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
24 using namespace llvm;
25
26 namespace {
27 struct PatchableFunction {
28 bool run(MachineFunction &F);
29 };
30
31 struct PatchableFunctionLegacy : public MachineFunctionPass {
32 static char ID;
PatchableFunctionLegacy__anon17b8255e0111::PatchableFunctionLegacy33 PatchableFunctionLegacy() : MachineFunctionPass(ID) {
34 initializePatchableFunctionLegacyPass(*PassRegistry::getPassRegistry());
35 }
runOnMachineFunction__anon17b8255e0111::PatchableFunctionLegacy36 bool runOnMachineFunction(MachineFunction &F) override {
37 return PatchableFunction().run(F);
38 }
39
getRequiredProperties__anon17b8255e0111::PatchableFunctionLegacy40 MachineFunctionProperties getRequiredProperties() const override {
41 return MachineFunctionProperties().setNoVRegs();
42 }
43 };
44
45 } // namespace
46
47 PreservedAnalyses
run(MachineFunction & MF,MachineFunctionAnalysisManager & MFAM)48 PatchableFunctionPass::run(MachineFunction &MF,
49 MachineFunctionAnalysisManager &MFAM) {
50 MFPropsModifier _(*this, MF);
51 if (!PatchableFunction().run(MF))
52 return PreservedAnalyses::all();
53 return getMachineFunctionPassPreservedAnalyses();
54 }
55
run(MachineFunction & MF)56 bool PatchableFunction::run(MachineFunction &MF) {
57 MachineBasicBlock &FirstMBB = *MF.begin();
58
59 if (MF.getFunction().hasFnAttribute("patchable-function-entry")) {
60 const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
61 // The initial .loc covers PATCHABLE_FUNCTION_ENTER.
62 BuildMI(FirstMBB, FirstMBB.begin(), DebugLoc(),
63 TII->get(TargetOpcode::PATCHABLE_FUNCTION_ENTER));
64 return true;
65 } else if (MF.getFunction().hasFnAttribute("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(FirstMBB, FirstMBB.begin(), DebugLoc(),
73 TII->get(TargetOpcode::PATCHABLE_OP))
74 .addImm(2);
75 MF.ensureAlignment(Align(16));
76 return true;
77 }
78 return false;
79 }
80
81 char PatchableFunctionLegacy::ID = 0;
82 char &llvm::PatchableFunctionID = PatchableFunctionLegacy::ID;
83 INITIALIZE_PASS(PatchableFunctionLegacy, "patchable-function",
84 "Implement the 'patchable-function' attribute", false, false)
85