| //===-- PatchableFunction.cpp - Patchable prologues for LLVM -------------===// |
| // |
| // 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 implements edits function bodies in place to support the |
| // "patchable-function" attribute. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/CodeGen/MachineFunctionPass.h" |
| #include "llvm/CodeGen/MachineInstrBuilder.h" |
| #include "llvm/CodeGen/Passes.h" |
| #include "llvm/CodeGen/TargetFrameLowering.h" |
| #include "llvm/CodeGen/TargetInstrInfo.h" |
| #include "llvm/CodeGen/TargetSubtargetInfo.h" |
| #include "llvm/InitializePasses.h" |
| |
| using namespace llvm; |
| |
| namespace { |
| struct PatchableFunction : public MachineFunctionPass { |
| static char ID; // Pass identification, replacement for typeid |
| PatchableFunction() : MachineFunctionPass(ID) { |
| initializePatchableFunctionPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| bool runOnMachineFunction(MachineFunction &F) override; |
| MachineFunctionProperties getRequiredProperties() const override { |
| return MachineFunctionProperties().set( |
| MachineFunctionProperties::Property::NoVRegs); |
| } |
| }; |
| } |
| |
| /// Returns true if instruction \p MI will not result in actual machine code |
| /// instructions. |
| static bool doesNotGeneratecode(const MachineInstr &MI) { |
| // TODO: Introduce an MCInstrDesc flag for this |
| switch (MI.getOpcode()) { |
| default: return false; |
| case TargetOpcode::IMPLICIT_DEF: |
| case TargetOpcode::KILL: |
| case TargetOpcode::CFI_INSTRUCTION: |
| case TargetOpcode::EH_LABEL: |
| case TargetOpcode::GC_LABEL: |
| case TargetOpcode::DBG_VALUE: |
| case TargetOpcode::DBG_LABEL: |
| return true; |
| } |
| } |
| |
| bool PatchableFunction::runOnMachineFunction(MachineFunction &MF) { |
| if (MF.getFunction().hasFnAttribute("patchable-function-entry")) { |
| MachineBasicBlock &FirstMBB = *MF.begin(); |
| const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo(); |
| // The initial .loc covers PATCHABLE_FUNCTION_ENTER. |
| BuildMI(FirstMBB, FirstMBB.begin(), DebugLoc(), |
| TII->get(TargetOpcode::PATCHABLE_FUNCTION_ENTER)); |
| return true; |
| } |
| |
| if (!MF.getFunction().hasFnAttribute("patchable-function")) |
| return false; |
| |
| #ifndef NDEBUG |
| Attribute PatchAttr = MF.getFunction().getFnAttribute("patchable-function"); |
| StringRef PatchType = PatchAttr.getValueAsString(); |
| assert(PatchType == "prologue-short-redirect" && "Only possibility today!"); |
| #endif |
| |
| auto &FirstMBB = *MF.begin(); |
| MachineBasicBlock::iterator FirstActualI = FirstMBB.begin(); |
| for (; doesNotGeneratecode(*FirstActualI); ++FirstActualI) |
| assert(FirstActualI != FirstMBB.end()); |
| |
| auto *TII = MF.getSubtarget().getInstrInfo(); |
| auto MIB = BuildMI(FirstMBB, FirstActualI, FirstActualI->getDebugLoc(), |
| TII->get(TargetOpcode::PATCHABLE_OP)) |
| .addImm(2) |
| .addImm(FirstActualI->getOpcode()); |
| |
| for (auto &MO : FirstActualI->operands()) |
| MIB.add(MO); |
| |
| FirstActualI->eraseFromParent(); |
| MF.ensureAlignment(Align(16)); |
| return true; |
| } |
| |
| char PatchableFunction::ID = 0; |
| char &llvm::PatchableFunctionID = PatchableFunction::ID; |
| INITIALIZE_PASS(PatchableFunction, "patchable-function", |
| "Implement the 'patchable-function' attribute", false, false) |