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 "WebAssemblyAsmPrinter.h"
19#include "WebAssemblyISelLowering.h"
20#include "WebAssemblyMachineFunctionInfo.h"
21#include "WebAssemblyUtilities.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
33using namespace llvm;
34
35// This disables the removal of registers when lowering into MC, as required
36// by some current tests.
37cl::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(Val: false));
42
43static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI);
44
45MCSymbol *
46WebAssemblyMCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
47 const GlobalValue *Global = MO.getGlobal();
48 if (!isa<Function>(Val: Global)) {
49 auto *WasmSym = cast<MCSymbolWasm>(Val: Printer.getSymbol(GV: 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(AS: 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(F: CurrentFunc, TM, Ty: GlobalVT, ValueVTs&: VTs);
61
62 WebAssembly::wasmSymbolSetType(Sym: WasmSym, GlobalVT, VTs);
63 }
64 return WasmSym;
65 }
66
67 const auto *FuncTy = cast<FunctionType>(Val: 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>(Val: Global);
75 computeSignatureVTs(Ty: FuncTy, TargetFunc: F, ContextFunc: CurrentFunc, TM, Params&: ParamMVTs, Results&: ResultMVTs);
76 auto Signature = signatureFromMVTs(Ctx, Results: ResultMVTs, Params: ParamMVTs);
77
78 bool InvokeDetected = false;
79 auto *WasmSym = Printer.getMCSymbolForFunction(
80 F, EnableEmEH: WebAssembly::WasmEnableEmEH || WebAssembly::WasmEnableEmSjLj,
81 Sig: Signature, InvokeDetected);
82 WasmSym->setSignature(Signature);
83 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
84 return WasmSym;
85}
86
87MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
88 const MachineOperand &MO) const {
89 return Printer.getOrCreateWasmSymbol(Name: MO.getSymbolName());
90}
91
92MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO,
93 MCSymbol *Sym) const {
94 MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None;
95 unsigned TargetFlags = MO.getTargetFlags();
96
97 switch (TargetFlags) {
98 case WebAssemblyII::MO_NO_FLAG:
99 break;
100 case WebAssemblyII::MO_GOT_TLS:
101 Kind = MCSymbolRefExpr::VK_WASM_GOT_TLS;
102 break;
103 case WebAssemblyII::MO_GOT:
104 Kind = MCSymbolRefExpr::VK_GOT;
105 break;
106 case WebAssemblyII::MO_MEMORY_BASE_REL:
107 Kind = MCSymbolRefExpr::VK_WASM_MBREL;
108 break;
109 case WebAssemblyII::MO_TLS_BASE_REL:
110 Kind = MCSymbolRefExpr::VK_WASM_TLSREL;
111 break;
112 case WebAssemblyII::MO_TABLE_BASE_REL:
113 Kind = MCSymbolRefExpr::VK_WASM_TBREL;
114 break;
115 default:
116 llvm_unreachable("Unknown target flag on GV operand");
117 }
118
119 const MCExpr *Expr = MCSymbolRefExpr::create(Symbol: Sym, Kind, Ctx);
120
121 if (MO.getOffset() != 0) {
122 const auto *WasmSym = cast<MCSymbolWasm>(Val: Sym);
123 if (TargetFlags == WebAssemblyII::MO_GOT)
124 report_fatal_error(reason: "GOT symbol references do not support offsets");
125 if (WasmSym->isFunction())
126 report_fatal_error(reason: "Function addresses with offsets not supported");
127 if (WasmSym->isGlobal())
128 report_fatal_error(reason: "Global indexes with offsets not supported");
129 if (WasmSym->isTag())
130 report_fatal_error(reason: "Tag indexes with offsets not supported");
131 if (WasmSym->isTable())
