1 // WebAssemblyMCInstLower.cpp - Convert WebAssembly MachineInstr to an MCInst //
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 /// \file
10 /// This file contains code to lower WebAssembly MachineInstrs to their
11 /// corresponding MCInst records.
12 ///
13 //===----------------------------------------------------------------------===//
14
15 #include "WebAssemblyMCInstLower.h"
16 #include "TargetInfo/WebAssemblyTargetInfo.h"
17 #include "Utils/WebAssemblyTypeUtilities.h"
18 #include "Utils/WebAssemblyUtilities.h"
19 #include "WebAssemblyAsmPrinter.h"
20 #include "WebAssemblyISelLowering.h"
21 #include "WebAssemblyMachineFunctionInfo.h"
22 #include "llvm/CodeGen/AsmPrinter.h"
23 #include "llvm/CodeGen/MachineFunction.h"
24 #include "llvm/IR/Constants.h"
25 #include "llvm/MC/MCAsmInfo.h"
26 #include "llvm/MC/MCContext.h"
27 #include "llvm/MC/MCExpr.h"
28 #include "llvm/MC/MCInst.h"
29 #include "llvm/MC/MCSymbolWasm.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Support/raw_ostream.h"
32
33 using namespace llvm;
34
35 // This disables the removal of registers when lowering into MC, as required
36 // by some current tests.
37 cl::opt<bool>
38 WasmKeepRegisters("wasm-keep-registers", cl::Hidden,
39 cl::desc("WebAssembly: output stack registers in"
40 " instruction output for test purposes only."),
41 cl::init(false));
42
43 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI);
44
45 MCSymbol *
GetGlobalAddressSymbol(const MachineOperand & MO) const46 WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
47 const GlobalValue *Global = MO.getGlobal();
48 if (!isa<Function>(Global)) {
49 auto *WasmSym = cast<MCSymbolWasm>(Printer.getSymbol(Global));
50 // If the symbol doesn't have an explicit WasmSymbolType yet and the
51 // GlobalValue is actually a WebAssembly global, then ensure the symbol is a
52 // WASM_SYMBOL_TYPE_GLOBAL.
53 if (WebAssembly::isWasmVarAddressSpace(Global->getAddressSpace()) &&
54 !WasmSym->getType()) {
55 const MachineFunction &MF = *MO.getParent()->getParent()->getParent();
56 const TargetMachine &TM = MF.getTarget();
57 const Function &CurrentFunc = MF.getFunction();
58 Type *GlobalVT = Global->getValueType();
59 SmallVector<MVT, 1> VTs;
60 computeLegalValueVTs(CurrentFunc, TM, GlobalVT, VTs);
61
62 WebAssembly::wasmSymbolSetType(WasmSym, GlobalVT, VTs);
63 }
64 return WasmSym;
65 }
66
67 const auto *FuncTy = cast<FunctionType>(Global->getValueType());
68 const MachineFunction &MF = *MO.getParent()->getParent()->getParent();
69 const TargetMachine &TM = MF.getTarget();
70 const Function &CurrentFunc = MF.getFunction();
71
72 SmallVector<MVT, 1> ResultMVTs;
73 SmallVector<MVT, 4> ParamMVTs;
74 const auto *const F = dyn_cast<Function>(Global);
75 computeSignatureVTs(FuncTy, F, CurrentFunc, TM, ParamMVTs, ResultMVTs);
76 auto Signature = signatureFromMVTs(ResultMVTs, ParamMVTs);
77
78 bool InvokeDetected = false;
79 auto *WasmSym = Printer.getMCSymbolForFunction(
80 F, WebAssembly::WasmEnableEmEH || WebAssembly::WasmEnableEmSjLj,
81 Signature.get(), InvokeDetected);
82 WasmSym->setSignature(Signature.get());
83 Printer.addSignature(std::move(Signature));
84 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
85 return WasmSym;
86 }
87
GetExternalSymbolSymbol(const MachineOperand & MO) const88 MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
89 const MachineOperand &MO) const {
90 return Printer.getOrCreateWasmSymbol(MO.getSymbolName());
91 }
92
lowerSymbolOperand(const MachineOperand & MO,MCSymbol * Sym) const93 MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO,
