1//=- AArch64MachineFunctionInfo.cpp - AArch64 Machine Function Info ---------=//
2
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9///
10/// \file
11/// This file implements AArch64-specific per-machine-function
12/// information.
13///
14//===----------------------------------------------------------------------===//
15
16#include "AArch64MachineFunctionInfo.h"
17#include "AArch64InstrInfo.h"
18#include "AArch64Subtarget.h"
19#include "llvm/IR/Constants.h"
20#include "llvm/IR/Metadata.h"
21#include "llvm/IR/Module.h"
22#include "llvm/MC/MCAsmInfo.h"
23
24using namespace llvm;
25
26yaml::AArch64FunctionInfo::AArch64FunctionInfo(
27 const llvm::AArch64FunctionInfo &MFI)
28 : HasRedZone(MFI.hasRedZone()) {}
29
30void yaml::AArch64FunctionInfo::mappingImpl(yaml::IO &YamlIO) {
31 MappingTraits<AArch64FunctionInfo>::mapping(YamlIO, MFI&: *this);
32}
33
34void AArch64FunctionInfo::initializeBaseYamlFields(
35 const yaml::AArch64FunctionInfo &YamlMFI) {
36 if (YamlMFI.HasRedZone)
37 HasRedZone = YamlMFI.HasRedZone;
38}
39
40static std::pair<bool, bool> GetSignReturnAddress(const Function &F) {
41 if (F.hasFnAttribute(Kind: "ptrauth-returns"))
42 return {true, false}; // non-leaf
43 // The function should be signed in the following situations:
44 // - sign-return-address=all
45 // - sign-return-address=non-leaf and the functions spills the LR
46 if (!F.hasFnAttribute(Kind: "sign-return-address"))
47 return {false, false};
48
49 StringRef Scope = F.getFnAttribute(Kind: "sign-return-address").getValueAsString();
50 if (Scope == "none")
51 return {false, false};
52
53 if (Scope == "all")
54 return {true, true};
55
56 assert(Scope == "non-leaf");
57 return {true, false};
58}
59
60static bool ShouldSignWithBKey(const Function &F, const AArch64Subtarget &STI) {
61 if (F.hasFnAttribute(Kind: "ptrauth-returns"))
62 return true;
63 if (!F.hasFnAttribute(Kind: "sign-return-address-key")) {
64 if (STI.getTargetTriple().isOSWindows())
65 return true;
66 return false;
67 }
68
69 const StringRef Key =
70 F.getFnAttribute(Kind: "sign-return-address-key").getValueAsString();
71 assert(Key == "a_key" || Key == "b_key");
72 return Key == "b_key";
73}
74
75AArch64FunctionInfo::AArch64FunctionInfo(const Function &F,
76 const AArch64Subtarget *STI) {
77 // If we already know that the function doesn't have a redzone, set
78 // HasRedZone here.
79 if (F.hasFnAttribute(Kind: Attribute::NoRedZone))
80 HasRedZone = false;
81 std::tie(args&: SignReturnAddress, args&: SignReturnAddressAll) = GetSignReturnAddress(F);
82 SignWithBKey = ShouldSignWithBKey(F, STI: *STI);
83 // TODO: skip functions that have no instrumented allocas for optimization
84 IsMTETagged = F.hasFnAttribute(Kind: Attribute::SanitizeMemTag);
85
86 // BTI/PAuthLR are set on the function attribute.
87 BranchTargetEnforcement = F.hasFnAttribute(Kind: "branch-target-enforcement");
88 BranchProtectionPAuthLR = F.hasFnAttribute(Kind: "branch-protection-pauth-lr");
89
90 // The default stack probe size is 4096 if the function has no
91 // stack-probe-size attribute. This is a safe default because it is the
92 // smallest possible guard page size.
