1 //===-- ARMMCInstLower.cpp - Convert ARM MachineInstr to an MCInst --------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains code to lower ARM MachineInstrs to their corresponding
11 // MCInst records.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "ARM.h"
16 #include "ARMAsmPrinter.h"
17 #include "ARMBaseInstrInfo.h"
18 #include "ARMMachineFunctionInfo.h"
19 #include "ARMSubtarget.h"
20 #include "MCTargetDesc/ARMAddressingModes.h"
21 #include "MCTargetDesc/ARMBaseInfo.h"
22 #include "MCTargetDesc/ARMMCExpr.h"
23 #include "llvm/ADT/APFloat.h"
24 #include "llvm/CodeGen/MachineBasicBlock.h"
25 #include "llvm/CodeGen/MachineInstr.h"
26 #include "llvm/CodeGen/MachineOperand.h"
27 #include "llvm/IR/Constants.h"
28 #include "llvm/MC/MCContext.h"
29 #include "llvm/MC/MCExpr.h"
30 #include "llvm/MC/MCInst.h"
31 #include "llvm/MC/MCInstBuilder.h"
32 #include "llvm/MC/MCStreamer.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include <cassert>
35 #include <cstdint>
36
37 using namespace llvm;
38
GetSymbolRef(const MachineOperand & MO,const MCSymbol * Symbol)39 MCOperand ARMAsmPrinter::GetSymbolRef(const MachineOperand &MO,
40 const MCSymbol *Symbol) {
41 MCSymbolRefExpr::VariantKind SymbolVariant = MCSymbolRefExpr::VK_None;
42 if (MO.getTargetFlags() & ARMII::MO_SBREL)
43 SymbolVariant = MCSymbolRefExpr::VK_ARM_SBREL;
44
45 const MCExpr *Expr =
46 MCSymbolRefExpr::create(Symbol, SymbolVariant, OutContext);
47 switch (MO.getTargetFlags() & ARMII::MO_OPTION_MASK) {
48 default:
49 llvm_unreachable("Unknown target flag on symbol operand");
50 case ARMII::MO_NO_FLAG:
51 break;
52 case ARMII::MO_LO16:
53 Expr =
54 MCSymbolRefExpr::create(Symbol, SymbolVariant, OutContext);
55 Expr = ARMMCExpr::createLower16(Expr, OutContext);
56 break;
57 case ARMII::MO_HI16:
58 Expr =
59 MCSymbolRefExpr::create(Symbol, SymbolVariant, OutContext);
60 Expr = ARMMCExpr::createUpper16(Expr, OutContext);
61 break;
62 }
63
64 if (!MO.isJTI() && MO.getOffset())
65 Expr = MCBinaryExpr::createAdd(Expr,
66 MCConstantExpr::create(MO.getOffset(),
67 OutContext),
68 OutContext);
69 return MCOperand::createExpr(Expr);
70
71 }
72
lowerOperand(const MachineOperand & MO,MCOperand & MCOp)73 bool ARMAsmPrinter::lowerOperand(const MachineOperand &MO,
74 MCOperand &MCOp) {
75 switch (MO.getType()) {
76 default: llvm_unreachable("unknown operand type");
77 case MachineOperand::MO_Register:
78 // Ignore all non-CPSR implicit register operands.
79 if (MO.isImplicit() && MO.getReg() != ARM::CPSR)
80 return false;
81 assert(!MO.getSubReg() && "Subregs should be eliminated!");
82 MCOp = MCOperand::createReg(MO.getReg());
83 break;
84 case MachineOperand::MO_Immediate:
85 MCOp = MCOperand::createImm(MO.getImm());
86 break;
87 case MachineOperand::MO_MachineBasicBlock:
88 MCOp = MCOperand::createExpr(MCSymbolRefExpr::create(
89 MO.getMBB()->getSymbol(), OutContext));
90 break;
91 case MachineOperand::MO_GlobalAddress:
92 MCOp = GetSymbolRef(MO,
93 GetARMGVSymbol(MO.getGlobal(), MO.getTargetFlags()));
94 break;
95 case MachineOperand::MO_ExternalSymbol:
96 MCOp = GetSymbolRef(MO,
97 GetExternalSymbolSymbol(MO.getSymbolName()));
98 break;
99 case MachineOperand::MO_JumpTableIndex:
100 MCOp = GetSymbolRef(MO, GetJTISymbol(MO.getIndex()));
101 break;
102 case MachineOperand::MO_ConstantPoolIndex:
103 if (Subtarget->genExecuteOnly())
104 llvm_unreachable("execute-only should not generate constant pools");
105 MCOp = GetSymbolRef(MO, GetCPISymbol(MO.getIndex()));
106 break;
107 case MachineOperand::MO_BlockAddress:
108 MCOp = GetSymbolRef(MO, GetBlockAddressSymbol(MO.getBlockAddress()));
109 break;
110 case MachineOperand::MO_FPImmediate: {
111 APFloat Val = MO.getFPImm()->getValueAPF();
112 bool ignored;
113 Val.convert(APFloat::IEEEdouble(), APFloat::rmTowardZero, &ignored);
114 MCOp = MCOperand::createFPImm(Val.convertToDouble());
115 break;
116 }
117 case MachineOperand::MO_RegisterMask:
118 // Ignore call clobbers.
