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 "WebAssemblyMachineFunctionInfo.h"
21 #include "llvm/CodeGen/AsmPrinter.h"
22 #include "llvm/CodeGen/MachineFunction.h"
23 #include "llvm/IR/Constants.h"
24 #include "llvm/MC/MCAsmInfo.h"
25 #include "llvm/MC/MCContext.h"
26 #include "llvm/MC/MCExpr.h"
27 #include "llvm/MC/MCInst.h"
28 #include "llvm/MC/MCSymbolWasm.h"
29 #include "llvm/Support/ErrorHandling.h"
30 #include "llvm/Support/raw_ostream.h"
31 using namespace llvm;
32
33 // This disables the removal of registers when lowering into MC, as required
34 // by some current tests.
35 cl::opt<bool>
36 WasmKeepRegisters("wasm-keep-registers", cl::Hidden,
37 cl::desc("WebAssembly: output stack registers in"
38 " instruction output for test purposes only."),
39 cl::init(false));
40
41 extern cl::opt<bool> EnableEmException;
42 extern cl::opt<bool> EnableEmSjLj;
43
44 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI);
45
46 MCSymbol *
GetGlobalAddressSymbol(const MachineOperand & MO) const47 WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
48 const GlobalValue *Global = MO.getGlobal();
49 if (!isa<Function>(Global)) {
50 auto *WasmSym = cast<MCSymbolWasm>(Printer.getSymbol(Global));
51 // If the symbol doesn't have an explicit WasmSymbolType yet and the
52 // GlobalValue is actually a WebAssembly global, then ensure the symbol is a
53 // WASM_SYMBOL_TYPE_GLOBAL.
54 if (WebAssembly::isWasmVarAddressSpace(Global->getAddressSpace()) &&
55 !WasmSym->getType()) {
56 const MachineFunction &MF = *MO.getParent()->getParent()->getParent();
57 const TargetMachine &TM = MF.getTarget();
58 const Function &CurrentFunc = MF.getFunction();
59 SmallVector<MVT, 1> VTs;
60 computeLegalValueVTs(CurrentFunc, TM, Global->getValueType(), VTs);
61 if (VTs.size() != 1)
62 report_fatal_error("Aggregate globals not yet implemented");
63
64 bool Mutable = true;
65 wasm::ValType Type = WebAssembly::toValType(VTs[0]);
66 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
67 WasmSym->setGlobalType(wasm::WasmGlobalType{uint8_t(Type), Mutable});
68 }
69 return WasmSym;
70 }
71
72 const auto *FuncTy = cast<FunctionType>(Global->getValueType());
73 const MachineFunction &MF = *MO.getParent()->getParent()->getParent();
74 const TargetMachine &TM = MF.getTarget();
75 const Function &CurrentFunc = MF.getFunction();
76
77 SmallVector<MVT, 1> ResultMVTs;
78 SmallVector<MVT, 4> ParamMVTs;
79 const auto *const F = dyn_cast<Function>(Global);
80 computeSignatureVTs(FuncTy, F, CurrentFunc, TM, ParamMVTs, ResultMVTs);
81 auto Signature = signatureFromMVTs(ResultMVTs, ParamMVTs);
82
83 bool InvokeDetected = false;
84 auto *WasmSym = Printer.getMCSymbolForFunction(
85 F, EnableEmException || EnableEmSjLj, Signature.get(), InvokeDetected);
86 WasmSym->setSignature(Signature.get());
87 Printer.addSignature(std::move(Signature));
88 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
89 return WasmSym;
90 }
91
GetExternalSymbolSymbol(const MachineOperand & MO) const92 MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
93 const MachineOperand &MO) const {
94 return Printer.getOrCreateWasmSymbol(MO.getSymbolName());
95 }
96
lowerSymbolOperand(const MachineOperand & MO,MCSymbol * Sym) const97 MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO,
98 MCSymbol *Sym) const {
99 MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None;
100 unsigned TargetFlags = MO.getTargetFlags();
101
102 switch (TargetFlags) {
103 case WebAssemblyII::MO_NO_FLAG:
104 break;
105 case WebAssemblyII::MO_GOT:
106 Kind = MCSymbolRefExpr::VK_GOT;
107 break;
108 case WebAssemblyII::MO_MEMORY_BASE_REL:
109 Kind = MCSymbolRefExpr::VK_WASM_MBREL;
110 break;
111 case WebAssemblyII::MO_TLS_BASE_REL:
112 Kind = MCSymbolRefExpr::VK_WASM_TLSREL;
113 break;
114 case WebAssemblyII::MO_TABLE_BASE_REL:
115 Kind = MCSymbolRefExpr::VK_WASM_TBREL;
116 break;
117 default:
118 llvm_unreachable("Unknown target flag on GV operand");
119 }
120
121 const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx);
122
123 if (MO.getOffset() != 0) {
124 const auto *WasmSym = cast<MCSymbolWasm>(Sym);
125 if (TargetFlags == WebAssemblyII::MO_GOT)
126 report_fatal_error("GOT symbol references do not support offsets");
127 if (WasmSym->isFunction())
128 report_fatal_error("Function addresses with offsets not supported");