132 report_fatal_error(reason: "Table indexes with offsets not supported");
133
134 Expr = MCBinaryExpr::createAdd(
135 LHS: Expr, RHS: MCConstantExpr::create(Value: MO.getOffset(), Ctx), Ctx);
136 }
137
138 return MCOperand::createExpr(Val: Expr);
139}
140
141MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand(
142 SmallVectorImpl<wasm::ValType> &&Returns,
143 SmallVectorImpl<wasm::ValType> &&Params) const {
144 auto Signature = Ctx.createWasmSignature();
145 Signature->Returns = std::move(Returns);
146 Signature->Params = std::move(Params);
147 MCSymbol *Sym = Printer.createTempSymbol(Name: "typeindex");
148 auto *WasmSym = cast<MCSymbolWasm>(Val: Sym);
149 WasmSym->setSignature(Signature);
150 WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
151 const MCExpr *Expr =
152 MCSymbolRefExpr::create(Symbol: WasmSym, Kind: MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx);
153 return MCOperand::createExpr(Val: Expr);
154}
155
156static void getFunctionReturns(const MachineInstr *MI,
157 SmallVectorImpl<wasm::ValType> &Returns) {
158 const Function &F = MI->getMF()->getFunction();
159 const TargetMachine &TM = MI->getMF()->getTarget();
160 Type *RetTy = F.getReturnType();
161 SmallVector<MVT, 4> CallerRetTys;
162 computeLegalValueVTs(F, TM, Ty: RetTy, ValueVTs&: CallerRetTys);
163 valTypesFromMVTs(In: CallerRetTys, Out&: Returns);
164}
165
166void WebAssemblyMCInstLower::lower(const MachineInstr *MI,
167 MCInst &OutMI) const {
168 OutMI.setOpcode(MI->getOpcode());
169
170 const MCInstrDesc &Desc = MI->getDesc();
171 unsigned NumVariadicDefs = MI->getNumExplicitDefs() - Desc.getNumDefs();
172 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
173 const MachineOperand &MO = MI->getOperand(i: I);
174
175 MCOperand MCOp;
176 switch (MO.getType()) {
177 default:
178 MI->print(OS&: errs());
179 llvm_unreachable("unknown operand type");
180 case MachineOperand::MO_MachineBasicBlock:
181 MI->print(OS&: errs());
182 llvm_unreachable("MachineBasicBlock operand should have been rewritten");
183 case MachineOperand::MO_Register: {
184 // Ignore all implicit register operands.
185 if (MO.isImplicit())
186 continue;
187 const WebAssemblyFunctionInfo &MFI =
188 *MI->getParent()->getParent()->getInfo<WebAssemblyFunctionInfo>();
189 unsigned WAReg = MFI.getWAReg(VReg: MO.getReg());
190 MCOp = MCOperand::createReg(Reg: WAReg);
191 break;
192 }
193 case MachineOperand::MO_Immediate: {
194 unsigned DescIndex = I - NumVariadicDefs;
195 if (DescIndex < Desc.NumOperands) {
196 const MCOperandInfo &Info = Desc.operands()[DescIndex];
197 if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
198 SmallVector<wasm::ValType, 4> Returns;
199 SmallVector<wasm::ValType, 4> Params;
200
201 const MachineRegisterInfo &MRI =
202 MI->getParent()->getParent()->getRegInfo();
203 for (const MachineOperand &MO : MI->defs())
204 Returns.push_back(Elt: WebAssembly::regClassToValType(
205 RC: MRI.getRegClass(Reg: MO.getReg())->getID()));
206 for (const MachineOperand &MO : MI->explicit_uses())
207 if (MO.isReg())
208 Params.push_back(Elt: WebAssembly::regClassToValType(
209 RC: MRI.getRegClass(Reg: MO.getReg())->getID()));
210
211 // call_indirect instructions have a callee operand at the end which
212 // doesn't count as a param.