119 return false;
120 }
121 return true;
122 }
123
LowerARMMachineInstrToMCInst(const MachineInstr * MI,MCInst & OutMI,ARMAsmPrinter & AP)124 void llvm::LowerARMMachineInstrToMCInst(const MachineInstr *MI, MCInst &OutMI,
125 ARMAsmPrinter &AP) {
126 OutMI.setOpcode(MI->getOpcode());
127
128 // In the MC layer, we keep modified immediates in their encoded form
129 bool EncodeImms = false;
130 switch (MI->getOpcode()) {
131 default: break;
132 case ARM::MOVi:
133 case ARM::MVNi:
134 case ARM::CMPri:
135 case ARM::CMNri:
136 case ARM::TSTri:
137 case ARM::TEQri:
138 case ARM::MSRi:
139 case ARM::ADCri:
140 case ARM::ADDri:
141 case ARM::ADDSri:
142 case ARM::SBCri:
143 case ARM::SUBri:
144 case ARM::SUBSri:
145 case ARM::ANDri:
146 case ARM::ORRri:
147 case ARM::EORri:
148 case ARM::BICri:
149 case ARM::RSBri:
150 case ARM::RSBSri:
151 case ARM::RSCri:
152 EncodeImms = true;
153 break;
154 }
155
156 for (const MachineOperand &MO : MI->operands()) {
157 MCOperand MCOp;
158 if (AP.lowerOperand(MO, MCOp)) {
159 if (MCOp.isImm() && EncodeImms) {
160 int32_t Enc = ARM_AM::getSOImmVal(MCOp.getImm());
161 if (Enc != -1)
162 MCOp.setImm(Enc);
163 }
164 OutMI.addOperand(MCOp);
165 }
166 }
167 }
168
EmitSled(const MachineInstr & MI,SledKind Kind)169 void ARMAsmPrinter::EmitSled(const MachineInstr &MI, SledKind Kind)
170 {
171 if (MI.getParent()->getParent()->getInfo<ARMFunctionInfo>()
172 ->isThumbFunction())
173 {
174 MI.emitError("An attempt to perform XRay instrumentation for a"
175 " Thumb function (not supported). Detected when emitting a sled.");
176 return;
177 }
178 static const int8_t NoopsInSledCount = 6;
179 // We want to emit the following pattern:
180 //
181 // .Lxray_sled_N:
182 // ALIGN
183 // B #20
184 // ; 6 NOP instructions (24 bytes)
185 // .tmpN
186 //
187 // We need the 24 bytes (6 instructions) because at runtime, we'd be patching
188 // over the full 28 bytes (7 instructions) with the following pattern:
189 //
190 // PUSH{ r0, lr }
191 // MOVW r0, #<lower 16 bits of function ID>
192 // MOVT r0, #<higher 16 bits of function ID>
193 // MOVW ip, #<lower 16 bits of address of __xray_FunctionEntry/Exit>
194 // MOVT ip, #<higher 16 bits of address of __xray_FunctionEntry/Exit>
195 // BLX ip
196 // POP{ r0, lr }
197 //
198 OutStreamer->EmitCodeAlignment(4);
199 auto CurSled = OutContext.createTempSymbol("xray_sled_", true);
200 OutStreamer->EmitLabel(CurSled);
201 auto Target = OutContext.createTempSymbol();
202
203 // Emit "B #20" instruction, which jumps over the next 24 bytes (because
204 // register pc is 8 bytes ahead of the jump instruction by the moment CPU
205 // is executing it).
206 // By analogy to ARMAsmPrinter::emitPseudoExpansionLowering() |case ARM::B|.
207 // It is not clear why |addReg(0)| is needed (the last operand).
208 EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::Bcc).addImm(20)
209 .addImm(ARMCC::AL).addReg(0));
210
211 MCInst Noop;
212 Subtarget->getInstrInfo()->getNoop(Noop);
213 for (int8_t I = 0; I < NoopsInSledCount; I++)
214 OutStreamer->EmitInstruction(Noop, getSubtargetInfo());
215
216 OutStreamer->EmitLabel(Target);
217 recordSled(CurSled, MI, Kind);
218 }
219
LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr & MI)220 void ARMAsmPrinter::LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr &MI)
221 {
222 EmitSled(MI, SledKind::FUNCTION_ENTER);
223 }
224
LowerPATCHABLE_FUNCTION_EXIT(const MachineInstr & MI)225 void ARMAsmPrinter::LowerPATCHABLE_FUNCTION_EXIT(const MachineInstr &MI)
226 {
227 EmitSled(MI, SledKind::FUNCTION_EXIT);
228 }
229
LowerPATCHABLE_TAIL_CALL(const MachineInstr & MI)230 void ARMAsmPrinter::LowerPATCHABLE_TAIL_CALL(const MachineInstr &MI)
231 {
232 EmitSled(MI, SledKind::TAIL_CALL);
233 }
234