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| Rev | Author | Line No. | Line |
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| 14 | pmbaty | 1 | //===---- IndirectThunks.h - Indirect Thunk Base Class ----------*- C++ -*-===// |
| 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 | /// \file |
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| 10 | /// Contains a base class for Passes that inject an MI thunk. |
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| 11 | /// |
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| 12 | //===----------------------------------------------------------------------===// |
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| 13 | |||
| 14 | #ifndef LLVM_CODEGEN_INDIRECTTHUNKS_H |
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| 15 | #define LLVM_CODEGEN_INDIRECTTHUNKS_H |
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| 16 | |||
| 17 | #include "llvm/CodeGen/MachineFunction.h" |
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| 18 | #include "llvm/CodeGen/MachineModuleInfo.h" |
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| 19 | #include "llvm/IR/IRBuilder.h" |
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| 20 | #include "llvm/IR/Module.h" |
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| 21 | |||
| 22 | namespace llvm { |
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| 23 | |||
| 24 | template <typename Derived, typename InsertedThunksTy = bool> |
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| 25 | class ThunkInserter { |
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| 26 | Derived &getDerived() { return *static_cast<Derived *>(this); } |
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| 27 | |||
| 28 | protected: |
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| 29 | // A variable used to track whether (and possible which) thunks have been |
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| 30 | // inserted so far. InsertedThunksTy is usually a bool, but can be other types |
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| 31 | // to represent more than one type of thunk. Requires an |= operator to |
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| 32 | // accumulate results. |
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| 33 | InsertedThunksTy InsertedThunks; |
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| 34 | void doInitialization(Module &M) {} |
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| 35 | void createThunkFunction(MachineModuleInfo &MMI, StringRef Name, |
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| 36 | bool Comdat = true); |
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| 37 | |||
| 38 | public: |
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| 39 | void init(Module &M) { |
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| 40 | InsertedThunks = InsertedThunksTy{}; |
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| 41 | getDerived().doInitialization(M); |
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| 42 | } |
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| 43 | // return `true` if `MMI` or `MF` was modified |
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| 44 | bool run(MachineModuleInfo &MMI, MachineFunction &MF); |
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| 45 | }; |
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| 46 | |||
| 47 | template <typename Derived, typename InsertedThunksTy> |
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| 48 | void ThunkInserter<Derived, InsertedThunksTy>::createThunkFunction( |
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| 49 | MachineModuleInfo &MMI, StringRef Name, bool Comdat) { |
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| 50 | assert(Name.startswith(getDerived().getThunkPrefix()) && |
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| 51 | "Created a thunk with an unexpected prefix!"); |
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| 52 | |||
| 53 | Module &M = const_cast<Module &>(*MMI.getModule()); |
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| 54 | LLVMContext &Ctx = M.getContext(); |
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| 55 | auto Type = FunctionType::get(Type::getVoidTy(Ctx), false); |
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| 56 | Function *F = Function::Create(Type, |
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| 57 | Comdat ? GlobalValue::LinkOnceODRLinkage |
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| 58 | : GlobalValue::InternalLinkage, |
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| 59 | Name, &M); |
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| 60 | if (Comdat) { |
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| 61 | F->setVisibility(GlobalValue::HiddenVisibility); |
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| 62 | F->setComdat(M.getOrInsertComdat(Name)); |
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| 63 | } |
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| 64 | |||
| 65 | // Add Attributes so that we don't create a frame, unwind information, or |
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| 66 | // inline. |
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| 67 | AttrBuilder B(Ctx); |
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| 68 | B.addAttribute(llvm::Attribute::NoUnwind); |
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| 69 | B.addAttribute(llvm::Attribute::Naked); |
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| 70 | F->addFnAttrs(B); |
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| 71 | |||
| 72 | // Populate our function a bit so that we can verify. |
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| 73 | BasicBlock *Entry = BasicBlock::Create(Ctx, "entry", F); |
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| 74 | IRBuilder<> Builder(Entry); |
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| 75 | |||
| 76 | Builder.CreateRetVoid(); |
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| 77 | |||
| 78 | // MachineFunctions aren't created automatically for the IR-level constructs |
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| 79 | // we already made. Create them and insert them into the module. |
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| 80 | MachineFunction &MF = MMI.getOrCreateMachineFunction(*F); |
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| 81 | // A MachineBasicBlock must not be created for the Entry block; code |
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| 82 | // generation from an empty naked function in C source code also does not |
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| 83 | // generate one. At least GlobalISel asserts if this invariant isn't |
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| 84 | // respected. |
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| 85 | |||
| 86 | // Set MF properties. We never use vregs... |
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| 87 | MF.getProperties().set(MachineFunctionProperties::Property::NoVRegs); |
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| 88 | } |
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| 89 | |||
| 90 | template <typename Derived, typename InsertedThunksTy> |
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| 91 | bool ThunkInserter<Derived, InsertedThunksTy>::run(MachineModuleInfo &MMI, |
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| 92 | MachineFunction &MF) { |
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| 93 | // If MF is not a thunk, check to see if we need to insert a thunk. |
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| 94 | if (!MF.getName().startswith(getDerived().getThunkPrefix())) { |
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| 95 | // Only add a thunk if one of the functions has the corresponding feature |
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| 96 | // enabled in its subtarget, and doesn't enable external thunks. The target |
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| 97 | // can use InsertedThunks to detect whether relevant thunks have already |
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| 98 | // been inserted. |
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| 99 | // FIXME: Conditionalize on indirect calls so we don't emit a thunk when |
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| 100 | // nothing will end up calling it. |
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| 101 | // FIXME: It's a little silly to look at every function just to enumerate |
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| 102 | // the subtargets, but eventually we'll want to look at them for indirect |
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| 103 | // calls, so maybe this is OK. |
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| 104 | if (!getDerived().mayUseThunk(MF, InsertedThunks)) |
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| 105 | return false; |
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| 106 | |||
| 107 | InsertedThunks |= getDerived().insertThunks(MMI, MF); |
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| 108 | return true; |
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| 109 | } |
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| 110 | |||
| 111 | // If this *is* a thunk function, we need to populate it with the correct MI. |
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| 112 | getDerived().populateThunk(MF); |
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| 113 | return true; |
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| 114 | } |
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| 115 | |||
| 116 | } // namespace llvm |
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| 117 | |||
| 118 | #endif |