213 if (WebAssembly::isCallIndirect(Opc: MI->getOpcode()))
214 Params.pop_back();
215
216 // return_call_indirect instructions have the return type of the
217 // caller
218 if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT)
219 getFunctionReturns(MI, Returns);
220
221 MCOp = lowerTypeIndexOperand(Returns: std::move(Returns), Params: std::move(Params));
222 break;
223 } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) {
224 auto BT = static_cast<WebAssembly::BlockType>(MO.getImm());
225 assert(BT != WebAssembly::BlockType::Invalid);
226 if (BT == WebAssembly::BlockType::Multivalue) {
227 SmallVector<wasm::ValType, 1> Returns;
228 getFunctionReturns(MI, Returns);
229 MCOp = lowerTypeIndexOperand(Returns: std::move(Returns),
230 Params: SmallVector<wasm::ValType, 4>());
231 break;
232 }
233 }
234 }
235 MCOp = MCOperand::createImm(Val: MO.getImm());
236 break;
237 }
238 case MachineOperand::MO_FPImmediate: {
239 const ConstantFP *Imm = MO.getFPImm();
240 const uint64_t BitPattern =
241 Imm->getValueAPF().bitcastToAPInt().getZExtValue();
242 if (Imm->getType()->isFloatTy())
243 MCOp = MCOperand::createSFPImm(Val: static_cast<uint32_t>(BitPattern));
244 else if (Imm->getType()->isDoubleTy())
245 MCOp = MCOperand::createDFPImm(Val: BitPattern);
246 else
247 llvm_unreachable("unknown floating point immediate type");
248 break;
249 }
250 case MachineOperand::MO_GlobalAddress:
251 MCOp = lowerSymbolOperand(MO, Sym: GetGlobalAddressSymbol(MO));
252 break;
253 case MachineOperand::MO_ExternalSymbol:
254 MCOp = lowerSymbolOperand(MO, Sym: GetExternalSymbolSymbol(MO));
255 break;
256 case MachineOperand::MO_MCSymbol:
257 assert(MO.getTargetFlags() == 0 &&
258 "WebAssembly does not use target flags on MCSymbol");
259 MCOp = lowerSymbolOperand(MO, Sym: MO.getMCSymbol());
260 break;
261 }
262
263 OutMI.addOperand(Op: MCOp);
264 }
265
266 if (!WasmKeepRegisters)
267 removeRegisterOperands(MI, OutMI);
268 else if (Desc.variadicOpsAreDefs())
269 OutMI.insert(I: OutMI.begin(), Op: MCOperand::createImm(Val: MI->getNumExplicitDefs()));
270}
271
272static void removeRegisterOperands(const MachineInstr *MI, MCInst &OutMI) {
273 // Remove all uses of stackified registers to bring the instruction format
274 // into its final stack form used thruout MC, and transition opcodes to
275 // their _S variant.
276 // We do this separate from the above code that still may need these
277 // registers for e.g. call_indirect signatures.
278 // See comments in lib/Target/WebAssembly/WebAssemblyInstrFormats.td for
279 // details.
280 // TODO: the code above creates new registers which are then removed here.
281 // That code could be slightly simplified by not doing that, though maybe
282 // it is simpler conceptually to keep the code above in "register mode"
283 // until this transition point.
284 // FIXME: we are not processing inline assembly, which contains register
285 // operands, because it is used by later target generic code.
286 if (MI->isDebugInstr() || MI->isLabel() || MI->isInlineAsm())
287 return;
288
289 // Transform to _S instruction.
290 auto RegOpcode = OutMI.getOpcode();
291 auto StackOpcode = WebAssembly::getStackOpcode(Opcode: RegOpcode);
292 assert(StackOpcode != -1 && "Failed to stackify instruction");
293 OutMI.setOpcode(StackOpcode);
294
295 // Remove register operands.
296 for (auto I = OutMI.getNumOperands(); I; --I) {
297 auto &MO = OutMI.getOperand(i: I - 1);
298 if (MO.isReg()) {
299 OutMI.erase(I: &MO);
300 }
301 }
302}
303

source code of llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp