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 "MCTargetDesc/WebAssemblyMCAsmInfo.h"
17 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
18 #include "TargetInfo/WebAssemblyTargetInfo.h"
19 #include "Utils/WebAssemblyTypeUtilities.h"
20 #include "WebAssemblyAsmPrinter.h"
21 #include "WebAssemblyMachineFunctionInfo.h"
22 #include "WebAssemblyUtilities.h"
23 #include "llvm/CodeGen/AsmPrinter.h"
24 #include "llvm/CodeGen/MachineFunction.h"
25 #include "llvm/IR/Constants.h"
26 #include "llvm/MC/MCAsmInfo.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCExpr.h"
29 #include "llvm/MC/MCInst.h"
30 #include "llvm/MC/MCSymbolWasm.h"
31 #include "llvm/Support/ErrorHandling.h"
32 #include "llvm/Support/raw_ostream.h"
33
34 using namespace llvm;
35
36 // This disables the removal of registers when lowering into MC, as required
37 // by some current tests.
38 static cl::opt<bool>
39 WasmKeepRegisters("wasm-keep-registers", cl::Hidden,
40 cl::desc("WebAssembly: output stack registers in"
41 " instruction output for test purposes only."),
42 cl::init(false));
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 Type *GlobalVT = Global->getValueType();
60 SmallVector<MVT, 1> VTs;
61 computeLegalValueVTs(CurrentFunc, TM, GlobalVT, VTs);
62
63 WebAssembly::wasmSymbolSetType(WasmSym, GlobalVT, VTs);
64 }
65 return WasmSym;
66 }
67
68 const auto *FuncTy = cast<FunctionType>(Global->getValueType());
69 const MachineFunction &MF = *MO.getParent()->getParent()->getParent();
70 const TargetMachine &TM = MF.getTarget();
71 const Function &CurrentFunc = MF.getFunction();
72
73 SmallVector<MVT, 1> ResultMVTs;
74 SmallVector<MVT, 4> ParamMVTs;
75 const auto *const F = dyn_cast<Function>(Global);
76 computeSignatureVTs(FuncTy, F, CurrentFunc, TM, ParamMVTs, ResultMVTs);
77 auto Signature = signatureFromMVTs(Ctx, ResultMVTs, ParamMVTs);
78
79 bool InvokeDetected = false;
80 auto *WasmSym = Printer.getMCSymbolForFunction(F, Signature, InvokeDetected);
81 WasmSym->setSignature(Signature);
82 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
83 return WasmSym;
84 }
85
GetExternalSymbolSymbol(const MachineOperand & MO) const86 MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
87 const MachineOperand &MO) const {
88 return Printer.getOrCreateWasmSymbol(MO.getSymbolName());
89 }
90
lowerSymbolOperand(const MachineOperand & MO,MCSymbol * Sym) const91 MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO,
92 MCSymbol *Sym) const {
93 auto Spec = WebAssembly::S_None;
94 unsigned TargetFlags = MO.getTargetFlags();
95
96 switch (TargetFlags) {
97 case WebAssemblyII::MO_NO_FLAG:
98 break;
99 case WebAssemblyII::MO_GOT_TLS:
100 Spec = WebAssembly::S_GOT_TLS;
101 break;
102 case WebAssemblyII::MO_GOT:
103 Spec = WebAssembly::S_GOT;
104 break;
105 case WebAssemblyII::MO_MEMORY_BASE_REL:
106 Spec = WebAssembly::S_MBREL;
107 break;
108 case WebAssemblyII::MO_TLS_BASE_REL:
109 Spec = WebAssembly::S_TLSREL;
110 break;
111 case WebAssemblyII::MO_TABLE_BASE_REL:
112 Spec = WebAssembly::S_TBREL;
113 break;
114 default:
115 llvm_unreachable("Unknown target flag on GV operand");
116 }
117
118 const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Spec, Ctx);
119
120 if (MO.getOffset() != 0) {
121 const auto *WasmSym = cast<MCSymbolWasm>(Sym);
122 if (TargetFlags == WebAssemblyII::MO_GOT)
123 report_fatal_error("GOT symbol references do not support offsets");
124 if (WasmSym->isFunction())
125 report_fatal_error("Function addresses with offsets not supported");
126 if (WasmSym->isGlobal())
127 report_fatal_error("Global indexes with offsets not supported");
128 if (WasmSym->isTag())
129 report_fatal_error("Tag indexes with offsets not supported");
