Initial Commit

thirdparty/capstone/suite/synctools/tablegen/include/llvm/CodeGen/IndirectThunks.h

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+//===---- IndirectThunks.h - Indirect Thunk Base Class ----------*- 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Contains a base class for Passes that inject an MI thunk.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_INDIRECTTHUNKS_H
+#define LLVM_CODEGEN_INDIRECTTHUNKS_H
+
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Module.h"
+
+namespace llvm {
+
+template <typename Derived> class ThunkInserter {
+  Derived &getDerived() { return *static_cast<Derived *>(this); }
+
+protected:
+  bool InsertedThunks;
+  void doInitialization(Module &M) {}
+  void createThunkFunction(MachineModuleInfo &MMI, StringRef Name,
+                           bool Comdat = true);
+
+public:
+  void init(Module &M) {
+    InsertedThunks = false;
+    getDerived().doInitialization(M);
+  }
+  // return `true` if `MMI` or `MF` was modified
+  bool run(MachineModuleInfo &MMI, MachineFunction &MF);
+};
+
+template <typename Derived>
+void ThunkInserter<Derived>::createThunkFunction(MachineModuleInfo &MMI,
+                                                 StringRef Name, bool Comdat) {
+  assert(Name.startswith(getDerived().getThunkPrefix()) &&
+         "Created a thunk with an unexpected prefix!");
+
+  Module &M = const_cast<Module &>(*MMI.getModule());
+  LLVMContext &Ctx = M.getContext();
+  auto Type = FunctionType::get(Type::getVoidTy(Ctx), false);
+  Function *F = Function::Create(Type,
+                                 Comdat ? GlobalValue::LinkOnceODRLinkage
+                                        : GlobalValue::InternalLinkage,
+                                 Name, &M);
+  if (Comdat) {
+    F->setVisibility(GlobalValue::HiddenVisibility);
+    F->setComdat(M.getOrInsertComdat(Name));
+  }
+
+  // Add Attributes so that we don't create a frame, unwind information, or
+  // inline.
+  AttrBuilder B(Ctx);
+  B.addAttribute(llvm::Attribute::NoUnwind);
+  B.addAttribute(llvm::Attribute::Naked);
+  F->addFnAttrs(B);
+
+  // Populate our function a bit so that we can verify.
+  BasicBlock *Entry = BasicBlock::Create(Ctx, "entry", F);
+  IRBuilder<> Builder(Entry);
+
+  Builder.CreateRetVoid();
+
+  // MachineFunctions aren't created automatically for the IR-level constructs
+  // we already made. Create them and insert them into the module.
+  MachineFunction &MF = MMI.getOrCreateMachineFunction(*F);
+  // A MachineBasicBlock must not be created for the Entry block; code
+  // generation from an empty naked function in C source code also does not
+  // generate one.  At least GlobalISel asserts if this invariant isn't
+  // respected.
+
+  // Set MF properties. We never use vregs...
+  MF.getProperties().set(MachineFunctionProperties::Property::NoVRegs);
+}
+
+template <typename Derived>
+bool ThunkInserter<Derived>::run(MachineModuleInfo &MMI, MachineFunction &MF) {
+  // If MF is not a thunk, check to see if we need to insert a thunk.
+  if (!MF.getName().startswith(getDerived().getThunkPrefix())) {
+    // If we've already inserted a thunk, nothing else to do.
+    if (InsertedThunks)
+      return false;
+
+    // Only add a thunk if one of the functions has the corresponding feature
+    // enabled in its subtarget, and doesn't enable external thunks.
+    // FIXME: Conditionalize on indirect calls so we don't emit a thunk when
+    // nothing will end up calling it.
+    // FIXME: It's a little silly to look at every function just to enumerate
+    // the subtargets, but eventually we'll want to look at them for indirect
+    // calls, so maybe this is OK.
+    if (!getDerived().mayUseThunk(MF))
+      return false;
+
+    getDerived().insertThunks(MMI);
+    InsertedThunks = true;
+    return true;
+  }
+
+  // If this *is* a thunk function, we need to populate it with the correct MI.
+  getDerived().populateThunk(MF);
+  return true;
+}
+
+} // namespace llvm
+
+#endif