129 if (WasmSym->isGlobal())
130 report_fatal_error("Global indexes with offsets not supported");
131 if (WasmSym->isTag())
132 report_fatal_error("Tag indexes with offsets not supported");
133 if (WasmSym->isTable())
134 report_fatal_error("Table indexes with offsets not supported");
135
136 Expr = MCBinaryExpr::createAdd(
137 Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx);
138 }
139
140 return MCOperand::createExpr(Expr);
141 }
142
lowerTypeIndexOperand(SmallVector<wasm::ValType,1> && Returns,SmallVector<wasm::ValType,4> && Params) const143 MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand(
144 SmallVector<wasm::ValType, 1> &&Returns,
145 SmallVector<wasm::ValType, 4> &&Params) const {
146 auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns),
147 std::move(Params));
148 MCSymbol *Sym = Printer.createTempSymbol("typeindex");
149 auto *WasmSym = cast<MCSymbolWasm>(Sym);
150 WasmSym->setSignature(Signature.get());
151 Printer.addSignature(std::move(Signature));
152 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
153 const MCExpr *Expr =
154 MCSymbolRefExpr::create(WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx);
155 return MCOperand::createExpr(Expr);
156 }
157
158 // Return the WebAssembly type associated with the given register class.
getType(const TargetRegisterClass * RC)159 static wasm::ValType getType(const TargetRegisterClass *RC) {
160 if (RC == &WebAssembly::I32RegClass)
161 return wasm::ValType::I32;
162 if (RC == &WebAssembly::I64RegClass)
163 return wasm::ValType::I64;
164 if (RC == &WebAssembly::F32RegClass)
165 return wasm::ValType::F32;
166 if (RC == &WebAssembly::F64RegClass)
167 return wasm::ValType::F64;
168 if (RC == &WebAssembly::V128RegClass)
169 return wasm::ValType::V128;
170 if (RC == &WebAssembly::EXTERNREFRegClass)
171 return wasm::ValType::EXTERNREF;
172 if (RC == &WebAssembly::FUNCREFRegClass)
173 return wasm::ValType::FUNCREF;
174 llvm_unreachable("Unexpected register class");
175 }
176
getFunctionReturns(const MachineInstr * MI,SmallVectorImpl<wasm::ValType> & Returns)177 static void getFunctionReturns(const MachineInstr *MI,
178 SmallVectorImpl<wasm::ValType> &Returns) {
179 const Function &F = MI->getMF()->getFunction();
180 const TargetMachine &TM = MI->getMF()->getTarget();
181 Type *RetTy = F.getReturnType();
182 SmallVector<MVT, 4> CallerRetTys;
183 computeLegalValueVTs(F, TM, RetTy, CallerRetTys);
184 valTypesFromMVTs(CallerRetTys, Returns);
185 }
186
lower(const MachineInstr * MI,MCInst & OutMI) const187 void WebAssemblyMCInstLower::lower(const MachineInstr *MI,
188 MCInst &OutMI) const {
189 OutMI.setOpcode(MI->getOpcode());
190
191 const MCInstrDesc &Desc = MI->getDesc();
192 unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs();
193 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
194 const MachineOperand &MO = MI->getOperand(I);
195
196 MCOperand MCOp;
197 switch (MO.getType()) {
198 default:
199 MI->print(errs());
200 llvm_unreachable("unknown operand type");
201 case MachineOperand::MO_MachineBasicBlock:
202 MI->print(errs());
203 llvm_unreachable("MachineBasicBlock operand should have been rewritten");
204 case MachineOperand::MO_Register: {
205 // Ignore all implicit register operands.
206 if (MO.isImplicit())
207 continue;
208 const WebAssemblyFunctionInfo &MFI =
209 *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>();
210 unsigned WAReg = MFI.getWAReg(MO.getReg());
211 MCOp = MCOperand::createReg(WAReg);
212 break;
213 }
214 case MachineOperand::MO_Immediate: {
215 unsigned DescIndex = I - NumVariadicDefs;
216 if (DescIndex < Desc.NumOperands) {
217 const MCOperandInfo &Info = Desc.OpInfo[DescIndex];
218 if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
219 SmallVector<wasm::ValType, 4> Returns;
220 SmallVector<wasm::ValType, 4> Params;
221
222 const MachineRegisterInfo &MRI =
223 MI->getParent()->getParent()->getRegInfo();
224 for (const MachineOperand &MO : MI->defs())
225 Returns.push_back(getType(MRI.getRegClass(MO.getReg())));
226 for (const MachineOperand &MO : MI->explicit_uses())
227 if (MO.isReg())
228 Params.push_back(getType(MRI.getRegClass(MO.getReg())));
229
230 // call_indirect instructions have a callee operand at the end which
231 // doesn't count as a param.