130 if (WasmSym->isTable())
131 report_fatal_error("Table indexes with offsets not supported");
132
133 Expr = MCBinaryExpr::createAdd(
134 Expr, MCConstantExpr::create(MO.getOffset(), Ctx), Ctx);
135 }
136
137 return MCOperand::createExpr(Expr);
138 }
139
lowerTypeIndexOperand(SmallVectorImpl<wasm::ValType> && Returns,SmallVectorImpl<wasm::ValType> && Params) const140 MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand(
141 SmallVectorImpl<wasm::ValType> &&Returns,
142 SmallVectorImpl<wasm::ValType> &&Params) const {
143 auto Signature = Ctx.createWasmSignature();
144 Signature->Returns = std::move(Returns);
145 Signature->Params = std::move(Params);
146 MCSymbol *Sym = Printer.createTempSymbol("typeindex");
147 auto *WasmSym = cast<MCSymbolWasm>(Sym);
148 WasmSym->setSignature(Signature);
149 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
150 const MCExpr *Expr =
151 MCSymbolRefExpr::create(WasmSym, WebAssembly::S_TYPEINDEX, Ctx);
152 return MCOperand::createExpr(Expr);
153 }
154
getFunctionReturns(const MachineInstr * MI,SmallVectorImpl<wasm::ValType> & Returns)155 static void getFunctionReturns(const MachineInstr *MI,
156 SmallVectorImpl<wasm::ValType> &Returns) {
157 const Function &F = MI->getMF()->getFunction();
158 const TargetMachine &TM = MI->getMF()->getTarget();
159 Type *RetTy = F.getReturnType();
160 SmallVector<MVT, 4> CallerRetTys;
161 computeLegalValueVTs(F, TM, RetTy, CallerRetTys);
162 valTypesFromMVTs(CallerRetTys, Returns);
163 }
164
lower(const MachineInstr * MI,MCInst & OutMI) const165 void WebAssemblyMCInstLower::lower(const MachineInstr *MI,
166 MCInst &OutMI) const {
167 OutMI.setOpcode(MI->getOpcode());
168
169 const MCInstrDesc &Desc = MI->getDesc();
170 unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs();
171 const MachineFunction *MF = MI->getMF();
172 const auto &TLI =
173 *MF->getSubtarget<WebAssemblySubtarget>().getTargetLowering();
174 wasm::ValType PtrTy = TLI.getPointerTy(MF->getDataLayout()) == MVT::i32
175 ? wasm::ValType::I32
176 : wasm::ValType::I64;
177
178 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
179 const MachineOperand &MO = MI->getOperand(I);
180
181 MCOperand MCOp;
182 switch (MO.getType()) {
183 default:
184 MI->print(errs());
185 llvm_unreachable("unknown operand type");
186 case MachineOperand::MO_MachineBasicBlock:
187 MI->print(errs());
188 llvm_unreachable("MachineBasicBlock operand should have been rewritten");
189 case MachineOperand::MO_Register: {
190 // Ignore all implicit register operands.
191 if (MO.isImplicit())
192 continue;
193 const WebAssemblyFunctionInfo &MFI =
194 *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>();
195 unsigned WAReg = MFI.getWAReg(MO.getReg());
196 MCOp = MCOperand::createReg(WAReg);
197 break;
198 }
199 case MachineOperand::MO_Immediate: {
200 unsigned DescIndex = I - NumVariadicDefs;
201 if (DescIndex < Desc.NumOperands) {
202 const MCOperandInfo &Info = Desc.operands()[DescIndex];
203 if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
204 SmallVector<wasm::ValType, 4> Returns;
205 SmallVector<wasm::ValType, 4> Params;
206
207 const MachineRegisterInfo &MRI =
208 MI->getParent()->getParent()->getRegInfo();
209 for (const MachineOperand &MO : MI->defs())
210 Returns.push_back(WebAssembly::regClassToValType(
211 MRI.getRegClass(MO.getReg())->getID()));
212 for (const MachineOperand &MO : MI->explicit_uses())
213 if (MO.isReg())
214 Params.push_back(WebAssembly::regClassToValType(
215 MRI.getRegClass(MO.getReg())->getID()));
216
217 // call_indirect instructions have a callee operand at the end which
218 // doesn't count as a param.