94 MCSymbol *Sym) const {
95 MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None;
96 unsigned TargetFlags = MO.getTargetFlags();
97
98 switch (TargetFlags) {
99 case WebAssemblyII::MO_NO_FLAG:
100 break;
101 case WebAssemblyII::MO_GOT_TLS:
102 Kind = MCSymbolRefExpr::VK_WASM_GOT_TLS;
103 break;
104 case WebAssemblyII::MO_GOT:
105 Kind = MCSymbolRefExpr::VK_GOT;
106 break;
107 case WebAssemblyII::MO_MEMORY_BASE_REL:
108 Kind = MCSymbolRefExpr::VK_WASM_MBREL;
109 break;
110 case WebAssemblyII::MO_TLS_BASE_REL:
111 Kind = MCSymbolRefExpr::VK_WASM_TLSREL;
112 break;
113 case WebAssemblyII::MO_TABLE_BASE_REL:
114 Kind = MCSymbolRefExpr::VK_WASM_TBREL;
115 break;
116 default:
117 llvm_unreachable("Unknown target flag on GV operand");
118 }
119
120 const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx);
121
122 if (MO.getOffset() != 0) {
123 const auto *WasmSym = cast<MCSymbolWasm>(Sym);
124 if (TargetFlags == WebAssemblyII::MO_GOT)
125 report_fatal_error("GOT symbol references do not support offsets");
126 if (WasmSym->isFunction())
127 report_fatal_error("Function addresses with offsets not supported");
128 if (WasmSym->isGlobal())
129 report_fatal_error("Global indexes with offsets not supported");
130 if (WasmSym->isTag())
131 report_fatal_error("Tag indexes with offsets not supported");
132 if (WasmSym->isTable())
133 report_fatal_error("Table indexes with offsets not supported");
134
135 Expr = MCBinaryExpr::createAdd(
136 Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx);
137 }
138
139 return MCOperand::createExpr(Expr);
140 }
141
lowerTypeIndexOperand(SmallVector<wasm::ValType,1> && Returns,SmallVector<wasm::ValType,4> && Params) const142 MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand(
143 SmallVector<wasm::ValType, 1> &&Returns,
144 SmallVector<wasm::ValType, 4> &&Params) const {
145 auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns),
146 std::move(Params));
147 MCSymbol *Sym = Printer.createTempSymbol("typeindex");
148 auto *WasmSym = cast<MCSymbolWasm>(Sym);
149 WasmSym->setSignature(Signature.get());
150 Printer.addSignature(std::move(Signature));
151 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
152 const MCExpr *Expr =
153 MCSymbolRefExpr::create(WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx);
154 return MCOperand::createExpr(Expr);
155 }
156
getFunctionReturns(const MachineInstr * MI,SmallVectorImpl<wasm::ValType> & Returns)157 static void getFunctionReturns(const MachineInstr *MI,
158 SmallVectorImpl<wasm::ValType> &Returns) {
159 const Function &F = MI->getMF()->getFunction();
160 const TargetMachine &TM = MI->getMF()->getTarget();
161 Type *RetTy = F.getReturnType();
162 SmallVector<MVT, 4> CallerRetTys;
163 computeLegalValueVTs(F, TM, RetTy, CallerRetTys);
164 valTypesFromMVTs(CallerRetTys, Returns);
165 }
166
lower(const MachineInstr * MI,MCInst & OutMI) const167 void WebAssemblyMCInstLower::lower(const MachineInstr *MI,
168 MCInst &OutMI) const {
169 OutMI.setOpcode(MI->getOpcode());
170
171 const MCInstrDesc &Desc = MI->getDesc();
172 unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs();
173 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
174 const MachineOperand &MO = MI->getOperand(I);
175
176 MCOperand MCOp;
177 switch (MO.getType()) {
178 default:
179 MI->print(errs());
180 llvm_unreachable("unknown operand type");
181 case MachineOperand::MO_MachineBasicBlock:
182 MI->print(errs());
183 llvm_unreachable("MachineBasicBlock operand should have been rewritten");
184 case MachineOperand::MO_Register: {
185 // Ignore all implicit register operands.
