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/PatchableFunction.h"
15#include "llvm/CodeGen/MachineFunction.h"
16#include "llvm/CodeGen/MachineFunctionPass.h"
17#include "llvm/CodeGen/MachineInstrBuilder.h"
18#include "llvm/CodeGen/TargetInstrInfo.h"
19#include "llvm/CodeGen/TargetSubtargetInfo.h"
20#include "llvm/InitializePasses.h"
21#include "llvm/Pass.h"
22#include "llvm/PassRegistry.h"
23
24using namespace llvm;
25
26namespace {
27struct PatchableFunction {
28 bool run(MachineFunction &F);
29};
30
31struct PatchableFunctionLegacy : public MachineFunctionPass {
32 static char ID;
33 PatchableFunctionLegacy() : MachineFunctionPass(ID) {
34 initializePatchableFunctionLegacyPass(*PassRegistry::getPassRegistry());
35 }
36 bool runOnMachineFunction(MachineFunction &F) override {
37 return PatchableFunction().run(F);
38 }
39
40 MachineFunctionProperties getRequiredProperties() const override {
41 return MachineFunctionProperties().setNoVRegs();
42 }
43};
44
45} // namespace
46
47PreservedAnalyses
48PatchableFunctionPass::run(MachineFunction &MF,
49 MachineFunctionAnalysisManager &MFAM) {
50 MFPropsModifier _(*this, MF);
51 if (!PatchableFunction().run(F&: MF))
52 return PreservedAnalyses::all();
53 return getMachineFunctionPassPreservedAnalyses();
54}
55
56bool PatchableFunction::run(MachineFunction &MF) {
57 MachineBasicBlock &FirstMBB = *MF.begin();
58
59 if (MF.getFunction().hasFnAttribute(Kind: "patchable-function-entry")) {
60 const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
61 // The initial .loc covers PATCHABLE_FUNCTION_ENTER.
62 BuildMI(BB&: FirstMBB, I: FirstMBB.begin(), MIMD: DebugLoc(),
63 MCID: TII->get(Opcode: TargetOpcode::PATCHABLE_FUNCTION_ENTER));
64 return true;
65 } else if (MF.getFunction().hasFnAttribute(Kind: "patchable-function")) {
66#ifndef NDEBUG
67 Attribute PatchAttr = MF.getFunction().getFnAttribute("patchable-function");
68 StringRef PatchType = PatchAttr.getValueAsString();
69 assert(PatchType == "prologue-short-redirect" && "Only possibility today!");
70#endif
71 auto *TII = MF.getSubtarget().getInstrInfo();
72 BuildMI(BB&: FirstMBB, I: FirstMBB.begin(), MIMD: DebugLoc(),
73 MCID: TII->get(Opcode: TargetOpcode::PATCHABLE_OP))
74 .addImm(Val: 2);
75 MF.ensureAlignment(A: Align(16));
76 return true;
77 }
78 return false;
79}
80
81char PatchableFunctionLegacy::ID = 0;
82char &llvm::PatchableFunctionID = PatchableFunctionLegacy::ID;
83INITIALIZE_PASS(PatchableFunctionLegacy, "patchable-function",
84 "Implement the 'patchable-function' attribute", false, false)
85