recursively looking into elements of arrays, structs |
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| 63 | /// and expressions to find a trivial pointer element that is located at the |
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| 64 | /// given offset (relative to the beginning of the whole outer Constant). |
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| 65 | /// |
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| 66 | /// Used for example from GlobalDCE to find an entry in a C++ vtable that |
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| 67 | /// matches a vcall offset. |
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| 68 | /// |
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| 69 | /// To support Swift vtables, getPointerAtOffset can see through "relative |
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| 70 | /// pointers", i.e. (sub-)expressions of the form of: |
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| 71 | /// |
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| 72 | /// @symbol = ... { |
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| 73 | /// i32 trunc (i64 sub ( |
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| 74 | /// i64 ptrtoint (<type> @target to i64), i64 ptrtoint (... @symbol to i64) |
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| 75 | /// ) to i32) |
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| 76 | /// } |
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| 77 | /// |
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| 78 | /// For such (sub-)expressions, getPointerAtOffset returns the @target pointer. |
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| 79 | Constant *getPointerAtOffset(Constant *I, uint64_t Offset, Module &M, |
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| 80 | Constant *TopLevelGlobal = nullptr); |
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| 81 | |
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| 82 | /// Given a vtable and a specified offset, returns the function and the trivial |
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| 83 | /// pointer at the specified offset in pair iff the pointer at the specified |
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| 84 | /// offset is a function or an alias to a function. Returns a pair of nullptr |
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| 85 | /// otherwise. |
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| 86 | std::pair<Function *, Constant *> |
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| 87 | getFunctionAtVTableOffset(GlobalVariable *GV, uint64_t Offset, Module &M); |
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| 88 | |
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| 89 | /// Finds the same "relative pointer" pattern as described above, where the |
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| 90 | /// target is `F`, and replaces the entire pattern with a constant zero. |
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| 91 | void replaceRelativePointerUsersWithZero(Function *F); |
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| 92 | |
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| 93 | } // namespace llvm |
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| 94 | |
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| 95 | #endif |
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| 96 | |
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