186 if (MO.isImplicit())
187 continue;
188 const WebAssemblyFunctionInfo &MFI =
189 *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>();
190 unsigned WAReg = MFI.getWAReg(MO.getReg());
191 MCOp = MCOperand::createReg(WAReg);
192 break;
193 }
194 case MachineOperand::MO_Immediate: {
195 unsigned DescIndex = I - NumVariadicDefs;
196 if (DescIndex < Desc.NumOperands) {
197 const MCOperandInfo &Info = Desc.operands()[DescIndex];
198 if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
199 SmallVector<wasm::ValType, 4> Returns;
200 SmallVector<wasm::ValType, 4> Params;
201
202 const MachineRegisterInfo &MRI =
203 MI->getParent()->getParent()->getRegInfo();
204 for (const MachineOperand &MO : MI->defs())
205 Returns.push_back(
206 WebAssembly::regClassToValType(MRI.getRegClass(MO.getReg())));
207 for (const MachineOperand &MO : MI->explicit_uses())
208 if (MO.isReg())
209 Params.push_back(
210 WebAssembly::regClassToValType(MRI.getRegClass(MO.getReg())));
211
212 // call_indirect instructions have a callee operand at the end which
213 // doesn't count as a param.
214 if (WebAssembly::isCallIndirect(MI->getOpcode()))
215 Params.pop_back();
216
217 // return_call_indirect instructions have the return type of the
218 // caller
219 if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT)
220 getFunctionReturns(MI, Returns);
221
222 MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params));
223 break;
224 } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) {
225 auto BT = static_cast<WebAssembly::BlockType>(MO.getImm());
226 assert(BT != WebAssembly::BlockType::Invalid);
227 if (BT == WebAssembly::BlockType::Multivalue) {
228 SmallVector<wasm::ValType, 1> Returns;
229 getFunctionReturns(MI, Returns);
230 MCOp = lowerTypeIndexOperand(std::move(Returns),
231 SmallVector<wasm::ValType, 4>());
232 break;
233 }
234 }
235 }
236 MCOp = MCOperand::createImm(MO.getImm());
237 break;
238 }
239 case MachineOperand::MO_FPImmediate: {
240 const ConstantFP *Imm = MO.getFPImm();
241 const uint64_t BitPattern =
242 Imm->getValueAPF().bitcastToAPInt().getZExtValue();
243 if (Imm->getType()->isFloatTy())
244 MCOp = MCOperand::createSFPImm(static_cast<uint32_t>(BitPattern));
245 else if (Imm->getType()->isDoubleTy())
246 MCOp = MCOperand::createDFPImm(BitPattern);
247 else
248 llvm_unreachable("unknown floating point immediate type");
249 break;
250 }
251 case MachineOperand::MO_GlobalAddress:
252 MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO));
253 break;
254 case MachineOperand::MO_ExternalSymbol:
255 MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO));
256 break;
257 case MachineOperand::MO_MCSymbol:
258 assert(MO.getTargetFlags() == 0 &&
259 "WebAssembly does not use target flags on MCSymbol");
260 MCOp = lowerSymbolOperand(MO, MO.getMCSymbol());
261 break;
262 }
263
264 OutMI.addOperand(MCOp);
265 }
266
267 if (!WasmKeepRegisters)
268 removeRegisterOperands(MI, OutMI);
269 else if (Desc.variadicOpsAreDefs())
270 OutMI.insert(OutMI.begin(), MCOperand::createImm(MI->getNumExplicitDefs()));
271 }
272
removeRegisterOperands(const MachineInstr * MI,MCInst & OutMI)273 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) {
274 // Remove all uses of stackified registers to bring the instruction format
275 // into its final stack form used thruout MC, and transition opcodes to
276 // their _S variant.
277 // We do this separate from the above code that still may need these
278 // registers for e.g. call_indirect signatures.
279 // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for
280 // details.
281 // TODO: the code above creates new registers which are then removed here.
282 // That code could be slightly simplified by not doing that, though maybe
283 // it is simpler conceptually to keep the code above in "register mode"
284 // until this transition point.
285 // FIXME: we are not processing inline assembly, which contains register
286 // operands, because it is used by later target generic code.
287 if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm())
288 return;
289
290 // Transform to _S instruction.
291 auto RegOpcode = OutMI.getOpcode();
292 auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode);
293 assert(StackOpcode != -1 && "Failed to stackify instruction");
294 OutMI.setOpcode(StackOpcode);
295
296 // Remove register operands.
297 for (auto I = OutMI.getNumOperands(); I; --I) {
298 auto &MO = OutMI.getOperand(I - 1);
299 if (MO.isReg()) {
300 OutMI.erase(&MO);
301 }
302 }
303 }
304