93 uint64_t ProbeSize = 4096;
94 if (F.hasFnAttribute(Kind: "stack-probe-size"))
95 ProbeSize = F.getFnAttributeAsParsedInteger(Kind: "stack-probe-size");
96 else if (const auto *PS = mdconst::extract_or_null<ConstantInt>(
97 MD: F.getParent()->getModuleFlag(Key: "stack-probe-size")))
98 ProbeSize = PS->getZExtValue();
99 assert(int64_t(ProbeSize) > 0 && "Invalid stack probe size");
100
101 if (STI->isTargetWindows()) {
102 if (!F.hasFnAttribute(Kind: "no-stack-arg-probe"))
103 StackProbeSize = ProbeSize;
104 } else {
105 // Round down to the stack alignment.
106 uint64_t StackAlign =
107 STI->getFrameLowering()->getTransientStackAlign().value();
108 ProbeSize = std::max(a: StackAlign, b: ProbeSize & ~(StackAlign - 1U));
109 StringRef ProbeKind;
110 if (F.hasFnAttribute(Kind: "probe-stack"))
111 ProbeKind = F.getFnAttribute(Kind: "probe-stack").getValueAsString();
112 else if (const auto *PS = dyn_cast_or_null<MDString>(
113 Val: F.getParent()->getModuleFlag(Key: "probe-stack")))
114 ProbeKind = PS->getString();
115 if (ProbeKind.size()) {
116 if (ProbeKind != "inline-asm")
117 report_fatal_error(reason: "Unsupported stack probing method");
118 StackProbeSize = ProbeSize;
119 }
120 }
121}
122
123MachineFunctionInfo *AArch64FunctionInfo::clone(
124 BumpPtrAllocator &Allocator, MachineFunction &DestMF,
125 const DenseMap<MachineBasicBlock *, MachineBasicBlock *> &Src2DstMBB)
126 const {
127 return DestMF.cloneInfo<AArch64FunctionInfo>(Old: *this);
128}
129
130bool AArch64FunctionInfo::shouldSignReturnAddress(bool SpillsLR) const {
131 if (!SignReturnAddress)
132 return false;
133 if (SignReturnAddressAll)
134 return true;
135 return SpillsLR;
136}
137
138static bool isLRSpilled(const MachineFunction &MF) {
139 return llvm::any_of(
140 Range: MF.getFrameInfo().getCalleeSavedInfo(),
141 P: [](const auto &Info) { return Info.getReg() == AArch64::LR; });
142}
143
144bool AArch64FunctionInfo::shouldSignReturnAddress(
145 const MachineFunction &MF) const {
146 return shouldSignReturnAddress(SpillsLR: isLRSpilled(MF));
147}
148
149bool AArch64FunctionInfo::needsShadowCallStackPrologueEpilogue(
150 MachineFunction &MF) const {
151 if (!(isLRSpilled(MF) &&
152 MF.getFunction().hasFnAttribute(Kind: Attribute::ShadowCallStack)))
153 return false;
154
155 if (!MF.getSubtarget<AArch64Subtarget>().isXRegisterReserved(i: 18))
156 report_fatal_error(reason: "Must reserve x18 to use shadow call stack");
157
158 return true;
159}
160
161bool AArch64FunctionInfo::needsDwarfUnwindInfo(
162 const MachineFunction &MF) const {
163 if (!NeedsDwarfUnwindInfo)
164 NeedsDwarfUnwindInfo = MF.needsFrameMoves() &&
165 !MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
166
167 return *NeedsDwarfUnwindInfo;
168}
169
170bool AArch64FunctionInfo::needsAsyncDwarfUnwindInfo(
171 const MachineFunction &MF) const {
172 if (!NeedsAsyncDwarfUnwindInfo) {
173 const Function &F = MF.getFunction();
174 const AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
175 // The check got "minsize" is because epilogue unwind info is not emitted
176 // (yet) for homogeneous epilogues, outlined functions, and functions
177 // outlined from.
178 NeedsAsyncDwarfUnwindInfo =
179 needsDwarfUnwindInfo(MF) &&
180 ((F.getUWTableKind() == UWTableKind::Async && !F.hasMinSize()) ||
181 AFI->hasStreamingModeChanges());
182 }
183 return *NeedsAsyncDwarfUnwindInfo;
184}
185