232 if (WebAssembly::isCallIndirect(MI->getOpcode()))
233 Params.pop_back();
234
235 // return_call_indirect instructions have the return type of the
236 // caller
237 if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT)
238 getFunctionReturns(MI, Returns);
239
240 MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params));
241 break;
242 } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) {
243 auto BT = static_cast<WebAssembly::BlockType>(MO.getImm());
244 assert(BT != WebAssembly::BlockType::Invalid);
245 if (BT == WebAssembly::BlockType::Multivalue) {
246 SmallVector<wasm::ValType, 1> Returns;
247 getFunctionReturns(MI, Returns);
248 MCOp = lowerTypeIndexOperand(std::move(Returns),
249 SmallVector<wasm::ValType, 4>());
250 break;
251 }
252 } else if (Info.OperandType == WebAssembly::OPERAND_HEAPTYPE) {
253 assert(static_cast<WebAssembly::HeapType>(MO.getImm()) !=
254 WebAssembly::HeapType::Invalid);
255 // With typed function references, this will need a case for type
256 // index operands. Otherwise, fall through.
257 }
258 }
259 MCOp = MCOperand::createImm(MO.getImm());
260 break;
261 }
262 case MachineOperand::MO_FPImmediate: {
263 const ConstantFP *Imm = MO.getFPImm();
264 const uint64_t BitPattern =
265 Imm->getValueAPF().bitcastToAPInt().getZExtValue();
266 if (Imm->getType()->isFloatTy())
267 MCOp = MCOperand::createSFPImm(static_cast<uint32_t>(BitPattern));
268 else if (Imm->getType()->isDoubleTy())
269 MCOp = MCOperand::createDFPImm(BitPattern);
270 else
271 llvm_unreachable("unknown floating point immediate type");
272 break;
273 }
274 case MachineOperand::MO_GlobalAddress:
275 MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO));
276 break;
277 case MachineOperand::MO_ExternalSymbol:
278 // The target flag indicates whether this is a symbol for a
279 // variable or a function.
280 assert(MO.getTargetFlags() == 0 &&
281 "WebAssembly uses only symbol flags on ExternalSymbols");
282 MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO));
283 break;
284 case MachineOperand::MO_MCSymbol:
285 // This is currently used only for LSDA symbols (GCC_except_table),
286 // because global addresses or other external symbols are handled above.
287 assert(MO.getTargetFlags() == 0 &&
288 "WebAssembly does not use target flags on MCSymbol");
289 MCOp = lowerSymbolOperand(MO, MO.getMCSymbol());
290 break;
291 }
292
293 OutMI.addOperand(MCOp);
294 }
295
296 if (!WasmKeepRegisters)
297 removeRegisterOperands(MI, OutMI);
298 else if (Desc.variadicOpsAreDefs())
299 OutMI.insert(OutMI.begin(), MCOperand::createImm(MI->getNumExplicitDefs()));
300 }
301
removeRegisterOperands(const MachineInstr * MI,MCInst & OutMI)302 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) {
303 // Remove all uses of stackified registers to bring the instruction format
304 // into its final stack form used thruout MC, and transition opcodes to
305 // their _S variant.
306 // We do this separate from the above code that still may need these
307 // registers for e.g. call_indirect signatures.
308 // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for
309 // details.
310 // TODO: the code above creates new registers which are then removed here.
311 // That code could be slightly simplified by not doing that, though maybe
312 // it is simpler conceptually to keep the code above in "register mode"
313 // until this transition point.
314 // FIXME: we are not processing inline assembly, which contains register
315 // operands, because it is used by later target generic code.
316 if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm())
317 return;
318
319 // Transform to _S instruction.
320 auto RegOpcode = OutMI.getOpcode();
321 auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode);
322 assert(StackOpcode != -1 && "Failed to stackify instruction");
323 OutMI.setOpcode(StackOpcode);
324
325 // Remove register operands.
326 for (auto I = OutMI.getNumOperands(); I; --I) {
327 auto &MO = OutMI.getOperand(I - 1);
328 if (MO.isReg()) {
329 OutMI.erase(&MO);
330 }
331 }
332 }
333