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
23using namespace llvm;
24
25namespace {
26struct 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
40bool PatchableFunction::runOnMachineFunction(MachineFunction &MF) {
41 MachineBasicBlock &FirstMBB = *MF.begin();
42
43 if (MF.getFunction().hasFnAttribute(Kind: "patchable-function-entry")) {
44 const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
45 // The initial .loc covers PATCHABLE_FUNCTION_ENTER.
46 BuildMI(BB&: FirstMBB, I: FirstMBB.begin(), MIMD: DebugLoc(),
47 MCID: TII->get(Opcode: TargetOpcode::PATCHABLE_FUNCTION_ENTER));
48 return true;
49 } else if (MF.getFunction().hasFnAttribute(Kind: "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(BB&: FirstMBB, I: FirstMBB.begin(), MIMD: DebugLoc(),
57 MCID: TII->get(Opcode: TargetOpcode::PATCHABLE_OP))
58 .addImm(Val: 2);
59 MF.ensureAlignment(A: Align(16));
60 return true;
61 }
62 return false;
63}
64
65char PatchableFunction::ID = 0;
66char &llvm::PatchableFunctionID = PatchableFunction::ID;
67INITIALIZE_PASS(PatchableFunction, "patchable-function",
68 "Implement the 'patchable-function' attribute", false, false)
69