219 if (WebAssembly::isCallIndirect(MI->getOpcode()))
220 Params.pop_back();
221
222 // return_call_indirect instructions have the return type of the
223 // caller
224 if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT)
225 getFunctionReturns(MI, Returns);
226
227 MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params));
228 break;
229 }
230 if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) {
231 auto BT = static_cast<WebAssembly::BlockType>(MO.getImm());
232 assert(BT != WebAssembly::BlockType::Invalid);
233 if (BT == WebAssembly::BlockType::Multivalue) {
234 SmallVector<wasm::ValType, 2> Returns;
235 // Multivalue blocks are emitted in two cases:
236 // 1. When the blocks will never be exited and are at the ends of
237 // functions (see
238 // WebAssemblyCFGStackify::fixEndsAtEndOfFunction). In this case
239 // the exact multivalue signature can always be inferred from the
240 // return type of the parent function.
241 // 2. (catch_ref ...) clause in try_table instruction. Currently all
242 // tags we support (cpp_exception and c_longjmp) throws a single
243 // pointer, so the multivalue signature for this case will be
244 // (ptr, exnref). Having MO_CATCH_BLOCK_SIG target flags means
245 // this is a destination of a catch_ref.
246 if (MO.getTargetFlags() == WebAssemblyII::MO_CATCH_BLOCK_SIG) {
247 Returns = {PtrTy, wasm::ValType::EXNREF};
248 } else
249 getFunctionReturns(MI, Returns);
250 MCOp = lowerTypeIndexOperand(std::move(Returns),
251 SmallVector<wasm::ValType, 4>());
252 break;
253 }
254 }
255 }
256 MCOp = MCOperand::createImm(MO.getImm());
257 break;
258 }
259 case MachineOperand::MO_FPImmediate: {
260 const ConstantFP *Imm = MO.getFPImm();
261 const uint64_t BitPattern =
262 Imm->getValueAPF().bitcastToAPInt().getZExtValue();
263 if (Imm->getType()->isFloatTy())
264 MCOp = MCOperand::createSFPImm(static_cast<uint32_t>(BitPattern));
265 else if (Imm->getType()->isDoubleTy())
266 MCOp = MCOperand::createDFPImm(BitPattern);
267 else
268 llvm_unreachable("unknown floating point immediate type");
269 break;
270 }
271 case MachineOperand::MO_GlobalAddress:
272 MCOp = lowerSymbolOperand(MO, GetGlobalAddressSymbol(MO));
273 break;
274 case MachineOperand::MO_ExternalSymbol:
275 MCOp = lowerSymbolOperand(MO, GetExternalSymbolSymbol(MO));
276 break;
277 case MachineOperand::MO_MCSymbol:
278 assert(MO.getTargetFlags() == 0 &&
279 "WebAssembly does not use target flags on MCSymbol");
280 MCOp = lowerSymbolOperand(MO, MO.getMCSymbol());
281 break;
282 }
283
284 OutMI.addOperand(MCOp);
285 }
286
287 if (!WasmKeepRegisters)
288 removeRegisterOperands(MI, OutMI);
289 else if (Desc.variadicOpsAreDefs())
290 OutMI.insert(OutMI.begin(), MCOperand::createImm(MI->getNumExplicitDefs()));
291 }
292
removeRegisterOperands(const MachineInstr * MI,MCInst & OutMI)293 static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) {
294 // Remove all uses of stackified registers to bring the instruction format
295 // into its final stack form used thruout MC, and transition opcodes to
296 // their _S variant.
297 // We do this separate from the above code that still may need these
298 // registers for e.g. call_indirect signatures.
299 // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for
300 // details.
301 // TODO: the code above creates new registers which are then removed here.
302 // That code could be slightly simplified by not doing that, though maybe
303 // it is simpler conceptually to keep the code above in "register mode"
304 // until this transition point.
305 // FIXME: we are not processing inline assembly, which contains register
306 // operands, because it is used by later target generic code.
307 if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm())
308 return;
309
310 // Transform to _S instruction.
311 auto RegOpcode = OutMI.getOpcode();
312 auto StackOpcode = WebAssembly::getStackOpcode(RegOpcode);
313 assert(StackOpcode != -1 && "Failed to stackify instruction");
314 OutMI.setOpcode(StackOpcode);
315
316 // Remove register operands.
317 for (auto I = OutMI.getNumOperands(); I; --I) {
318 auto &MO = OutMI.getOperand(I - 1);
319 if (MO.isReg()) {
320 OutMI.erase(&MO);
321 }
322 }
323 }
324