1 //===-- PatchableFunction.cpp - Patchable prologues for LLVM -------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements edits function bodies in place to support the 10 // "patchable-function" attribute. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/CodeGen/MachineFunction.h" 15 #include "llvm/CodeGen/MachineFunctionPass.h" 16 #include "llvm/CodeGen/MachineInstrBuilder.h" 17 #include "llvm/CodeGen/TargetInstrInfo.h" 18 #include "llvm/CodeGen/TargetSubtargetInfo.h" 19 #include "llvm/InitializePasses.h" 20 #include "llvm/Pass.h" 21 #include "llvm/PassRegistry.h" 22 23 using namespace llvm; 24 25 namespace { 26 struct PatchableFunction : public MachineFunctionPass { 27 static char ID; // Pass identification, replacement for typeid 28 PatchableFunction() : MachineFunctionPass(ID) { 29 initializePatchableFunctionPass(*PassRegistry::getPassRegistry()); 30 } 31 32 bool runOnMachineFunction(MachineFunction &F) override; 33 MachineFunctionProperties getRequiredProperties() const override { 34 return MachineFunctionProperties().set( 35 MachineFunctionProperties::Property::NoVRegs); 36 } 37 }; 38 } 39 40 bool PatchableFunction::runOnMachineFunction(MachineFunction &MF) { 41 MachineBasicBlock &FirstMBB = *MF.begin(); 42 43 if (MF.getFunction().hasFnAttribute("patchable-function-entry")) { 44 const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo(); 45 // The initial .loc covers PATCHABLE_FUNCTION_ENTER. 46 BuildMI(FirstMBB, FirstMBB.begin(), DebugLoc(), 47 TII->get(TargetOpcode::PATCHABLE_FUNCTION_ENTER)); 48 return true; 49 } else if (MF.getFunction().hasFnAttribute("patchable-function")) { 50 #ifndef NDEBUG 51 Attribute PatchAttr = MF.getFunction().getFnAttribute("patchable-function"); 52 StringRef PatchType = PatchAttr.getValueAsString(); 53 assert(PatchType == "prologue-short-redirect" && "Only possibility today!"); 54 #endif 55 auto *TII = MF.getSubtarget().getInstrInfo(); 56 BuildMI(FirstMBB, FirstMBB.begin(), DebugLoc(), 57 TII->get(TargetOpcode::PATCHABLE_OP)) 58 .addImm(2); 59 MF.ensureAlignment(Align(16)); 60 return true; 61 } 62 return false; 63 } 64 65 char PatchableFunction::ID = 0; 66 char &llvm::PatchableFunctionID = PatchableFunction::ID; 67 INITIALIZE_PASS(PatchableFunction, "patchable-function", 68 "Implement the 'patchable-function' attribute", false, false) 69